I post too Much on Here!!
- Jan 29, 2011
You are so wrong on this it is painful. As it the statement you say is correct, it isn’t.Oh boy! We've been through this so many times. I'd like to know what, other than lens aperture, distance to subject and focal length of the lens, is going to affect depth of field? Real depth of field, not perception of depth of field.
In this example the depth of field does not change.
What changes is, as the image is enlarged, it is easier for the eye to perceive the lack of focus. The reverse is true as well, the smaller the image size the sharper the image is going to appear to the human eye. But, the actual depth of field never changes, it's simply that the larger the image, the easier it is for the human eye to see that an object is not in focus. And, yes, viewing distance will make a difference in perceived depth of field. A billboard viewed from the street may appear sharp, but when viewed from three feet away, any lack of sharpness will become apparent. Depth of field doesn't magically change, it is simply a limitation of our own biology.
This is a correct statement:
Depth of field is determined by two things after you have defined the ‘acceptable focus part’. CoC defines the acceptable focus, the end result subject magnification and the size of the aperture (not the f stop) determine the dof.
Now because subject magnification changes the dof, distance from the print or screen also changes the dof.
The simplest answer is from Gale Tattersall, DP of the TV show HOUSE : a larger sensor requires a longer lens to achieve the same field of view. The longer the lens the less DOF. (aperture staying the same of course) Which aperture: the f-stop or the physical one? If it is the former, start...