Graphics Programs Reference
In-Depth Information
have undergone no change whatsoever, simply picking the right
profile makes a huge improvement. Click
OK
to assign this
profile to the
Kodak_660_Linear.tif
document.
The truth is, this original untagged image was produced on a Kodak 660
digital camera in what is known as Linear capture mode. There is no tone
curve but rather a linear, data capture of this image. After the image was
produced, I built a custom ICC profile to describe this unique capture
behavior. When you assigned this
Kodak_660_Linear.icc
input profile,
the color appearance is fine.
This illustrates several important points. First, while the image looked
grossly under-exposed, it appeared that way only because the actual data
was untagged and Photoshop was using the incorrect RGB working space
as a guess for the definition of the numbers. This guess was a mile off
and in fact, every guess you made in step 2 was equally wrong. The data
is fine and pristine. It appears too dark simply because no embedded
profile informed Photoshop how to preview the data properly. By simply
assigning the correct profile, you produced what looks like a correction
but in fact, no pixels underwent any alterations. This illustrates how an
image can appear to be very over- or underexposed, or have an awful
color cast when in fact the data is fine but the incorrect color manage-
ment, in this case an untagged document, can fool Photoshop and the
user. No amount of color or tone corrections using Photoshop's tool set
would produce the color appearance you saw by simply assigning the
correct profile to the document. In addition, this correction, if we can
even call it that, took a mere second to produce and did not cause any
data loss in the image since we never altered the pixel data.
Now that the image appears correct and has the correct input profile
assigned, we will examine the effect of conversion into a working space.
Notice that the Histogram still shows all the data bunched up toward
one end.
1.
Choose
Image-Mode-Convert to Profile
in Photoshop CS or
Edit-Convert to Profile
in CS2 as seen in Fig. 9-7-3.
From the
Profile
pop-up menu, select
Adobe RGB (1998)
.
From the
Engine
pop-up menu, select
Adobe ACE
.
From the
Intent
pop-up menu, select
Relative Colorimetric
.
Have
Use Black Point Compensation
and
Use Dither
check
boxes on.
Be sure the
Preview
check box is on.
Click
OK
.
2.
Examine the Histogram and notice that by converting from the
correct source profile into our working space, the data is now
spread out. This is normal and expected behavior since the
working space gamma is not linear like the original capture.
Note that had we not assigned the correct input profile for this
