Zonemaster calibration

[Blighty]

Fellow Apuggers,
I'm having trouble calibrating my Zonemaster to use Forte Polygrade RC. For some reason the prints look sort of washed out. I've tried (and tried) but with no success. I've calibrated other papers without problem. Does anyone out there have the calibration data for this paper? Many thanks, Blights.

 

[RH Designs]

Blights -

When you say "washed out" do you mean underexposed (i.e. blank highlights and pale shadows) or lack of contrast (i.e. highlights OK but no real blacks). Once you've established whether it's exposure or contrast that's the problem, we can go from there. We don't have any figures at present for Forté papers I'm afraid, but if you'd like to send me a 10x8 sheet I can do a "starting point" calibration using Ilford filters. Alternatively we do have a bespoke calibration service - pm me for details.

 

[jstraw]

I'm having some trouble with the calibration process and I'm sure that I'm not grasping something that's fundemental.

I'm setting my enlarger head all the way up. I'm finding the aperture that when the light source is metered from that height, falls between 10 and 20 seconds.

Then I put in my filter, meter and then adjust the meter so it's metering for the grade that corresponds with the filter and run the seven step test strip sequence.

If I understand correctly, a 1/4 stop sequence is -3/4, -1/2, -1/4, 0, +1/4, +1/2, +3/4.

The "0" exposure based on this metering is coming up as 17 seconds for a bright highlight for a grade zero filter.

The shortest exposure on the test strip comes out almost black. I'm looking for the strip that matches the highlight sample that was shipped with the unit.

The the LED on the zonemaster's tonal scale is illuminated at the far left, indicating an exposure for the lightest highlight.

What elementary item am I completely missing?

 

[RH Designs]

Then I put in my filter, meter and then adjust the meter so it's metering for the grade that corresponds with the filter and run the seven step test strip sequence.

If you are taking another reading with the filter in place, then that is your problem. Always remove the filter before taking measurements, and replace it before making the exposure.

What sort of enlarger, filters and paper are you using?

 

[GeorgesGiralt]

Hi Blighty !
I'm just trough calibration of some papers into my Analyser Pro.
For a starting point, get the fact sheet about the paper you plan to calibrate.
You need ISO R and ISO P values.
The ISO P are speed markings you've to translate them into offset towards Ilford's Multigrade IV RC which is the default paper for RH-Design's products.
Compute the difference in stops (1/12 th) between the speed of the unknown and MGIV. A plus sign means the unknown paper is slower, a minus sign means (unlikely) that the unknown is faster.
Enter these values as OFF values for the channel you allotted to the unknown paper. Then enter the ISO R values for the contrast et voila ! You've good starting values. You'll need to refine them for flare filter's wear and processing but you'll be quite good on the first run PROVIDED you pick the ISO R values for the filter set you use. Do no try to use ISO R values obtained with Ilford filters with a Durst filtration color head, you'll be fooled.
Hope this helps

 

[ath]

FWIW, here are my calibration values of very fresh Forte Polywarmtone RC for Ilford filters (above the lens type) and opal bulb with condensor:

Grade / offset / ISO-R
00 / 24 / 169
0 / 26 / 135
1 / 26 / 105
2 / 25 / 89
3 / 20 / 89
4 / 11 / 89
5 / 3 / 89

I think I have to fine tune this one day, because the paper was very fresh. I expect lower ISO-R at the higher grades.

P.S. just saw, that you spoke about the polygrade. Forget my post, but maybe its helpful for others.

 

[Blighty]

Thanks Andreas (and everyone else) your set-up is pretty much the same as mine. I'll give your calibration settings a go!

 

[jstraw]

If you are taking another reading with the filter in place, then that is your problem. Always remove the filter before taking measurements, and replace it before making the exposure.

What sort of enlarger, filters and paper are you using?

Richard,

I'm using a Beseler 45 with a Zone VI head with a new V54 lamp and a stabilizer.

I'm using the softest Ilford filter (so far) and Kentmere fineprint FB.

The difference between metering with no filter and with a 00 filter would cause a bit of over exposure but not a black test strip.

At stabilizer setting "E" with the enlarger all the way up and the aperture at f11 and no filter it was telling me something like 11.7 seconds...but the question occurs to me "for what?"

What tone, by default, is it giving me a time to produce?

 

[GeorgesGiralt]

Jstraw,
My understanding of the Analyser (and the Zonemaster) is that when it measure a light level WITHOUT a ny filter in the light path, it can compute any value from that measurement whatever grade setting.
So you never put ANY filter in the light path when taking a measurement.
When properly calibrated, if you make one measurement and make the seven test strips (going from 00 to grade 5) you'll get 7 identical test strips ! The device adjust finely to take care of contrast change and exposure between grades ! The goal being to get the same density as the one facing the lighted led on the bar graph.
Hope I' m clear enough

 

[RH Designs]

Richard,

I'm using a Beseler 45 with a Zone VI head with a new V54 lamp and a stabilizer.

There's your reason - cold light has a very different spectrum to incandescent, in particular it's much lower in red. The Analyser/ZoneMaster is set up for incandescent light (which is the most widely used in the UK at least) and it will suggest much longer exposures for cold light than are actually required. This is explained in the user manual, section 17.3. We recommend you reduce the indicated exposure by 2 or 3 stops (24-36 steps) to start with, then once you are in the ballpark you can refine the amount using the normal calibration procedure.

If you have a "known good negative" i.e. one which you know prints well with a full range of tones, and which you have the exposure data for, put that in the enlarger and take a couple of meter readings. The difference between your known exposure and the indicated one will be close to the required adjustment.

Hope that helps!

 

[jstraw]

There's your reason - cold light has a very different spectrum to incandescent, in particular it's much lower in red. The Analyser/ZoneMaster is set up for incandescent light (which is the most widely used in the UK at least) and it will suggest much longer exposures for cold light than are actually required. This is explained in the user manual, section 17.3. We recommend you reduce the indicated exposure by 2 or 3 stops (24-36 steps) to start with, then once you are in the ballpark you can refine the amount using the normal calibration procedure.

If you have a "known good negative" i.e. one which you know prints well with a full range of tones, and which you have the exposure data for, put that in the enlarger and take a couple of meter readings. The difference between your known exposure and the indicated one will be close to the required adjustment.

Hope that helps!

That helps a lot. Thanks Richard. Once I get the meter sussed out, I'm sure it will be the boon that the timer has proved to be.