Re: Depth of field preview

[P3D Paul Talbot <ptww@xxxxxxxxx>]

Lincoln asked:
> >.. depth of field preview.  Does any one know how that works?

And William Carter replied:
> 
> The camera lens would normally be at it's widest opening, giving you it's
> brightest image and shortest depth of focus. As you depress the trigger half
> way (I assume this would be your preview function) the aperture closes to
> it's set value.

A minor clarification:  Modern SLRs I am familiar with typically use
the "depress half way" action to electronically trigger the autofocus
function.  DOF preview is more a mechanical action, stopping down the
lens to the taking aperture, and therefore normally uses a separate
button on the camera body near where the lens is mounted.  In the
viewfinder the image becomes darker, but with more of it in focus,
both of course due to the now reduced viewing aperture.

Lincoln also wonders:
>>.. would it probably be a bad idea to get an slr that has auto focus...

The concern for stereo should probably not be to avoid an SLR with
auto focus, but to be sure the autofocus can be disabled as needed.
The fact that the camera has DOF preview suggests it was designed
to be used as eiter an automatic or a manual camera, but it would
be best to ask first.

Hope this helps!

Paul Talbot


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