This is an appendix to my three posts on the 8-bit vs.16-bit editing issue.
Much of my post is critical of those who insist that 16-bit editing is of
paramount importance yet decline to show any real-world images where
there is any indication that editing in 16-bit is better. I am posting here
extensive excerpts of what they say in their own defense as to why they do
not.

Before turning it over to them, I have only one remark. These individuals have
argued that editing in 16-bit is "extremely critical", that it is "the difference
between professional and recreational users of Photoshop", that doing so
results in "a night and day difference" that is "totally obvious to anyone who
looks".

If anything even remotely close to that were true, a demonstration could be
made of it almost instantaneously. For example, if I had to argue for why
gradients should be created and edited in 16-bit and not 8-bit, I could create a
convincing example showing why in less than ten minutes. Both of the
invididuals quoted here spend a great deal of time in on-line groups. They
have each, conservatively, spent tens of hours, possibly more than a hundred
apiece, explaining why they are too busy to take these ten minutes.

Dan Margulis

********************
Note: Jeff Schewe, one of the posters here, often uses ellipses (. . .) in his
messages. Where these appear, they are in Jeff's original and do not
represent deletions. Some extraneous paragraphs have been deleted from
the beginnings and ends of messages, but there is no editing of the text.

Jeff Schewe - 10:32pm Aug 5, 2001 Pacific
I have no interest in "Educating Dan". That's his job. Dan is right about a lot
and wrong about a lot. It's very easy to see that substantial color & tone
editing will eventually result in data loss and banding. A lot of people have
banding problems, very few people know when and where that banding
occurs, but it's due to the fact that editing 8 bit files causes the banding.

If you start with an 8 bit file and do tone and color adjustments, you lose
levels. . .maybe only a few. But, combined with data loss due to rounding
errors running filters, rounding errors due to layer blending, errors due to re-
brushing all accumulate to eventually produce enough loss of data from the
orriginal that eventually you get banding.

But. . .I have no interest in debating Dan's position on the value of 16 bit
editing. . .I prove him wrong every day. If he wants to pay me to come teach
him the value of 16 bit editing, I'll be happy to. . .but I'm certainly not going to
do his job for him for free <BG>.

He asked me to prove it to him. . .I declined. If he wants to take one of my
classes, he's welcome to. . .I'll give him a discount. . .

User 1 - 11:53am Aug 9, 2001 Pacific
Jeff, I will address you here, but my point really goes out to all. Please don't
take it personally.

Regarding Margulis' challenge Jeff writes: "He asked me to prove it to him.
. .I declined. If he wants to take one of my classes, he's welcome to. . .I'll give
him a discount. . . "

While I appreciate your humor here, I am mystified as to why you (and
others who feel as confident as you in the matter) decline his challenge...
Taking Dan's challenge would be to our benefit, not Dan's

Here is a sampling of Dan's challenge to you:
"…. I have for several years asked here and elsewhere for those who
advocate these methods if they might not be able to provide me, say, two or
three sample original high-bit images, with a record of what moves were
applied to them, so that I could verify that there is a quality gain, however
slight, in applying them to a 16-bit image as opposed to an 8-bit one.
Since I have been making this request, what I have received is a large
number of histograms purporting to prove that 16-bit is better, a large number
of assurances that '16-bit has worked better for me', and a large number of
excuses for why the images in which it has worked better are either
unavailable or under NDA. As time has gone on I have grown to suspect that
perhaps the reason no one can supply such images is that there are no such
images to supply.
Can you help me out? If you or anyone else can supply such example
images and they really demonstrate the merit of working in 16-bit, I'll be glad
to let this list know and if the differences are significant I'll print them in my
column at a size large enough for people to see. If you or anyone else has
such images, just let me know and I'll give you shipping instructions."

To my mind Dan is being very fair in the matter, while those who decline
his challenge prove his accusations right, even if his assumptions about bit
depth may be wrong. He is certainly in the minority opinion on the subject, yet
he is the only one to my knowledge who is willing to back up his assertions
with examples. Why not back up your declarations to the degree that Dan is
willing to back up his?

