[LargeFormat] Macro depth of field

[Mike Finley]

Found the formulae, and done the math. It's nowhere near as clear cut as I
expected.

Assuming realistic figures for minimum aperture (f32 for a 35mm macro lens,
f64 for a large format macro lens (eg G-Claron)) the 5x4 format gives the
least depth of field, as expected, but 35mm gives only about 10% extra as a
result of the larger aperture. A roll film back on the 5x4 gives the best
depth of field, 25% better than the 5x4.

With the f45 minimum of my current lenses, however, the 35mm camera easily
gives the best depth of field. Time to look for a second hand G-Claron I
think.

-----Original Message-----
From: largeformat-admin@f32.net [mailto:largeformat-admin@f32.net]On
Behalf Of Mike Finley
Sent: 22 January 2003 12:28
To: largeformat@f32.net
Subject: RE: [LargeFormat] Macro depth of field


but depth of field does depend on acceptable circle of confusion on the
negative, surely?
I think the other factors have a greater effect than this. I'll look up the
math and check.

-----Original Message-----
From: largeformat-admin@f32.net [mailto:largeformat-admin@f32.net]On
Behalf Of Ole Tjugen
Sent: 22 January 2003 11:24
To: largeformat@f32.net
Subject: Re: [LargeFormat] Macro depth of field


22.01.03 11:57:21, "Mike Finley" <mike@efikim.freeserve.co.uk> wrote:

<snip>
>
>There are then two things affecting depth of field (assuming same lens and
>aperture):
>I can use a larger circle of confusion on the 5x4 negative, as it won't be
>enlarged as much, increasing depth of field.
>I am shooting at a higher magnification on the 5x4 (1.5x rather than
0.75x),
>decreasing depth of field.
>
>I think, from looking at a couple of negatives, that the latter has greater
>effect, giving me overall less depth of field with 5x4 film than a
roll-film
>back, assuming the same aperture. I haven't tested this properly though.
>
>Can anyone confirm this?
>
>thanks,
>mike
>

In one word: Yes.
The reproduction ratio ON THE FILM determines DOF - that's why "cheap"
consumer digital cameras have too much DOF to be usable for
macro.

Using the same ratio at the same aperture, DOF is the same regardless of
film type and size - as well as lens focal length!

Ole



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