Micro Focus Adjustment

[Tucson T4R]

I have been noticing that many of my captures, especially at F2.8 (narrow depth of field) at 200MM on my 70-200 lens seemed a little soft. I first just blamed it on my technique. Then I saw repeated shots of say wildlife surrounded by gravel or grass and it was quite clear that my camera was focusing a bit in front of the intended subject.

After doing some research on micro focus adjustment procedures I can across Jeffrey Friedl's 5 year old blog on his approach which hit home with me.

http://regex.info/blog/photo-tech/focus-chart

Yesterday I printed out a few of the focus charts and gave it a shot on my 7D with my 3 different lenses. Following his instructions it was very easy to quickly see exactly where my camera was focusing. Both my F2.8 70-200mm and my F2.8 17-55mm lenses were front focusing. My 10-22 wide angle was spot on and did not need to be adjusted. My 7D allows you to micro adjust the focus for individual lenses so I did that for the two giving me a problem.

Both lenses were verified with re-shooting the focus chart as well as field testing on subjects that would easily show up incorrect focal planes. It took a +9-10 back focus micro adjustment to get these lenses to consistently lock on accurately. Now all my lenses are spot on and if I get fuzzy shots, I now know it's a personal problem. :sombrero:

I'm just throwing this out there for folks that may feel their gear seems a bit off on auto focus and want and easy way to verify if you have a gear issue or not. I don't know if all DSLRs have a micro focus option but if yours does, this is an easy and accurate way to make those adjustments.

 

[Pathfinder]

I routinely perform micro focus adjustments for my lenses on my 7D or other bodies. As described above, it can definitely improve your number of keepers, especially with long glass.

 

[Tucson T4R]

From and uneducated until yesterday, I agree.

 

[Tucson T4R]

I routinely perform micro focus adjustments for my lenses on my 7D or other bodies. As described above, it can definitely improve your number of keepers, especially with long glass.

When you say you do this routinely, do you find the adjustments drift over time on the same lens/body combo or do you mean you do it for each new lens? Thanks.

 

[Every Miles A Memory]

I'll have to print one of those charts out and see what my 7D is doing with various lenses

 

[Tucson T4R]

Note that the instructions say to find which chart has the light enough background grey boxes so your auto focus can not lock onto it and only focus capture the center dark bar. I found with my equipment I had to drop all the way down to the grey 5 or 10 before my camera stopped locking on to the light grey background boxes. Once you find the right chart for your camera, the rest is a piece-o-cake.

 

[goodtimes]

Once you find the right chart for your camera, the rest is a piece-o-cake.

Unless of course you have a 5DC . . . in which case you can't make the adjustments.

 

[Tucson T4R]

Unless of course you have a 5DC . . . in which case you can't make the adjustments.

How rude. I figured there would be lots of cameras that wouldn't have the micro focus adjustments. If you think you are having an auto focus problem you could still do the test to verify the accuracy. Then if your camera consistently front or back focuses you could send it in under warranty and request a factory adjustment.

 

[Pathfinder]

When you say you do this routinely, do you find the adjustments drift over time on the same lens/body combo or do you mean you do it for each new lens? Thanks.

I haven't been doing it long enough to tell if it drifts over time. I suspect it may over long periods of time - say years, not months. Rough treatment or droppage might alter this too.

I do have a 300m lens that, while quite sharp, required -19 AF adjustment to really bring out its best, and I am going to ship it off to Canon Factory Service for evaluation and correction. The largest adjustment on my 7D is + or - 20.

That said I also sharpen and us the lens profiles in LightRoom and that is important as well, especially if shooting in RAW. You can have jpgs sharpened by the in camera rendering however you desire.

I am not OCD about doing it for lenses that always seem tack sharp, but if I am going on a workshop, I like to verify that my gear is at its optimum before I leave. If there is any question about the sharpness of a lens, Micro AF i worth doing. I have done if for Tamron and Sigma lenses, as well as Canon lenses. My 300mm is an L lens and needs service as I said, so it never hurts to verify what is going on.

 

[goodtimes]

How rude. I figured there would be lots of cameras that wouldn't have the micro focus adjustments. If you think you are having an auto focus problem you could still do the test to verify the accuracy. Then if your camera consistently front or back focuses you could send it in under warranty and request a factory adjustment.

I'll probably do it just to see . . . but it looks like Canon "introduced" the technology to their cameras in 2007. My 5D mk I is certainly older than that (which also means that there is no warranty).

I haven't used the camera a whole lot - but I like to know that the equipment is right. Nothing worse than spending 6 or 8 months fighting a problem that you think is an operator issue, just to learn that it was an equipment issue all along.

 

[Pathfinder]

When you say you do this routinely, do you find the adjustments drift over time on the same lens/body combo or do you mean you do it for each new lens? Thanks.

I haven't been doing it long enough to tell if it drifts over time.

I do have a 300mm lens that, while quite sharp, required -19 AF adjustment to really bring out its best, and I am going to ship it off to Canon Factory Service for evaluation and correction. The largest adjustment on my 7D is - + 20.

That said I also sharpen and us the lens profiles in LightRoom and that is important as well, especially if shooting in RAW. You can have jpgs sharpened by the in camera rendering however you desire.

Remember, you can always compare the results of your camera's AF with the best you can do manually via LiveView and a 10X image - always do this on a tripod mounted camera of course

 

[Tucson T4R]

Let us know what you find with your testing. It will be interesting to see how prevalent front or back auto focusing is. I agree this is much more of an impact with long lenses shooting wide open.