Jeff Schewe - 08:16pm Aug 9, 2001 Pacific
I know Dan pretty well. . .I have ZERO interest in being a subject of an
upcoming article (I feel one coming from Dan) where he can takes what Bruce
or I may say about 16 bit and twist it around. Suffice it to say that remaining
under Dan's radar is far more comfortable <BG>

In the old days (before learning the value of editing in 16 bit) I suffered from
slight to severe banding on transparency and CMYK output. since switching
to the 16 bit appraoch, I no longer get banding. . .that's all the proof I need. I
have no need to "prove it to Dan". Sorry. . .I say what I say. . .I'm willing to
spend time teaching how to work in 16 bit (and do things the engineers never
dreamed of), but I have zero interest in proving anything to ol' Danny boy. . .

I doubt Dan has ever seriously manipulated an image or done a 6 element
assembly. I seriously doubt that Dan is after the most suprime high end
quality. . .even if it's only marginally better. . .but working in 16 bit is seriously
a better habit leading to better quality in the end. . .which is all I care about.

P.S. ask Dan about copyrights some time. . .he's got his head firmly lodged
up an oriface about that as well <BG>.

User 1 - 09:53pm Aug 9, 2001 Pacific
Jeff,
Well, I hear ya, but…….
I was just hoping that someone would prove the point in the material world,
rather than theoretically, or anecdotally. Somehow this has become about
Dan Margulis the man, rather than the point he makes. It's ironic that although
it's him against the world on this, he's the only one (seemingly) willing to post
evidence to support his claims. Shouldn't the benefits of a 16-bit workflow be
demonstrated anyway, regardless of the fact that Dan has issued a
challenge? Why, with all that is published about PS in print and on the web, is
such a presentation not already extant? That's just weird.

User 2 - 08:00am Aug 10, 2001 Pacific (#37 of 52) [Another 16-bit advocate]
wrote: "What do you want someone to do? Prepare a costly print run or film
recorder output using both good image preparation and bad image
preparation so that you can be satisfied that we know what we're talking
about?"

Certainly not, that would be unreasonable. That's why I asked if the
difference could be seen on a monitor, and you said at 100% magnification or
higher it could.

Even so, I'm not asking that you supply images for monitor viewing. Your time
is valuable, and you have been very generous with it on this forum.

OTOH, it seems that someone who advocates a 16 bit work flow could
supply a set of files for comparison. Lots and lots and lots of time has been
spent discussing this issue, here and elsewhere, which is still unresolved in
the minds of many people, and it could so easily be put to bed by just showing
us the comparisons. Otherwise, as Rich said, it becomes tiring.

Jeff Schewe - 09:40am Aug 10, 2001 Pacific
Your points are taken. . .but proving anything is not my job. When I do notes
for classes or lectures, it takes on average about 8-12 hours to prepare them. I
do have notes on editing in 16 bit on my web site (I'm going to be changing
the url this weekend for an upcomming class but they will be in the site map),
but those are just techniques for working in 16 bit. To go through and offer
scientific "proof" is something that would require even more time-which I don't
have.

------------------------------------------------------------------------
Jeff Schewe - 05:30pm Aug 12, 2001 Pacific
All this debate is pretty typical of good old Dan. You notice he recently said
that he has not taken the position that editing 16 bit is NOT better. . .only that
he's never had anybody PROVE it to him.

I'm almost getting pissed off enough by Dan's "positioning" that I might
decide to "prove it". But I don't have a great deal of time in the next week or so,
so it would have to wait a bit.

Date: Wed, 15 May 2002 22:37:56 -0500
From: Jeff Schewe
Subject: Re: 8- and 16-bit correction
I watched, with amusement, when Dan challenged anybody to come up with a
16
bit image that could prove the benefits of editing in 16 bit over 8 bit. I
now understand there's a bounty out there of $100 if somebody can prove that
edits in 16 bit vs edits in 8 bit is superior. . .

That's a waste of time (and believe me, $100 is no incentive to me).

Fact is there is no image that can prove that one to several edits in 16 bit
vs 8 bits is better. I've never advocated editing in 16 bit merely as a
method of improving a few tone/color corrections. That's silly. The edits
done in the beginning of a tone/color correction does not cause banding. It
does indeed "spend bits" and I advocate spending your bits wisely. Where the
_REAL_ difference between 16 & 8 bit editing comes is well down the road.
Well after your original edits.

