From: donl@glass.esd.sgi.com (donl mathis)
Newsgroups: rec.photo
Subject: Re: Kodak Ektacolor Paper
Date: 8 Oct 92 03:52:04 GMT
Reply-To: donl@glass.esd.sgi.com (donl mathis)
Organization: Silicon Graphics, Inc., Mountain View, CA, USA


In article <n0b95t@ofa123.fidonet.org>,
Ed.Sukach@f173.n324.z1.fidonet.org writes:
|> "In a continuing effort to communicate better with our customers, we are 
|> providing the following information. KODAK EKTACOLOR PORTA II Paper / 
|> type 2839 incorporates an improvement in the upper-scale curve shape over 
|> KODAK EKTACOLOR PORTRA PAPER / Type 2818. EKTACOLOR PORTRA II Paper 
|> features richer blacks, increased shadow detail, greater sharpness, more 
|> saturated colors and greater exposure latitude. 

All of this means they increased the paper's exposure scale on the
dense end, and doesn't necessarily have anything to do with the rest
of the scale.

|> Other than the somewhat contradictory "increase in red speed which permits 
|> shorter exposure times" and "no speed change is associated with this paper" 
|> . . . Shorter exposure times with no speed change? . . c'est incredable, 

Kodak's statement is, at the very least, badly worded, but there
is a possible explanation.  I'm speculating, but the principles are
valid even if this isn't what Kodak is getting at.

Consider that the typical filtration pack consists of lots of yellow
and lots of magenta.  That means the typical color of the light, by the
time it reaches the paper, is "lots of red, a little blue, and a little
green."  Now, suppose your red light is at maximum; i.e. the yellow and
magenta filters are at or near maximum.  The only way to get enough
light to the paper in the proper balance is to increase the total
exposure time.

If the paper is new and improved, with a faster red layer, but with
blue and green remaining the same, you now need a little blue, a little
green, and a moderate amount of red light.  This can be accomplished by
turning down the yellow and magenta dials to let more blue and green
through, and then shorten the exposure time to put everything back in
balance.  Shorter exposure times, with different filtration, and no
noticeable change in paper speed.

|> and the reasoning behind increasing color saturation in a portrait paper 
|> . . (reduced saturation is why I use Agfa Portra film), . . . what gives? 

Saturation is not the same as high contrast.  Saturation is a measure
of how much white has been mixed into the colors.  It is essentially
the quality of the dyes -- is the green really green, and so on.
Ideally, we probably don't want the paper diluting the colors; the film
should record them accurately, and the paper should convey them
accurately.  Light greens will still be rendered light green, not
somehow boosted up in an artificial way.  In other words, let the print
look as much as possible like the subject, or at least the negative's
rendering of the subject.

Contrast is a measure of how much the final density changes with
respect to some fixed change in the brightness of the subject.  In the
simplest view of a perfect system, a one-stop change in subject
brightness will result in a one-stop change in the reflection density
in the print.  Color negatives often come close to approximating this
situation.  Transparencies, on the other hand, typically yield *more*
than one stop of change in the final density for each one stop change
in the subject; i.e. the overall reproduction ratio is greater than 1,
for the low-to-middle values, and a ratio of less than 1 for the middle
to high values.  The overall reproduction curve for transparencies is
rather unrealistic, though dramatic.

In other words, don't be afraid that the increased saturation in the
paper is going to make your portraits look like they were done on
Velvia and printed on Cibachrome -- the characteristics are of a
different nature.

|> Could my random gray streaking have something to do with this change? 

I don't see how, but that doesn't necessarily mean anything.  :)

|> Have there been any changes in Ektacolor Supra or Ultra? 

Probably.  :)  Kodak changes their materials when they need to, and they
don't necessarily talk much about it when it happens.

|> BTW, I really like the shorter processing times with the RA papers, but 
|> I'm wondering about the availability of Kodak RA processing chemistry - 
|> I've only been able to obtain Besseler (Tetenal) and Photocolor. 
|> Anthing form Kodak coming in the near future? 

Kodak, of course, has been making RA chemistry from the beginning - it's
*their* process.  All of the others are follow-alongs.  I have bought the
10 liter kits; I understand that smaller kits are now available.  The
price seems roughly the same as the EP-2 chemistry, when all is said and
done.

- donl mathis at Silicon Graphics Computer Systems, Mountain View, CA
donl@sgi.com

Warn your kids -- "Math is tough."