Depth of field - APS-C vs Full Frame

[Cubsprout19]

If I use my RF100mm macro on the R6 at f/11, and then swap the body to the R7 at f/11- keeping subject distance the same, what is the change in DOF please? Is it the new DOF equivalent to the R6 DOF*1.6. I've looked online and there seem to be contradictory views on this, adn I'm confused. I always thought that an APS-C camera had a greater DOF at a given focal length at the same distance and aperture than a Full frame camera.

Any help very gratefully received

 

[JustUs7]

I don't see the situation where the DOF changes by cropping the image.

It’s all predicated on the assumption that the final image is blown up to the same viewing size and viewed from the same distance. If you crop and blow up an image, then everything is blown up. The noise. The blurry parts. The flaws. Everything. This the zone of acceptable sharpness (aka: Depth of Field) changes.

 

[AntonLargiader]

I think it's a slippery slope to lump all of that in with DOF. By similar logic, if I hold a photograph 6" from my face, and then look at it from 3' away, the DOF is different each time.

 

[Archibald]

I think it's a slippery slope to lump all of that in with DOF. By similar logic, if I hold a photograph 6" from my face, and then look at it from 3' away, the DOF is different each time.

Yes, you got it. (In essence...)

 

[Archibald]

But seriously, we are not going to change the definition of DOF. It is defined assuming standard viewing distances and normal viewers. And that is the right way to do it.

So an 8x10" print might be viewed in one's hands, whereas a billboard of the same photo will be viewed from 30 feet away. The subtended angles are about the same.

But yeah, if you hold that 8x10" print really close, or very far away, perceptions of sharpness change. That does not change the calculated DOF.

 

[Cubsprout19]

Download a depth of field calculator. And app called Digital DOF is free and easy to use.

In your circumstances, DOF would be shallower with APS-C.

Now if you moved back for identical framing, APS-C would have greater depth of field. Or if you changed focal length to a 62.5mm lens and kept the same subject distance, APS-C would also have greater depth of field.

But the same lens from the same distance at the same aperture with the only variable being the sensor, then APS-C actually has shallower depth of field. Consider what would happen on full frame if you used a 160mm lens from that spot.

Thanks for taking the time to reply. I looked at online DOF calculators, but couldn't find one with the R6 or R7 as a choice of camera. The explanation you've given makes perfect sense -thank you again for such a well worded easy to undrstand answer.

 

[Cubsprout19]

It’s all predicated on the assumption that the final image is blown up to the same viewing size and viewed from the same distance. If you crop and blow up an image, then everything is blown up. The noise. The blurry parts. The flaws. Everything. This the zone of acceptable sharpness (aka: Depth of Field) changes.

Appreciate your thoughts, but I'm not cropping the image. Same shot from the same place with same lens just 2 different bodies. JustUs7 above has the answer I needed, but thanks for taking the time to reply.

 

[JustUs7]

I think it's a slippery slope to lump all of that in with DOF. By similar logic, if I hold a photograph 6" from my face, and then look at it from 3' away, the DOF is different each time.

That’s absolutely correct.

 

[Archibald]

Thanks for taking the time to reply. I looked at online DOF calculators, but couldn't find one with the R6 or R7 as a choice of camera. The explanation you've given makes perfect sense -thank you again for such a well worded easy to undrstand answer.

DOF doesn't depend on the camera model. Just pick a format that has the same sensor size.