# do image stabilisers decrease image quality?



## rhysgray (Nov 7, 2012)

it seems all of canons sharpest lenses have no IS.
is this co-incidence or is it because the addition of an IS system somehow negatively affects image quality?????


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## rhysgray (Nov 7, 2012)

everybody knows the advantages of an IS system but are there any disadvantages other than size weight and price???


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## Narcolepsy (Nov 7, 2012)

EF 70-200mm f2.8L IS II
Image Stabilization & a very sharp lens


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## neuroanatomist (Nov 7, 2012)

Narcolepsy said:


> EF 70-200mm f2.8L IS II
> Image Stabilization & a very sharp lens



300/400/500/600 II superteles. Image Stabilization & even sharper.


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## Mt Spokane Photography (Nov 7, 2012)

rhysgray said:


> it seems all of canons sharpest lenses have no IS.
> is this co-incidence or is it because the addition of an IS system somehow negatively affects image quality? ??? ?


I do not believe that is accurate. The newest lenses are the sharpest, and most have IS. They have a more complex optical formula, and cost more as well. So what is true, is that newer lenses are sharpest, and prime lenses of the same generation and price range are usually sharper than a zoom.


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## Daniel Flather (Nov 7, 2012)

neuroanatomist said:


> Narcolepsy said:
> 
> 
> > EF 70-200mm f2.8L IS II
> ...



What, no love for the 200/2IS? The sharpest of them all.


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## PackLight (Nov 7, 2012)

Yes they do decrease IQ. If you don't believe me start shooting with yours turned off when you are doing hand held shooting and see how much your pictures improve.


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## tnargs (Nov 7, 2012)

PackLight said:


> Yes they do decrease IQ. If you don't believe me start shooting with yours turned off when you are doing hand held shooting and see how much your pictures improve.



That's not what the OP is asking. He is asking about a lens with no IS vs a lens with IS.

The most sensible way to discuss is to compare say Canon lenses where the same optical model is available (at the same time) with or without IS.

Canon probably publish MTF curves for both models and this might be a good starting point.


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## PackLight (Nov 7, 2012)

tnargs said:


> PackLight said:
> 
> 
> > Yes they do decrease IQ. If you don't believe me start shooting with yours turned off when you are doing hand held shooting and see how much your pictures improve.
> ...



That is not what the question posed in the "Subject" line says, sorry I didn't answer both of his questions.

As for his second question the OP posed in the thread, the IS was left out of the 24-70mm II for weight and size reasons. Compare the MTF chart of the 24-70mm II to the new 24-70mm f/4 IS at 70mm. The f/4 wins.


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## PavelR (Nov 7, 2012)

Daniel Flather said:


> neuroanatomist said:
> 
> 
> > Narcolepsy said:
> ...


+1


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## neuroanatomist (Nov 7, 2012)

tnargs said:


> The most sensible way to discuss is to compare say Canon lenses where the same optical model is available (at the same time) with or without IS.



Nice, in theory. But in practice, the addition of IS changes the optical formula and the other elements need to be changed in concert, so there's no real direct comparison.

But it's likely easiest to make a general comparison with the 70-200mm zooms. In descending order of from sharpest to least sharp, they are:

[list type=decimal]
[*]70-200mm f/2.8L IS II
[*]70-200mm f/4L IS
[*]70-200mm f/2.8L
[*]70-200mm f/2.8L IS
[*]70-200mm f/4L
[/list]

The fact that two IS lenses are at the top argues that IS doens't need to result in a loss of IQ...but those two lenses are also the newset in the bunch, and Mt. Spokane's point about newer lenses being sharper is true.



Daniel Flather said:


> What, no love for the 200/2IS? The sharpest of them all.



The 200/2L IS is quite sharp, but the 300/2.8L IS II is sharper away from the center, as is the 500 II. But probably not a significant difference overall - they're all damn sharp!


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## weixing (Nov 8, 2012)

Hi,
IMHO, every element added will decrease IQ by a bit, so a lens without IS will have slightly better IQ than lens with IS (when both lens are from the same generation and same grade) under perfect shooting condition. The decrease of IQ is minimum using modern coating and lens manufacturing technology, so the advantage of IS outweigh the decrease in IQ. 

So the question is: do you want some of your images to be very sharp (no IS) or most of your images to be sharp (with IS)? I think most of us would prefer the IS.

Have a nice day.


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## wickidwombat (Nov 8, 2012)

neuroanatomist said:


> Narcolepsy said:
> 
> 
> > EF 70-200mm f2.8L IS II
> ...



i can't believe you missed the 200 f2L IS!


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## Mt Spokane Photography (Nov 8, 2012)

weixing said:


> Hi,
> IMHO, every element added will decrease IQ by a bit, so a lens without IS will have slightly better IQ than lens with IS (when both lens are from the same generation and same grade) under perfect shooting condition.


So you believe a lens with one element is sharpest? Maybe one with no elements is the ultimate?


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## PackLight (Nov 8, 2012)

Mt Spokane Photography said:


> weixing said:
> 
> 
> > Hi,
> ...



