Please Help Me Tweak My 7D to Improve Image Quality

Started Mar 10, 2013 | Discussions thread
OP steve88 Contributing Member • Posts: 905
Point of Focus

TTMartin wrote:

steve88 wrote:

. . . Why can't the image be better coming out of the camera so that post-processing doesn't require a PhD? . . .

It can, you just need to make sure that from your point of focus you have adequate depth of field.

In neither of the photos posted that was the case. In the first photo, there is a lot of depth of field (due to the subject distance), but, the point of focus is behind the batter (point of focus may have been moving from/to the backstop).

In the second photo, the point of focus is on the runners front hand, but, there is inadequate depth of field for the runners face and body to be sharp.

Either your point of focus has to be spot on (hard for fast moving sport photos), or your depth of field has to be a little deeper to compensate for it.

The closer the subject the shallower the depth of field. So someones football player photo taken at 200mm f/2.8 and from 100 feet away, will have a 4 times greater depth of field than another photo taken at 200mm f/8 and 30 feet away.

Subject distance 100 ft - 200mm - f/2.8

Depth of field
Near limit 96.1 ft
Far limit 104.2 ft
Total 8.15 ft
In front of subject 3.91 ft (48%)
Behind subject 4.24 ft (52%)

Subject distance 30 ft - 200mm - f/8

Depth of field
Near limit 29 ft
Far limit 31.1 ft
Total 2.04 ft
In front of subject 0.99 ft (48%)
Behind subject 1.06 ft (52%)

Actually, in the first photo I'm using a single manual focus point and it's the one farthest to the right.  The focus point is actually covering the batters left elbow, left sleve, and the front part of her shirt with the lettering "Mason" over it.  So, I think there's enough contrast in there for it to lock on and produce a sharper image...I think.  The focus point is definitely not behind the batter on the wall.

In the second photo, the focus point is on her shirt just above the belt buckle but it seems to have grabbed her left hand instead.  Perhaps there wasn't enough contrast on the shirt but you would think stripes against solids would provide enough contrast?

Thanks for the info on depth of field and distances...I obviously still have a lot to learn!

 steve88's gear list:steve88's gear list
Canon EOS 7D Canon EF 28mm f/1.8 USM Canon EF 85mm f/1.8 USM Canon EF 200mm f/2.8L II USM
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