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Re: [OM] QP Card QP Color Correction Card (2 Cards) GQP201 - B&H Photo

Subject: Re: [OM] QP Card QP Color Correction Card (2 Cards) GQP201 - B&H Photo
From: Moose <olymoose@xxxxxxxxx>
Date: Mon, 18 Oct 2010 15:19:12 -0700
  On 10/15/2010 3:46 PM, Chuck Norcutt wrote:
> Anyone know anything about this?  I saw it mentioned on another list today.  
> It supposedly builds a custom profile rather than a simple white balance.
>
> <http://www.bhphotovideo.com/c/product/286652-REG/QP_Card_GQP201.html#features>

It looks to me like a variation on the ideas behind the ICC IT8 targets and ICC 
color profiles. In fact, Coca offers to 
build ICC profiles from QP card shots. Whether the QP software builds ICC 
format color profiles or it's own version, it 
is simply another of several ways of mapping the results of image capture to a 
known subject/source.

For that use, I can't see where QP offers anything new, or particularly useful:

1. QP targets -
a. Cost $16.65 apiece, incl. shipping from B&H in the US.
b. Have 30 B&W and color reference patches on a 5.6 x 1.6" (142 x 40mm) card
c. Do not appear to have any reference between their colors and correct colors. 
Either they have very special printing 
technology or just don't care about that level of detail.
d. May require proprietary software to use, at least as intended.

2. IT8 targets:
a. Cost $10 (or €10), incl. shipping (and get to me quicker from Germany than 
ground shipping from NY) from Wolf Faust. 
<http://www.targets.coloraid.de/>
b. Have 228 color and 24 B&W reference patches on a 4x5" sheet of photographic 
paper.
c. Come with a standardized color reference file documenting the differences 
between the target colors and correct 
colors and readable by apps that create ICC profiles.
d. Are an international standard supported by many, many apps.

I know which I would use. ;-)

But let's back up a bit and look at the uses for such technology.

1. Correcting for inherent bias in an imaging system.

    This is the way in which I use ICC profiles. By profiling a film/scanner 
combo, sensor system or sensor system and
    RAW converter combo, I can correct for imperfections in their capture of 
reflective color in images.

    Used this way in light other than that in which the profile was made will 
show color differences from the same
    subject in the reference lighting. This way, subjects shot in 'magic hour' 
lighting looks like magic hour light
    shots, and so on.

2. Adjusting an image so that it appears to have been captured in different 
light than was actually illuminating it.

    In this use, one may, for example, shoot in tungsten light, including an 
image of the standard target in the same
    light, create a profile and use that profile to correct color so the 
resultant images appear to have been taken in
    daylight, with a highly color accurate camera.

    This way, subjects shot in 'magic hour' lighting looks like they were shot 
in midday light - except for the angle of
    the shadows, etc.

3. One may combine the two basic techniques.

    For example, one may use a simple neutral reference item to correct for 
difference from daylight in an image or set
    of images and a color profile to correct for camera/film specific 
irregularities in color response.

So here comes the question. What do you want to do?
===============================================

Correct for camera/film inaccuracies?
-----------------------------------

This is simple. Use an IT8 target and create ICC profiles to be used in 
scanning or in post. It's the cheapest, simplest 
and most accurate.

Correct natural subjects?
-----------------------------------
Most of the time, I don't want to correct shots in other light to look like 
midday light. I carry a WhiBal around in my 
camera bag, but very seldom use it. Actually, I tend to forget it's there, but 
that' at least in part because of my 
prior experience with it.

To me, the problem is simple to state, somewhat trickier to deal with. I shoot 
mostly outdoors, by natural light. Much 
of that shooting is in light from various degrees of cloud/overcast, shade, 
often colored by the foliage it has passed 
through and light from open sky or sunlight at times other than midday.

The result is colors that aren't correct, in the color profile sense, but are 
perceptually correct. It's possible to 
correct a shot of a color target shot in any of these lights to look just like 
one shot in midday sun. But when I apply 
such correction to shots of natural subjects, they end up looking unnatural.

There are all sorts of clues other than color alone that let us know in what 
kind of light a subject was shot. When a 
familiar subject is color corrected to a light much different from that in 
which is was captured, it tends to look 
"off", although it's often hard to say exactly why.

My experience with the WhiBal is that it tends to overcorrect, at least 
perceptually, so the image is just wrong looking 
, to at least some extent, in other than relatively ordinary, midday light. 
When I have used it, I usually ended up 
applying it to a layer, then adjusting the opacity to find a middle ground that 
looks "right", like some combination of 
how I remember the scene and how millions of other, similar, subjects have 
looked to me.

Since I can do essentially the same thing with the WB sliders in ACR, without 
taking extra shots with a reference item 
in the shot, I don't find much need for the WhiBal.

I've thought for a long time that Dpreview's endless rants against Auto WB in 
tungsten light JPEGs from Canon cameras is 
misdirected. I'm sure Canon is capable of making cameras that output "correct" 
WB in incandescent light. So why don't 
they? I think the answer is that their research has shown that most users don't 
like the look of such shots fully 
corrected. We expect some shots to be warm, and like it that way. Other visual, 
perceptual and memory clues let us 
'know' that daylight colors in those settings aren't right, aren't what we saw.

In summary, I just don't see the need for anything more sophisticated than a 
neutral reference card or other gadget in 
any but a few specific lighting situations.

Correct studio work?
-----------------------------------

Not my area, portrait, product or what have you photography. Still, I can't 
imagine the QP system can be as accurate as 
the ICC profile system, nor is it likely to be as good as the Greytag/Macbeth 
systems in use by so many pro studios.

In Summary
===========

I may be missing something, but I don't see where it offers anything worthwhile 
that isn't already available cheaper and 
likely more accurate. I can understand someone looking for a way to make an 
honest bit of dosh, but I don't see where 
this product succeeds in offering value.

A. Critical Moose

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