That would be so. Looking through a hollow tube will always give you the clearest sharpest image. You can not improve the light when it is in it's near perfect unrestricted form.


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## Mt Spokane Photography (Nov 8, 2012)

PackLight said:


> Mt Spokane Photography said:
> 
> 
> > weixing said:
> ...


If you believe that, then why buy a lens? You can get a sharp image without one? Why don'y you start selling them, you can sell sharper lenses for just the cost of a roll of toilet paper.
Multiple lens elements do, in fact correct the various abberations that come from just one element. Thats why the lenses that are sharpest have multiple elements.
Your theory seems pretty badly flawed when compared with the real world.


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## PackLight (Nov 8, 2012)

Mt Spokane Photography said:


> PackLight said:
> 
> 
> > Mt Spokane Photography said:
> ...



Exactly what do you think lenses do?
They take the pure raw light and the bend it, skew it, rearrange it then focus it.
Multiple elements correct the aberrations that the first few elements create. Multiple elements are used to put the light back in the arrangement it started with. It doesn't improve what is natural.
Without one element the light isn't flawed, it isn't until light hits the glass that it changes and bends and compresses.

Weixing is partially right, in that when it touches the first element something is lost. Every element it touches after it looses something, but the following elements are putting it back in the right order for focus. Put enough elements in a lens the light will never make it through.


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## bycostello (Nov 8, 2012)

if weight and size were not issues they all would have it


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## neuroanatomist (Nov 8, 2012)

PackLight said:


> Put enough elements in a lens the light will never make it through.



How many would that take? Let's try 65:







Nope, not enough - light still makes it through.


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## PackLight (Nov 8, 2012)

neuroanatomist said:


> PackLight said:
> 
> 
> > Put enough elements in a lens the light will never make it through.
> ...



Keep adding, but it was this article that came to mind when I was typing that.

But, I do have two single element lenses in the house that have near perfect focus with no aberrations. If Canon RD would get their act together they could perform the same miracle these two lenses perform daily...or maybe Canon RD will never get there.


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## sanj (Nov 8, 2012)

But how does IS reduce quality? 
I am really trying to understand this for a while now.
Pls educate! THx


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## PackLight (Nov 8, 2012)

sanj said:


> But how does IS reduce quality?
> I am really trying to understand this for a while now.
> Pls educate! THx



I don't think it does. Not to any amount that is significant. Canon's sharpest lenses all have IS.


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## sanj (Nov 8, 2012)

Mt Spokane Photography said:


> PackLight said:
> 
> 
> > Mt Spokane Photography said:
> ...



Well one does need a lens to take a picture!!

It seems correct that one cannot improve on light/optics 'when it is in it's near perfect unrestricted form.'

No flaw here.


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## unfocused (Nov 8, 2012)

This is all very amusing, but it doesn't seem as though anyone is answering the OP's question. As I understand it, he/she is asking if the addition of optical image stabilization negatively impacts the sharpness of a lens.

I'm like the least technical person on this whole forum, so I'm certainly not qualified to answer this. But it does seem like a good question. I might expand on it a bit.

First, the idea that adding lens elements would degrade an image seems irrelevant because, as I understand it, stabilized lenses don't have any more or less elements. (That doesn't mean there aren't a different number of lens elements in a stabilized lens vs. an stabilized lens, just that the two are not related to one another.)

I think a more relevant question might be whether or not the construction of a stabilized lens sacrifices sharpness under certain conditions. From what I have read, the difference between stabilized and non-stabilized lenses is in how a group of lens elements are mounted within the lens – not the actual design of the lens elements. In a stabilized lens, a group of elements are mounted in a housing that uses gyroscopes to keep the elements stable when the housing shifts or moves. So, I guess the question really would be: since the lens elements effectively "float" within the IS housing, is there a reason why they might not be as sharp as elements that are solidly mounted within a lens tube? 

One reason this seems like a logical question is that Canon recommends turning off stabilization when a lens is mounted on a tripod. If you get a sharper image without stabilization on, when the camera is firmly mounted, it does at least raise the possibility that a non-stabilized lens would be sharper than a stabilized lens.

Okay, all you tech geeks, have at it.


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## Daniel Flather (Nov 8, 2012)

neuroanatomist said:


> away from the center



That's a variance. Like a half-truth, just sayin'.




neuroanatomist said:


> they're all damn sharp!



Agreed.


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## agierke (Nov 8, 2012)

you actually dont need a lens to take a picture. you do however need an aperture to direct light towards a medium that will record the picture. unless you consider photograms using non silver chemistry and then you dont even need an aperture.

i dont know the engineering or physics involved with IS as it pertains to image quality but i do know that a person who doesn't understand how IS is intended to be used can quickly find their image quality degrade from user error. i work with a guy who repeatedly insists on shooting in daylight with IS turned on with shutterspeeds slower than 1/60th of a sec on a 70-200mm and is shocked that he continues to get camera shake in his images.... 

*edit*

a gyro will create some level of vibration so at a certain point image stabilization becomes moot due to increasingly slow shutterspeeds being much more sensitive to the vibration. i imagine that is why canon recommends turning IS off when on a tripod because the assumption is that your shutterspeeds will decrease with the use of a tripod.


