7D AF Microadjustment

[Trev4]

After several disappointing outings with my new 7D, especially when using the 100-400 L, I decided to check the camera's AF settings. Having never ventured into this area, I searched this forum without too much success, then searched the net. There are many sites of varying usefulness, but one stood out as simple enough for me to understand and it had a link to what I felt is a good chart and instructions/advice. The link is: Linky

I checked all my lenses using the chart that is available from the above site, and the 2 lenses that had been suspect needed some adjustment. I had to apply -6 to the 100-400 L, and -1 to the 17-85 IS, the rest of the lenses seemed ok with their original settings.

This seems quite a large adjustment for the 100-400.
What I am unsure about is why these lenses seemed ok on the 50D, but didn’t perform so good on the 7D, yet the rest of my lenses didn’t need adjustment.
Is it because the 7D is more critical of the glass it uses?
Because I haven’t had concerns before, I didn’t check the microadjustment of these lenses on the 50D.

The 100-400 showed different setting needs at the extremes of focal length, so a compromise was settled on in-between the 2 lengths, but biased towards the 400 end as that’s where I use it most.

While I have known about this adjustment facility on the 50D and the 7D, its something I have shied away from, but with the help of the site linked to here it became relatively straight forward, but time consuming to get it right.
So far I haven’t had a chance to try the new settings out in the field, the light had gone today by the time I finished. However, I have tried a few indoor shots using flash, and the results look better, but this isn’t really using the lens to its full capacity.

Has anyone else had similar problems with lenses reacting differently on different bodies, and if you have made these adjustments, is -6 a high figure or is it in a normal range of adjustments that you would expect to see.
Is it just me that hasnt made these adjustments before :shrug:

Hopefully the site I have linked to here will be of use to anyone who needs to use the microadjustment on their camera.

Cheers, Trev

 

[CT]

Have a look at this chart Trev which allows you to calibrate using your computer monitor. LINKY

I did at first have some misgivings about the performance of the 100-400L on the 7D, but after playing with the micro adjust I concluded that all was well on the default setting, and more care is needed in taking shots with it.

While the 7D sensor is only 3 million pixels more dense than the 50D, I think it's enough to make a big difference in showing up any minor focusing errors or slight camera shake.

I wouldn't have thought an adjustment of -6 was a particularly big adjustment or anything to be overly concerned about.

 

[tdodd]

Bodies and lenses are all built within manufacturing tolerances. Sometimes there can be errors which add up to create a noticeable problem, and sometimes the errors can cancel each other out, to end up with a perfect matched pair.

e.g. suppose your 100-400 is running with a calibration error of +3 and your 50D is running with a calibration error of -3. Stick that lens on that body and you get a perfect match with an error of 0. But what if your 7D has a calibration error of +3? Stick the 100-400 on that and you will end up with an error of +6 in total, and that is why you need to adjust the 7D/100-400 combo by -6 but not the 50D+100-400 combo.

Also, as CT says, the 7D will highlight any error just a little more than the 50D would.

I do not consider an adjustment of +/-6 to be anything to cause alarm.

 

[Trev4]

Have a look at this chart Trev which allows you to calibrate using your computer monitor. LINKY

I did at first have some misgivings about the performance of the 100-400L on the 7D, but after playing with the micro adjust I concluded that all was well on the default setting, and more care is needed in taking shots with it.

While the 7D sensor is only 3 million pixels more dense than the 50D, I think it's enough to make a big difference in showing up any minor focusing errors or slight camera shake.

I wouldn't have thought an adjustment of -6 was a particularly big adjustment or anything to be overly concerned about.

Thanks CT, I have tried test shots of a stationery subject using a tripod, mirror up, remote control, and got poor results, not that I think I cant improve my technique, I know I can, but this seemed to indicate a mismatch somewhere. I'll try the link tomorrow, it looks informative and more accurate. Cheers

Bodies and lenses are all built within manufacturing tolerances. Sometimes there can be errors which add up to create a noticeable problem, and sometimes the errors can cancel each other out, to end up with a perfect matched pair.

e.g. suppose your 100-400 is running with a calibration error of +3 and your 50D is running with a calibration error of -3. Stick that lens on that body and you get a perfect match with an error of 0. But what if your 7D has a calibration error of +3? Stick the 100-400 on that and you will end up with an error of +6 in total, and that is why you need to adjust the 7D/100-400 combo by -6 but not the 50D+100-400 combo.

Also, as CT says, the 7D will highlight any error just a little more than the 50D would.

I do not consider an adjustment of +/-6 to be anything to cause alarm.

Cheers Tim, that explanation makes sense. TBH I wasnt sure if maybe 1 was normall and 6 was a move to the end of the earth Having never done this before I hadnt got anything to compare with. Thanks for replying

 

[chris321]

Oh I do wish everyone would stop talking about their 7Ds and 50Ds, it's giving me massive gear envy after playing with them in a shop last week! :nuts:

I wasnt sure if maybe 1 was normall and 6 was a move to the end of the earth Having never done this before I hadnt got anything to compare with. Thanks for replying

It goes to +/- 20 (I think?), so 6 isn't vast in the grand scheme of things!

Chris

 

[tdodd]

Cheers Tim, that explanation makes sense. TBH I wasnt sure if maybe 1 was normall and 6 was a move to the end of the earth Having never done this before I hadnt got anything to compare with. Thanks for replying

Having adjusted nine lenses against a 50D, 1D3 and 7D I'm not bothered any longer when I find a bit of adjustment is needed. Indeed, it seems a bit of a miracle when I find a combination that is mm perfect out of the box. While I'd prefer not to have to make the adjustments I think anything up to +/-10 is probably OK. Beyond that I'd be irritated and would consider sending it to Canon to sort out, especially if the gear is still within warranty. I think my largest adjustment with a Canon lens has been +10. Most of them need a +ve adjustment and around +5 to +7 is not unusual. I did buy a Sigma - my first and only off brand lens - and that needed +15. I sent it back and did not rebuy.