correct colors

  • Thread starter Thread starter kjk
  • Start date Start date
K

kjk

Hi Folks,

Does anybody know of the existence of a flatbed photo and slide
scanner which can capture correct colors and brightness,
automatically, every time, without my having to correct them? Any
advice would be much appreciated. Thanks.

Ken
 
kjk said:
Hi Folks,

Does anybody know of the existence of a flatbed photo and slide
scanner which can capture correct colors and brightness,
automatically, every time, without my having to correct them? Any
advice would be much appreciated. Thanks.

Ken
Click to expand...


Most slide software have automatic settings. My slide scanner software has
auto-gamma and auto white point. When I scan using Digital ROC (part of
Digital ICE3) my colors are pretty well corrected.

I think you probably already have the auto features, but you need to check
the settings on your scanner software. You are probably scanning with the
auto features turned off.
 
Even if your scanner captured colors accurately how would you know if they
were accurate if your monitor was not calibrated?
 
You are correct. Accurate was the wrong word. Let me rephrase that :
Does anybody know of the existence of a flatbed photo and
slide scanner which can capture consistent colors and
brightness, automatically, every time, without my having
to correct them?
Click to expand...

Depending upon the makeup of the picture, colors seem to sometimes be
shifted in one way and other times in another way. If it was
consistent, one could set up an adjustment in the scanner software
which would work the same way in each picture, like a simple color
profile, but that doesn't seem to be true.

Try scanning a typical color photo, a grayscale photo (which we
commonly refer to as black & white), and an old sepia photo, and see
if the automatic results are consistent for all three.

This became important to me because I've been trying to create a
digital archive of old family photos, capturing each one way they
exist today, instead of trying to make each one look as good as
possible. If I later find that my monitor wasn't accurate, I could
then use a macro to apply the same adjustment to every picture.
 
This became important to me because I've been trying to create a
digital archive of old family photos, capturing each one way they
exist today, instead of trying to make each one look as good as
possible. If I later find that my monitor wasn't accurate, I could
then use a macro to apply the same adjustment to every picture.
Click to expand...


Find a setting that captures the histograms of all
three color channels with no clipping. Use that
setting and make sure you scan in 16-bits per color
and save the images as 16-bit TIFs.

That will give you images that can be processed
eight-ways-till-Sunday later on. They may look
flat and off-color, but you can be sure you've
captured all the image data, to the best of the
scanner's ability.


rafe b
www.terrapinphoto.com
 
Thanks. What you suggest is just about what I've been doing. This
approach, however, will require some time editing each picture to get
the color and brightness to match the original print as closely as
possible. With my initial query I was hoping that somebody would know
of a scanner that would actually give me the pictures the way they
really look. Based upon the lack of specific suggestions, I guess I'm
dreaming the impossible dream.

Ken

-------------------------------------
 
Your slide's perceived color is dependent upon your viewing light
source and personal factors such as your "opinion" about what you're
seeing (which will distort your visual judgement). As well, reflective
color (prints), slides, and monitors are inherently not capable of
being "correct" when compared to each other, they are inherently seen
differently...what we do, when we decide there's a match, is make a
compromise, accept approximation.

"The way they really look" is a notion that has value ranging from
"some" to "none", depending upon your personal honesty with yourself
about what you're seeing (people usually impose ideas on images), the
personal visual skills that you've learned (scanning requires personal
skill), and the viewing setup that you're employing.
 
If you assume that it's not possible to objectively perceive colors,
then the whole discussion of perceived color is pure fantasy . . .
which may be true.

If, however, I do a color scan of a grayscale print and Photoshop's
Info Palette tells me that the result has a green color cast, that's
not fantasy.

If I then do a color scan of another grayscale print, with a different
distribution of grays, and Photoshop tells me that the result has been
shifted a different amount toward the green . . . that's
inconsistency. To me, that indicates not just a color profile issue,
but that the scanner and/or software is giving me what it thinks the
color should be, instead of what it really is.

Does anybody out there know of a scanner/software combination that
will produce consistent results with every picture (even if the result
is wrong) which can then be reliably adjusted by applying the same
correction to every scan?

-------------------------------
 
kjk said:
If you assume that it's not possible to objectively perceive colors,
then the whole discussion of perceived color is pure fantasy . . .
which may be true.

If, however, I do a color scan of a grayscale print and Photoshop's
Info Palette tells me that the result has a green color cast, that's
not fantasy.

If I then do a color scan of another grayscale print, with a different
distribution of grays, and Photoshop tells me that the result has been
shifted a different amount toward the green . . . that's
inconsistency. To me, that indicates not just a color profile issue,
but that the scanner and/or software is giving me what it thinks the
color should be, instead of what it really is.

Does anybody out there know of a scanner/software combination that
will produce consistent results with every picture (even if the result
is wrong) which can then be reliably adjusted by applying the same
correction to every scan?
Click to expand...
You're asking the scanner to produce accurate, balanced images without
any reference to go on.

Just what reference does the scanner have? Only the image that you're
scanning, and no other. It's possible to calibrate a scanner in the
same manner as one calibrates a monitor or a printer, by making an ICC
profile. Then, at least the scanner can reproduce what it sees on the
platen - provided the spectral characteristics of the image you want to
scan is the same as the calibrated image you made the profile with.

