# Something New to Argue About



## unfocused (Apr 1, 2011)

I get bored with the never ending bigger megapixels vs. more megapixels war.

So, I thought I'd ask a new question that could start up a different battle for a change. Seriously though, I would like hear some informed opinions on this.

In practice, is there a diminishing return on focal length and if so, at what focal length would most people consider that diminishing return to occur? 

Let me explain: As a user who is not an engineer, my experience has been that there are big gains in reach at the mid-range of telephotos. (Going from a 135mm to a 200mm feels like a big jump and going from 200mm to 300 also feels like a big jump. Going from 200 to 400 is huge.)

But, it seems like at some point, the gain in reach from a longer lens doesn't really offset the downsides of size, weight, speed, cost, etc. 

I'm not talking about professional sports or wildlife shooters, but rather, for us mere mortals who have to pay for the equipment ourselves and can't charge it off to a client base. 

Of course, ISO speed enters into this as well. Shoot with a shorter lens at a lower ISO and crop, or use a longer lens and a higher ISO? 

Telephotos are often described by angle of view and the gains in angle of view get incrementally smaller as the lens gets longer. Is it really worth shaving a couple of degrees off the angle of view? What's that really mean in practice?

And, of course, there is the whole issue of APS-C crops. Since a 200mm feels like a 320mm and a 300 feels like a 480mm on a 1.6 crop sensor, how does that affect the trade off at the long end.

I got the idea for the question while reading the discussion board on the Sigma 50-500 and wondering, with my 7D the Canon 100-400 scales out to 640mm, while the "Bigma" scales out to 800mm. But really, what does that mean in practical terms? Would that extra 160mm really be noticeable at those lengths?

Just offering this up as new point of discussion while we all wait for news from Japan.


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## neuroanatomist (Apr 1, 2011)

At least in the Canon lineup, the logical break-point would seem to be 400mm (or 420 mm if you want to count the 300/4 + 1.4x). You can get 'affordable' (a relative term, I know), primes and even a zoom out to 400mm, with very good IQ, as long as you're ok with an f/5.6 aperture at that length. Once you get over 400mm (or faster than f/5.6, but the topic is focal length), the cost goes up dramatically - not many amateurs/hobbiests can afford >$7K for a lens. There are some exceptions to this, one being people who don't mind (or even prefer) manual focus and can use longer, manual primes that are in the $2K range (used), like the Minolta MD 600mm f/6.3.


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## Lawliet (Apr 1, 2011)

About the practical terms: At longer focal lengths the resolution of the lens , the quality of the support and the clarity of the air are more important then 20-30% more fl. The more MP you have, the sooner the effect kicks in. 

I wouldn't be surprised to get more details from an upsized crop of a picture taken with a 70-300L then from one taken with a Sigma50-500 non OS, at least with the shooting techniques usually used.

Regarding the numbers: don't think in mm, but in factors. Going from 85 to 135 to 200mm are 50% increases, from 400 to 500 only 25%, like zooming from 40 to 50mm. Sound less impressive then the additional apparent 160mm of the Sigma on a crop camera.


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## unfocused (Apr 1, 2011)

> like zooming from 40 to 50mm



Great point. I hadn't thought about that comparison. Puts it into perspective. 

Anyone disagree?


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## neuroanatomist (Apr 1, 2011)

unfocused said:


> > like zooming from 40 to 50mm
> 
> 
> 
> ...



I disagree. For a given subject, the perspective at 40-50mm is going to be very different from the perspective at 400-500mm...


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## kubelik (Apr 1, 2011)

well, there's all sorts of ways to get to where you'd want to be in terms of focal length.

with APS-C bodies, it's pretty easy to get up to 480mm-equivalent through a common 70-300 zoom. the quality is very good in terms of the price, and the weight will be very good as well. on any of the current Canon APS-C bodies, this gets you an 18MP image at nearly 500mm.

on a full frame body, as neuro observed, 400 is the realistic stopping point for the common photographer. you can get there easily a number of ways: 300mm f/4 + 1.4x, 70-200 + 2x, 100-400, or 400 f/5.6. on the 5D Mark II, this gets you a 21MP image at 400mm. if you crop it down to 18MP, you get a 1.08x crop factor, which is a 433mm equivalent focal length. if you crop to a 1.3x crop factor, you get 12MP image at 520mm equivalent.

a decent 400mm lens on a crop body will get you all the way up to 640mm. if you're a birder on the cheap, get a 7D and the 400 f/5.6 L, that is a killer combination for little more than the price of a 5D Mark II body.

there are Sigma zooms that will get you cheaply and quickly to a 500mm range but I have owned and used these lenses and you pay for what you get -- a.k.a. not much.


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## Admin US West (Apr 1, 2011)

I see the break point as being the size and weight where I can no longer handhold a lens easily. I've no problem with lenses like the 100-400mmL, the 70-200mm f/2.8, etc. Lenses like my Tamron 200-500 with f/6.3 and being very long were a pain to use handheld as well.

However, the 300mm f/2.8 might be just at or over my capability, I've had a Nikkor 300mm f/2.8, and it was barely manageable handheld. I used it on my Canon DSLR for a while, and then sold it. Manually focusing required me to tripod mount it.

Certainly my 600mm f/4 was way over. Just for the heck of it, I did hand hold it for a very few photos. I removed everything I could to lighten it up, but after 5 or 6 shots, I had to put it down. I sold it only because carrying around a heavy duty tripod and big Wimberly head made a simple photography trip into an expedition, so I just left it at home.


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## Aaron (Apr 1, 2011)

neuroanatomist said:


> unfocused said:
> 
> 
> > > like zooming from 40 to 50mm
> ...



I think you miss the point of the poster. They aren't talking about perspective, they are talking about the "zoom multiplier." In the 10 - 22mm zoom, although it is only a 12mm difference, it is a 2.2x. That is why people would buy a lens like that, but nobody would buy a 100 - 112 mm zoom (a 1.12X)


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## neuroanatomist (Apr 1, 2011)

Aaron said:


> I think you miss the point of the poster. They aren't talking about perspective, they are talking about the "zoom multiplier." In the 10 - 22mm zoom, although it is only a 12mm difference, it is a 2.2x. That is why nobody would by a 100 - 112 mm zoom.



Yes, I know. I think _you_ missed the  , which in this case, denotes sarcasm.


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## Aaron (Apr 1, 2011)

neuroanatomist said:


> Aaron said:
> 
> 
> > I think you miss the point of the poster. They aren't talking about perspective, they are talking about the "zoom multiplier." In the 10 - 22mm zoom, although it is only a 12mm difference, it is a 2.2x. That is why nobody would by a 100 - 112 mm zoom.
> ...



Very funny, I guess it is April fools. Cheers.


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## kubelik (Apr 1, 2011)

scalesusa said:


> Certainly my 600mm f/4 was way over. Just for the heck of it, I did hand hold it for a very few photos. I removed everything I could to lighten it up, but after 5 or 6 shots, I had to put it down. I sold it only because carrying around a heavy duty tripod and big Wimberly head made a simple photography trip into an expedition, so I just left it at home.



given the quality coming out of the new extenders and their ability to pair excellently with the version II 70-200 f/2.8, I think it's hard to justify hauling around a 600mm f/4 when you could create a 600 f/5.6 from a 300 f/2.8 + 2x. I think the 2.5 kilo mark is the point where any person would need to evaluate why exactly they are hauling around that much gear...

how much were we guesstimating that crazy 200-400+1.4x would weigh? to me that seems like it could really hit the sweet spot for all types of wildlife and sports shooters.


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## neuroanatomist (Apr 1, 2011)

Aaron said:


> That is why people would buy a lens like that, but nobody would buy a 100 - 112 mm zoom (a 1.12X)



In fact, lots of people actually by 'zoom lenses' with a very short range like that, only they don't know they're buying zoom lenses because the lens is labeled with a single focal length, and people are unfamiliar with the phenomenon of focus breathing. That's when the apparent focal length changes as a result of focusing (and is a real problem for dSLR video shooters). For example, the Canon 100mm L Macro drops to an apparent focal length of close to 80mm at 1:1 magnification, or a 1.25x zoom if you prefer that terminology. People buying that lens don't know they're actually buying an 80-100mm zoom. 

The 'ultimate' expression of this (or ultimate utility, depending on your viewpoint) is the Canon MP-E 65mm - it's a 1x-5x 'zoom lens' with manual focus, but there's only one ring on the barrel - i.e., as you focus you zoom, or vice versa. 

The effect is often worse with actual zoom lenses - for example, the Nikon 70-200mm f/2.8 VR II, when set to the long end of 200mm, rerportedly delivers an apparent focal length of only 134mm at the minimum focus distance.


