Re: Measuring

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From: Judy Seigel (jseigel@panix.com)
Date: 03/27/02-12:05:41 AM Z


On Tue, 26 Mar 2002, Sandy King wrote:

> In numerous tests with several UV banks I have not seen any
> appreciable speed gain between 2" and 4" spacing, or even between 2"
> and 6" for that matter. There may some slight gain from the closer
> clearance but it has been too small in my tests to visually evaluate.

And that's exactly what my recent batch of tests corroborated -- as I
said, the *blue* rose up to the same point in all tests -- or all tests
with the same 21-step. I used the same two 21-steps for all tests, but
they were quite different in density. The thinner one printed about 2
steps more than the denser. (As I explained yesterday, they were
apparently made at different times, had different Stouffer logos on them,
and I have no idea whether tablets from same batch can have such great
disparity... And no desire to test that, either, but think I wouldn't
switch strips in an ongoing project any more.

> I think tube spacing would also have to be considered in any
> comparative tests, along with actually clearance.

Tube spacing was standard for all tests, and will be forevermore. Covering
alternate bulbs was a different project, finished.

> However, if we are going to bet a million dollars on this issue I
> won't be able to accept as proof such statements as "the 21-steps
> Looked quite different at different heights." You would need to read

Sandy, if you want that million dollars, you have to read more carefully.
What I said was that I'd noticed a different look in the different heights
in the EARLIER project (the one of bulbs further apart at different
heights, using diluted emulsion exposed only 30 seconds), which made me
wonder about your statement that different heights yielded same exposure,
hence this latest series.

No more changing spacing of the bulbs... that's over. From here to
eternity, the usual -- bulbs as close together as possible. And these
exposures all 6 minutes.

> ... the steps with a densitometer and then plot the curve to satisfy me.
> Moreover, we would need also to make sure we both understand what is
> meant by speed gain. Is it to be measured by IDMax or by IDMin, or by
> the convention used for silver papers?

For "speed" in this case I simply meant how high up the ladder the blue
went. So in that sense, as noted, I don't find a speed gain, but I did
find *the curves* different -- that is, the middle height (3-1/4 inches,
or maybe it was 3-1/2, I don't have my notes in front of me) had one extra
step of shadow separation, or 9 steps, I think because the D-max was
greater, while the others, one closer to bulbs, one further, only yielded
8 steps. I also speculated about why that happened. And need I say that
the denser of the two tablets had fewer steps ?

I don't know how important this is in the grand scheme of things, because
the same density change might be effected with double coating -- or other
adjustment of variables, but it's surely an interesting result.

I meant to add that my findings -- difference in the range at different
heights, & difference in printing between the two tablets -- suggest
that if you want to maximize range by distance from bulb, one size does
NOT fit all. You'd have to test each emulsion, paper, & negative combo.

Meanwhile, I did find range change at the different heights provocative.
That's not to say that same range couldn't be effected by other means
(such as double coating), but that it ALSO varied with height.

Judy


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