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11/05/2007 11:47:52 AM · #1 |
I went out to the zoo this past weekend with my new Canon 70-200mm f/2.8L on my 40D. It was a sunny day. I was shooting at iso 200 and 400 with shutter speeds of at least 1/200 and IS turned on. I shot in AV mode set at f/4.0 with one shot AF and camera set at 5 megapixel. Most pics were "in focus" but when viewed at 100% only about half the pictures were razor sharp. Razor sharp meaning you could count the elephants eyelashes and see the texure on the skin. The rest were blurry (not razor sharp but semi focused) when viewed at 100%
Here is my question: what is the best way to focus? On the 40D the outter focus points are optimized for lenses f/5.6 and center point f/2.8. Does that mean if i have my lens set at f/4 and i choose one of the outter (f/5.6) focus points, the picture wont be completely focused? For example if i want to shoot at f/2.8 will i have to use the center focus point? And do you trigger the shutter right after the camera has achieved focus or is it ok to get focused and trigger shutter like 1 second after focus.
this one was shot at f/2.8 through the bars.
sample
another one. both unsharpened from the camera
sample2
Thanks in advance. Learning photography is an never ending process... |
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11/05/2007 11:55:11 AM · #2 |
Only way I have ever been able to get that sort of detailed focus in the shot (counting eyelashes) is manual focus. That's across three camera bodies with various lenses. I guess I just assumed auto-focus was 99% accurate and manual focus was for the real precision. So my response would be what you see is normal behavior, but then I look forward to being shown why I'm wrong so I can get better shots with AF and not have to screw around with MF.
Message edited by author 2007-11-05 11:55:26. |
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11/05/2007 12:04:54 PM · #3 |
Observations:
1. The lens is always at f/2.8 for focusing; it doesn't stop down until the mirror flips up. So that's not the issue.
2. Setting camera to "5 mp" is robbing you of resolution. Why buy a 10 mp camera and then shoot at lower resolution? You gain nothing but the capability to put more images on a single CF card. Buy a bigger card if you need to.
3. f/2.8 doesn't leave a lot of DOF at 200mm for semi-closeups like these shots. You need to be very careful as to precisely where the camera is focusing.
4. IS is a great feature, but it can't compete with a tripod for critical sharpness. If you want to shoot telephoto hand-held, you will need to work on learning how to stabilize your body when shooting.
6. "Straight from camera" is not a good way to judge sharpness of an image from a dSLR anyway; you have half-a-dozen different sharpness settings you can dial in from the menu, and anyway dSLRs are set up on the assumption you will PP for sharpness.
R.
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11/05/2007 12:18:59 PM · #4 |
Originally posted by routerguy666:
Only way I have ever been able to get that sort of detailed focus in the shot (counting eyelashes) is manual focus. That's across three camera bodies with various lenses. I guess I just assumed auto-focus was 99% accurate and manual focus was for the real precision. So my response would be what you see is normal behavior, but then I look forward to being shown why I'm wrong so I can get better shots with AF and not have to screw around with MF. |
You are correct that AF is basically hit-or-miss most of the time, especially when shooting close in and wide open. MF is the only way to be sure of critical focus, and even then you need to be damned good at it :-)
R.
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11/05/2007 12:25:38 PM · #5 |
| if you want extreme sharpness, you should use a tripod (what Bear said) and turn OFF image stabilization. IS helps to make sharpness passable, but at the expense of tiny moves of your glass, which may add some small blur visible at high resolution. |
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