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## Radiating (Nov 8, 2012)

The inclusion of an image stabilization system in a lens DOES often lead to reduced image quality, BUT not all lenses that are poor quality have image stabilization and not all lenses that are of good quality lack image stabilization. For proof look at any lens that comes in IS and NON-IS format released in the SAME technological cycle. Tamron, Canon, Nikon, Sigma etc al have had lenses that meet that criteria and the IS version has worse IQ. 

Adding image stabilization is like making a rocket that can land on the moon then deciding to make it go to mars afterwards, it's going to be harder than just making a rocket that goes to the moon, but that doesn't mean you can't achieve IQ perfection with IS, you certainly can, it's just harder.


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## PackLight (Nov 8, 2012)

unfocused said:


> This is all very amusing, but it doesn't seem as though anyone is answering the OP's question. As I understand it, he/she is asking if the addition of optical image stabilization negatively impacts the sharpness of a lens.
> 
> I'm like the least technical person on this whole forum, so I'm certainly not qualified to answer this. But it does seem like a good question. I might expand on it a bit.
> 
> ...



I think you described it right from all I have read and seen. The IS doesn't add another element so if it is turned off it wouldn't have any affect. 

If you have the IS on while on the tripod and it kicks on it could cause motion blur, and then would affect IQ. That is one reason to turn it off. The other is battery life. 

The OP's question might have been better said can they design a sharper lens by leaving the IS out. Chuck Westfall mentioned this at the release of the 24-70mm II, if memory serves. The comment was that the IS was left out to get the very best image quality out of the 24-70mm II. What this really meant who knows, but it could have meant just as easily that other versions that could have been in the target price range wouldn't have had the same quality lens grouping. It could be that IS could have been put in the new 24-70mm II for a substantial price above the $2300 the lens is going for now. Imagine how a $3000 24-70mm f/2.8 II version would have been received by the public. I don't think Westfall's comments shed any light on the question the OP posed.

I am of the opinion that IS has no affect, other than if it is miss used or malfunctions.


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## sanj (Nov 8, 2012)

Yeah, the question: "How does IS reduce quality." needs to be addressed. NOT how IS can reduce quality. 
All lenses have IS on/off switch.

I really want to know.

Thx!


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## PackLight (Nov 8, 2012)

Sanj, how could it do anything to IQ? It is a mechanical device outside of the row of elements in the lens, it is not optical.

The only way it would affect optics is if it doesn't work properly.

But really this thread is about a non issue. There is no IS vs non IS lens that Canon makes that would be equal, those that are close the IS version is superior to the Non IS version.


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## Hillsilly (Nov 8, 2012)

Is there ever an advantage in turning IS off? (Ignoring tripod mounted cameras and assuming a sufficently fast shutter speed for a sharp photo.) I often see it stated that it results in sharper images, but my experiences have been inconclusive. Any thoughts?


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## Mt Spokane Photography (Nov 8, 2012)

PackLight said:


> Mt Spokane Photography said:
> 
> 
> > PackLight said:
> ...


 
Yes, something is lost, and it is light. 
But ... does IQ get worse with each additional element, as he said? If so, why not a 1 or a 2 element lens? IQ should be much better than those 22 element lenses - less CA, sharper, less distortion, etc - Really ?? Where are those one or two element lenses with superior IQ, or for that matter, 5 element lenses?
Its a nice theory, but the best lenses with the best IQ have many elements, and they do lose light, but not all that much. The 9 element 85mm f/1.8 has a Tstop of 2, so it loses 0.2 stops in the glass. The 20 element 70-200mm f/4L IS has a Tstop of 4.6, so it loses 0.6 stops. 20 elements, and it has suburb IQ and sharpness! 
So, how many elements until you lose a stop? Maybe 30 some elements? Your worry that light won't make it thru a lens due to the number of elements seems a bit far fetched.


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## Mr Bean (Nov 8, 2012)

My feeling is that IS would affect IQ as the lens or lenses in the IS unit are moved off center, to negate movement of the photographer. This process of moving the lenses off axis in the optical path would have been "allowed" in the design, but it'll be a case of "....the lesser of 2 evils".


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## PackLight (Nov 8, 2012)

Mt Spokane Photography said:


> Yes, something is lost, and it is light.
> But ... does IQ get worse with each additional element, as he said? If so, why not a 1 or a 2 element lens? IQ should be much better than those 22 element lenses - less CA, sharper, less distortion, etc - Really ?? Where are those one or two element lenses with superior IQ, or for that matter, 5 element lenses?
> Its a nice theory, but the best lenses with the best IQ have many elements, and they do lose light, but not all that much. The 9 element 85mm f/1.8 has a Tstop of 2, so it loses 0.2 stops in the glass. The 20 element 70-200mm f/4L IS has a Tstop of 4.6, so it loses 0.6 stops. 20 elements, and it has suburb IQ and sharpness!
> So, how many elements until you lose a stop? Maybe 30 some elements? Your worry that light won't make it thru a lens due to the number of elements seems a bit far fetched.



