Re: Materials for Flat-Fielding
Re: Materials for Flat-Fielding
- Subject: Re: Materials for Flat-Fielding
- From: "Fleisher, Ken" <email@hidden>
- Date: Tue, 05 Jun 2007 08:07:46 -0400
- Thread-topic: Materials for Flat-Fielding
Thanks to everyone for all of the suggestions. Lots of good ideas.
I don't think a sphere will work for us since we need to photograph objects
of many sizes from just a few inches to many feet in length. I didn't
understand what was meant by sphere because I have always referred to this
as a dome (I automatically associated sphere with a spectrophotometer).
> One last question; if you have the largest flat-field standardising sample
> that you require then why do you require smaller ones? (This is definitely
> where my ignorance comes into play!)
Well, we have four different photo studios with each set up for shooting
different sized originals. If we have a 30 x 40 inch board for one studio,
then that will not fit on a copy stand that has a 16 x 20 inch maximum, for
example. Also, sometimes it's just easier to use a board that is a similar
size as the original because as the camera is moved very close to the
object, a very large board becomes difficult, and sometimes impossible, to
handle in the limited space that is being worked with.
> One comment. Regular changes in radiance due to the surface irregularities
> of a reflector are pure math functions and they can be corrected by a
> Fourier filter. I am not going to volunteer!
True, but I am trying to find solutions using commercial software. Right now
we are using Sinar's CaptureShop. Besides, it's better to find a
non-textured surface than to correct for a textured surface. I'm just trying
to reduce the possible errors as much as possible for each stage of the
process.
I'll investigate all of the different materials that have been suggested.
After making a decision and testing it out for a while, I'll report back
here what the solution was in case it will be of use to others.
Thanks again for the suggestions.
--
Ken Fleisher
Photographer
Imaging & Visual Services
National Gallery of Art
Washington, D.C.
Phone: (202) 712-7471
email@hidden
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