I have a question about depth of field with comparing two lenses. Which can achieve narrower depth of field when shot wide open? I know the 100 is a macro lens and at macro distances F2.8 is not usually possible, but let's talk short tele/portraiture distance. For a given focal length, the wider the aperture the narrower the depth of field; but for a given aperture, the longer the focal length the narrower the depth of field. So does the 50G at F1.4 or the 100G VR at F2.8 give narrower DOF? Thanks all!
Thanks for the link! Sorry for my typo, I meant 105 micro. The results at all distances were that the 105 at F2.8 ha significantly shallower DOF than 50mm at F1.4....I would not have guessed it would be by so much! -Loren
Loren E wrote:
The results at all distances were that the 105 at F2.8 ha significantly shallower DOF than 50mm at F1.4....I would not have guessed it would be by so much!
Would you use the lenses at the same distance, though? It's likely you'd shoot the fifty at half the distance, to appropriately fill the frame with your chosen subject. This reduces the difference in depth of field.
False, with the same framing of your subject, the 50mm f/1.4 will have shallower depth of field.
50mm @ f/1.4, subject distance is 10 ft with depth of field of 0.68 ft.
105mm @ f/2.8, subject distance is 21 ft with depth of field of 1.36 ft.
Both have a horizontal field of view of 4' 9.6" at their subject distances (aka, same framing). These numbers are for Nikon DX cameras. Realize however, that portraits look better with longer lenses and at f/2.8, you'll have sharper images (for better or for worse).
Specularist wrote:
It's likely you'd shoot the fifty at half the distance, to appropriately fill the frame with your chosen subject. This reduces the difference in depth of field.
Funny you should say half the distance since the numbers came out to be almost exactly half.
Strictly in terms of DOF, a 50/1.4 lens will have less DOF than a 105/2.8 at equivalent subject magnification, for all subject distances.
However, one can go further and state that the extent of background blur is nearly always greater with the 50/1.4, at equivalent subject magnification and equivalent subject-to-background distances. For small subject-to-background distances, the blur circle diameter is approximately twice that of the 105/2.8, with the difference decreasing with increasing subject-to-background distance. When this distance is very large, the 105/2.8 has approximately equal background blur.
