On 10/18/2010 5:10 PM, Chuck Norcutt wrote:
> It will take me a month of Sunday to digest all that but
:-) I thought maybe you didn't have enough to do.
> , in the interim...
>
> The QP target was recommended on another photography list in response to
> someone who was having difficulty getting proper CMYK conversions ...
>
> Because ... The person who responded with the QP target suggestion was
> obviously looking for a complex white balance solution.
>
> It might also be that the room in question has a combination of tungsten,
> halogen, fluorescent and sunlight and there's no simple solution. I don't
> know what the actual lighting is.
My main point in this particular regard is simply that an IT8 target and ICC
profiling is a cheaper, more accurate, more
standardized solution.
If the mixed lighting is fairly even across the subject, ICC profiling and
correction should do a good job, as it makes
no color temp assumptions, simply maps color points. If lighting is
significantly uneven, the classic solution is to be
a real pro and create your own lighting. Many years ago, I was a subject in
such a situation of mixed light, and the
photog. simply fixed it with his own.
I suppose you could photograph an IT8 target in the brightest area of each kind
of lighting, create separately corrected
layers and do some mask painting ...
Moose
> Chuck Norcutt
>
>
> On 10/18/2010 6:19 PM, Moose wrote:
>> 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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