From: Judy Seigel (jseigel@panix.com)
Date: 10/28/01-08:45:34 PM Z
On Sun, 28 Oct 2001, Sandy King wrote:
> He is of course correct. However, since actual printing times are
> established by the time needed to print the first maximum black (or
> 90% of maximum black) it is my opinion that Dmax or 90% of Dmax
> should be the step that establishes the printing speed of an
> alternative process with any given light source. The overall contrast
> of the print will be established by the sensitivity of the process as
> determined by the number of steps between Dmax and Dmin (or between
> IDMax and IDmin).
This is highly theoretical; the operation I spoke of was more practical.
True, I'm a bit smoked right now, having burnt a bag of Paul Newman
popcorn in the microwave, and don't mind telling you you haven't breathed
fire til you've had same fill yr humble abode with dark gray in about 2
seconds (we had to douse it with water and it STILL smoked), so I may be
foggier than usual.... but then again I think others may not see the above
distinctions as the operative ones here, either.
Whichever, I hasten to assure you that, addressing the issue in terms of
number of STEPS of density, I meant from same bottom D-Max... otherwise
it wouldn't be a valid comparison, would it? And even those of us capable
of incinerating an entire bag of popcorn, I mean to the WILD FLAME point
(sob!), while being so very careful not to burn the hamburgers on the
other side of the room know better than that.
Neighbor wasn't printing step tablets, but his usual negatives, which
previously he'd printed by sunlight. (He'd borrowed my bulbs on at least
one occasion during a rainy spell just before a show -- tho that as I
recall was for POP.) As winter closed in and the sun became iffier, he
built a light table with fluorescent bulbs. It wasn't working well --
that is, times were verrrrry long.
Asked to opine, I noted several possible problem points: distance to the
bulbs in this new light "table" was too great, bulbs were rather far
apart, and were also BLB. Friend cut down the distance to the bulbs, which
helped, but time was still too long. Having spent about $30 per bulb on
the BLBs, he wasn't eager to throw them out... I brought over mine as
"proof", and -- this from memory of about 8 years ago -- a couple of
21-steps. These tests showed 20 to 25% greater "speed" (excuse me if term
is wrong) and finally he decided to switch to the BLs. I brought my bulbs
home and ran the tests again here -- including with his bulbs (which I
believe I gave back). Times would have been different (the overall
configuration being different) but the ratios about the same.
My cyano file was once, but is no longer, as exquisite as my gum file.
Odds are I can lay hands on those tests again -- tho I doubt there's any
more info in the notes than what I've just written. Nobody was contesting
it -- the difference between BL & BLB was more or less a given -- I'd been
told it many times by those in the business, & had no reason to doubt.
As for the 350 nanometer BL you mention now -- I recall that about 1990
the engineer from Voltarc told me they were test marketing a *365* nm
bulb, but it wasn't in full production, and only way I could find to get
any was by buying a lot from Bulbtronics on Long Island. I forget whether
that meant 20 or 100, but I wasn't interested in either, as at the time
I was for the most part printing with the NuArc mercury vapor bulb.
If there is a 350 BL in general use now, that may be analagous to the
*new* mordancage... that is, terms & usage evolve.
I doubt neighbor has those bulbs any more, and since mine are from
about 3 makers (Sylvania, GE, Phillips, whatever, bought at different
times), also quite a bit older than his, comparisons would have been
useless anyway.
I understand also, BTW, that the *halide* bulb now sold with and for the
plateburners such as the NuArc are different from the bulb I had with
mine, expose in about half the time, & are other metal than mercury. I
forget the other details, having to jettison what I don't need to make
room for smoke, but merely make the point that generalizations about
"halides" at this point might not be fully general in any event, either.
> If there is any specific reason why it would be better to use the
> convention observed for silver papers, i.e, the speed point is 0.6 +
> Dmin, instead of Dmax I would be very interested to understand the
> logic. I have to say quite frankly that I don't understand the
> rationale for the convention and perhaps am missing an important
> consideration.
As noted, you're over my head here, but I'd assume anyway speedpoint would
vary with the paper, so comparison of times for number of steps may be
more generally applicable or meaningful.
Judy
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