IS On or Off & More On Image Stabilization

[Geoff Warnock]

great to bring some real scientific measurements into the discussion Roger, excellent work. I look forward to your new data. Do you have a plot of the above tests without IS on? This seems like an excellent way to assess the effectiveness of IS rather than the subjective tests normally seen (i.e. number of sharp-rated shots out of 10/20 etc. at lengthening SS).

[Desmond Chan]

great to bring some real scientific measurements into the discussion Roger, ...This seems like an excellent way to assess the effectiveness of IS rather than the subjective tests normally seen (i.e. number of sharp-rated shots out of 10/20 etc. at lengthening SS).

As true as it may sound, does it really matter to you or anybody else for all practical purposes if you or anybody else cannot see the impact of its effectiveness in the raw files if not the final images?

[Geoff Warnock]

Desmond, my point is more that many people trot out these/their subjective measurements as fact, including 'selling' particular ways of holding the camera, without any data to back up their claims. Roger's data really highlights the error introduced JUST by mirror slap, and he can start to bring the 1/focal length rule into the digital age with real data. People have sensibly started to include a 'crop factor' mod in their 1/mm calc, but Roger's posts are the first time I've seen clear evidence for a conversion based on actual pixel sizes and his accelerometer measurements.

As in many things, the variation in the general population means that the ultimate results will vary for some people, the same way some people over/undersaturate their photos because of differences in colour perception. However, without real measured data to start from I find people's claims that one way is better than another pretty meaningless.

Now we need to find Roger some funding for a panning robot to remove the human factor (him) from his data!

[Roger Clark]

Desmond, my point is more that many people trot out these/their subjective measurements as fact, including 'selling' particular ways of holding the camera, without any data to back up their claims. Roger's data really highlights the error introduced JUST by mirror slap, and he can start to bring the 1/focal length rule into the digital age with real data. People have sensibly started to include a 'crop factor' mod in their 1/mm calc, but Roger's posts are the first time I've seen clear evidence for a conversion based on actual pixel sizes and his accelerometer measurements.

As in many things, the variation in the general population means that the ultimate results will vary for some people, the same way some people over/undersaturate their photos because of differences in colour perception. However, without real measured data to start from I find people's claims that one way is better than another pretty meaningless.

Now we need to find Roger some funding for a panning robot to remove the human factor (him) from his data!

Hi Geoff,

I agree with Desmond. The reason is the accelerometer data shows what the camera body is doing, but it does not tell the effect on the image with IS on because the IS is compensating for the camera movement. The only way to evaluate the effectiveness of the IS is to evaluate the images. I posted the data because one person made a statement that IS only helped to stabilize the image for the AF system and another said it was effective only at shutter speeds of about 1/1000 second and slower. The data do show that vibrations effect exposures at 1/2000, though the effect is getting smaller as shutter speed gets shorter.

I do agree that such data could improve imaging methods, and could help diagnose a problem an individual may be having if they were tested. As I work with the data more, I am beginning to understant more of the effects. The data I showed in the above plots was a summary, but single axis data I think is more informative. I can see clearly the start and stop of the mirror movement in the z-axis data (up-down). I'll post it once I get a little further along in the analysis.

Another example is long lens technique with a big telephoto on a tripod. My preliminary data points to another method that is slightly more effective (or at least similar in effectiveness) and more comfortable for me. I'll post that when I get more data analyzed.

Accelerometer data can also provide a quantitative measure of the effectiveness of tripods and tripod heads.

Roger

[Jim Cash]

I was shooting some telephoto landscape pictures on a very windy day with a 100-400 zoom at 400mm, on a tripod, from about 1/4 to 1/15th second. The wind was sometimes causing the lens to vibrate enough to keep from getting a sharp image. I was hoping the IS would help to stabilize the vibration of the lens, but it seemed to make the image wander and jump around too much whenever the wind slowed down a little, as I was watching through live view. It seems that there wasn’t quite enough movement for the IS to work well. I got several shots that were not very sharp.


Then I got an idea to try something. Just before tripping the shutter with a remote cord with IS on, (in live view mode), I jiggled the lens a little, tapping it with my finger, and then immediately fired the shutter. Amazingly that shot was tack sharp, much sharper than any others that were made using IS or not.
I’m not sure if this fits into this discussion, but maybe … there has to be some movement for the IS to work, and the wind was not quite enough, so I created some more and the IS worked great.


The old IS on the 100-400 is different, I know.

Just wondering if anybody else has tried this. I only tried it once, so it may be a fluke, but it worked perfectly that time.

[arash_hazeghi]

I meant 1/EFL (Equivalent Focal length) so that somewhat takes into account the pixel size.

I also agree your data does shows qualitative trends but I wouldn't extract numbers from it as is, it also depends how you attach the accelerometer and how you handhold your gear when you are shooting.

I think the bottom line for me is that I am not seeing blur by mirror vibration at 1/1000sec with the 500 f/4 when I handhold the gear, because I have made many sharp shots consistently (with the 1D4 and at 10 fps and IS OFF) but I understand for different handholding techniques the threshold might be different.

In any case the point of this discussion was the IS (mode 2) is beneficial for handheld flight photography which we all seem to agree on The only time I turn it off is on tripod and for slower shutter speeds as discussed above.

thanks for comments

[Roger Clark]

I meant 1/EFL (Equivalent Focal length) so that somewhat takes into account the pixel size.

Arash,
Actually it (Equivalent Focal length) only propogates the crop factor myth. For example, apply it to a Canon 5D Mark II (full frame) and a 30D (1.6x crop). Both have the same pixel size so if you were using a 500 mm lens on both cameras, your formula would give different answers for the same pixel size, the same number of pixels on a subject, and where the exposure time rule should be the same.

Roger

[arash_hazeghi]

Arash,
Actually it (Equivalent Focal length) only propogates the crop factor myth. For example, apply it to a Canon 5D Mark II (full frame) and a 30D (1.6x crop). Both have the same pixel size so if you were using a 500 mm lens on both cameras, your formula would give different answers for the same pixel size, the same number of pixels on a subject, and where the exposure time rule should be the same.

Roger

I agree pixel size has to be taken into account not the crop factor.

[Charlie Woodrich]

I was shooting some telephoto landscape pictures on a very windy day with a 100-400 zoom at 400mm, on a tripod, from about 1/4 to 1/15th second. The wind was sometimes causing the lens to vibrate enough to keep from getting a sharp image. I was hoping the IS would help to stabilize the vibration of the lens, but it seemed to make the image wander and jump around too much whenever the wind slowed down a little, as I was watching through live view. It seems that there wasn’t quite enough movement for the IS to work well. I got several shots that were not very sharp.


Then I got an idea to try something. Just before tripping the shutter with a remote cord with IS on, (in live view mode), I jiggled the lens a little, tapping it with my finger, and then immediately fired the shutter. Amazingly that shot was tack sharp, much sharper than any others that were made using IS or not.
I’m not sure if this fits into this discussion, but maybe … there has to be some movement for the IS to work, and the wind was not quite enough, so I created some more and the IS worked great.


The old IS on the 100-400 is different, I know.

Just wondering if anybody else has tried this. I only tried it once, so it may be a fluke, but it worked perfectly that time.

When shooting landscapes I normally switch to manual focus. It eliminates the possibility of the AF choosing something not planned on.