Dof?

grado · 23rd May 2004

Is it true that even for the same focal length, different lens have different DOF? And lets say if i use a 70mm lens on a Nikon D70, even though the focal length will increase to 105mm, the DOF remains as if it were the same 70mm lens? It seems like it is harder to get the beautiful shallow DOF I get with my minolta film camera...

clive · 23rd May 2004

http://www.nikonians.org/dcforum/DCForumID6/4083.html

loupgarou · 23rd May 2004

imho
DOF is controlled by the ACTUAL focal length (not modified by FOV crop factor) and aperture and focusing point .

the shorter the focal length, the deeper the depth of field (which is why wide angles have huge DOF and p&s with their extremely short focal length)

the wider the aperture, the shallower the depth of field

focusing point: the closer you are to the minimum focusing distance for your lense, the shallower the dof.

grado · 23rd May 2004

Originally Posted by loupgarou

imho
DOF is controlled by the ACTUAL focal length (not modified by FOV crop factor) and aperture and focusing point .

the shorter the focal length, the deeper the depth of field (which is why wide angles have huge DOF and p&s with their extremely short focal length)

the wider the aperture, the shallower the depth of field

focusing point: the closer you are to the minimum focusing distance for your lense, the shallower the dof.

I used to think so too, but from my limited experience so far, I don't think that your first sentence is true, because I can't seem to achieve the same bokeh as my film based camera with the same (x1.5) equivalent focal length.

majere2sg · 23rd May 2004

Originally Posted by grado

I used to think so too, but from my limited experience so far, I don't think that your first sentence is true, because I can't seem to achieve the same bokeh as my film based camera with the same (x1.5) equivalent focal length.

You mean u tried 70mm on D70 and the same 70mm on your film camera and both lenses have the same aperture ?

grado · 23rd May 2004

Originally Posted by clive

http://www.nikonians.org/dcforum/DCForumID6/4083.html

Thanks Clive, i think that sorta comfirms my suspicion...

clive · 23rd May 2004

to summarize for the benifit of all:

apparatus: say we have: film body, digital body(1.5xFLM), 70mm/f2 lens, 105mm/f2 lens

scene 1: film body + 105mm lens, shoot at f2.8

and

scene 2: digital body + 70mm lens, shoot at f2.

result: both shots will have
1. same effective angle of view
2. same DOF

23rd May 2004	#1
grado Member Join Date: Dec 2003 Posts: 819	Dof? Is it true that even for the same focal length, different lens have different DOF? And lets say if i use a 70mm lens on a Nikon D70, even though the focal length will increase to 105mm, the DOF remains as if it were the same 70mm lens? It seems like it is harder to get the beautiful shallow DOF I get with my minolta film camera...

23rd May 2004	#2
clive Senior Member Join Date: Oct 2002 Posts: 2,573	similar case http://www.nikonians.org/dcforum/DCForumID6/4083.html

23rd May 2004	#3
loupgarou Member Join Date: Sep 2003 Posts: 1,794	imho DOF is controlled by the ACTUAL focal length (not modified by FOV crop factor) and aperture and focusing point . the shorter the focal length, the deeper the depth of field (which is why wide angles have huge DOF and p&s with their extremely short focal length) the wider the aperture, the shallower the depth of field focusing point: the closer you are to the minimum focusing distance for your lense, the shallower the dof.