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## HughHowey (Apr 1, 2011)

While you're talking about focal length, have any of you shot with the 200mm non-IS 2.8L? I'm thinking of getting one, but I'm not sure if I need it in addition to my 135mm 2L. There are times I would like to be closer, and I don't want to spend more for the 70-200mm. Only thing I worry about is the lack of IS at that focal length (which is offset some by the speed of the lens).


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## kubelik (Apr 1, 2011)

looking through past rumors, there was also the patent for a new 300mm f/4 L IS II that showed up around the same time as the 200-400+1.4x announcement. I know patents have no correlation with real products, but if you look at canon's current strategy of redoing their entire telephoto lineup ... it's bound to happen sooner or later. my guess is we see a new 300 f/4 prime before 2015. which will pair awesomely and be much lighter than a 70-200+2x combination. and be cheaper.

I know the original intent was to get away from any discussion of MP count, but honestly, in our modern age of digital photography, MP count is directly related to equivalent reach. I'd love to see a 5DIII with improved AF, framerate, and higher MP count so that it can get cropped as needed for extra reach. if it had 7D AF, 5.0 fps, and 28-30 MP it would be a "one body to rule them all" type of camera for most of us who are enthusiasts and thus multi-purpose shooters.


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## neuroanatomist (Apr 1, 2011)

HughHowey said:


> While you're talking about focal length, have any of you shot with the 200mm non-IS 2.8L? I'm thinking of getting one, but I'm not sure if I need it in addition to my 135mm 2L. There are times I would like to be closer, and I don't want to spend more for the 70-200mm. Only thing I worry about is the lack of IS at that focal length (which is offset some by the speed of the lens).



I had a 200mm f/2.8L II for a while. It's a very nice lens, with excellent IQ. You do need to keep the shutter fast, which sometimes meant I needed to use a higher ISO than I'd otherwise use. I sold it only because I got the 70-200mm f/2.8L IS II, which duplicated the focal length and aperture and added IS (at the cost of weight and $).

Do you have a 1.4x extender? The 135L is compatible with them, yielding a 189mm f/2.8 lens - IQ is decent (but not as good as the bare prime, obviously).


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## lol (Apr 1, 2011)

As a user wishing of ever longer focal lengths, this is something I've thought about...

On eventual size of practical lenses... there's a few factors I guess. Price today limits to around 400mm (f/5.6) as a relatively affordable limit. Going beyond that starts to need serious cash.

If you're sticking with phase AF on all bodies, that'll limit you to f/5.6. Based on similar lenses, I'd say for most people the practical limit of hand holding is around 100mm front diameter, so that would be in the ball park of a 500mm f/5.6, possibly 600mm f/5.6 or equivalent lens. Either way that's expensive... the 200-400 extender I expect would be in this weight class.

To push beyond that in length, you could contrast AF beyond f/5.6, but diffraction limit isn't far off. I think you could get away with f/8, but I'm not sure most people would want a lens with a max aperture even worse than that. With the above assumptions, that'll be 800mm f/8... with an IS system, that is still hand holdable.

Personally, I don't think I'd want to go beyond 1000mm actual focal length on crop even with IS as it gets ever more difficult to aim.

As people have said before, the above would assume the lens has decent quality right wide open. Having a long focal length is no use if the quality is poor, that you might as well upscale from a shorter length.

As specific examples, I'm very happy with the 100-400L as a general walkabout lens. Recently I got a 300 f/2.8 (not IS) which will be primarily used with a 2x extender to get that extra reach while maintaining AF. The weight is already being an issue here and I don't like to carry that for too long! Back to the 100-400L, I have used that with a 2x extender in live view, where contrast AF works. That's usable... stacking a 1.4x with 2x on 400 giving 1120mm is a step too far. Even if the quality was good enough, hand holding that is very challenging.


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## kubelik (Apr 1, 2011)

a 500 f/5.6 would be awesome, I'm still hoping that canon replaces the old 400 f/5.6 L with a 500 f/5.6 L IS...


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## HughHowey (Apr 1, 2011)

neuroanatomist said:


> I had a 200mm f/2.8L II for a while. It's a very nice lens, with excellent IQ. You do need to keep the shutter fast, which sometimes meant I needed to use a higher ISO than I'd otherwise use. I sold it only because I got the 70-200mm f/2.8L IS II, which duplicated the focal length and aperture and added IS (at the cost of weight and $).
> 
> Do you have a 1.4x extender? The 135L is compatible with them, yielding a 189mm f/2.8 lens - IQ is decent (but not as good as the bare prime, obviously).



