Re: 16 bits = 15 bits in Photoshop?
Re: 16 bits = 15 bits in Photoshop?
- Subject: Re: 16 bits = 15 bits in Photoshop?
- From: email@hidden
- Date: Sun, 17 Apr 2005 13:40:38 EDT
Marco Ugolino writes,
>>This reminds me of the famous joke by Richard Pryor, the one in which a
woman catches her husband in flagrante delicto, engaged in carnal congress
with another woman. The husband promptly jumps out of bed, and then
self-righteously addresses his wife thusly: "I didn't do anything! Who are
you going to believe? Me or your lying eyes?">>
I have to respond for fear of being accused of lifting material from this
group. The Richard Pryor line is my standard response in large group sessions
when people ask me to show histograms. I've used it for years.
>>But Mr. Margulis is a canny sophist, a man of rare verbal skills, and tries
to convince us that our lying eyes cannot be trusted.>>
Lying eyes cannot be trusted to honestly evaluate neutral colors displayed on
a monitor. With that single exception, there is no one in this industry who
is remotely as associated with the concept of using one's lying eyes as I am.
Bruce Fraser and I have had this friendly on-line spar for about ten years now,
and invariably I'm on the side of the lying eyes and he is defending some
specious mathematical notion. Consultants who frequent this list have a long
record of attacking me for saying that calibration is best accomplished by making
more use of the lying eyes and less use of instrumentation.
In this case, *I* am the one who is saying to trust the lying eyes, along
with Jim Rich. I show in my book picture after picture, not at postage-stamp size
but at quarter-page or larger. Then I blow them up to as much as 1,000%
magnification to see if there is any degradation. Then I show individual channels
at high magnification as well. The corrections are often massive and the
pictures are of every type. And I invite the readers to use their own lying eyes to
determine whether there is any qualitative difference of any significance
between the 8-bit and 16-bit versions, and I put copies of the digital files on
the book's CD so that the reader can verify that the results haven't been
jiggered.
By contrast, those who say there's an advantage rely on histograms, and--as
in your case--pure faith. If I may summarize the logic of yourself, Bruce, and
Gariba (who I contacted off line, and found he had never tested anything
either):
1. I personally work in 16-bit.
2. I am satisfied with the results.
3. I do not see any of the defects that I believe would be there if I used
8-bit.
4. Therefore, 16-bit is clearly better.
This approach does *not* employe the lying eyes. It uses the imagination,
which is much more mendacious. Your, and Bruce's and Gariba's, comparison is not
between two competing images, which your lying eyes could make for you. It is
between your own image and an *imaginary* bad picture that your mind has
concocted for you.
That nasty imagination is also the main obstacle photographers have in
learning image manipulation. You say that your corrected images are good, and I know
Gariba feels the same way. And very possibly they *are* good. But it's also
entirely possible that they aren't good at all. Your lying eyes have only the
original, uncorrected version to refer to in comparison to your own work. It's
possible that somebody else could have done a much better job, producing an
image that was incontestably preferable in every way. If you saw such a thing,
then your lying eyes would immediately tell you that it was better. But you
can't imagine it.
Photographers have it much worse in this respect than others, because they
generally are in a solo environment that doesn't permit them to compare their
work to what somebody else might have done with the same file. This is conducive
to developing a lot of bad habits.
I get to work closely with 30 or 40 professional photographers per year in my
classes, where their work gets compared to that of others. That's where the
lying eyes come in. It's unusual for photographers, even world-renowned ones,
to be in the top half of a mixed group at the outset. It's *not* at all unusual
for them to come in *thinking* that their work will be much better than
anyone else's. And then we get to see some world-renowned photographer with his
mouth open when the work is compared, and his own lying eyes tell him that
somebody with only six months experience with Photoshop produced a much better
result than he did.
By the end of the three days, the photographers usually are at the top of the
group, as their greater experience and better judgment come to the fore. But
first, they have to open their lying eyes to see how to eliminate the little
sloppinesses that their imagination tells them are unimportant.
In the image I was discussing with Bruce, he made what appears to be a very
trivial error--he mis-set his highlight slightly in one of the images. It's
hard to see in the picture and it's hard to see in the histogram. And because the
picture looks reasonably good in isolation, he can't imagine that the mistake
has a serious impact, any more than he can imagine that his 16-bit
corrections would have looked just as good if he had done them in 8-bit. It's a very
common mistake among photographers, because their imaginations allow them to
ignore the conventional wisdom that blowing off the highlight is a serious mistake.
Fortunately, their lying eyes will convince them to mend their ways--provided
that they have some other, better images to compare their own to. Having our
own mistakes exposed is the only way to get better. That's how I learned color
correction, and that's how I continue to get better--I'm sitting there with
what I'm positive is going to be the best image in the room, and pow, somebody
with much less experience comes up with something obviously better. And then I
go forth and lick my wounds and figure out how it happened.
Assuming on faith that 16-bit is better is just as bad as me assuming on
faith that my color corrections are always best. We both need our lying eyes to
tell us whether we were right or not, and for them to do that, we have to have a
real image to compare to, not something our imaginations conjure up.
Dan Margulis
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