U of S | Mailing List Archive | alt-photo-process-l | Re: OT: 16 bit editing myth or reality?

Re: OT: 16 bit editing myth or reality?


At first one would say you are right but with digital imaging we are stuck
with 8 bit integers when printing our images and at first it doesn't seem
much, With a limited number of levels this can cause the famous stair case
effect. Some have said in previous reply that we can see up to 7 bits, that
means we can not see the difference in two consecutive levels of 1 in 128
(2^7 bit) or smaller but this is an average and means some people can do
better then that and some do worst. With 8 bit we can create 256 levels and
the difference is now 1 in 256. This implies that the vast majority of
humans if not all of them will see such an image as continuous tone. In
other words, we can see the steps they are way to small.

Now with application such as Photoshop we can work with 8 bit or 16 (15) bit
integers while inside the appication and even on disk but our printer system
forces us to convert our work into 8 bit integer because until recently they
use only 8 bit integers. The argument in this topic is about this needed
conversion to 8 bit and what it implies. If you look at the histogram of an
image edited in 8 bit mode there will most likely be holes or empty bins in
the histogram, this implies the step or the difference between to
consecutive an available level to becomes larger and thus it will become
visible to us. If you do your editing in 16 bit mode the steps are so small
you can loose quite a few before it becomes visible to us. This is true and
I think no one here is saying it's not true, including me.

My argument is that these nice looking images (16 bits) and histograms have
to be converted back to 8 bit before we send them to the printer either
explicitely or implicitely. I would think that up to now no one would say
otherwise with the exception of the newer hi bit printers.

What I basically say is this, if you take a normal multi megapixels image
and edit it such that it looks good in either 8 bit or 16 bit mode, a
"normal" human under "normal" viewing conditions wont be able to tell which
is which. I'll admit that under close scrutiny one will be able to see some
differences in both image but to say those differences where caused by 8 or
16 bit editing, that's another story.

You see I speek french and however hard I try to think in english (as one
should), when it comes to explaining conceptual stuff I just can't and it
become extremely difficult for me to find the proper words in the proper
way. The time I loose doing this, I usually loose track of what I was
thinking. This simple reply took me close to 2 hours to write believe it or
not. You can imagine I get frustated quite a lot, not at you all but at
myself and I think it shows sometime and I have to retry several time before
I get it right so the folk here can understand what I mean.

Happy Holidays

----- Original Message -----
From: "Greg Schmitz" <gws1@columbia.edu>
To: <alt-photo-process-l@usask.ca>
Sent: Wednesday, December 19, 2007 7:15 AM
Subject: Re: OT: 16 bit editing myth or reality?

> Seems to me that analog (a negative, a light source, and a lens) would
> solve the problem hands down - no fuss, no muss.  "Old school" analog
> solutions do blow away (in terms of data density) 8-bit, 16-bit, or for
> that matter just about any quantity of bits available at present.  With
> analog, None of this would be necessary, we could argue about grain size.
> Just my .02; for now.
> Ludites unite now!  If it's the final image that counts - kill your
> computer ;)
> Best --greg
> P.S. Just started reading Oliver's book on Woodburytype (one of my
> favorite processes).  Would you care to work out the pressure requirements
> for my new stamping press?
> On Wed, 19 Dec 2007, Yves Gauvreau wrote:
> > 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 worke
> d 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
> >