Re: paper and film testing

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sstoney@pdq.net
Date: 10/13/02-03:50:13 PM Z


Sandy wrote:

> 1) a family of curves for the different times of development,

Right, got that.

> 2) a SBR chart which shows the time of development needed for a
> subject brightness range from perhaps a high of 10 or 11 to a low of 5.
> This is for use with the incident metering system.

The high of 10 or 11 is true for cyanotype, but for azo the highest SBR
covered by this test was about 7.4. Also, the way I determine subject
brightness range is with a reflection meter rather than an incident meter.
 Does this make any difference?

> 3) a chart showing CI, also called G or average gradient, for the
> different times of development.

Yes.

> 4) A chart showing time of development needed for different N
> development, typically from N-3 to N+1

Actually it goes from N to N+ 1.66.

> 5) A special printout of a curve for each of the five times of
> development.On the right hand side of the chart, on the Y axis, you
> will see the figures for base + fog (b+f), IDmin (ideal minimum
> density), DR (density range) and IDmax (ideal maximum density). At
> bottom of the chart, on the X axis). The information on the bottom of
> the chart relates to effective film speed. Notice the point on the
> curve that corresponds to IDmin. That point shifts to the left with the
> increase in speed which is typical of longer development times.

Yes!

 6) When
> the negative curves were produced by the Plotter program it was assumed
> that your printing process has either an exposure scale of 1.24
> (silver=Ilford) printing) or 1.38 (AZO printing).In other words, you
> have two separate print outs of the TRI-X tests, one for silver
> printing with conventional materials, the other for printing with AZO.

Yes. The trouble is, only the Ilford curves show the ISOs for the
different curves. On the Azo chart, the ISO squares were left blank. Am
I to assume that the ISOs for Azo are about the same as for Ilford?
This is my main question.

>
> From the paper curves the only thing of real importance at this point
> is the ES, or the Exposure Scale, which you will see in log values at
> the bottom of paper chart. Basically, when you develop your film you
> need to develop long enough to get a negative DR that matches the ES of
> the paper, assuming you want a print with a full range of tones. So,
> assuming that you want to make a silver (=Ilford) print of a scene
> with normal subject brightness range of 7, find the time of development
> from the TRI-X tests that were plotted to give a DR of 1.24 that shows
> a SBR of 7.

OK. I used to figure this out just by printing a step tablet and then
experimenting with film development times until I got a time that yielded
the right density for that paper. The problem was, this test had to be
repeated for every subject brightness range. I thought if I did this test,
I would know all the SBRs and their corresponding development times and
ISOs at once. As it turns out, now I know the development times for SOME
of the SBRs I encounter, and I know the right ISOs for when I plan to
print on Ilford, but I"m still not sure I"m shooting at the right ISOs for
Azo. I guess I need to call Fred back again and clarify this. (Also I
probably need to run another test with a more dilute developer to find out
the curves for SBRS of 8 or more.) He said I could use the same ISOs for
all four papers, but could this really be true? I guess it could be
insofar as the shadow density for all four papers should be about the
same; it's the highlight density that varies. Thus shooting for Ilford
and shooting for cyanotype on Arches might be the same, despite the fact
that the ES for Ilford is 1.24 and for cyanotype it's more like 1.9-2.1.

IF this were true it would be convenient because you wouldn't have to
decide how you were going to print a negative until later, when you went
to develop.

 .
>
> You do the same for the set of TRI-X curves that were plotted for AZO
> (ES=1.38). If you compare the curves for silver and AZO you will see
> that for the same SBR you will need to develop the TRI-X longer for AZO
> than for silver (Ilford).

Yes.

I'm beginning to think that developing by inspection is looking more and
more attractive...

Thanks,

--shannon


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