I'm hesitant to pick up an extender. I've had several people tell me they see very little difference between a cropped image and an image with an extender. Losing a stop for something people quibble over when the free option might be just as nice ... I just can't see investing in one.

I'd rather pick up a 200mm or save up for the venerable 70-200 or the new 70-300mm. The latter was given a nice review (guess where?), and I wouldn't mind the extra throw in case I move to FF.

Thanks for the help, again. You are quite the excellent forum member.


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## unfocused (Apr 1, 2011)

> While you're talking about focal length, have any of you shot with the 200mm non-IS 2.8L? I'm thinking of getting one, but I'm not sure if I need it in addition to my 135mm 2L.



Since I'm the OP, I guess I'll exercise the right to digress here. Way back in the old days, I owned both a 135 f2 and a 200 f2.8 for my F1. I loved that 200mm 2.8. Next to my 24mm wide angle, it was my favorite lens. It was tack sharp and with the wide aperture, you could really isolate an image. Much more so than at 135mm. 

I never found hand holding to be a significant issue. Of course, back in those days, we were more reasonable in our expectations. But, I found subject movement to be a more limiting factor than camera shake. With a little bracing, it wasn't that hard to shoot at 1/125th and you could even push it to 1/60th if you leaned on something, held your breath and concentrated. 

Believe it or not, it was a great portrait lens as well. You could stay far enough away from your subject to keep them from being self-conscious, and, as I said, really isolate the subject. 

A zoom lens is incredibly convenient, but for a third the price, you can usually just take a few steps backwards.

Getting back to the original post, I hope others are enjoying this discussion as much as I am. It seemed like things were getting a little stale and maybe we needed to explore a new path for awhile. I hope you agree.


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## HughHowey (Apr 2, 2011)

unfocused said:


> Since I'm the OP, I guess I'll exercise the right to digress here. Way back in the old days, I owned both a 135 f2 and a 200 f2.8 for my F1. I loved that 200mm 2.8. Next to my 24mm wide angle, it was my favorite lens. It was tack sharp and with the wide aperture, you could really isolate an image. Much more so than at 135mm.



Ordered. Thank you sir for being so kind about my non sequitur.


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## epsiloneri (Apr 3, 2011)

*Re: Focal length limits*

Depends on the application, of course. Amateur astronomers regularly use 500mm-2000mm lenses (telescopes) at typically f/4-f/11. No AF, rarely IS, and never hand held - a rigid mount, sometimes motorised, is required.

There _is_ an upper useful focal length limit, but it depends on the pixel pitch of the detector. The limit is set by the resolution deterioration from the atmosphere and depends greatly on local conditions. For astronomical applications at good sites (e.g. nothing extreme like Antarctica or remote locations in the Andes) you are usually limited to a resolution of ~ 1 arcsecond (1/3600 degree), which means that there is little point in having smaller pixels than 0.5 arcsec/pixel. For terrestrial daytime applications this limit is generally much higher, as the air close to the ground is denser and more affected by turbulence than if you look straight up.

For a 7D with 232 pix/mm, a resolution limit of 0.5 arcsec/pix corresponds to a focal length of 1780 mm, while for a 5D2 you have 156 pix/mm and thus can increase the focal length to 2640 mm before getting resolution-limited by the atmosphere. The opening aperture also needs to be larger than ~10 cm to not limit the image resolution by diffraction.

The record-braking 120 MP APS-C sensor Canon showed off a while ago has 455 pix/mm, which would result in a maximal useful focal length of 900 mm. It would put very severe constraints on tolerances and the quality of the optics, however. In principle one could go even further with even higher MP detectors, but tolerances and dynamic range per pixel would likely be limiting factors. With "perfect" detectors the resolution would be completely determined by the optics. Still, I don't think it would be practically possible to get 1 arcsec resolution on anything shorter than 200mm, because already that would require an f/2 lens (to not be diffraction limited).

Looking at distant objects on the ground limits useful focal lengths to much shorter than the above estimates.


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## branden (Apr 4, 2011)

Wow, thank you epsiloneri, very interesting information there, I didn't know any of that. 

Regarding the EF 200mm f/2.8L lens, I have one of these, and I love the photos it takes. I've always been wondering if I should have instead gone with the 135mm f/2 and an extender, but the posts above actually convinced me otherwise. 

I have the 300mm f/2.8L on my wish list, but that's a "if I win the lottery" type of item.


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