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Mark Mark,
A simple question, did you try the test I suggested
in an HONEST way? No! You said it yourself below.
By the way, your correction below is still, lets
say inexact:
"Editing a 16 bit file will leave a rich file that when
converted to 8 bit mode for printing has no gaps in THE
HISTOGRAM...."
Editing a 16
bit file will leave a rich file that when converted to 8 bit mode for printing
has no VISIBLE gaps in THE HISTOGRAM....
It is not because you don't see something it is not
there.
Human nature surprises me almost every day, must be in our
genes. We are so conservative that it makes us almost blind and deaf to all new
ideas. Look at history it's full of example and it's still goes on even
today.
The test you propose below proves nothing new, it is
design to fail from the start and it as nothing, absolutely nothing to do with
real world image and real world editing. This is what I mean with what I said
above, people listen to you (more or less) because you wrote a book and you say
what everyone expect you to say, they could even have respect for you I don't
know. When you propose things like below people say He! He! he got him now,
come on, it may surprise you but I have respect for you, you worked a lot and
you broth something usefull to the community and that as merits. But I know some
people here wont take the time to verify if what you said is meaningful or not
and they'll think what you said is as good as money in the
bank.
I even said it myself, with the test I proposed it is EASY
to make it fail, just do what you suggest at #3 below and it wont work. I was
septic as well untill I did the test HONESTLY not to make it fail,
this is to easy, but out of curiosity, this is also in our genes. You can even
write to me offlist, I promise I wont tell anyone how surprised you
where.
Happy Holidays to you and your family and to
all.
Yves
----- Original Message -----
Sent: Tuesday, December 18, 2007 10:37
PM
Subject: Re: OT: 16 bit editing myth or
reality?
Yves,
My reference below to tonality when
converting a 16 bit file to 8 bit should have read
"Editing a 16 bit file will
leave a rich file that when converted to 8 bit mode for printing has no gaps
in THE HISTOGRAM...."
Instead of
"Editing a 16 bit file will leave a
rich file that when converted to 8 bit mode for printing has no gaps in
TONE...."
Since there would certainly be 16 bit tones that would have
to be dropped in order to convert the file to 8 bits.
Sorry if you
interpreted the my reference to Ryuji's statement that working in 16 bit is a
"no-brainer" to implying that you were "a brainless whatever"—it's just
a figure of speech and not intended to be a reference to your
intelligence—besides how would I know how intelligent you are—I've never met
you.
I did say that I thought that if you wished to conduct some sort
of experiment in Photoshop and report the results to the list that I would be
interested in what you found.
In the mean time, I have Christmas
shopping to do! I don't need to do any experiments to know that working
in 16 bit is better, did those long ago—sorry!
Ok, here is a fun one I
did years ago to test Photoshop & 16 bit—and you don't even have to edit
your heart out—or any other organ you value:
1. Make a 16 bit
color file that is about 10 pixels high and 30,000 pixels long (Max Photoshop
will do in length). Fill it with a gradient fill from 0 to 255 (black to
white).
2. Duplicate the file and convert it to 8
bit.
3. Apply a Levels Adjustment to both files, bringing the
OUTPUT WHITE POINT SLIDER down from 255 to 20.
4. Now for Yves
sake, make the 16 bit file an 8 bit file
5. To make sure there
is no cache funny stuff happening, close both files and reopen
them.
6. Examine the histograms of both files (hint: the one that
looks like 20 toothpicks marching is the 8 bit file that had the levels
adjustment applied to it in 8 bit mode)
7. If you want, print out
the two gradients, view them from across the room and see if you can tell one
from the other... the one that looks like a 21 step tablet is the 8 bit file
that had the levels adjustment applied in 8 bit mode.
Happy Holidays
All !
Mark
Nelson
Precision Digital Negatives -
The System
PDNPrint
Forum at Yahoo Groups
www.MarkINelsonPhoto.com
In a message dated
12/18/07 5:01:30 PM, gauvreau-yves@cgocable.ca writes:
Mark,
I'm sorry to say this but the second
phrase you wrote below is not true in the strict sence of words. In
fact it's practically sure there will still be gaps in 16 bit edited file,
I'll admit they could and probably will be much less then it would
have if all editing had been done in 8 bit, I have no problem with
that, my first message is the proof of that.
Comparing me to a
brainless whatever doesn't proove that I'm wrong. Have you tried the little
experiment I suggested, it will take you less then 10 minutes? In case it's
already in the waste basket here it is again.
Find yourself a hi bit
color image, one your sure it as more then 8 bit depth (as you said yourself
below, some claims of hi bit depth can be deciving). Make a copy of it and
convert the copy to 8 bit, to make sure PS doesn't just put a tag on the
image and keep the hi bit values in memory, save the copy, close it and
reload it. Now you are sure you have both an 8 bit and a hi bit image to
work with. For the effect to be more convincing I suggest you don't use any
form of random editing or one you can't repeat exactly on both image, in
principle a random process (gaussian stuff) can not be repeated twice
and for the effect to be more evident I recommend not to use them for
now.
