Focus Issues??

Hi,

I've had a 30D with the 50 1.8II for about 6 months or so. I've noticed that alot of my images seem to have focusing issues. I've attached an image I just took yesterday. The center focus point was on the lower right corner of her mouth. Look how soft her eyes and mouth are and how sharp the zipper on her coat is. Is this what is meant by front or back focusing? I've used that focus chart from focustestchart.com and the lens seems to be good with that test.

thanks,

EXIF

1/125
f4
ISO 100

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No - that's a problem that technique can take care of. You used the center point on a lens with shallow depth of field at close range and the focus-lock-recompose technique. Unfortunately, that's just the conditions to not use that technique. What's happened is that when you recomposed, you changed the distance from your subject ever so slightly. However, since the depth of field was so shallow, that was enough to throw off the focus on the important point (her mouth) and shift it to the parka.

Thanks Jon. I was hoping it was just me. I figured f4 would give me plenty of depth of field. I guess I better find a depth of field calculator and see what it actually is at that f stop and distance. I was about 4 feet away. I suppose one way to correct that is use one of the other 8 focusing points. I think I rely on the "use the center point and re-compose" technique to much. Any other suggestions.

thanks for your help!!

http://www.dofmaster.c​om/dofjs.htmlDepth of field

Near limit 3.86 ft
Far limit 4.15 ft
Total 0.28 ft
In front of subject 0.14 ft (48%)
Behind subject 0.15 ft (52%

I focus/lock/recompose most of the time - it's a habit left over from the film days when I'd meter/lock/recompose (focusing manually).

Jon's identified your problem - and using another focus point is the solution, as you've already said.

Just one thing: if you're not recomposing it's a good idea to zoom out a bit so you can get the chosen focus point exactly where you want it and then crop in post processing for the composition you want.

-js

Thanks sas8888 and number six. I found that calculator with Google. Interesting stuff.

I'm going to try not to focus lock so much but with a two year old you have to move fast. I know there's a custom setting to use the joystick to set the focus point. I'll have to give that try.

Or just focus take the picture then crop in PP after

Yes, that sounds like a better solution. It's so easy to crop in Lightroom. I'll just have to make sure I step back enough to get everthing in the frame.

sas8888 wrote in post #4213403
Or just focus take the picture then crop in PP after

Right, but it's not only about cropping, you also need to position the main subject properly within the cropped frame.

To do that, you may need more captured space around the main subject and therefore number six' advice to zoom out a bit to get more composing freedom seems very sound to me.

You loose pixels, of course.