Microadjustment for Sigma 50

My Sigma 50 appears to be back focussing a tad on my 5DM2, so I set about trying to microadjust the AF using the method of shooting (from a tripod) from -20 to +20 in 5 step increments and checking the shots before refining.

Problem is, the focal point doesn't seem to be changing at all; the shots look effectively identical, even the -20 and the +20. What am I doing wrong? I am shooting black text on white at a pretty close range and at wide aperture. Is this the issue?

Grateful for any tips.

Try setting up in live view on a tripod and use manual focus and to see if you can get a sharp focus. Maybe the lens needs to head back to the shop.

I cant find a picture of it but you can try the battery test. Line up 5 batteries next to each other diagonally from near to far. Focus on the center battery and see if its focus.

from: http://dojoklo.wordpre​ss.com …-7d-vs-5d-vs-50d-part-ii/

Maybe you just have to send it in..

fidens wrote in post #10352428
at a pretty close range

What is "pretty close range" mean exactly? Farther is better.

Need more info. How are you testing this? What settings? You want to do this with the lens wide open. Also, whats your target. I have found that shooting a ISO resolution chart works great as you can clearly see when the lens is resolving at the max. ALso, what distance are you? Canon recommends 50x the focal length.

Try shooting this chart. Print it out on 11x17 of possible, set up up 2.5 meters away (about 8 feet) and repeat you test. If you look at the gradations in the chart, you'll see when it is max resolving. Here is a chart to print out.
http://www.graphics.co​rnell.edu/~westin/misc​/res-chart.html

Looks like this.

This is my Canon 400mm forst a zero MFA than at +10.

Thanks for the tips all, much appreciated.

I just got a Sigmalux late last week and spent about 2 hrs checking focus. I used both the focus chart method and the method espoused on Northlight Images. The latter I couldn't get to work for the life of me. The best I could do was to get the autofocus to move very slightly when going from MF to AF, but I could not get it to stay still. With the chart, it front focused at just outside of MFD at f1.4. At +8 its pretty good. From what I've read, the DOF is not symmetric; i.e., assuming 'DOF' is 4cm total, it may be +1.8 and -2.2 from the point of focus. If this is the case then I guess I'm OK with that. With non-test shots at MFD, wide open, I still get some completely OOF shots, but I think a few are acceptable. Some others are really quite sharp wide open. I'm going to go on vacation next week and this lens is going to live on my Mark III. When I get back I'll check out my shots and make the decision whether to send it into Sigma for calibration.