Photoshop is pure math. . .everything is numbers. Everything done in
Photoshop is the result of an algorithm. And believe me, Photoshop's
precision is not infinite. Where the benefits of original 16 bit editing
shows is down the road after doing corrections and applying a filter or two
(or dozen). Add a dozen layers with various opacities and blending modes
and
maybe a layer effect or 2. Do a gradated adjustment layer. Do any series of
extended retouching or manipulations that many image artists do every day.
Then you'll find out that at some point in the process, you've rounded
enough data and spent enough bits that the gradation between point "A" and
"B" no longer has enough bits to produce a smooth gradation of tone or
color. Guess what, you've got banding. And, guess what else, you've just
proved that _STARTING_ with your initial tone/color edits in 16 bits and
conserving your data bits to spend later in the editing process allows you
to avoid the dreaded banding.

If you scan a chrome and do a slight to moderate curve correction and
transform from RGB > CMYK, should you scan in 16 bits? Nope. If you do
slight to moderate to even substantial tone/color edits and then plan on
assembling 1/2 dozen composited images with filters, layer blending and
effects and maybe 20 hours in image manipulations, will you benefit a _LOT_
from doing your original edits in 16 bits? You bet your ass you will.

I started scanning in 16 bits because I ran into constant problems of ending
up spending hours working on an image only to find that at some point, a
tone gradation in an image banded. Once banded, there's nothing you can do
to recover the lost spent data.

My point is that if you need maximum flexibility and edit ability and you
don't want to worry about banding, start your creative retouching in a
"perfect 8 bits/channel". That only comes after doing initial tone/color
corrections in 16 bit.

Sure, you can use the scanner software to do tone/color corrections in the
scanner's high bit depth and thus benefit from 10, 12, 14 or 16 bits of
data. The big problem I have with that workflow is this. . .there ain't a
scanner on earth who's software allows you to do "local" corrections of
tone/color. Scanners don't come with the ability to put a lasso around an
area to adjust just that area. The other weak point of scanner (or camera
software for that matter) is that a scanner preview just purely isn't as
accurate as Photoshop to show exactly what the pixels look like. Scanners
give "previews" but you don't see the full resolution till _AFTER_ you've
applied the tone/color corrections during the scan. At that point if you
touch it again you won't have a full 8 bit file. . .you're spending the bits
on a wasted edit. I also think, and perhaps I'm biased, that Photoshop is
the best "pixel viewing" application on the planet. I know of no other app
that is as accurate in showing on screen, exactly how a set of pixels will
look when you output. . .either photo or halftone reproduction. So, if I
want the most accurate on screen representation of just exactly how those
pixels will look reproduced, I'm just not interested in using a scanner
software or camera capture software's interpretation of those pixels.

Nope. . .Dan and the rest of you are welcome to continue scanning in 8 bits
and doing whatever you want to do to your images. . .but if you want
absolute total control over tone and color without the risk of breaking the
image somewhere down the road. . .you better learn to edit in 16 bits.

Yes, the tools are more limited and yes the files are 2x the size. . .so?
Ram is cheap and so are hard drives these days. I've learned to edit in 16
bit to the point where even the Photoshop engineers couldn't believe how far
one can go if you're determined. You can paint (using history), you can
copy/paste (using clone between 2 16 bit documents), you can use
adjustment
layers (in an 8 bit duplicate and save out as a setting), you can use color
range in 8 bit and transfer the 8 bit selection into 16 bits for
application. You can clone and heal and run enough filters to do just about
anything you need to do to start off your imaging in the "perfect 8 bits".

And yes, I'll stand by the line "recreational" if you squander and waste
your data bits just getting an image tone/color corrected in 8 bit. . .cause
if you do that, you're working with considerably less than 8 bits/channel
and deserve the banding you are likely to incur.

Dan and others who claim 16 bit editing isn't better than 8 bit editing for
routine scanning and corrections are correct. But, I'm a photographer and
image manipulator. I choose to spend my data bits wisely because because
what I do to images isn't routine. I manipulate the heck out of images. I
choose to do all initial tone/color correction in 16 bit to avoid banding
down the road. And, personally I feel no compulsion to prove anything to
anybody except my clients that pay me a lot of money.

Regards,
Jeff Schewe
16 bit advocate and proud of it. . .

-----------------------------
Date: Fri, 15 Apr 2005 14:36:12 -0700
From: bruce fraser
The major problem with the methodology (leaving aside the minor ones)
is that by making identical edits to the 8-bit and the 16-bit, you're
throwing out any benefit the extra bits may bring. They aren't useful
unless you DO SOMETHING with them!