Otherwise, how does the scanner know what it's looking at? It cannot,
all it can do is use data such as black point and white point to align
the ends of the histograms for each primary color. That says nothing
about intermediate tones, or whether the scanned image has an inherent
color cast, or even whether the spectral characteristics of the source
image colors match the scanner filters.

A case in point is with so-called black and white images. Is the image
printed with true monochromatic ink, or with a three-color printer
mixing CMY colors to make a 'visual' gray? The scanner's response to
true mono ink will be different to a CMY gray image, depending on the
spectral components of the visual gray. A true gray will have the same
appearance in different lights, a metameric gray from CMY inks will look
different in different light - and the scanner lamp has a different
spectral distribution to daylight, so what your eye sees is not what the
scanner sees.

In a nutshell, I think your expectations are somewhat unrealistic.

Colin D.
 
Let's say that I take a number of different color pictures using the
same digital camera, and I then print each of these pictures using a
black toner laser printer. When I scan these laser prints . . .

1) Why wouldn't the scanner produce a result with equal R, G, and B
values throughout the image?

2) If it doesn't produce equal values, why wouldn't it give me the
exact same color cast in each picture? For example, G 10 points
higher than R & B throughout.

If it was consistent, an adjustment in the scanner software would
solve the problem, and then it would scan every picture consistently,
regardless of whether the original was grayscale, sepia, or full
color. I haven't found this to be true. The color shift varies
depending upon the coloring of the original.

--------------------------
 
kjk said:
Let's say that I take a number of different color pictures using the
same digital camera, and I then print each of these pictures using a
black toner laser printer. When I scan these laser prints . . .

1) Why wouldn't the scanner produce a result with equal R, G, and B
values throughout the image?
Click to expand...

With monochrome prints done on a regular (non-color) laser printer, I
would expect the scanner to produce consistent results from different
images, provided they were all printed on the same type of paper. The
spectral characteristics of the paper used can alter the scanner response.
2) If it doesn't produce equal values, why wouldn't it give me the
exact same color cast in each picture? For example, G 10 points
higher than R & B throughout.
Click to expand...

With monochrome images as above, it should. Note if the paper size is
not as big as the scanner lid, and there is a difference between the
spectral characteristics of the paper and the white lid, the scanner
response may vary.
If it was consistent, an adjustment in the scanner software would
solve the problem, and then it would scan every picture consistently,
regardless of whether the original was grayscale, sepia, or full
color. I haven't found this to be true. The color shift varies
depending upon the coloring of the original.
Click to expand...

Unfortunately, no. A good match for a gray-scale print doesn't
necessarily guarantee a good match for color. The spectral output from
the scanner lamp, and the match - or mismatch - between the dye or ink
spectra and the filters in the scanner all contribute to inaccurate
color. This is why an ICC profile is required for accurate matching.
An ICC profile is basically a look-up table (lut) that converts the
pixel color in the image to the required pixel color in the output image
correcting for inaccuracies in the scanner response.

Google for ICC profiles for more info.
 
Tell me if I have this right. The scanner doesn't accurately scan
colors, and the inaccuracy is different for different colors, so it's
inconsistent, is that right?

If so, I can understand that an ICC profile is necessary to convert
the results before they are sent to a monitor or printer, but
shouldn't the scanner software contain its own ICC profile to correct
the scans to be at least consistently inaccurate? That would allow
for the possibility of manually adjusting the the monitor controls and
the printer software to make the images look visually very close to
the original.

-------------------------
 
kjk said:
Tell me if I have this right. The scanner doesn't accurately scan
colors, and the inaccuracy is different for different colors, so it's
inconsistent, is that right?
If so, I can understand that an ICC profile is necessary to convert
the results before they are sent to a monitor or printer, but
shouldn't the scanner software contain its own ICC profile to correct
the scans to be at least consistently inaccurate?
Click to expand...
It's not the scanner's fault. Prints, negatives and slides have quite
different characteristics. If you scanner has a Kodachrome mode or a
slide mode, you're getting tweaked settings to compensate for known
charateristics of different media. I only know my scanner but it does
come with its own ICC profile for slides (works okay but the TWAIN
scanner driver gives little control).

You can do this yourself by scanning a IT8 print or slide, or shooting
a greycard/whitecard on negative film. As these changes are
software-based (exception: Nikon analog gain), you could make your own
levels or curves presets in Photoshop to give you a consistent starting
point for the materials you work with from your scanner. It's what I
do and the scans are quite consistent from scan to scan.

That would allow
for the possibility of manually adjusting the the monitor controls and
the printer software to make the images look visually very close to
the original.
Click to expand...

With a profiled scanner, monitor and printer you should have pretty
consistent color. However consistent may not be the goal as what's
attractive on a slide might not look so great on a reflective print
without tweaking.

Roger
 
Thank you jeremy, bmoag, rafe b, Djon, Colin_D, and Roger S. for your
comments in this thread. What I was looking for apparently doesn't
exist, but I learned a lot in the process.

Ken
 
There is a thing called 'Color Management'.

Color Management is a system of calibrated scanner, monitor and printer. In
the complete system, the final output is a controlled environment of color
that closely matches the original document within the limits of the system.

Being that scanners and printers are non-linear devices, you can not get
perfect color reproduction, but you can get a visual representation of what
looks pretty darn close.

http://en.wikipedia.org/wiki/Color_management
 
Back
Top