Re: Stereo Macro

[P3D Sam Smith <sam@xxxxxxxxxxxx>]

Sam wrote,


 Is the depth of
>> field the same at  1:1 magnification for all focal length lenses, or does it
>> narrow down with the higher focal lengths ? I'm trying to see if there is an
>> advantage to MF macro. No formulas please !

  John replied,

>Sure, as long as the magnification and the f/number are the same, the depth 
>of field is the same.  Of course you have to use the same criterion for the 
>acceptable maximum size of the fuzzy circle for both cases or else it would 
>be "unfair".  8-)  An exception to my statement would be when the lens is 
>very short so its hyperfocal distance is large compared to the distance to 
>the subject.  But in this case, that couldn't happen because you're saying
>1:1 so the lens is halfway between the film and the subject.
> 
>Now that's looking at it in terms of geometrical optics; if you want to look
>at physical optics too, it gets a little more complicated.  Then you have dif-
>fraction effects and I should think about that before answering or else get my
>spreadsheetfrom my anonymous ftp site and just try a few numbers to see what
>happens.  Generally, diffraction isn't a major effect if you have a reasonably
>large aperture (low f/number).
> 
>John B
> 
>
>

Let's put it another way:  Is there any advantage of medium format macro
over realist format  macro? I can see reduced grain as an advantage, but
will the image be any sharper at a small aperture like f:45 or f:60 ? With
the ease of building MF stereo cameras, as well as the  availability of
several 75-90mm lenses for experimentation, I'm just trying to see if it's
worth pursuing. I am aware that both Pat Whitehouse  
and Jac Ferwerda built macro cameras using 120 rollfilm, but I was never
sure if they actually preferred it over 35mm because of convenience or
quality. If anyone has successfully tried it an had results worthy of
comment, I'd like to hear about them.

Sam


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