-----------------------------
Date: Sun, 17 Apr 2005 15:00:55 -0700
From: bruce fraser
Subject: Re: 16 bits == 15 bits in Photoshop?

At 12:39 PM -0400 4/17/05, Dan Margulis wrote:
>So, I ask if the following is a fair summary of your position:
>
>1) Bruce states that the argument has never been that identical edits applied
>to 8-bit and 16-bit files would produce better results in the 16-bit version,
>but he argues that it is possible that they might.
>
>2) Bruce has not offered up any images that would demonstrate such a
>superiority for 16-bit correction (as opposed to identical edits
>applied to 8-bit),
>but he suggests that such images might exist.
>
>3) Bruce's comments on "night and day difference" and "totally obvious to
>anyone who looks" are based on his experience and perceptions; however,
he has
>never personally tested a series of corrections done to a 16-bit
>file on a live
>image versus identical corrections done to an 8-bit one.

No, that's a when-did-you-stop-beating-your-wife characterization.

My position is very straightforward.

I proved to my own satisfaction many (>10) years ago that many of the
problems I encountered with 8-bit files-posterizaton, striped skies,
exaggerated saturation accompanying contrast moves, and unwanted hue
shifts-largely disappeared when I edited (and converted to output
space, which is a big edit) in 16-bit instead.

I seem to be far from alone in having noticed this phenomenon.

I quite sensibly decline to do all my work twice with the goal of
making half of it fail, and with the exception of beta-testing
procedures that need examples for bug reports, I don't make a habit
of saving the failures.

If someone wants to pay me my day rate to do so, I'm quite certain
that I can come up with real-world examples, but I decline to donate
my time to a foolish quest with whose premiss I'm in disagreement.

Anyone who sees no benefit to working in 16-bit space simply
shouldn't bother doing so. But they shouldn't come crying to me when
their images fall apart on output.

My personal opinion is that this is a manufactured controversy-I
decline to speculate on the motivation of those who have manufactured
it-and I'm utterly disinclined to waste my time arguing the point
when I have better things to do with it.

Date: Fri, 22 Apr 2005 01:29:17 -0500
From: Jeff Schewe
Subject: Re: 16 bits == 15 bits in Photoshop?
To: <colorsync-users@lists.apple.com>

Jim Rich said:
> It makes sense to capture everything as high bit images.Everyone seems
to
> agree on this.

> Save the high bit parent file in your archive.

> Create derivative 8 bit files from the parent file for production.

> Use Adjustment layers.

> If the 8 bit file breaks ( as they can in rare cases), then go back to
> the parent 16 bit file and use the previous Adjustment Layers.

I agree with the capture in high bit.

But I would argue that it critical than ALL MAJOR tone and color moves be
done in 16 bit. Ideally with Adjustment Layers for the simple reason that
setting black & white points (unless you do it accurately in say Camera Raw)
are the tip of the spear so to speak. Major gamma adjustments are second,
such as when you stretch one area and compress another area of the image's
histogram.

I would also argue that depending on the color space you may be in while in
16 bit, it would be a good idea, if at all possible, to do any major color
transforms while in 16 bit.

Bruce Fraser - 11:41pm Sep 16, 05 PST
If you want to work in 8 bit/channel mode, go ahead. But don't come crying
to me if your file breaks. That's really all I have to say on the subject.
OK. A little more.
Dan's "tests" are based on applying exactly the same traditional levels-
and-curves-based edits to 8-bit and 16-bit files, then looking for differences.
Those will likely be fairly hard to find. For the type of work Dan does, 8 bits/
channel is undoubtedly adequate, otherwise, being a rational person, he
wouldn't do it. Others may have different needs.

Bruce Fraser - 1:07pm Sep 19, 05 PST
I'd also suggest that you need to weigh the consequences of working in 8-
bit and finding you need 16 versus working in 16-bit and finding you only
need 8. My lack of clairvoyance is one of the factors that leads me to work in
16-bit....
I've demonstrated many times things that work better in 16-bit than in 8 bit,
but Dan has rejected these because they don't fit his narrow criterion of doing
exactly the same things to a 16-bit and an 8-bit file, then comparing the
results.

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