Depth of field question- Crop / Full Frame

Started 5 months ago | Discussions thread
bobn2
bobn2 Forum Pro • Posts: 58,589
Re: Depth of field question- Crop / Full Frame
9

Pk8887 wrote:

I'm looking for a crop set camera for sports to lose some weight and gain and gain some length but am confused about depth of field and would like some help figuring out the following.

I like the background separation look I can get at 100mm f2.8 on my full frame 5dmk iii.

If I were to buy a crop camera and the lens was f2.8 from what I understood the background separation wouldnt be as obvious and the apparent depth of field wouldn't be as shallow (similar to f4 or f4.5 as i have read) due to the smaller sensor.

BUT as the crop would be a longer focal length in reality (1.5 x 100mm) and as focal length impacts the depth of field would it actually be similar?

In practical sense if I'm using a 2.8 lens on crop camera will I be able to achieve a similar shallow depth of field/backgroudn separation compared to a full frame equivalent at the same 'looking' focal lengths.

I may have just confused myself!

As Tom Axford has said, the rule is very simple. The apparent DOF when viewed in the final image (sorry for all the qualifiers, necessary to pre-empt confusing arguments) between two format will be the same for lenses where the focal length and f-number are in proportion of the relative crop factor. So, if you like the DOF at 100mm, f/2.8 on FF, you'll get the same effect on a 1.5x crop camera using a 100/1.5 mm (67mm) lens set to f/(2.8/1.5) (f/1.9). With those settings, the aperture diameter and AoV is the same, so the geometry of all the light rays entering the lens is the same, therefore the apparent DoF in the scene must be the same.

Pretty simple. I'd ignore all the obtuse arguments about the theory of DoF - the proponents and up confusing themselves as much as anyone else. The rule above is simple and works.

-- hide signature --

Ride easy, William.
Bob

Post (hide subjects) Posted by
Bob
Bob
Bob
Bob
Bob
Bob
MOD Footski
Bob
Bob
Bob
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow