I believe so. When one doubles the linear size of the sensor
(quadruples the area) one has to double
the focal length of the lens to get back to the same angle of view.
When one doubles the focal length,
to get an entry pupil of the same size (area) as the lens with half
the focal length, one has to half the
F number.
I believe apparent depth of field is purely a function, not of focal
length, but of entry pupil size and
subject magnification.
So, for the same framing, an image made with 40/1.4 on MFT, or 80/2.8
on 35mm, will look pretty much
the same. Of course, different lenses have different styles of
rendering which may make the image look
a bit different, but in everything I have ever done, this relationship
seems to hold (from what I can see
in my own photos, when I compare 35mm to 6x7cm film).
It's interesting to me that 35mm remains the shallow DOF champion for
most use-cases (normal and longer
focal lengths), with one having slow lenses available both for smaller
sensor sizes (MFT) and larger sizes.
The exception is large format - where one can shoot some of the f/5.6
wide angle lenses wide open and get extremely
shallow DOF and wide angle of view. But a 24mm f/1.4 lens on a 35mm
camera can often do that too.
On 06 Jan 2010, at 5:25 PM, Chris Barker wrote:
> I get that, Dawid, but is it as simple an equation as you stated in
> your earlier post: 40/1.4 = 80/2.8 in DOF terms?
>
> Chris
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