HELP ! Is my DOF working

[rodbunn]

Can someone look at these pics and tell me if they look right to them. Both are exactly the same shot with a brand new CANON lense but I was in A mode and the first is F4 and the second is F8. I think there should be a lot more depth of field at f8 ??? I focused on the center battery, lens was set to 70mm. It doesn't look right with 2 other lenses I've tested either.

Thanks! Rod

F4 sample:
http://www.xposeu.com/samples/70mmf400014.JPG

F8 sample
http://www.xposeu.com/samples/70mmf800015.JPG

[justme_dc]

I don't know about your DOF but I do know that your second link is not working......

[rodbunn]

Sorry, Second link correction:

http://www.xposeu.com/samples/70mmf800015.JPG

[rampower]

I see a difference in the DOF

[Cal Maier]

Rod,

You didn't mention the model of lens that you used for this test. That would be a bit helpful. Also you say that you have 2 more lenses that exhibit similar results? What lenses and focal lengths did you use for those shots? Also how far apart are the batteries in your test?

The DOF on the shots that you posted look about right to me for a focal length of 70mm @ f8. You have to remember that DOF means that you will get acceptable focus in front of and behind the point of actual focus, you will only get sharp focus at the actual point of focus.

The longer the focal length of the lens the smaller the aperture has to be. F/8 will give reasonable DOF at 28mm or 35mm but at 70mm or 100mm you would need to stop down to f/16 to achieve the DOF of the shorter lens at f/8. Also the distance to the subject makes a difference to the DOF.

The acceptable DOF of my 70-200 2.8L at 70mm f/2.8 is about 3" and is about 12" at f/8, at a distance to the subject of 2 meters.

Hope this helps,

Cal

[henkbos]

Rod,

Go to the following calculator (http://www.dudak.baka.com/dofcalc.html) to calculate your DOF.

As for your 2 shots there is a difference in DOF. I think the POF of the 2nd is between the 3rd and 4th battery and not ON the 3rd. YOu should run this test again with a ruler next to the batteries.

Good luck

[rodbunn]

Thanks everyone for your help. I ran the test again and I do see a change. I guess what I'm not happy with is that at F8 or F16 with my lenses on a film camera I get REALLY CLEAR shots with a fair DOF. With my 10D I havn't taken ONE really clear shot of anything yet. I've tried shooting at F22 even and the 10D still doens't impress me. I use to get GREAT shots with my old C2020 with good DOF without even trying. I guess I thought the 10D would be clearer.

I hope I'm doing something wrong and that I eventually figure it out.

Thanks, Rod

[bluebomberx]

Are you using autofocus or manual focus? There is a known issue with the 10D and front-focusing on some units using long lenses. I have duplicated this error with my 10D and Sigma 70-200 f/2.8. Perhaps your other images you refer to are front-focused to some extent. Look for some point in the image that is more in focus than your intended subject. Have you adjusting the diopter in the viewfinder - an incorrect dioptric adjustment could make it difficult to manual focus your images.

These are just some other points that warrant some attention ;)

-Richie

[rodbunn]

Richie, ya know I thought about that. I do have to adjust the diopter. I was thinking, if the camera is front focusing and I adjust the diopter to what is in focus to the camera, when I manual focus won't I get the same thing (front focus???).

And thanks, I have been trying to use my Sigma 70-200 also with problems. I didn't know it was a known problem.... How are they going to fix it (or are they)?

Rod

[bluebomberx]

rodbunn wrote:
Richie, ya know I thought about that. I do have to adjust the diopter. I was thinking, if the camera is front focusing and I adjust the diopter to what is in focus to the camera, when I manual focus won't I get the same thing (front focus???).

And thanks, I have been trying to use my Sigma 70-200 also with problems. I didn't know it was a known problem.... How are they going to fix it (or are they)?

Rod

If I read you right, you are correct. When you adjust the diopter, you are adjusting for the square marks to be sharp to your eye. It's best done by looking at a bright light source. Once it's set, you shouldn't touch it again unless your vision changes.

As for Canon's stance on front focusing, others have sent their 10Ds to Canon for repair and I've read of their successes at other forums. It is considered a warranty repair. I haven't sent mine in yet; I need to though.

My Sigma 70-200 f/2.8 is worse with the Sigma 2x teleconverter attached. I think the longer focal lengths exacerbate the flaw.

-Richie

[rodbunn]

That's good info. I appreciate having this forum to share info.....

Take care, Rod