GeoKras1989 wrote in post #17671220
Perpetuating the myth. From the article:
"The depth of field achievable can also be affected by the size of the camera’s sensor. If your camera has a small sensor, such as those found in compacts, then the depth of field will be greater and less shallow. However, the larger sensor found in a DSLR is capable of increasingly amplified shallow depth of field, assuming you have the appropriate lenses to match."The comparison above is between a 6D and G15. There is effectively no difference in DOF. This article makes unfounded claims, with no supporting evidence. The author appears to be echoing what he heard somewhere else, and believes to be true. Guys like him are why I posted the photos above. Sensor size has no effect on DOF.
This guy knows what he is talking about. From the 2nd article:
"In general shooting, provided you keep angle of view, camera position and size of entrance pupil the same, depth of field and diffraction will be the same regardless of sensor size!" Umm, not quite. "The size of the entrance pupil" is not the same as "the f/stop"
For a crop camera with a "crop factor of, say, 5 (relative to 35mm full frame)" shooting with a 10 mm lens (actual FL) will give you a FoV about the same as using a 50 mm lens (actual FL) on a full frame camera. So far so good.
Same tripod location, so perspective isn't changed.
Let's use f/4 on each camera.
The actual aperture opening on the crop camera is 10/4 = 2.5 mm
The actual opening on the FF camera is 50/4 = 12.5 mm
So the physical aperture is 5x different.
The physical aperture calculated this way is not always the same as the "entrance pupil" but they are closely related (Theentrance pupil of a system is the image of the aperture stop as seen from a point on the optic axis in the object plane.) and for the purposes of most discussions we can say that "physical aperture in mm = entrance pupil in mm" (macro gets weird).
So the entrance pupil is 5x different.
So, for the two situations (same camera position, same f stop, different sensor size, same FoV) we have different FL and different physical apertures.
If we want to keep the physical aperture (entrance pupil) the same, as your "guy who knows what he's talking about" says, we have to change the f stop. To match the DoF we have to stop down to f/20 on the FF (to get 50/20 = 2.5 mm entrance pupil).
So, in this case, to get the same picture (and that means the same DoF, too) we have to stop down the lens on the larger sensor camera to match the physical opening. The other way to look at it is that the lens on the smaller sensor gives more DoF at the same f stop...
(Not sure exactly how you created the pictures above but don't forget that if you enlarge one more than the other from its original size on the sensor to get to the one on the screen or print, then DoF is also altered)
Edit: OK - it's a little clearer now what you are ,presenting. If you take a small piece of the FF sensor to match the size of the crop sensor, then it doesn't matter whether the crop you present came from a FF, a MF or an APS-C. The only thing relevant in your comparison are the two, little pieces of sensor being used. They captured the same optical image and they've been enlarged to the same degree when you put them on the screen in your post. SO, of course, they look the same - D'oh 
But you didn't use the "whole of the larger sensor" to capture the image - that's what my scenario (and most realistic ones) contemplate - "which camera should I use and how do I set it?
