Re: camera profiles
Re: camera profiles
- Subject: Re: camera profiles
- From: Dan Reid <email@hidden>
- Date: Mon, 06 May 2002 11:25:17 -0600
On Sun, 05 May 2002 21:06:22 -0400, Joseph Castay <email@hidden>
wrote:
>
>> in the case of cameras a
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>> profile is environment specific, in or out of the studio. This means you
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>> can have 1 really great 5000K general profile for day or strobe (a tough
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>> one). Or a specific profile for each environment (better).
>
>
>
> I would have to disagree with this entirely. The difference between shooting
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> under 5000k studio light and shooting outdoors is gray balance. By gray
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> balancing for each lighting condition you are 3relinearizing2 the camera to
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> function with your one profile. Profiling scenes is problematic because of
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> outside influences (color) reflected onto the target or uneven lighting. A
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> good profile requires the target be lit with great care so the comparison
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> between data and patches is not subject to scene specific shifts. A great
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> many of the problems being reported about profiles not working are most
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> likely related to the care in which they are made. Profiling scenes is a
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> silly idea that should stop being promoted. All it does is make for bad
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> results and does nothing to further the craft of building and using
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> profiles.
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>
>
>
My reason for using 5000K is for a familiar point of reference, pick a Temp
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(inside or out) that works best for you. If you use 2 - 10,000 lights and
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use one gray balance what might happen. What you are suggesting is that all
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the light is mix together creating one environment (bucket). One gray
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reference point (card, round ball, or what ever) strategically lit and
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placed in a well balance scene. This could happen.
Don't forget to white balance! Grey balance eliminates color cast in middle
tonal values while white balance compensates for high key color casts.
>
>
Let us take the above, except for one light source, it is not influencing
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the gray reference point, but it is in the scene. Depending on its
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strength/influence, you may see a cast because it is not represented at the
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gray reference point. The cast may even be weak and you do not care or it
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may be too strong and you do care. How do you balance the cast? The easiest
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way is to filter the light that is creating the cast, the old fashion way.
Filtering the light source is the best approach. Digi cameras are FAR more
sensitive to improperly color balanced lighting compared to gelatin silver
films -- we are talking just a couple hundred degrees. So yeah, first grab
your color meter and get the lights balanced, then white and gray balance.
>
>
The question as I took it, was a concern with color cast. Can a profile rid
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you of the cast? How do you compensate for a color cast? Let us add 3
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digital cameras producing different results. Lets add at least 2 different
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strobe manufacturers. What the heck lets just mix them at any give moment.
That's not the role of an input profile. The input profile should not
COMPENSATE for color casts or exposure! Each camera I can guarantee (from
experience) will have slightly differing color rendering qualities. You will
need to create separate input profile for each camera!
>
>
As far as creating a profile for every environment: I do not think it I so
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silly. It is not always necessary. Sometimes one good general profile will
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do what you need it to do. Like anything else, you need to pay attention
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what you are doing when creating profiles (all). You are likely to get a
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reflection in "just about" any environment.
True this is why shooting the chart is absolutely critical. As Jack has
stated earlier most of users problems in creating useable input profiles
stems from improper lighting, approach, and camera settings. Heh, no one
said this would be easy!
Sometimes you may want a solid
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reference point, not to profile, but to get the best gray balance possible.
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There are times when you want an evening lit cast; a gray balance would
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color correct the evening cast to a neutral.
Integrated Color's ColorEyes DCAM has a nifty gray balance card designed
exactly for these occasions. Basically there are gray swatches with color
bias. So you can gray balance but retain a little, more, or a lot of the
color cast but still be able to CALIBRATE the camera in that lighting. Jack
will fill us in on how and why.
However, if you are using a
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strobe as your main under the same evening light you may want to gray
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balance the strobe, the evening light in the background will still be as it
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is.
Now things get tricky. Do you want to preserve the night sky and nullify the
strobe lights color bias? This is a good excuse of potentially NOT gray
balancing. That's fine. If you made a good camera profile you can still use
it for this situation. Why? The camera CCD sensors do not change sensitivity
based on the scene or lighting. That's why we remove exposure and lighting
from influencing the profiling process.
Do you need a profile for strobe; no, you do not. Gray balance is all
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you need. However, what if you want to optimize the color recorded from the
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strobe light and the CCD. A profile could do that. On the job this may not
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produce the best profile, but could you create a good profile for that
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strobe; yes you can, and use it when ever you wish.
>
>
And a great profile and a bad profile are used in the same manner. They both
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are at work. The craft of building a great profile depends most on the
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crafty creators capability to cook. A good cook will tell you it is all in
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the preparation.
Ain't that the truth!
>
>
Now you can create a profile with the "whatever" light source before hand in
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a wonderfully control environment. Then use the profile time and time again,
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no matter where you are doing. This is now called a "general profile". And
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most manufacturers provide general profiles that are created in controlled
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environments (I would think). So why profile any camera, why all you have
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to do is gray balance. In addition, you do not need to color correct for
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cast or contrast, etc.
Good question. The *canned* profiles that come from any manufacturer either
printer or camera do not provide instructions on HOW TO CALIBRATE back to
THEIR standard which they created the profile. If you can't calibrate back
to their standard then you may not predictable results. Also Canned
profiles do not really represent what your camera/optic combo is recording
for color. So a custom input profile will always improve color accuracy
reducing color and tonal editing in Photoshop.
P.S. Without exception, most printer and camera generic profiles are
absolutely hideous. Plot them in any 3D grapher like ColorThink and you'll
be surprised the garbage you'll see with strange color volumes. A good
camera profile is smooth and doesn't have weird spikes and truncated color.
--
Dan B. Reid
RENAISSANCE PHOTOGRAPHIC IMAGING
Color Imaging Solutions Provider
http://www.rpimaging.com | email@hidden
Toll Free: (866) RGB-CMYK [ 866-742-2695 ]
Local: (505) 471-4126
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