# When to use IS and how many stop does it really save?



## Marsu42 (Mar 4, 2012)

I just got a 70-300L and am very happy with it - some members of this forum might remember me struggling with the decision and then the problem of telling if a copy is broken.

Having shot for a couple of days and having looked through a couple of thousand pictures, I am not certain about two things and would like to have some advice from more experienced users if possible:

1. When to use IS? As seen in many pictures posted here, IS does not magically freeze the world and might even fool you to use a slower shutter time introducing unwanted motion blur on moving objects. Of course I'll turn it on if shooting indoors and low light. On tele shots, I'm doing what I'm used to do with macro shots: take a burst and then select the sharpest picture. With live objects and 300mm, I good good results with 1/1000 to 1/2000 sec, on something moving fast I use 1/8000 if possible - and with these speeds, my hand shake shouldn't be a problem? And why would I use IS mode 2 on a monopod with fast shutter speeds?

* Question: Do you use IS at all when taking pictures with fast shutter speeds because in the worst case, it does nothing? Or in what circumstances do you turn it on?

2. How many stops does the IS (the newer version on my 70-300L that is) really save? I know IS just increases the good:bad shot ratio, but I'm used to the good ol' formula speed=1/(lenght x crop factor).

* Question: If using Tv mode, what speed do you set for 70mm and 300mm on static objects?


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## Actionpix (Mar 4, 2012)

Common "rule" is that, on full frame, a picture can be taken handheld at a shutter speed of 1 sec/focal length in mm. Meaning, most shots will be acceptable. Look into camera shake. Every movement, unless you make nice circular movements, has a start, middle and end. At the ends of a pendular movement the speed is zero. When you take several shots you will end up with a very blurred one, taken in the middle of the movement, a frozen one, taken at a turning point of the movement and probably one in between these. The shutter speeds mentioned in the question to me are very short for action. In my pictures I like to show movement thus I use shutter speeds 10 times the rule. Meaning 1/30 for 300mm. At these speeds I find IS help full. At shorter speeds the IS will not be very help full, meaning not very visible, and with longer exposure times the IS will come short.
For action shots I use the speed I need to show the action how I like. Meaning, as example, the prop of an airplane makes a full circle during the shot. I do not care what this speed is in relation to "formulas". I use what I need. If I adjust something it will be the support or the number of shots needed to get the shot I want to end up with.


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## MikeHunt (Mar 4, 2012)

IS is overrated! I often switch it off on my EF 70-200mm f/4L IS USM and can still shoot at 1/25th. Only use it when fully zoomed. Impossible to shoot video with it cos' its louder than ambient environment!!


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## scottkinfw (Mar 4, 2012)

IMHO, I also agree that IS is a bit over rated. I would recommend that you keep the shutter speed at least 1/focal length (take into consideration the crop factor) if possible. Remember what you want to accomplish with shutter speed, depth of field, and keeping iso as low as possible.

I would also turn it off when on a tripod. Not as sure about monopod. I don't really see a down side to leaving it on at all other times.

The marketing information on web site will tell you how many stops improvement you get.
sek



Marsu42 said:


> I just got a 70-300L and am very happy with it - some members of this forum might remember me struggling with the decision and then the problem of telling if a copy is broken.
> 
> Having shot for a couple of days and having looked through a couple of thousand pictures, I am not certain about two things and would like to have some advice from more experienced users if possible:
> 
> ...


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## lol (Mar 4, 2012)

When hand holding, I tend to leave IS on regardless of the focal length of shutter speed. I can't say I see any difference with it on or off once the shutter becomes "fast", so just leave it on to stabilise the viewfinder image.

It does make a difference to me if, for a static subject, you do want to use a longer exposure. In one indoor case of extremely low light, I found myself using 300mm. "4 stops" IS would imply a usable speed of 1/30s. I was using even longer than that, and getting a low but not zero hit rate. Without IS, it would have been practically zero. So if you're operating on the limit, and you have a static enough subject, it does provide value.


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## SPG (Mar 4, 2012)

Whether it's overrated is a question of what you expect. It's not magic, but just another tool to use in the right situation. 
For video it can make the difference on handheld shots being jittery and unusable or slightly moving and interesting. If you're using a more directional mic on your camera you won't hear the IS in most situations. I never really use the in built mic so I can't say whether that will pick up the IS noise, but I guess we wouldn't have the complaints if it didn't.
For the video alone I wouldn't want a walkabout lens without IS. Stills is a mixed bag for me, I leave it on a lot and haven't seen any negative effects so why not?


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## Marsu42 (Mar 4, 2012)

scottkinfw said:


> The marketing information on web site will tell you how many stops improvement you get.


... and we all trust the marketing information, don't we  ?



SPG said:


> Stills is a mixed bag for me, I leave it on a lot and haven't seen any negative effects so why not?


Well, it is a motor and wears down over time - for example the IS of the 17-55 is know to break just outside Canon warranty.


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## Meh (Mar 4, 2012)

Overrated? Nonsense! IS is a phenomenal advancement in camera technology. 

The rule-of-thumb of 1/L is, for most people, a minimum hand holding shutter speed. I say for most people because it depends how steady your hands are, how much vodka you drank the night before, how late in the day it is, how many cups of coffee you've had, etc. And it is minimum hand holding speed to get good/acceptable sharpness. If sharpness is critical for a particular shot, you may want at least 1/2L. If you're working in good light and already getting greater than 1/2L then IS will be of minimal benefit and you might get even sharper results from turning it off... those moving elements can actually cause a slight decrease in sharpness (so I've read, never tested it and it's probably negligible in most cases)

But in lower light if you're not getting at least 1/2L shutter speeds then IS is going to improve your shots (unless you have very steady hands and perhaps the folks who think it's overrated have very steady hands therefore don't see so much difference in their shots with and without IS)

IS counters camera shake. It does not counter subject movement. It is said that even for a static model... a person holding still posing for a shot... you still need at least 1/60 s to freeze motion. If the subject is moving at all, you need at least 1/200 s to freeze motion. So for shooting people, minimum shutter speed should be between 1/60 and 1/200 and if for example you're shooting with a 100mm or greater focal length, IS is definitely going to improve the sharpness of your shots for most people.

IS on the newest Canon lenses is claimed to give about 4 stops improvement while some of the older lenses are 2 or 3 stops improvement and I believe that has in fact been demonstrated in independent testing. Again, that is countering camera shake only... not subject movement and not camera movement, for example if you're panning which is what Mode 2 is for.


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## 00Q (Mar 5, 2012)

Meh said:


> Overrated? Nonsense! IS is a phenomenal advancement in camera technology.
> 
> The rule-of-thumb of 1/L is, for most people, a minimum hand holding shutter speed. I say for most people because it depends how steady your hands are, how much vodka you drank the night before, how late in the day it is, how many cups of coffee you've had, etc. And it is minimum hand holding speed to get good/acceptable sharpness. If sharpness is critical for a particular shot, you may want at least 1/2L. If you're working in good light and already getting greater than 1/2L then IS will be of minimal benefit and you might get even sharper results from turning it off... those moving elements can actually cause a slight decrease in sharpness (so I've read, never tested it and it's probably negligible in most cases)
> 
> ...



IS is indeed over rated. The best solution is to buy faster glass. 

In low light situations, your metering with a f/4 lens means that you need a shutter speed of say 1/4 of a second. And this is the same with or without IS. 

Now with IS, if your hands shake *within* with 1/4 of a second, then it helps. In this case, sure, the IS holds it more steady for you. *but, if you are shooting a moving subject in the same lighting condition the shutter is still going to be the same at 1/4 sec* so you will get a blurred image. To get a sharp image of a moving subject in low light, you need faster glass, not IS. 

Further, in bright lighting conditions, your shutter might be 1/250 of a sec. This means that with or without IS, you should both get a sharp picture so it is not too useful in bright light. 

overall, IS is over rated. Only time it is useful is if you shoot still objects in low light. You lose 1 stop for example with a f/4 IS compared with a f/2.8 non IS. But then you gain a few stops with the IS making your shots sharper with the IS on it. Overall, only limited usage.


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## Marsu42 (Mar 5, 2012)

00Q said:


> IS is indeed over rated. The best solution is to buy faster glass.


It is interesting that there are so many different opinions about IS around. It seems to me that apart from marketing propaganda nobody really has a definite clue on when to turn IS off. Or the people who figured it out how and when to use it don't post in this thread 

But your statement stands out: "faster glass" might be a solution for wide angle, but definitely not for tele shots. With my 70-300L, even at f5.6 and 1.6x300mm the dof is often too thin so I have to shoot at f8+ to get a sharp picture of an object that is not in a position exactly right angle to the lens.


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## Hesbehindyou (Mar 5, 2012)

> IS is indeed over rated. The best solution is to buy faster glass.

The _best_ solution is more light


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## ejenner (Mar 7, 2012)

Faster glass is over-rated. You might get a stop or two, but then you have to deal with a very, very shallow DOF and likely a much heavier/more expensive lens or a prime-only.

If you need f5.6, you need f5.6 and with a 200mm lens you can use a shutter speed of 1/100-1/160s which is comfortably fast enough to freeze a model, or anyone posing and with IS you're not going to get shake.

OK, I'm playing devils advocate, but IS is not a replacement for faster glass, any more than faster glass can make up for IS. They are totally different. How can you get shallow DOF with IS? How do you get an f1.8 (or less) 70-300mm zoom? And if you could would you want to shoot 300mm @ f1.8 much?


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## pwp (Mar 7, 2012)

MikeHunt said:


> IS is overrated! I often switch it off on my EF 70-200mm f/4L IS USM and can still shoot at 1/25th. Only use it when fully zoomed. Impossible to shoot video with it cos' its louder than ambient environment!!



Mike, I envy your steady hands! Most of us with a worse case of the wobbles than you definitely benefit from IS.
When I got my first 70-200 f/2.8is there was an immediate increase in the number of keepers. 

I recently added a 24-70 f/2.8 (would you believe on the same day the 24-70 f/2.8II was announced) to complement my freakily good 24-105 f/4is. I was surprised how much I had come to depend on the IS on the 24-105, even at the wide end. 

To the OP, I couldn't say how many stops the improvement is, but IS is an indispensable tool for those of us less steady than Mike. Your new 70-300L is a great lens. There may be times when you choose to switch it out but I'd just leave IS switched on all the time as default. 

Paul Wright


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## briansquibb (Mar 7, 2012)

Camera Model: Canon EOS-1D Mark IV
Image Date: 2012-03-02 17:29:50 (no TZ)
Focal Length: 50.0mm
Aperture: f/2.8
Exposure Time: 0.100 s (1/10)
ISO equiv: 200
Flash Fired: Yes (enforced)


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