Issue with 70-200 l F4 IS ?

[BTrigaux]

I have some doublts regarding the quality of my canon lens.


Context : used on 5D M2 (top class with 24-70 f2.8).


See 2 photos taken on tripod timer 2secs, zoom 200mm, iso 400,IS off. The images are viewed via DPP at 100% with AF set on central focus point.


Single difference : Photo 1 at f8 and photo 2 at f4. The quality difference (blur) between the two is so important compared to the results of different tests made with that lens (a.o. on this site).


Thanks for your opinion on this observation.





Bernard.


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[Sinh Nhut Nguyen]

How many images did you take with f/4 aperture? The second image seems out of focus to me.

[BTrigaux]

Several times tried.


How can I progress in my investigation ? Any hint ?

[neuroanatomist]

How can I progress in my investigation ? Any hint ?

First step is to test AF performance vs. lens performance. Take the shot at f/4 a couple of times with autofocus, and a couple of times with Live View, manually focusing at 10x magnification on the LCD. If it's sharp with Live View and not with AF, then you need to do an AF microadjustment. If you can't get a sharp image at the focus point with MF and Live View, it's likely the lens needs service.

[BTrigaux]

Thanks !


I will try this in the coming days.


Results will be shared here.

[BTrigaux]

Results of second round of tests following your recommendations :


Conditions of test :


- done on a stable tripod


- with timer set at 10 sec withou any wind


- IS off


- UV filter removed


- each setting tested 3 times


Very consistently same results as during 1st round both with AF and MF.


Now time to send it back for calibration.


Any idea about cost of such a service ?


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[HDNitehawk]

Now time to send it back for calibration.


Any idea about cost of such a service ?

You could send it in now but its not necessarily time. You have a 5D Mark II which can do microadjustment for the lens. You could adjust it yourself and see if you can get acceptable focus.


Take a look at this:


http://www.The-Digital-Picture.com/Reviews/Datacolor-SpyderLensCal-Review.aspx


There have been numerous threads about how to do this on this forum as well. Just do a search of AF Microadjustment also AFMA or MFA.


Three shots really do not establish anything because of other variables involved. For instance light, in lower light your lens may have more difficulty. In this one instance it may have trouble reading the contrast of the subject. A vertical target set at 90% is best. The AF system on the 5D could be considered a precision tool, its not as precise as you think. Of all the tests I have done on my 5D you will get a fair amount that focus exactly where you want, then there is a fair percentage that focus behind and in front. You look for the best average of shots that hit the area you want.


Lighting is a big part. When you set up to do the microadjustment you need it to be well lit. Low light can give worse results.


You should also be shooting in single shot, single point selected mode.


Set the lens as you did to F4


Your set up look very stable. The suggestions I would make is to get a vertical target instead of a flat one. You could buy one of the tools they make, like the spyder or the lens align. Or make something similar yourself. Use a tape or something similar to read the results, but use the flat vertical target to aim. The target should be vertical and level to the camera.


You can go here to find what lensalign recommends for distance:


http://www.whibalhost.com/lensalign/ldt/index.html


Good luck





Rick