f/1.8 on m4/3, ASP-C, FF; are they the same?

Started Nov 1, 2010 | Discussions thread
jpzundel Regular Member • Posts: 103
Re: f/1.8 on m4/3, ASP-C, FF; are they the same?

Depth of field depends on f stop and magnification only.

So the DOF of a 20mm 1.7 on 4/3 is the same as the DOF of a 40mm 1.7 on 35mm for the same subject magnification.

Unless someone teaches me something new, these statements about DOF of 4/3 being less because it is a smaller sensor are hogwash.

DOF is pure geometry and when the geometry is the same, i.e. same f stop and same magnification give the same geometry to the image making light rays therefore the same circle of confusion relative to the whole image.
Trace the rays, it will be obvious.

Actually DOF does not depend on focal length either, only on f stop and magnification.

An image of the same magnification of the subject has the same depth of field, be it taken with a 20mm or an 80mm. Of course you have to stand much further with the 80mm to have the same magnification as with a 20mm.

 jpzundel's gear list:jpzundel's gear list
Sony RX100 Panasonic Lumix DMC-LF1 Olympus E-300 Olympus E-510 Olympus E-M1
Post (hide subjects) Posted by
(unknown member)
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow