RE: null conversion
RE: null conversion
- Subject: RE: null conversion
- From: "Michael Fox Photography News Account" <email@hidden>
- Date: Fri, 25 Nov 2005 20:18:06 -0800
- Organization: Michael Fox Photography
Hi Graeme,
Thanks for your response. A follow-up question below, if you don't mind.
> -----Original Message-----
> > Is there a reason why a RIP wouldn't be able to tell if the profile in
> > the image is the same as the output profile configured in the RIP?
>
> Lots of reasons. The profiles might notionaly be the same colorspace,
> but be based on different measurement charts, or they might be
> based on the same measurement data, but be made with different
> profiling software, or they might be the same profile, but rebranded
> by different vendors and therefor be different in some non-essential way.
>
> It's easy enough to tell if a profile is bit for bit identical with
> another, but not if it's functionally identical.
O.K. That's clear.
>
> > Even if there is no way to tell for sure, then why wouldn't the math
> > simply result in a null change?
>
> Because unless the profiles are purely mathematical ones (such as a matrix
> and gamma function), the interpolation tables are approximations of the
> desired transformations, and mathematically cannot be exact inverses of
> each other (most CMM's don't attempt to invert clut tables, they use the
> A2B for a forward transform, and the B2A for the reverse transform.)
O.K. That's clear, too.
>
> Also consider that if you are dealing with CMYK profiles, then processing
> through
> the profiles will almost certainly be different from not, because the
> former
> causes the black to be regenerated, while the latter leaves the black
> levels
> unchanged. In some situations it might be desirable to do such a null-
> transform
> to enforce total ink limit on a file.
Hmmm. Can you describe such a situation?
If it helps, in my case, yes the printer profile is a CMYK profile. So, in
the scenario above, the file is converted from the working space to the
printer profile, then saved. At that point, it should have the
desired/proper black levels. Later, the file is sent to the RIP. In what
situation would processing back to the PCS and back again to the output
space ever be a good thing?
Thanks,
Michael
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden