70-200 2.8 IS + Micro Adjustment....

paparios wrote in post #7780522
This example was taken with the 50d and the 70-200 f4L IS. Shot taken at ISO200, 200mm, f4, 1/80.
The target was the ruler, located at a 45 degree angle, at about 2.4 meters, and the focus was the black vertical line at the 8 inches marker. You can see the small DOF, which on the cm scale goes from 19 to 21 cm. The MA will move this DOF range to the left (using +x) or to the right (using -x), but the main thing is that anything within the DOF range will appear on focus.
In this case, my opinion is that my copy is quite on the target and does not need any adjustment.

Miguel

Interesting, thanks. I will post my ruler shots in a few hrs later today when I return home.

Yuck...Looks like my 70-200 is going back. I am just unsure whether to the dealer, or to Canon for calibration. As per bohdank's suggestion, I would want to keep the copy if it's sharp and just needs calibrating, or exchange it,if it is soft ON TOP OF the front-focusing problem. There is front-focusing, for sure. no adjustment vs. +20 adjustment below..

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And as for sharpness, full size, and crop...(BTW this was manually focused using Live View). Front-focusing sharp copy? Or front-focusing soft copy? Send back to dealer, or to Canon for adjustment? What do you guys think?

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pawelx wrote in post #7779588
Yes, I use manual focus to confirm that the lens is sharp ( I think it is - I will post some images later on today when I return home, bus stands from around 20meters distance, where I can read the bus schedule written in lettering of no more than 20pts etc.).
I think that my lens is front-focusing at long end, and positive (+) microadjustment seems to give better results than no adjustment.

so a (+) adjustment fixes front-focusing
and a (-) adjustment fixes back-focusing?

Sfordphoto wrote in post #7782880
so a (+) adjustment fixes front-focusing
and a (-) adjustment fixes back-focusing?

Yes, as Pawelx shows in his sample, you see that the DOF of the left image goes from 3 to 11 cm, while the right image (after a +20 adjustment) goes from 9 to 16 cm. So the center of the DOF moved from 7cm to 12.5cm after the adjustment. I would think that, in my opinion, the microadjustment was successful in his case (the 12.5cm point is clearly sharp). I would also repeat this tests several times just to make sure the results are repeatable. One minor point is that in the test images you should have a good vertical line, since the AF sensor, in general, likes better vertical lines.

Miguel

Sfordphoto wrote in post #7782880
so a (+) adjustment fixes front-focusing
and a (-) adjustment fixes back-focusing?

I think so. My copy is front-focusing, and positive (+) adjustment gives better results.

As for sharpness, what do you guys think? Good copy for 1500£ worth of lens? (sharpness-wise)?

pawelx wrote in post #7782933
As for sharpness, what do you guys think? Good copy for 1500£ worth of lens? (sharpness-wise)?

Sharpness looks good to me. Just to be sure, I assume you used a tripod and turned off the IS?

Miguel

paparios wrote in post #7782996
Sharpness look good to me. Just to be sure, I assume you used a tripod and turned off the IS?

Miguel

Yes, tripod, IS off, 2-sec release. No mirror lock, however.

pictures posted at this thread:
https://photography-on-the.net …hread.php?t=675​268&page=4

mine just went back to the dealer. Hopefully the next copy I receive in not any less sharp than the one I had.

Sfordphoto wrote in post #7782880
so a (+) adjustment fixes front-focusing
and a (-) adjustment fixes back-focusing?

If a camera is front focusing, the focus point as the camera sees it is in front of the object to be in focus. So you want to move it back, therefore use a negative adjustment. Right?

photoman754 wrote in post #7789832
If a camera is front focusing, the focus point as the camera sees it is in front of the object to be in focus. So you want to move it back, therefore use a negative adjustment. Right?

Wrong. Just see Pawelx first example. The left image was without MA, and its focus was around 7 cm, instead of the correct distance of 12.5cm (that is, it was front focusing). The right image is with a MA of +20, which corrected the problem. The down side of the chart, in both images, is closer to the camera.

Miguel

Bad news..Sent the lens over to the dealer, they mounted it on their 1D body and found no issues with AF. So basically, they're telling me it's my body that needs to be calibrated - and for that, a trip to Canon is needed, and a 2-3 weeks' wait.. Shame.
I'll probably take the risk and get a replacement copy from the same dealer (alternative would be to get a refund - but I want a 70-200 f/2.8!). Maybe the front-focusing won't be as severe, and I'll just leave with a micro-adjustment of +7, or +10, or something. I'm just reluctant to send both the lens and the camera over to Canon and not have it for 2 or 3 weeks, especially with holiday coming up next week. The worst case scenario is, the new copy arrives, it's front focusing even worse, such that even +20 micro-adjustment can't fix it!

pawelx-

It might be that your lens and body are in spec by themselves, but together they are out of spec. In this case you will benefit quite a lot from sending both the camera and lens in.

Read here: http://www.lensrentals​.com …s-is-soft-and-other-myths


I am in this boat right now also, my 70-200 front focuses and if I put it to +20 to fix @200 then 70mm backfocuses a ton.