7D + MF lens focus confirmation

[thekingb]

Calling on the TDP forum collective wisdom here....


I love my 7D and I love my Zeiss 35 f/2. When I have the time to use live view and MF at 5x or 10x, and the subject is stationary, the results are fantastic. But I am struggling with MF using the viewfinder and the 7D's focus confirmation -- too many OOF shots. I depress the shutter when I hear the beep, oftentimes pulling focus in and out and waiting for another beep just to be sure. Sometimes the grid actually lights up red too, but I can't seem to make that happen with any regularity or predictability.


I have read that the 7D's viewfinder is not optimized for this kind of shooting, and you can't add a focus screen. Any insights/suggestions to improve my results?


Here's an example at f/2 using live view. So it's clearly not the lens.


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Thanks!

[Dr Croubie]

I've read somewhere (i think TDP) that certain Zeiss lenses have a bit of a focus shift when stopping down. TDP doesn't have a 35/2 review, so it might have been another model, but the 35/2 could do it too.


Is it only closer subjects, only farther away? Only low-light, only bright light? only wide aperture, stopped down?


.


also:


a) have you checked the results using the DOFpreview button? the Focus Points won't light up, but if it's less than f/5.6, your eyes should be enough to tell how bad it is. (and over f/5.6, depth of field should be long enough to negate oof enough)


b) a test i'd do, is set up on a tripod, and focus using the viewfinder. then turn on liveview, zoom in and see how well focussed it is, between liveview and DOFpreview button.


c) if it's not stop-down-focus-shift, then i'm a bit stumped. i'd prefer to trust my eyes than a beep, although that seems to front-focus when i do that (i should adjust my diopter one day...)


.


ps, it was the 85 1/4 that had the focus-shift issues on stopping down: http://www.the-digital-picture.com/Reviews/Zeiss-85mm-f-1.4-ZE-Planar-Lens-Review.aspx

[andnowimbroke]

You might consider this site. I believe there is a thread somewhere that talks about it. I haven

[thekingb]

Excellent suggestions! Thanks so much. I knew there

[neuroanatomist]

I've often wondered...an AF system works via feedback between the AF sensor/processor and the motor in the lens, with the motor moving the focus elements until the AF system 'sees' maximal merging of the phase-separated lines. In an autofocus system, either the lens or the camera, or both, can be 'off' - often it's both, sometimes with the errors in the same direction and thus canceling each other out. WIth an MF lens, the photographer is the 'motor' but in the event of a slight misalignment of the image and AF sensors (i.e., the camera is 'off'), I think that might be a situation that AFMA would correct for an AF lens, but for am MF lens, the result would simply be focus comfirmation that was slightly off.

[HDNitehawk]

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Hitting focus with the 35mm 1.4L canon is marginal at times even with AF. Relying on the camera's confirmation I would imagine would be less reliable.


Unlike the telephoto primes the wide lenses like the 35mm and the 24mm are not quit as consistent. What makes up for it with the wide angle lenses is that they are forgiving when stopped down with a deeper DOF or at farther distances. Close up, say 3 or 4 feet, shooting wide open is very demanding on the system. I did a series of tests with my 35mm and lens align. A normal series of tests at the recommended distance would produce the following results, (this was at the plus 3 setting) 18 shots back focus, 10 shots on focus and 11 shots front focus. I did a series of tests all total I used 1200 shots, these type of results were typical. Keep in mind when I say back focus or front focus, many of those pictures would be acceptable as the 0 point on the scale fell within the focus area, however it may have fell far to the back or front which in your picture above could really matter.


I always had trouble manual focusing lenses with the 5D and 7D because it was hard to see the subject, the 1D IV I have had better luck.


Good Luck, I know I didn't give you a solution to your question but maybe it gives you an idea at least of what I would expect to see. I couldn't imagine the confirmation light out performing an AF lens.


Rick
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