How do I know if the IS is working?

[cbolton]

Hello,

I just purchased a:

Canon EF 70-200mm f/2.8L IS

lens as an upgrade over my 70-200 f/4. I have taken a lot of pictures and the pictures are turning out pretty good.

One thing that has surprised me is the IS functionality. I have IS enabled on Mode 1 with AF. I am still seeing quite a bit of motion blur on photographs I take in less than ideal lighting conditions. An example, picture taken of a completely still object at:

70mm, ISO200 1/6sec at f/13

That resulted in a blurry image. I know that's a pretty slow shutter speed so perhaps I am expecting too much from the IS system. Is there any way to check and make sure that the IS is functioning properly? I am using this lens on the Rebel XTi...

I have done some searching around looking for an answer to this and haven't found one yet. Hope someone can help.

Craig

[ak_powder_monkey]

that seems like a really really slow exposure to me, also if anything in the frame is moving there will be motion blur

[RedMatrixXRS]

your not going to get good results at 1/6. won't stop any action for sure. use it at 2.8 and see what you get. it's a 2.8 for gods sake and open it up.

if you listen closely, you will hear the gyros when you activate your AF.

[red hot sheep]

For 70mm, 1/6 is expecting a bit much. Go into Tv, and select something like 1/20. Then take a few shots with IS on, and then IS off. If both of these are sharp, go for a slower shutter speed, and you should be able to see that the ones with IS on are consistantly sharper.

[Citizensmith]

IS can't stop action and the fact that it lets you use slower shutter speeds means you are more likely to get motion blur.

Take a shot with IS, take it again with it turned off. That will let you check how well its working for you.

[ed rader]

Originally Posted by cbolton

Hello,

I just purchased a:

Canon EF 70-200mm f/2.8L IS

lens as an upgrade over my 70-200 f/4. I have taken a lot of pictures and the pictures are turning out pretty good.

One thing that has surprised me is the IS functionality. I have IS enabled on Mode 1 with AF. I am still seeing quite a bit of motion blur on photographs I take in less than ideal lighting conditions. An example, picture taken of a completely still object at:

70mm, ISO200 1/6sec at f/13

That resulted in a blurry image. I know that's a pretty slow shutter speed so perhaps I am expecting too much from the IS system. Is there any way to check and make sure that the IS is functioning properly? I am using this lens on the Rebel XTi...

I have done some searching around looking for an answer to this and haven't found one yet. Hope someone can help.

Craig

as a general rule of thumb you shouldn't be using an aperature smaller than f11 on a 1.6 crop camera (diffraction).

and on a 70-200 zoom i normally shoot wide open or close.

your shutter speed is too slow.

ed rader

[dicktay]

Normal hand holding guide, on a crop camera, is 1/(Focal length * 1.6) Seconds : 70*1.6= ~105 therefore 1/100 second. IS is usually good for 2-3 stops ie: 1/25 to 1/12 of a second.
If non crop camere it would normally be from 1/70 second to ~1/8 second maximum.

With my 17-85 IS at 85 on a 350D I will go down to ~ 1/15 second

See here for some full size test shots with 17-85 IS.

http://www.poseruniverse.com/Photogr...n_1600_IS.html

[Anke]

...plus you should hear the lens make more noise than usual when the IS kicks in, at least it does on my 100-400L and 24-105L

[spoofuser]

Zoom out to 200mm and try to keep your centre focus point on a particular spot, try for a good 5-10 seconds and observe how much the lens actually moves. Then half-press the shutter for a second or so and compare how things now don't wobble nearly as much.

After the IS activates try moving slowly left-right and up-down to experience the beginnings of motion sickness as the IS tries to compensate and what you see isn't what your brain thinks it should be seeing

IS compensates for unavoidable lens wobble of hand-held shots. A fast shutter speed and/or flash is still necessary to freeze subject movement.

[Collin85]

Although 1/6th second exposures at 70mm can turn out decent, it's a shutter speed a little too slow for relying on shots turning out blur-free each time. I can get a fairly decent ratio of my 70-200 f/4 IS shots turning out well at 1/13th sec @ 200mm, but it's not exactly an ideal shooting situation I'd wanna be in alot.

