Archived posting to the Leica Users Group, 2009/02/07
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Since Depth of Field is a perceptual thing, it's subjective. In the
extremes, if you don't care very much about 'sharpness', but only
about overall shapes and tones, your expectations and requirements
for DoF are very generous. If you want true and full 'sharpness' and
the finest detail, DoF doesn't really exist.
Between these two extremes we have most people, and a concept of DoF
that has been somewhat standardized. It relates to a circle of
confusion on a print viewed at normal distances. Aperture,
magnification, blah blah blah. We know all that.
However, then comes the matter of format. To get to the same size
print we have to enlarge (magnify) the captured image by different
factors to get to the same size print. Yes, you can say that you're
not going to blow up an image from a 3Mp camera (do those still exist
except in phones?) to the same size as an image taken on 8x10 sheet
film. True, but if the prints are the same size and the same circle
of confusion is used as an acceptance criteria, the formats can be
compared and then have a definite effect on DoF. In practice, of
course, we expect 8X10 pictures to hold more detail and be 'sharper'
than 8x11mm Minox pictures, and so the criteria for DoF get shifted a
bit.
In the end, though, DoF does depend on format as it's the final
'magnification' that enters into the calculations, and therefore the
DoF IS greater for 8x10 cameras than for 35mm cameras, using the same
focal length at the same f-stop and same distance because the final
'magnification' is so much less therefore the 'slop' in the DoF at
the taking stage is far less apparent.
BTW, the Sinar actually has a depth of focus scale on the focus knob,
and depth of focus is independent of focal length and magnification
until you get close to 1:1. To a certain degree depth of focus
relates directly to depth of field, and therefore the Sinar solution
is an elegant and simple way of handling this for certain types of
shooting.
At 7:57 AM -0600 2/7/09, George Lottermoser wrote:
>Henning,
>
>No. Never "used" a Sinar. Played with them in other's studios.
>
>My experience with format changes goes more like this:
>8x10 back on Deardorf (or at one time Calumet).
>Focus on scene.
>Feels too wide.
>Put 5x7 back on Camera.
>Feels right.
>No change in focus, distance from subject or DOF.
>Just a smaller section from the image circle.
>
>I also realize that
>if you want to achieve
>the same composition or field of view,
>with the same lens on different formats,
>things change a great deal:
>distance from subject,
>distance between lens and plane of focus,
>then, of course, effective DOF,
>as well as the apparent perspective.
>
>Seems like two different ways to think about DOF.
>Both correct and useful in their own ways.
>
>Regards,
>George Lottermoser
>george@imagist.com
>http://www.imagist.com
>http://www.imagist.com/blog
>http://www.linkedin.com/in/imagist
>
>On Feb 7, 2009, at 2:29 AM, Henning Wulff wrote:
>
>> George, you've used a Sinar, haven't you? On the depth of field
>>scale, attached to the rear fine focus adjustment, the DoF scales
>>are there for 4x5 or 5x7 or 8x10, or there is a combination scale.
>>They're different for each format.
>
>
--
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
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