Re: Materials for Flat-Fielding
Re: Materials for Flat-Fielding
- Subject: Re: Materials for Flat-Fielding
- From: "my name" <email@hidden>
- Date: Mon, 04 Jun 2007 17:16:40 -0400
I am new to this so please excuse any stupid mistakes! I design instruments
for colour measurement but never get to use them in all industries.
I presume that a non glossy ink jet paper is used; the goniometric
properties of glossy paper would create undesirable effects.
How do you mount the paper to the Gatorfoam board? The ink jet paper is very
translucent and hence its reflectivity is dependent upon its backing; air
gaps between the paper and the Gator will affect radiance! A gradual change
in colour can not be seen by the eye (it can be measured though) but an
abrupt change is exaggerated (the brain is looking for detail and so
exaggerates changes.)
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!)
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!
Meari.
From: Charlie Rieger <email@hidden>
To: "Fleisher, Ken" <email@hidden>,ColorSyncList
<email@hidden>
Subject: Re: Materials for Flat-Fielding
Date: Mon, 04 Jun 2007 15:33:54 -0400
Ken,
I have found that mounting a bright white inkjet paper to gator board works
well for this purpose. The base of the paper is much more uniform and
brighter than foam core, and the gator board gives additional rigidity.
--
Charlie Rieger
Director, Digital Imaging and IT
Rieger Imaging
email@hidden
Voice: 301-869-8300
Fax: 301-869-2786
Toll Free: 800-948-5320
On 6/1/07 2:03 PM, "Fleisher, Ken" <email@hidden> wrote:
> Hello. I have a question about flat-fielding for digital image
> capture.
>
> Currently, we use either white foam core or a white cardboard to
> capture the image for flat-fielding.
>
> I don't like using the foam core because it is too easy to dent and
> scratch and the surface very quickly becomes non-uniform. It also
> seems to hold a strong static charge and picks up dust and dirt very
> easily and is difficult to clean without marring the surface.
>
> The cardboard that we use has too much texture on the surface which
> isn't good for flat-fielding. We counteract this somewhat by settng
> the camera slightly out of focus. We can't seem to find a cardboard
> with a smoother surface.
>
> My question is what material(s) do you recommend/use for this task? We
> would need to ve able to get it in large sizes as well as smaller
> sizes.
>
> Thanks for any suggestions...
>
> --
> Ken Fleisher
>
> Photographer
> Imaging & Visual Services
> National Gallery of Art
> Washington, D.C.
>
> Phone: (202) 712-7471
> email@hidden
>
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