Re: 16 bits = 15 bits in Photoshop?
Re: 16 bits = 15 bits in Photoshop?
- Subject: Re: 16 bits = 15 bits in Photoshop?
- From: Robin Myers <email@hidden>
- Date: Tue, 19 Apr 2005 22:03:27 -0700
On 19 Apr 2005, at 20:36, Ray Maxwell wrote:
Hi Graeme,
I said exactly the same thing about 40 messages back on this thread.
I agree that this is the reason that we have a difference of opinion
expressed on
this subject. Very few people have seen real photographic images that
have a
low enough noise level to see the difference between 16 bit and 8 bit
images.
Every day I walk past a LightJet print of an 8-bit/channel image made
with a very low noise camera. There, in the sky in this image, are
plainly visible quantization artifacts. This older image was captured
with a Dicomed scanning camera. Newer versions of this type of camera
by Better Light are capable of making even lower noise images, so much
so that the newest version now captures all images in 16-bit/channel.
This was a deliberate design decision because the users of this camera
can easily produce prints with quantization artifacts with
8-bit/channel images. It does not require large edits in Photoshop,
just the tone curve that produces normal contrast images from the CCD's
linear data can produce these artifacts with 8-bit/channel data.
We will see if anyone listens to your reasoning. I for one and maybe
the only
one, agrees that this is at the root of this disagreement.
Thanks, now there are two of us that agree.
Make that three.
Ray Maxwell
Graeme Gill wrote:
A crucial factor in running such an experiment, is the level of
noise (or grain if you like), in the images. Such noise acts
as a "dither", that conceals quantization artefacts quite well.
The halftone screening of conventional printing and the stochastic
screening of inkjet printers also hides the quantization artifacts.
Perhaps enough so that the printing noise coupled with film noise
(older imaging technology) or sensor noise (newer imaging technology)
has masked it for most users. Hence this entire thread.
A lot of real world photographs fall into this category, due
both to the nature of real world objects, and the practical
limitations of capturing photons.
<snip>
Robin Myers
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