Depth of Field Revisited

[Pro-Vista]

I've already posted a thread about potential problems with DoF I seemed to be experiencing with my new 1Ds MkIII (having switched from a full frame Kodak 14MP DCS Nikon-fit camera).

On screen, I observed a noticable reduction in DoF with the Canon using the same focal length/aperture compaired to my Nikon-based gear. I have subsequently printed test images, and the DoF problem is less marked, but still there (i.e. I notice it, even if my customers are unaware).

I phoned the store I bought it from to discuss the matter, and was advised that the increase in pixel count (i.e. 14 to 21MP) meant that this would work against the 'circles of confusion' for what would be perceived to be 'in focus'. In short, whereas I used to shoot in-studio at f/8, I was told to change this to f/11 to get the same effect. It seems frustrating to have to do this, having forked out so much money for this camera. (In all other respects I think the Canon is fabulous/an improvement over the Kodak/Nikon.)

I could really do with somebody explaining, precisely, what an increase in pixel count means w.r.t. DoF.

Also, whilst I think I understand the argument, I can't help wondering whether my camera might be focusing too far 'forward' and if I tweaked the microadjustment setting so it focused a bit further back whether this would get me my DoF back?

Any pointers???

Pro-Vista
(Steve Clegg)

[KevinStecyk]

Originally Posted by Pro-Vista

I've already posted a thread about potential problems with DoF I seemed to be experiencing with my new 1Ds MkIII (having switched from a full frame Kodak 14MP DCS Nikon-fit camera).

On screen, I observed a noticable reduction in DoF with the Canon using the same focal length/aperture compaired to my Nikon-based gear. I have subsequently printed test images, and the DoF problem is less marked, but still there (i.e. I notice it, even if my customers are unaware).

I phoned the store I bought it from to discuss the matter, and was advised that the increase in pixel count (i.e. 14 to 21MP) meant that this would work against the 'circles of confusion' for what would be perceived to be 'in focus'. In short, whereas I used to shoot in-studio at f/8, I was told to change this to f/11 to get the same effect. It seems frustrating to have to do this, having forked out so much money for this camera. (In all other respects I think the Canon is fabulous/an improvement over the Kodak/Nikon.)

I could really do with somebody explaining, precisely, what an increase in pixel count means w.r.t. DoF.

Also, whilst I think I understand the argument, I can't help wondering whether my camera might be focusing too far 'forward' and if I tweaked the microadjustment setting so it focused a bit further back whether this would get me my DoF back?

Any pointers???

Pro-Vista
(Steve Clegg)

It's not related to pixels but rather full- versus partial-frame sensors.

As you know, partial-frame sensors show a "cropped" view. That is, a Canon 40D and your camera using the same lens, same focal length will show different scenes.

You might wish to Google "depth of field full frame".

Here's a post on ProPhoto that you might be familiar with:

Depth of Field Question

[Jerry Skrocki]

Both of the OP's cameras are full frame sensors.

The difference in depth of field is due to the optics. One manufactured by Nikon and the other by Canon. It is not just a matter of focal length and aperture but also the "speed" of the lens. Comparing two 50mm lenses @ f4 will give different results if one lens is able to stop down to f2.8 and the other f/4 minimum aperture.

[Tom Savage]

I tweaked all my lens because I found that none focused dead on, so that may be your problem. Put up a target, like a ruler, at 45 degrees and open the lens to minimize depth of field and focus on a center point then shoot. Adjust accordingly to get the lens to focus on the aim point.

Tom Savage

[KevinStecyk]

Originally Posted by Jerry Skrocki

Both of the OP's cameras are full frame sensors.

Ooops...Thanks Jerry.

[Johan_Elzenga]

Originally Posted by Jerry Skrocki

Comparing two 50mm lenses @ f4 will give different results if one lens is able to stop down to f2.8 and the other f/4 minimum aperture.

No, that should not be the case. At the same aperture, they should have the same DOF. The maximum aperture is not a variable in the DOF formula.

[Pro-Vista]

Thank you for this suggestion. I'll have a go, and see if it helps.
Steve

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