Now you can edit your heart out on
both image as long as you do the "exact" same thing on both image I also
suggest you be reasonable, do as you would in a normal situation, it would
be easy to do things to fool the test but you wouldn't normaly do this
in your usual workflow, when your done convert the hi bit image to 8
bit and just to make sure you truly have an 8 bit image, save it, close
it and reload it.
Next, click on image->apply
image... choose substract and set the offset to 128, click ok (don't forget
to select the other image).
Now at what magnification do you
begin to see some difference in levels in your test image? (I wasn't able to
see anything until I was at 200% mag with carefully chosen edits and at 100%
with some carelessness and I'm an old guy my vision is not that of a
teenager at its prime)
You can also look at the histogram
which will give you some data you could use to evaluate the test. If you
applied the exact same editing steps to both images and no random steps, the
histogram will tell you something like this, the vast majority of the
millions of pixels in the resulting image are at or very near 128 (A - B = 0
+ 128 = 128) and within 3 to 5 levels (more or less depending on how
carefull you where) on each side there will probably be nothing to
see.
There are some small different
between the images which implies there is probably a difference in both type
of editing, the histogram prooves that but where the edits the exact same?
Now these relatively small difference are spread all over the area of the
test image and if you where to view the two final image side by side you
probably couldn't see any of these difference on your monitor unless of
course you know where to look for or if you magnify to the sky.
Now lets raise the bet sort of
speak, lets print those 2 images at whatever size you like, I ask you only
one thing, view them at the recommended distance based on their size,
fair enough, ask anybody around you to compare the two image and ask them to
tell you which one was edited in hi bit mode or which one looks
better if you which, if the results of doing this test with a couple dozen
of people differ significantly from using a coin flip to decide which one
was edited in hi bit, I'll buy your book, just to say it's not a
bet.
Lets come back to the real world for
a minute, above I asked you not to use random editing because you can't do
the same exact edit twice. In the real world it would be almost impossible
to edit two image in the exact same fashion (which probably happened
already above), we have these random edits and we also have local edits
and whatever else you can think of that are quasi impossible to do
twice exactly the same way. In the test above I tried to elimimate these as
much as possible to reduce the difference to its minimum. In real life it
would be surprising someone would loose his time to do this but lets say one
those (any normal edits), the only difference would be a wider histogram and
then you could say Ha! Ha! I told you so. It happen I did it, yes, so I
know and the difference are still very hard to see at 200%
magnification on the actual images on the screen, I wasn't able to see
them but don't take my word for it, try it yourself (which is probably
what you did already).
By the way, have you or anyone else
for that matter, thought that converting a 16 (15) bit image to an 8 bit one
mean a compression of at least a 100 to 1, it's impossible not to
loose quite a bit in the process, just remember that.
Happy holidays
Yves
PS For the others on this list, I
wont buy your stuff but I defy you to "proove" what you say with facts (not
just words) and thus proove me wrong at the same time.
----- Original
Message -----
From:
Ender100@aol.com
To:
alt-photo-process-l@usask.ca
Sent: Tuesday, December 18, 2007 1:31
PM
Subject: Re: OT: 16 bit editing myth or
reality?
Yves,
It is true that most printers currently
print in 8 bit mode and even if you send a 16 bit file to them, the file is
converted to 8 bit mode—HOWEVER...
Editing a 16 bit file will leave a
rich file that when converted to 8 bit mode for printing has no gaps in
tone....
Editing in 8 bit mode will leave gaps that will still be
there when printed, possibly causing posterization.
As Ryuji stated,
this issue is really a "no-brainer" and has been considered such for years
by the experts. I'm not sure what your point is other than maybe
setting up a model to illustrate what the actual final difference is in
tonal richness for the same file in both 8 bit & 16 bit mode when given
the same adjustment. If you can come up with a model that would
demonstrate it, it would be interesting to know, but it won't change the
reality that 16 bit files are superior.
By the way, supposedly the
newest Epson printers working with Mac Leopard will be able to make "16 bit"
prints as soon as Epson releases the drivers to do so. Also one of the
other printer manufacturers has a plugin that is supposed to give around 14
bit prints......so the 8 bits/printer thing may soon be a thing of the
past.
Another side note, a custom scanning house of "good reputation"
was making drum scans for people that were supposedly 16 bit drum scans....
in fact, they were scanning in 8 bit because that was all their drum scanner
would do, then converting them to 16 bit and sending them out. This
is, however, rather easy to detect. Of course they were charging extra for
their "16 bit scans".
Happy Holidays,
Mark
Nelson
Precision Digital Negatives
- The System
PDNPrint Forum at Yahoo
Groups
www.MarkINelsonPhoto.com
In a message dated
12/18/07 12:18:13 PM, gauvreau-yves@cgocable.ca
writes:
All this above is true while in hi bit mode but the
question is what happen to these extra bits when you need to print the image
knowing the majority of consumer printers out there are 8 bit printers? The
simple answer is, they go back to the black hole they came from. The true
benefit of editing in hi bit mode is so small, it is for all practical
purpose insignificant on actual prints but I'll give you this it looks much
better while in this hi bit mode.
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