It is more than just light lost, it is the quality of the light itself, how the light breaks down going through the lens.

It does get worse with each element, because each progressive element corrects one problem and adds another, or not depending. If the lens has 20 elements the last element corrects flaws made through one or more of the previous 19. It will never be perfect and each element takes away, even if it is slightly. There is more lost than just light and loosing a stop, that is why we look for other flaws in our IQ other than just sharpness or quantity of light. No doubt the L lenses deliver great IQ with multiple elements, but it doesn't change that fact that a bit of quality is lost with each element.

A single lens that produces an image with little or no flaw is possible. The human eye has only one lens. Glass and Crystal lenses abilities are flawed in comparison.


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## Frodo (Nov 8, 2012)

"Its a nice theory, but the best lenses with the best IQ have many elements, and they do lose light, but not all that much. The 9 element 85mm f/1.8 has a Tstop of 2, so it loses 0.2 stops in the glass. The 20 element 70-200mm f/4L IS has a Tstop of 4.6, so it loses 0.6 stops. 20 elements, and it has suburb IQ and sharpness! "

Not sure that's correct. The first thing is that just because a lens says "1.8" or "4" does not mean that it is 1.8 or 4 in an optical sense. Just like 70mm on the 70-200mm is not actually 70.

Secondly, a 1.8 lens with a T-stop of 2 is a loss of 11%, whereas the f4 lines with a T-stop of 4.6 loses 15%. A loss of a full f-stop represents a 40% difference between f number and T-number, so the first lens loses about 0.27 of an f-stop and the second about 0.37 of an f-stop.

But my nit-picking aside, in principle you are right, extra elements will absorb or reflect more light, reducing the light passing through the lens, just not as much as you suggest. Others have commented on how extra elements can correct distortions and improve IQ.


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## sanj (Nov 8, 2012)

PackLight said:


> Sanj, how could it do anything to IQ? It is a mechanical device outside of the row of elements in the lens, it is not optical.
> 
> The only way it would affect optics is if it doesn't work properly.
> 
> But really this thread is about a non issue. There is no IS vs non IS lens that Canon makes that would be equal, those that are close the IS version is superior to the Non IS version.



I don't know but am trying my best to understand!
I bought the X100 and asked the Fuji 'guys' about IS and this is what they said:

Hello Greg and Billy.
Great video, great camera! Mine will be with me end of this month...!!
Could you please educate me on one point:
Why is incorporating Stabilization into the camera a bad idea: Does it:
a) Increase costs?
b) Increase size?
c) Reduce quality?
Asking because I am sure ISO 400 results in better quality than ISO 3200 (which 4 stops stabilization would provide.)
I understand that u guys strongly believe that this camera﻿ does not require IS but my question is: HOW CAN IT HURT?
Sanjay Gupta 1 year ago
Reply 
A) Yes, B) Yes, C) Yes as the ability for customization of the lens to the sensor would not be possible (well at least cost effective). I believe in I.S. however not so much with a 35mm equivalent lens. Especially the quality of ISO settings up to 3200 and a fast lens should allow﻿ for decent shutterspeeds for most situation. Others, use a tripod, or enable the flash.

Fuji Guys - X100 Frequently Asked Questions


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## PackLight (Nov 8, 2012)

Frodo said:


> But my nit-picking aside, in principle you are right, extra elements will absorb or reflect more light, reducing the light passing through the lens, just not as much as you suggest. Others have commented on how extra elements can correct distortions and improve IQ.



I am not sure how much I suggested, I didn't put a quantity to it. Maybe the difference is small and slight but it is still there.

Extra elements do not improve the quality of the original light. They correct the flaws of the other lenses. The additional elements improve the IQ and flaws in the light that was created by other lenses. Just because a lens has 20 elements doesn't make it a superior lens by quantity only, it is a lens that took 20 elements to get the IQ back to a usable form.

The elements do more than absorb and reflect, it also breaks down the light. It alters the colors that you will get. When comparing lenses it is common to talk about chromatic aberrations, sharpness, color, distortion and flare. All these items have an impact on IQ, and I haven't seen a lens made yet that took 100% of these lens created aberrations out.


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## mb66energy (Nov 8, 2012)

I think that there is no simple answer to your question. Trying to break it into different paths:
[list type=decimal]
[*]IS itself: If well programmed and eqiupped with good actor hardware it will not blurr the image by wrong corrective movements
[*]IS uses additional lens elements in most stabilized lenses and needs sometimes additional lens groups in the rest of the optical path. The number of lens elements is increased. Optical calculation of such systems is very complex because the moveable lns element has to correct movements correctly and at the same time it has to keep IQ at a high level.
This splits into to paths: 
[list type=decimal]
[*]If the calculation of the lens is done very carefully, IQ will remain very good. 
[*]If the calculation is done less carefully or the price limit cuts into optimization quality, IQ will decrease.
[/list]
[*]If you have a simple lens design movement of one lens element will give usable results, but I think extreme values of corrective movements will cut into IQ.
[*]If IS gives you 4 exposure steps, you have 16 times lower movements due to camera shake - if the IS element reduces resolution by a factor 1.2 you will gain roughly 12 times more sharpness in comparison to an unstabilized lens. 
[*]Additional lens elements reduce the contrast of a lens - if you use the same measures to suppress reflections and light scattering on lenses and structural elements. But if you go from 13 lens groups w/o IS to 15 lens groups w/ IS this is a small difference (70-200 4.0 non IS vs. IS). If you go from 6 to 12 groups it might be another thing (5.6/400 vs. 2.8/400 ii).
On the other hand additional lens elements improve IQ by correcting different aberrations if the calculation is done properly and if there is no strong price limit.
[/list]

