Re: Profiling Epson 5000
Re: Profiling Epson 5000
- Subject: Re: Profiling Epson 5000
- From: "Bruce J. Lindbloom" <email@hidden>
- Date: Fri, 03 Nov 2000 11:38:55 -0600
Bruce Fraser wrote:
>
in my experience, at least. once you get the RIP to produce
>
reasonably linear output from the Epson (which is quite easy to do),
>
it's quite profilable.
To which Glenn Kowalski replied:
>
What needs to be done to have the 5000 produce linear output? And an
>
even more basic question--what is linearization?
Glenn's question sounds obvious on the surface, but I think it is a really
good question. Linear means that if you plot the data on a piece of graph
paper, the points lie on a straight line. But the crux of Glenn's question
is "what does the data represent?".
If you linearize pixel value vs. reflectance you get one thing. If you
linearize pixel value vs. density, you get something completely different.
Technically, both situations are linear. So it is not enough to say that
something is linear. You must say that it is linear with respect to
_fill_in_the_blank_.
My opinion (and I'll probably get flamed for this) is that linearizing pixel
value vs. reflectance is a bad thing--it is the printing world equivalent of
using gamma = 1.0 in a monitor space or RGB reference space. You run the
risk of losing visually significant detail in the shadows to quantization.
For the past 10 or 12 years, I have been a proponent of using the CIE L*
function instead. Linearize everything to it.
Looking at it another way, it is fortunate that monitors have a "natural"
gamma of about 2.2. This behavior is close to the L* function. On the
printing side, most devices have "dot gain", which is actually helpful
because it gives the device a natural behavior which is closer to the L*
function than if it had no dot gain at all. FWIW.
--
Bruce J. Lindbloom, Pictographics Intl. Corp.