5dm3 AFMA Focal results

[rpt]

You have most of the answers. The one thing that confused FoCal when I used it first was tripod stability. I had raised the central column...

Ensure your camera is rock steady. Suspend a weight under the central column if you can. Ensure central column is not raised.

Oh! The other thing is ensure your lights are not fluorescent nor AC powered LEDs. That may cause strange readings to show up.

So since the world has not ended I guess it is back to the tripod for you

[scottkinfw]

This is for 25, so if you want to use the 50, multiply distance X 2

Neuro's suggestion is valid. As far as being concerned with the range, it seems you are operating outside the recommended 25x-50x focal length for the calibration on a number of your distances tested. I recommend that when you retest with higher EV 's you also work inside the recommended test ranges and use those figures initially until you can validate with some real shooting results.

If you need a quick calculator to confirm your target distances at different focal lengths, try the link below for a competitors product:

http://michaeltapesdesign.com/lensalign.html

[JaxPhotographer]

This is for 25, so if you want to use the 50, multiply distance X 2

Actually, the tool I linked offers a simple button to click for either 25x OR 50x focal length calculation so no extra math involved if you click on the correct choice. 

[CharlieB]

EV, without an ISO reference

most photographic discussions assume ISO 100 so the EV concept can be applied to real-world situations

I guess most photo discussions don't include folks who grew up using the EV system.....

When I see EV -2, I consider that to be the real EV -2, not a luminance value.

I find it strange that Canon chooses use the EV system for a function that is subject neither to shutter speed, or ISO.   Its not like you could manually bump either of those and have the camera suddenly start focusing.  Or, put another way, if you had the camera set to EV -5 things would call apart with focus, if the light were adequate.

My little peeve is when people say "it was so bright, it must have been EV 20 out...." or "it was EV -5, I couldn't see a thing" - neither of which is related to any brightness.

Too old school I guess....

[Basti187]

thanks for the tips...I will get back to testing once I get back home as I don't have a tripod with me as I m travelling at the moment and had to work with books and a table

[rpt]

thanks for the tips...I will get back to testing once I get back home as I don't have a tripod with me as I m travelling at the moment and had to work with books and a table

Good luck. Let us know how it goes.

[Phenix205]

If the testing results are so much sensitive to the lighting conditions, then in the real world shooting where the lighting condition can rarely be as ideal as the testing condition, would minor inconsistency in the AFMA results matter at all?  I've done a few rounds of tests on all my lenses and I had hard time keeping my lighting conditions consistent so I got slightly different results every time. It was kind of frustrating. So I ended up picking an average value and moving on.

Neuro, et al I'd appreciate you shedding some light on this. Would +/- 5 units be siginificant enough to make any difference in the real world shooting?

[neuroanatomist]

If the testing results are so much sensitive to the lighting conditions, then in the real world shooting where the lighting condition can rarely be as ideal as the testing condition, would minor inconsistency in the AFMA results matter at all?  I've done a few rounds of tests on all my lenses and I had hard time keeping my lighting conditions consistent so I got slightly different results every time. It was kind of frustrating. So I ended up picking an average value and moving on.

Neuro, et al I'd appreciate you shedding some light on this. Would +/- 5 units be siginificant enough to make any difference in the real world shooting?

Yes, you'd notice a 5-unit difference, maybe not too much with an f/5.6 lens, but definitely with an f/2.8 lens.  There are always going to be inconsistencies.  Any one shot may be a little off.  A properly calibrated system ensures that's cross many shots, the average is at the correct focus. Having the test setup for AFMA as close to 'ideal' as possible (aligned, well-lit, high-contrast target) ensures your AFMA doesn't introduce a systematic error.