Focus issues with area under selected sensor spot soft sometimes.

[louis_greene]

<p>Using the 1DsMk3 I am finding that sometimes I get shots that are soft. Not from camera shake, because there are areas of the image tack sharp. More like back or front focusing, but it is not consistent. I am thinking it is my 300F4 lens, but I am not sure. I am trying to decide if I should send the body or the lens, or both in to Canon. The test shots I did with cans came out pretty good though. Here is what I am talking about...these were taken in burst mode with the focus set to "one shot". You can see the same sensor was illuminated.<br>

good : eye is sharp<br>

<a href="http://i283.photobucket.com/albums/kk319/IPTalaska/focus-1.jpg">http://i283.photobucket.com/albums/kk319/IPTalaska/focus-1.jpg</a><br>

off : distant foot sharp<br>

<a href="http://i283.photobucket.com/albums/kk319/IPTalaska/focus-2.jpg">http://i283.photobucket.com/albums/kk319/IPTalaska/focus-2.jpg</a></p>

<p>another example:<br>

http://i283.photobucket.com/albums/kk319/IPTalaska/5-8.jpg</p>

[john_a5]

<p>You need to shoot a flat field and see what you get. It might need some micro focusing adjustments--I don't see the issue in your posts, so it is hard to know, but maybe it is just you are off a bit and the adjustment will correct the problem.</p>

[zml]

<p>Hard to tell: looks like a subject movement to me but still hard to tell. Run some static tests with 3 D targets (such as AA batteries placed at an angle, forget resolution charts and other flat targets) from your usual shooting distances with the lens wide open to see what, if anything is wrong. But (and this is a big but) AF points are not "points" per se but rather areas covering more than the AF rectangle on the screen and that sad fact is often the chief reason for AF issues, esp. with moving (and twitching, like birds do) subjects at relatively large f/stops. I have never used the 300/4 but my 1Ds3 performs admirably with fast long lenses in terms of AF. And to tell you the truth, I'd switch to Servo (with a bit faster setting of the C. Fn. for tracking sensitivity) for birds and shoot bursts of 3-5 shots if I were you.</p>

<p>Some MA may remedy the issue but should you decide to send your equipment to Canon by all means send both, the camera and the lens (call them first, of course.)</p>

[scott_ferris]

<p>The beaver is moving how could you expect One Shot to nail that one? Otherwise all Michael says.</p>

[louis_greene]

<p>Good points guys.<br>

The beaver was moving slowly, I didn't even think of using Al Servo but you are probably correct I should have done that.</p>

<p>I did a "field test" with some soda cans and for the most part it was maybe a 5% error and even then it was marginal.</p>

<p>It's shots like this one that baffle me. The entire sensor is on the moose yet the background brush is sharp. <a href="http://i283.photobucket.com/albums/kk319/IPTalaska/3-11.jpg">http://i283.photobucket.com/albums/kk319/IPTalaska/3-11.jpg</a></p>

<p>I am open to other ideas or input. I think there are some technical things I can do to improve my success. I'll make some changes like trying to use the Center point more often, lock it and recompose. Maybe Al Servo should be used more often too.</p>

<p> </p>

[louis_greene]

<p>Contrast on the wing to the body, center focus point, yet look at the sharpness of the knot on the rail behind the post the bird is on (which is considerably softer). What could I have done differently here? This can't be all me....<br>

<a href="http://i283.photobucket.com/albums/kk319/IPTalaska/RR1.jpg">http://i283.photobucket.com/albums/kk319/IPTalaska/RR1.jpg</a><br>

<a href="http://i283.photobucket.com/albums/kk319/IPTalaska/RR2.jpg">http://i283.photobucket.com/albums/kk319/IPTalaska/RR2.jpg</a></p>

<p> </p>

[louis_greene]

<p>hmmm, how come using the IMG tags from Photobucket I can't put an image directly into the thread?</p>

[scott_ferris]

<p>Have you micro af adjusted that lens as per <a href="http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html">this link?</a> One shot or servo? In one shot I would have pressed the focus button twice.</p>

[brian_donaldson3]

<p>Load the photos from your PC and they will appear in the post. I don't think Photobucket lets you hot-link to images.</p>