30D backfocusing

[andrew_luke2]

So I've always felt my 50 f/1.4 was a little softer than most examples I've seen

when used opened up. Today i believe I found out why. I shot a few coins

randomly laid out on my desk from a tripod using the 28 f/1.8, 50 f/1.4, and 85

f/1.8. every time I focused on the leading edge of a center quarter (nice and

contrasty) and every shot had the face of the coin (behind the edge) razor sharp

with the edge soft. Then I shot the face of the dime in front of it and sure

enough, the edge was sharp.

 

Still not completely satisfied I repeated it shooting newspaper taped to a wall

and shot from the side at a 45* angle. sure enough, everything just behind the

word i focused on was sharp.

 

so being out of warranty, I need service. anyone ever have this problem?

anyone know a ballpark cost/downtime? and last, should I wait until I pick up

my 24-70L and 70-200 28 IS later this year and just get them all calibrated

together? waiting is not so much an issue because I spend most of my time in

the f/11-16 range for my shooting lately and the images still come out fine.

I'd still like it dead on in case the instance comes up that I need to shoot a

concert or low light shot.

 

thanks

andrew

[marknagel]

Here is a good site with a focus chart to test your focusing. I'd try this before sending it in. Follow the directions and make sure you use a tripod.

 

m

 

 

http://www.focustestchart.com/chart.html

[jimstrutz]

Shooting a newspaper at an angle is a sure way to get poor results. Those AF points are a lot bigger than the indicators would suggest. Which would mean that you don't know what your camera was focusing on. Something like the test chart Mark posted will allow your center AF point to focus only on the center line. Then you should be able to tell something.

 

One problem with tests like this is that a lens may focus poorly at a near distance (used to take the test), but do quite well at a distance, or vice-versa. No test is fool proof.

[andrew_luke2]

Ok, so i shot these to give some idea of how it's working. this wall was shot at approx 10' straight ahead with the center focusing point selected and focusing on the black edge between the stucco and the frame.

[andrew_luke2]

and here's the other sample