On 3/2/2015 4:30 PM, William Vanden Dries wrote:
> One drawback I have experienced with this method includes the ability of
> the SLR to focus on the entire object. If I focus on the center of a record
> cover, the edges tend to be a little out of focus. I experienced this when
> imaging manuscript items on a large-format Digibook as well, which also
> uses a mounted SLR. I expect this wouldn't be an issue if the objects were
> scanned on a large-format flatbed scanner. However, I find it takes much
> less time per image using a copy stand instead of a flatbed scanner, and
> the focus issues are relatively minimal.
What you're describing is presumably "curvature of field", which is
often found in zoom lenses operated at wide apertures, as would probably
be the case in most "available light" situations. One possible solution
would be to use a fixed-focal-length lens, preferably one designed for
macro (close-up_ applications. Another would be working at smaller
apertures, which would be made easier by brighter light on the objects
being photographed. Obviously, you don't want to shine bright
floodlights on 78s, for fear of damage; however, equipping the copystand
with electronic flash units would be an alternative strategy.
Or, of course, you could close down the aperture and use longer
exposures, if vibration isn't a problem.