Odd 5DIII Focus Question

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PeterP1D
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p.1 #1 · Odd 5DIII Focus Question

Hi All -

I was on a shoot recently and was unhappy with the sharpness of my 5DIII/100-400 combination so I began to investigate.

Here is what I've found and my question

I can focus better in live view than AF (no surprise). Pretty pronounced difference and no amount of MA makes them equivalent though I can go from unsharp to sharper to unsharp as I move through the MA range. Sweet spot is around +5. My 100-400 is sharp on another 5DIII and their 100-400 is not sharp on my body (but sharp on theirs). Switch kit and it follows the kit and not the photog (not technique). Seems like some sort of AF issue.

Here is what I don't get. If I AF focus, and shoot with mirror lockup and then switch to live view and release the shutter without refocusing the live view images are sharper. Shooting off a stable tripod, using a remote, IS off, several seconds delay between lockup and releasing.

This is absolutely consistent. Does it make any sort of sense?

Feb 24, 2013 at 02:22 PM

EB-1
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p.1 #2 · Odd 5DIII Focus Question

Are you sure the lack of sharpness is due to focus error and not tripod, subject movement, etc.? If so then, I suggest your MA process is not optimal. Which system are you using?

EBH

Feb 24, 2013 at 02:34 PM

PeterP1D
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p.1 #3 · Odd 5DIII Focus Question

I'm pretty sure it is not motion blur. In the field we were shooting at very high shutter speeds (3200). In studio my tripod/ballhead/remote release/mirror lockup is all pretty stable.

I can't MA and release with lockup to get the same sharpness as I get in live view but if I AF with the MA and then switch to live view w/o refocus and release from there it is as sharp.

So - I suppose the question is how is releasing from live view different from releasing with lockup?

Feb 24, 2013 at 02:40 PM

stanj
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p.1 #4 · Odd 5DIII Focus Question

PeterP1D wrote:
I can't MA and release with lockup to get the same sharpness as I get in live view but if I AF with the MA and then switch to live view w/o refocus and release from there it is as sharp.

The "MA" in this sentence doesn't make sense to me, but English is a foreign language to me...

You didn't answer the above question, tho: which MA method / system are you using?

Feb 24, 2013 at 02:43 PM

PeterP1D
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p.1 #5 · Odd 5DIII Focus Question

The MA in that sentence means : I've adjusted the MA with FoCal. When I AF with MA on and release the shot is not tack sharp. If I AF with MA on, and then instead of releasing switch to live view and change nothing and release the captured shot is tack sharp.

Feb 24, 2013 at 02:49 PM

jerrykur
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p.1 #6 · Odd 5DIII Focus Question

Something sounds wrong. The key to accurate MA is to reduce the number of variables.

- Make sure you are conduction your test in bright light.
- Make sure you have a target with adequate contrast and big enough. I use the Lens Align Pro on a separate tripod and get very accurate and reproducable MA results.
- Make sure you shutter speed is fast enough. For a 400 mm lens it needs to be at least 1/400 and faster would be better.
- Make sure you camera is in Manual to reduce any AE issues.
- Before ever AF shoot de-focus the lens and let the AF refocus.

Also, why mirror lockup?
Have your tried MA without the software. Again, reduce the number of variables.

Feb 24, 2013 at 02:50 PM

PeterP1D
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p.1 #7 · Odd 5DIII Focus Question

Mirror lockup to reduce any vibration. Also, my understanding is that mirror lockup is essentially what happens when you use live view.

Feb 24, 2013 at 02:55 PM

PeterP1D
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p.1 #8 · Odd 5DIII Focus Question

OK - think I have it figured out.

In Live View/silent mode the camera uses an electronic rather than mechanical first curtain. This effectively reduces the vibration from releasing the shutter accounting for the sharper images.

If I turn silent mode off, the images are the same with live view release or mirror lockup as I would have expected.

You can find more about using electronic first curtain at the link below.

http://krebsmicro.com/Canon_EFSC/index.html

Feb 24, 2013 at 03:14 PM

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