IMO there are applications of IS lenses: If a tripod isn't allowed/appropriate and low aperatures are essentially needed to gain enough DOF/the light is limited.
The new 4.0 24-70 IS lens might address these application fields. I think it is a good addition of the EF lens family ... if the quality is phenomenal and the street price will come into the region of the 24-105.


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## sandymandy (Nov 8, 2012)

100mm 2.8L IS is one of the sharpest lenses out there i think  Probably Is can degrade IQ by helping u in situations where without IS u would get motion blur but IS reduces it like 98% for example but not 100%. So thats when it perhaps could cause "worse IQ"


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## sanj (Nov 8, 2012)

Mr Bean said:


> My feeling is that IS would affect IQ as the lens or lenses in the IS unit are moved off center, to negate movement of the photographer. This process of moving the lenses off axis in the optical path would have been "allowed" in the design, but it'll be a case of "....the lesser of 2 evils".



This makes a lot of sense to me!


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## neuroanatomist (Nov 8, 2012)

PackLight said:


> A single lens that produces an image with little or no flaw is possible. The human eye has only one lens. Glass and Crystal lenses abilities are flawed in comparison.



It has one structure called a lens, true, but actually the eye can be considered to have at least 4 elements, perhaps better thought of as 4 groups, 3 groups with one element each and one group (the lens itself) comprising multiple elements. The cornea actually does most of the refracting, but both the aqueous humour and vitreous humour have refractive indices that differ from the cornea and lens. The lens itself has a refractive index that varies through the structure, and the action of the ciliary muscles changes the shape of the lens, which alters not only the shape of the lens surfaces, but also the differential thickness of the regions of different internal refractive indices.

So if we assume the eye is producing an image with little or no flaws, understand that it's _far_ more complex than a single-element lens.


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## PackLight (Nov 8, 2012)

neuroanatomist said:


> PackLight said:
> 
> 
> > A single lens that produces an image with little or no flaw is possible. The human eye has only one lens. Glass and Crystal lenses abilities are flawed in comparison.
> ...



I would say it is more complex. Compared to Nikon its sensor has about 3x the dynamic range. I wonder how that would rate with DxO.

But I do have to admit it does have flaws, when I turned 50 I had to start using reading glasses. So I guess mine has a 5th element that I use for macro work.


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## mb66energy (Nov 8, 2012)

neuroanatomist said:


> PackLight said:
> 
> 
> > A single lens that produces an image with little or no flaw is possible. The human eye has only one lens. Glass and Crystal lenses abilities are flawed in comparison.
> ...



That's what I thought as I read the comment, that the human eye is a single lens construction. I would prefer to see it as a 4 element - 1 group system but that might be a matter of taste.

There are two further reasons why the eye doesn't compare to photographic lenses:

The eye has optimum quality only near the image center where the spatial resolution is maximal and spherical aberration or CAs arent a problem. The image borders are optimized for faster "frame rates" and only B&W ...
The brain corrects the raw data from the retina and adds fragments of detailed information from the image center (while scanning our surroundings) to give us the perception of a detailed larger picture with corrected perspective. 
EDIT: Image stabilized by coupling the eye to the vestibular system to keep the direction during slower motions + soft tissue between eyeball and bones to damp higher frequency motion.


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## Mr Bean (Nov 8, 2012)

Regarding the title of the post:
I think people are getting a little caught up on the number of lens elements in the optical path, which is really a separate issue to how IS works (in Canon lenses at least). Yes, IQ is affected by the number of lenses in the path, but bear in mind that multiple lenses are used to correct multiple optical issues. If you didn't have those lenses, then spherical or CA (or other issues) would degrade the quality. Its a balance.

IS on the other hand, is done by moving an element or elements on and off axis. This is going to create aberrations such as astigmatism. The effect would be much greater in lenses that are fast, as the latitude for astigmatism would be much smaller.

As an example, for those who wear glasses, hold them an inch or 2 in front of your eyes and move them around. As you will see, the image moves accordingly. This is, in effect, the same approach as IS in a Canon lens. Pushing it further, while holding the glasses in front, move the glasses so you are looking through the outer edge, not the center. In some cases, the IQ will drop, and the image blurs. This is the extreme example of an off axis lens.


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## Mt Spokane Photography (Nov 8, 2012)

PackLight said:


> Mt Spokane Photography said:
> 
> 
> > Yes, something is lost, and it is light.
> ...


