Depth of field question- Crop / Full Frame

Started 8 months ago | Discussions thread
Bob Contributing Member • Posts: 723
Re: Depth of field question- Crop / Full Frame

Excellent question - a common source of confusion for beginners, and as you will soon see from the flood of responses and the ensuing arguments, it’s a source of confusion for experienced photographers as well.

From what I can tell, answers to this question tend to fall into the following categories (all of which are sort of correct):

  • The Mathematical Answer
    • The “circle of confusion” will be quoted, which is the mathematical definition of depth of field.
    • Here, sensors size does matter, but you also have to factor in other considerations such as the size of the print and how far the observer’s eye is from that print.
  • The Practical Answer
    • Most beginners simply want to know if the background will be just as blurry with a smaller sensor.
    • This point of view suggests the sensor size does not impact DOF directly, but it does effect it indirectly because the small sensor will use a different focal length and different subject-to-camera distance to achieve the same angle of view as a larger sensor camera.
    • But, all things being equal (same lens, same distance, same aperture), cropping the image in Photoshop to match the field of view of the larger sensor image should result in very similar background blurriness.
    • In other words, if you have a small sensor camera, you will find yourself moving closer to the subject with a shorter lens.  Both of those will affect your DOF.
 Bob's gear list:Bob's gear list
Nikon D810 Hasselblad XCD 120mm F3.5 Macro
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