Crop Format Sensors and DOF

[Chris Dodkin]

Interesting and useful piece of info taken from this thread http://www.realphotographersforum.com/threads/1554-thinking-of-switching-to-canon- regarding dof and crop sensor cameras

Mmmm, looks like we're both right...

I looked it up and found the following explanation - this from BobAtkins.com:

• For an equivalent field of view, a Canon APS-C crop sensor camera has at least 1.6x MORE depth of field that a 35mm full frame camera would have - when the focus distance is significantly less then the hyperfocal distance (but the 35mm format needs a lens with 1.6x the focal length to give the same view).

• Using the same lens on a Canon APS-C crop sensor camera and a 35mm full frame body, the a Canon APS-C crop sensor camera image has 1.6x LESS depth of field than the 35mm image would have (but they would be different images of course since the field of view would be different)

• If you use the same lens on a Canon APS-C crop sensor camera and a 35mm full frame body and crop the full frame 35mm image to give the same view as the APS-C crop image, the depth of field is IDENTICAL

• If you use the same lens on a Canon APS-C crop sensor camera and a 35mm full frame body, then shoot from different distances so that the view is the same, the Canon APS-C crop sensor camera image will have 1.6x MORE DOF then the full frame image.

• Close to the hyperfocal distance, the Canon APS-C crop sensor camera has a much more than 1.6x the DOF of a 35mm full frame camera. The hyperfocal distance of a Canon APS-C crop sensor camera is 1.6x less than that of a 35mm full frame camera when used with a lens giving the same field of view.

 

[Hamish Gill]

I think that clears up a lot of confusion in this area ... good work on digging that out ... is it a direct quote ... do we need to credit it?

 

[Chris Dodkin]

Done

 

[Hamish Gill]

Good work... You couldn't make it a link could you, I like to see these people getting as much credit as we can give them really...

 

[Chris Dodkin]

Done

 

[Clive Meakins]

This explains why my 2x crop 4/3rds camera in combination with slow zooms gives me DoF results I'm not happy with. Thanks.

 

[Hamish Gill]

Yeh, same goes with compact cameras ... Tiny sensors, vastly wide angle lenses to get normal range equivalent focal lengths giving massive dof ... But let's not get me started on compact cameras

 

[Ian Grant]

There's a major flaw here, this is totally incorrect:

"• Using the same lens on a Canon APS-C crop sensor camera and a 35mm full frame body, the a Canon APS-C crop sensor camera image has 1.6x LESS depth of field than the 35mm image would have (but they would be different images of course since the field of view would be different)"

A lens has the same DOF at a given aperture and distance regardless of the format it's used with, only the first statement makes sense that as you go to a smaller formats the DOF increases compared to a lens with the equivalent angle of view on a larger format. That's common to all formats from ULF, LF - 10x8 & 5x4 down through MF, 35mm & Full frame Digital sensors etc.

Reading his other statements they are largely irrelevant and not really related to the choice of format. A very muddled set of statements that contradict each other.

Ian

 

[Julian de'Courcy]

There's a major flaw here, this is totally incorrect:

"• Using the same lens on a Canon APS-C crop sensor camera and a 35mm full frame body, the a Canon APS-C crop sensor camera image has 1.6x LESS depth of field than the 35mm image would have (but they would be different images of course since the field of view would be different)"

A lens has the same DOF at a given aperture and distance regardless of the format it's used with, only the first statement makes sense that as you go to a smaller formats the DOF increases compared to a lens with the equivalent angle of view on a larger format. That's common to all formats from ULF, LF - 10x8 & 5x4 down through MF, 35mm & Full frame Digital sensors etc.

Reading his other statements they are largely irrelevant and not really related to the choice of format. A very muddled set of statements that contradict each other.

Ian

I understand what you say Ian, you put it with clarity and agree. One way I look at it is the Nikon system and some other makers who give you the opportunity to use a crop mode on the output and how that effects the image purely through the crop alone.