I think your theory says it all. A 20 element lens has lower IQ than a 10 or 7 or 3 or one element lens.
The only problem cones in the FACT that actual measurements disprove it.


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## PackLight (Nov 8, 2012)

Mt Spokane Photography said:


> PackLight said:
> 
> 
> > Mt Spokane Photography said:
> ...



Theory? I didn't say that, but here since you want to add that Theory I will add it.

How does your theory test out and the FACT of actual measurments stack up. 70-200mm with 20 elements. 200mm f/2.8 with 17 and 300mm f/2.8 with 16. But wait, the 300mm is Canon's sharpest lens and it has 4 less elements.

By your reasoing shouldn't the 70-200mm be better, it has more elements?


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## neuroanatomist (Nov 8, 2012)

PackLight said:


> Theory? I didn't say that, but here since you want to add that Theory I will add it.
> 
> How does your theory test out and the FACT of actual measurments stack up. 70-200mm with 20 elements. 200mm f/2.8 with 17 and 300mm f/2.8 with 16. But wait, the 300mm is Canon's sharpest lens and it has 4 less elements.
> 
> By your reasoing shouldn't the 70-200mm be better, it has more elements?



Primes vs. a zoom - yep, that's a logical comparison. So PackLight's Postulate of Fewer Elements says the 35mm f/2, with only 7 elements, should have far better IQ than any of the above lenses. Does it?


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## DBCdp (Nov 8, 2012)

This is a very good question. It would seem that it's a matter of perspective. If one handholds the camera then IS helps make the obvious difference in your own body movement. If you handhold a lens without it, then the 1:1 shutter speed/focal length rules really come into application and if you don't observe this religiously your hit rate will suffer accordingly.

My 70-200 2.8 IS was a phenomenally sharp lens 5 1/2 years ago. Now I notice it's flaws. I think the variables within ourselves far outweigh the IQ differences in IS/non IS lenses and render it a mute point.

I also remember that little test with all the filters stacked on a lens. Given, light passed through. But the IQ was horribly mutilated as I recall.

I used to try and use my old 100mm 2.8 macro for portraits and was almost always disappointed. My own fault for not obeying the 1:1 rule. My new 100Macro with IS is a far better tool for this, as it helps me where I need the help. So, like all questions concerning lens/camera combinations...what are you using it for? What is your style? The person operating it is the weak link in most cases and the knowledge/abilities we have are almost always the limiting factor. Can you shoot a football game with a 300 2.8? Of course. Will you get more keepers with a 300 2.8 IS? Definately! Will either one of these great lenses save you from certain disaster when the play comes your way and 5 250lb+ guys land on top of you? Sorry, not gonna happen!

So the bottom line is that there are always trade-offs and it's up to us to know what applies and when then put the best key elements into play that are available to us to make our vision a reality. So, what am I missing?


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## DBCdp (Nov 8, 2012)

As an aside, let me ask you to point a laser at an object while standing, say...a doorknob across the room. Can you keep the dot exactly in the center? Sitting? Laying down? Now extend the distance to what you'd shoot with a 300mm or 400mm lens. How do you like the way that dot moves now? 

So basically, if we're touching the camera, we're disturbing the shot. Learn what foods and drinks skew your aim and how to control that bullseye accuracy necessary and watch your keeper rate go up! Funny how we spend thousands on the newest high tech equipment to help us in our quest, even while many of us let our own bodies go to pot (in varying degrees, intentional or not, as aging is unavoidable).

Good luck!


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## dafrank (Nov 8, 2012)

No lens elements, while leaving the light unchanged and, therefore, "perfect" obviously can't be called a lens. Yes, if one were able to correct all abberations and still define a desired focal length with only one physical lens element, it would necessarily be better than one which corrected the light equally with two, if only because _more_ light would be able to be transmitted through an equally transmissive single element than through two. In this same manner, because, practically, if not theoretically, IS lenses seem to always use more lens elements for the same generation of focal length and aperture lens made by the same companies, usually the non IS versions are and _should_ be better, other factors not withstanding. I'm not technically savy enough to explain this with certainty, but it does seem so in reality. Furthermore, one must take into consideration how IS works. Some element (usually a "group" of lens elements) must move within the lens to compensate for the optically equal and opposite movement of the camera/lens combination in order to cancel out that movement, thereby minimizing the blurring effects of said movement during exposure. It will always be harder, with a correspondingly greater degree of potential errors, to keep such a lens configuration with laterally moveable elements true to its ideal optical path as well as to make aberration corrections with the least number of lens elements and most effective design of those elements possible, as the elements that need to be moved must be designed and grouped for IS functioning, rather than for their ideal placement within the lightpath for abberration correction only. In other words, in IS lenses, compromises with pure optical performance must be made, even though they may sometimes be very small and sometimes even irrelevant when, for instance, an IS lens is able to use a generation newer and better lens element design and fabrication process over a non IS lens using older lens design technology. Well, that's my take.

Regards,
David


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## PackLight (Nov 9, 2012)

neuroanatomist said:


> PackLight said:
> 
> 
> > Theory? I didn't say that, but here since you want to add that Theory I will add it.
> ...



