Digital BW, The Print

Lloyd, Jeff, Paul, Antonis,

Thank you for the feed back. I guess there is no standard for how to back
semi-opaque samples for reading reflectance. Since almost all of our work in
this regard is to compare one process to another or "before & after"
situations all that matters is that we be consistent as you say. When we
post results we should note how the measurements were done, at least for
paper white and the lighter tones which are the most effected.

The white underneath to match mounted prints makes sense in one way but not
another. I speculate that the increase seen from light passing through the
paper and being reflected back out is a result of a very intense light
source for taking the reflected density light readings that may far exceed
any normal level of illumination for print viewing. So using a black backing
for density readings might actually give a more accurate reading for prints
that will wind up mounted. Don't know for sure.

I get the same result as Antonis, that is I get the same reading with no
backing as I do with black backing. So I think that I will go with black or
no backing for my own measurements since this will be consistent to with my
Spectrocam which uses a black measuring plate.

On the color readings the 811 has Tm for C-41 processed film, (I gather that
the instrument has circuits or programming to filter out the orange mask),
Ta for E-6 processed slide film and R for prints. To answer Austin's
question, the 810 and the 811 are identical except for the addition of the
E-6 profile in the 811. These were designed for process monitoring for
commercial film processing businesses. In each of the three modes you can
measure in "VIS" or "RGB". A bit annoying that you can't get all 4 to
display at once.

Any precanned software to let you access the serial output on these units?

Now that I know that R density = -C density I am wondering how you would
calculate CMYK% and Lab values from the RGB density numbers.

Did get new calibration plaques by the way and I was able to down load the
manual from X-Rite. Just basic operational info though.

For those interested I picked up the 811 on eBay for $325 including shipping
plus another $125 for new calibration plaques for a total of $450. The 811
sells new for $4,250 and the 810 for $3,500. So this seems like a good deal.
Quite a bit of X-Rite equipment on eBay at similar cost reductions if you
are interested.

Thanks,
Martin Wesley

http://www.borderless-photos.de/guests.html



----- Original Message -----
From: "Antonis Ricos" <antonisphoto@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Saturday, October 19, 2002 11:17 AM
Subject: [Digital BW] Re: Reflective Densitometer Method


> Martin,
>
> some "reflections" on your post:
>
>
> > In reading reflective density of inkjet prints there is the issue that
the paper is
> not completely opaque.
>
> With my 810 I find that on EAM I get the same readings whether I back it
with
> black or leave it alone. However, backing it with a second sheet raises
the
> paper white from 0.06 to 0.04. By the time you get to 15-20% of a
grayscale
> the difference is about 0.01 which is lost in the "noise" of the
instrument. For
> practical purposes, I always read EAM and Hahnemuhle without backing.
>
> Consistency matters, but I can also see the argument that backing it with
white
> matches a matted print better. In any case, worth disclosing when we
compare
> notes on highlight densities.
>
> Insterestingly, the DTP41 (XRite's strip reading spectrophotometer) has a
> block under the sensor that can be moved to either white or black. The
> instructions for PrintOpen, Heidelberg's profile-making software, asks
that you
> slide it over to expose the _white_  patch under the sensor.
>
>
>
>
> > The 811 has two transmission modes, one for E-6 and one for C-41. Which
> would be the best for standard developed B&W film?
>
>
> Visual, marked as T VIS for transmissive ( R VIS for paper).
>
>
> Which mode would be best for yellow/green stained pyro developed B&W
> film?
>
> Essentially none, but probably whichever gives you better separation of
> values. These densitometers separate the spectrum into the 3 primaries
> based on the peak frequency of the photographic color process dyes for
> which their "status" is intended. Outside of that, their color readings
are
> meaningless as far as any standard reference goes and only useful as
> "relative" values (perfectly functional for your purposes).
>
> Antonis
>
>
>
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