Also, are you shooting static scenes, or subjects in motion? IS doesn't help for subject blur - that's not what it's intended for.

As for knowing if it's working or not, it's quite evident via the viewfinder, in my opinion. Also, you may hear the clunking during act/deactivation and the characteristic whirring noise while it's activated.

[Citizensmith]

Originally Posted by ed rader

as a general rule of thumb you shouldn't be using an aperature smaller than f11 on a 1.6 crop camera (diffraction).

I've used f/16 when necessary and not had trouble. Never heard f/11 before. Also, what does being a crop camera have to do with at what appeture diffraction will become an issue. It's not like it affects what light flies out the back of the lens.


Got some links or anything to back up the statement?

[dicktay]

Originally Posted by Citizensmith

I've used f/16 when necessary and not had trouble. Never heard f/11 before. Also, what does being a crop camera have to do with at what appeture diffraction will become an issue. It's not like it affects what light flies out the back of the lens.


Got some links or anything to back up the statement?

http://www.cambridgeincolour.com/tut...hotography.htm

Try some of the smaller apertures like F32 with a 350D (rebel XT) you will see a differnce especially in large pics.
Here is some examples with original jpgs avialble.
http://www.poseruniverse.net/Photogr...300_IS_Top.htm

[ed rader]

Originally Posted by Citizensmith

I've used f/16 when necessary and not had trouble. Never heard f/11 before. Also, what does being a crop camera have to do with at what appeture diffraction will become an issue. It's not like it affects what light flies out the back of the lens.


Got some links or anything to back up the statement?

funny thing is you were the one who first told me about diffraction when i was first getting started with DSLR photography.

maybe you've bumped your head since then ?

general rule of thumb is f11 for 1.6 and f16 for FF.

i could provide the links but i'm too lazy to look around .

ed rader

[Citizensmith]

Originally Posted by ed rader

funny thing is you were the one who first told me about diffraction when i was first getting started with DSLR photography.

Was I? cool. Now the student defeats the master. Or something possibly involving light sabres

Did I say f/11? I'd always had it in my mind that f/16 was where you'd start to get stars showing on all your light sources.

My question was more targetted at the small sensor part as it didn't make sense to me. From reading up on the links (thanks by the way) it seems like its not sensor size specifically, but pixel size/interpolation that causes the issues. I'll have to remember that and reset my thumb with a new rule.

[wimg]

Originally Posted by Citizensmith

Was I? cool. Now the student defeats the master. Or something possibly involving light sabres

Did I say f/11? I'd always had it in my mind that f/16 was where you'd start to get stars showing on all your light sources.

My question was more targetted at the small sensor part as it didn't make sense to me. From reading up on the links (thanks by the way) it seems like its not sensor size specifically, but pixel size/interpolation that causes the issues. I'll have to remember that and reset my thumb with a new rule.

No, it si even more complicated than that. Diffraction is caused by aperture size in relation to image size on the medium, to start off with.

It is aperture related because diffraction is essentially caused by light bending around edges of holes, especially when the holes get very small. It is image size on the medium related because the latter determines the size of the smallest diffused circle we see as sharp, i.e., the smaller the image on the sensor (or film for that matter), the larger the effect of diffraction, relative to the size of this circle, which is also called Circle of Confusion (CoC).

With an APS-C sensor the CoC is approx. 0.02 mm, with FF about 0.03 mm. This means that about F/13 is at the diffraction limit for APS-C, and about F/18 or F/19 for FF.

The pixel size only comes into it because if it is too small, you can't resolve the details that could have been resolved theoretically. OTOH, smaller pixels allow for smaller details to be made visible, so in a way it is a trade-off. Larger apertures help here, because diffraction is less at larger apertures.

Finally, these CoCs are really based on what the human eye can resolve, on average, at about 10 inch, which is about 10 lp/mm. This is what complicates things a little more, because viewing distance and print size come into it as well .

Kind regards, Wim