It is as logical as the argument that by adding additional elements in of itself improves image quality. My belief would be the quantity of elements does not matter, what matters is having the appropriate number of elements to get the desired IQ. So the comparison was an unequal argument to a position with little merit.


But the point I was making to start with is that the majority of the elements are providing "correction", the elements are not improving the image quality that the Raw light would have already held in itself. It is modifying and manipulating it, the best lenses would of course loose the least amount of available IQ in the process. Obviously with the technology available today it takes a certain amount of elements, but that does not mean it will be so in the future.


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## risc32 (Nov 9, 2012)

so the lens elements, most of them you say, are "correcting" the image not improving it... hmmm. where i come from correcting problems IS improving the image. Maybe you are trying to say that all those silly elements are fouling things up, and that leads to more elements to fix these new problems, and so on, and so on. hmmm again, but i don't think so. i guess a billion dollar company with the better part of 100yrs making lenses can learn some stuff from us here.
note to Canon HQ- use much fewer lens elements from now on cause companies like leica make do with only a handful. 
I've watched a few Canon lens production videos on youtube, namely the 500mmf4, and to me at least it looks like they have things well under control.
as am typing and rereading your last post i've decided i don't even know what you're trying to say.


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## weixing (Nov 9, 2012)

Hi,
WOW! Still discussing on this... we must be very bore while waiting for new Rumors... ha ha ha ;D I'm also very bore while waiting for "news" on 70D or/and 7D2... 

Anyway, the OP questions about IS consist of 2 parts:
1) Does the IS action affect IQ?
I agree with what Mr Bean mention below.


Mr Bean said:


> My feeling is that IS would affect IQ as the lens or lenses in the IS unit are moved off center, to negate movement of the photographer. This process of moving the lenses off axis in the optical path would have been "allowed" in the design, but it'll be a case of "....the lesser of 2 evils".



2) Does the extra elements in IS affect IQ?
This questions also consist of 2 parts:
a) Does IS increase the elements in a lens?
This is a very difficult question to answer since I'm not an optics designer, but base on the trend in the lens specification:
Lens with IS had more elements than similar lens without IS. For example:
- EF 70-200mm f/2.8L IS USM has 23 elements, but EF 70-200mm f/2.8L USM only had 18 elements.
- EF 70-200mm f/4L IS USM has 20 elements, but EF 70-200mm f/4L USM only had 16 elements.

b) If IS does require more element, does the extra element affect IQ?
From the other thread, "Can a UV filter affect IQ (sharpness) on a lens?", most of poster agree that a filter does decrease IQ to a certain degree, but the decrease in IQ is negligible if the filter is a very good one. So if adding a filter does decrease the IQ, so does every element in the lens since a filter is also consider an optical element (even air in lens is also consider as an optical element). 

By the way, IMHO, using modern coating and manufacturing technology, the decrease in IQ cause by a few extra elements is very minimum, but you gain 3 to 4 stop of advantage with IS, so it's great to have IS as long as it's does not increase the price tag by a lot... ha ha ha ;D

Have a nice day.

PS: Where my 70D or/and 7D2 rumors!!


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## PackLight (Nov 9, 2012)

The 500mm video is really cool, if you are talking about the one at the assembly plant. The new 500mm II has 1 less element than the old 500mm. I guess by the more elements is better reasoning the old 500mm has better IQ.

Improving the image from what point though? Before it entered the first lens it didn't in improvement, it only need to be focused. Correcting other flaws we see in our images takes place at or after the first element.

I doubt Canon R&D will learn anything from reading this thread, since they already understand the principles they are working with. Canon marketing may take a lesson and start putting additional elements in the lenses so that the element counters among us can feel good.


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## marekjoz (Nov 9, 2012)

Happily nad hopefuly liquid lenses would not require IS at all  And guess who's got the patent for it.


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## SwissBear (Nov 9, 2012)

I observe (sometimes) with my 24-105 that if the IS kicks in heavily, the bokeh SUFFERS.
The focussed parts are still quite sharp, but the bokeh gets wild and rough.

This makes actually some sense, as the theory says that "good" bokeh comes from well aligned elements, we all agree that most primes have a "better" bokeh than zooms.


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## eddiemrg (Nov 9, 2012)

In my town this problem is called:"SEGA MENTALE".


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## Ewinter (Nov 9, 2012)

I'll just throw this out there for those who think that more optical elements affect IQ and stop the light being "pure".
That may well be true, but sometimes it's necessary.

After all, try ripping out your cornea and see how "pure and sharp" the image looks then.

As for the OP's question- depends on the situation. If it allows the image to be sharp handheld, then no, it helps the iq. If it messes up an action pan or causes vibration on a tripod then yes- just turn it off.


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## PackLight (Nov 9, 2012)

Ewinter said:


> After all, try ripping out your cornea and see how "pure and sharp" the image looks then.



