Re: Primer on photographic exposure, etc.
Re: Primer on photographic exposure, etc.
- Subject: Re: Primer on photographic exposure, etc.
- From: José Ángel Bueno García <email@hidden>
- Date: Tue, 21 May 2013 18:27:23 +0200
Dear Ben:
I own a variety of IT8.7 for each film and photographic paper from
different vendors. And I know that they contain the same pigments that the
documents I shoot to. I come from the field of the conservation of cultural
heritage on photographic artifacts.
As you might know, the angle of view is not a problem but the direction of
light yes. You may avoid specular reflections and have the target under
even illumination.
A single light source, be illuminant or not, doesn't mean that I make use
of only one bulb or flash unit but that I avoid other light source that the
one I put.
On the other hand, as my coments are to the words of Mr Thomas Lianza, I'm
going to wait for his answer.
Thank you
Jose Bueno
2013/5/21 Ben Goren <email@hidden>
> On May 21, 2013, at 5:33 AM, José Ángel Bueno García <email@hidden>
> wrote:
>
> > Hello:
> >
> > "If you are a fine art photographer, your target should
> > reflect (pardon the pun) the media you are photographing."
> >
> > Do you mean IT8.7/1 for slides, IT8.7/2 for photographic copies and
> > ColorChecker(s) for the rest of art objects?
>
> The IT8 targets are good for scanning photographs. More patches would be
> nice -- always! -- but they have enough for good results and the
> distribution is good. That's especially considering that there aren't very
> many pigments to worry about.
>
> I'm a huge fan of the ColorChecker Passport for field use to
> colorimetrically normalizing exposure and white balance. It's the only
> small chart I'd really consider for matrix profiles, but 50 patches really
> aren't enough for quality work. Even the ColorChecker SG doesn't have
> enough patches.
>
> What you need to do is build your own target. You'll want as many
> different paint samples as you can practically apply, and ideally a few
> different tints of each paint. You'll also want to fill out the rest of the
> chart with as many patches as you need to get into the hundreds (ideally
> several hundred or more) patch range by printing on high-quality fine art
> (OBA-free) paper on an inkjet with as many different inks as possible. You
> can use your favorite printer profiling package to generate the patch
> colors. Print the chart, paint the paints, measure with your
> spectrophotometer, and you've got a better chart than any you can buy.
>
> > What about the distance to the target?. If I have to reproduce original
> art
> > on paper near DIN A3 size I don´t change the distance to reproduce a
> > ColorChecker, and think is OK if the surface to reproduce is evenly
> > illuminated by a single light source and that that is the way to
> > characterize the sistem in a fixed condition.
>
> As I noted in the previous email, what matters most is angle of view, not
> target distance.
>
> But a single light source isn't going to give you even illumination unless
> it's very far away (such as the Sun). Ideal is a very large, very narrow
> ring light at 45° to the art. Two or more bare-bulb lights positioned in
> spots on an imagined virtual ring light work just fine, with more bulbs
> being better. I get great results with four Einstein flashes in a square.
> The traditional copy stand uses two lights to good effect.
>
> Cheers,
>
> b&
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