"How far can an SLR lens actually succeed in duplicating the characteristics of the human eye? The natural colors of the subject seen by a clear eye, precise expression that can focus directly on what it wants to look at, a swift angle of vision that losses no time in catching even the fastest moving objects. Canon's pursuit of the techniques and technologies that will allow photographic lenses to approach the purity, expression, and dynamism of the human eye will never be tarnished by compromise."

"lens elements invariably have properties and imperfections which prevent them from accurately converging light rays into a single point and which tend to disperse light near the edges. These properties which prevent a group of light rays from a single subject point from re converging at the ideal image point or cause dispersion when light rays pass through the lens, are called aberrations."

I wonder where those quotes came from....


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## tron (Nov 9, 2012)

PackLight said:


> Yes they do decrease IQ. If you don't believe me start shooting with yours turned off when you are doing hand held shooting and see how much your pictures improve.


 ;D


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## tron (Nov 9, 2012)

Seriously now. 

300mm f/4L non-IS IQ > 300mm f/4L IS

70-200 f/2.8L non-IS IQ > 70-200 f/2.8L IS 
Ok, many will complain and mention that version II is better but that was many years and many lens elements later. Not to mention the price. 

I understand that was then. Now if we pay much much more we get IS with high IQ


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## weixing (Nov 9, 2012)

Hi,
For those who interested in Canon lenses, you can download the Canon lens book "EF LENS WORK III" from the below website: 
http://www.canon-europe.com/Support/Documents/digital_slr_educational_tools/en/ef_lens_work_iii_en.asp

This is the Sep 2006 edition, so no information on the latest Canon lens, but very interesting to read. 

Have a nice day.


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## sanj (Nov 9, 2012)

SwissBear said:


> I observe (sometimes) with my 24-105 that if the IS kicks in heavily, the bokeh SUFFERS.
> The focussed parts are still quite sharp, but the bokeh gets wild and rough.
> 
> This makes actually some sense, as the theory says that "good" bokeh comes from well aligned elements, we all agree that most primes have a "better" bokeh than zooms.



Hmmm. 'Kicks in heavily'?? 'Wild and rough bokeh"??? hmmm. You seem to have a better eye than me!


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## tim (Nov 11, 2012)

Physicist specialising in optics here.

_Do image stabilisers decrease image quality?_

Yes. All other things being equal, they do, and for two reasons:
1. A certain optical formula requires a certain number of elements. Adding extra elements above the minimum required causes problems, such as extra internal reflections and extra aberrations or distortions which then have to be corrected by altering the optical formula. The overall formula is then no longer perfectly optimal.
2. The IS group puts extra constraints on the design of the rest of the lens. In the case of telephotos there is usually plenty of space available for an IS group, but wide-angles are much more crowded. Inserting IS forces the designer to reshuffle the main optical elements and make certain compromises in the design.

Here's the more interesting question:

_How much do image stabilisers decrease image quality?_

It depends. It depends on the skill of the designer, and whether he/she is allowed to employ expensive materials, expensive lens coatings, and strict manufacturing tolerances. There aren't too many examples of pairs of lenses which are identical except for addition/deletion of IS. Canon's 70-200mm f4 lenses (figure below) are superficially identical, but actually have slightly different optical formulae. In this case the (more expensive) IS version happens to be slightly better.







So if you're willing to pay for it, IS can -- in certain circumstances -- have little or no significant effect on image quality. However, even with the best designers and most expensive manufacturing, there are physical limits. Certain non-IS lenses will never have IS counterparts which are as good.


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## Click (Nov 11, 2012)

Very interesting info. Thanks Tim.


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## Ale (Nov 11, 2012)

For those who are looking for simple lens design should check out this 440mm f5.6:

http://www.rugift.com/photocameras/440mm-f56-telephoto-lens-canon.htm

Optical construction: 2 elements in one group ;D


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## sanj (Nov 11, 2012)

Thank you Tim!
Since you know what you talking about, could I please ask you two questions:
1. Does IS mechanism reduce only the sharpness of a lens or causes any other type of IQ reduction?
2. Is the IS reduction of IQ enough that it is visible to the eye? (I do not have IS and non IS version of the same lens to make a comparison.)
Appreciate your reply.


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## tim (Nov 11, 2012)

sanj said:


> 1. Does IS mechanism reduce only the sharpness of a lens or causes any other type of IQ reduction?



The IS group is just a bunch of lenses, and so in principle it can suffer from all the same aberrations and imperfections as any other lens. However my guess from looking at the design is that internal reflections are the most significant effect. That would show up as flare and reduced contrast.



> 2. Is the IS reduction of IQ enough that it is visible to the eye?



It's not something I worry about. It's going to be a subtle effect, if visible at all. To test for it you'd need a pair of lenses with the same optical formula except for the IS group, and I'm not aware of any such lenses.

Looking at Canon's 70-200 lenses, the IS versions are both _better _than their non-IS counterparts. They are also quite a lot more expensive, and my supposition is that the price difference includes upgraded optics in addition to the IS. So in practice, from the customer's point of view IS actually improves your image quality because you are buying a better lens overall.


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## dolina (Nov 12, 2012)

Yes they do! That's why they sell them at a higher price than lenses that do not have the feature.


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