[pure-silver] Re: Calibrating a colour enlarger to ISO paper grades wrt Way Beyond Monochrome

Jonathan

We are not trying to calibrate VC papers. We are trying to calibrate the dual-filter settings for color enlargers to give us a certain ISO grade. As far as I can tell from Steve's book, he is measuring the paper contrast for a given filtration. That's the opposite of what we are trying to achieve.





Regards



Ralph W. Lambrecht

http://www.darkroomagic.com


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On Dec 12, 2009, at 19:40, mail1 wrote:

I noticed Steve Anchell in his book “The Variable Contrast printing manual” covered a lot of information regarding light sources, filters and the different responses from quite a number of papers. His techniques on calibrating variable contrast papers are simple and effective. I felt to book was an easy read with lots of information.

Jonathan

From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx ] On Behalf Of Ralph W. Lambrecht
Sent: Friday, December 11, 2009 2:19 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Calibrating a colour enlarger to ISO paper grades wrt Way Beyond Monochrome

No, they are all different enough to justify having their own test.





Regards



Ralph W. Lambrecht

http://www.darkroomagic.com


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On Dec 11, 2009, at 22:40, Tom Kershaw wrote:


Ralph,

Thanks for confirming that. Although ILFORD gives figures for 'Kodak' type filtration on 'Multigrade' papers, using MGIVRC could be a good test case, before breaking out the expensive Adox MCC. In your experience do all the ILFORD Multigrade emulsion papers respond in the same way to filtration? i.e. cooltone, MGIV, and warmtone.

regards,

Tom

Ralph W. Lambrecht wrote:

Tom

Yes, spread your range from the softest yellow to the hardest magenta you need.






Regards




Ralph W. Lambrecht


http://www.darkroomagic.com



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On Dec 11, 2009, at 20:39, Tom Kershaw wrote:

Whether I should test the range of 0-100 yellow but 0-200 magenta; i.e. start with '100Y, 0M' and finish with '0Y, 200M'?

Tom

Ralph W. Lambrecht wrote:
Yes. What are you hinting at?






Regards




Ralph W. Lambrecht


http://www.darkroomagic.com



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On Dec 11, 2009, at 15:39, Tom Kershaw wrote:

Ralph,

Have you seen my most recent post on this topic dated December 8th, with regard to inconsistencies in ILFORD documentation?

Tom

Ralph W. Lambrecht wrote:
Tom

Correct. Combining the Durst Y/M filtration values (0-130) achieves very practical contrast with Ilford, Kodak and Agfa papers. Typically, I can get around ISO grade 0 (130Y/0M) and around grade 5 with (0Y/130M). If would ignore any filtration values which gives you much softer or harder grades. You won't need them.






Regards




Ralph W. Lambrecht


http://www.darkroomagic.com



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On Dec 08, 2009, at 12:37, Tom Kershaw wrote:

Ralph,

I've just got back to this topic, and will probably start performing the tests soon. Does your comment with regard to the DeVere 5108 yellow filtration levels suggest there is little or no practical application to using 200 units yellow, even if the ILFORD MGIV RC GLOSS paper can respond to such reduced contrast levels? I read your comment in the context of tone reproduction from a practical pictorial negative.

I intend to calibrate ILFORD MG and Adox MCC.

regards,

Tom

Ralph W. Lambrecht wrote:
Tom

Typical paper contrast ranges from grade 0 to grade 5. Calibrating an enlarger far outside this range has little practical application. Grade 0 and 5 are roughly equivalent to exposure ranges of 1.55 and 0.58, respectively (see page 62). Since you see differentiation across the entire step tablet, as in your scan, this suggests an exposure range of up to 3.0! This is far more than you ever need.

I suggest that you back off the yellow filtration until you get an exp range of no more than 1.8 and call that your new yellow limit.






Regards




Ralph W. Lambrecht


http://www.darkroomagic.com



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On Nov 28, 2009, at 20:41, Tom Kershaw wrote:

Made a few inroads in the calibration process today, starting with fibre base but over to resin coated paper for experimental purposes: The book chapter suggests that the print made from the step wedge should show areas of solid black and white before any tone variation is apparent. My own print using maximum yellow clearly shows (at least in the print) clear tonal variation between wedges 1, 2, 3, 4, etc. However the white zone doesn't show differentiation between wedges 30 and 31. Increasing exposure (keeping in mind the DeVere is projecting a significant amount of light) makes the print look muddier, with bleeding around the text increasing. Perhaps this means maximum yellow on the DeVere produces a lower contrast than maximum yellow on a '130' unit Durst.

See scan:

http://www.tomkershaw.com/files/tp31_45_sw_2009_11_28.jpg

Tom

Ralph W. Lambrecht wrote:
Tom

Thanks for asking. The 2nd edition is done. It's going through English edit and indexing at the moment. Everything has to be at the printer before Christmas, but I don't know the actual publication date yet.






Regards




Ralph W. Lambrecht


http://www.darkroomagic.com



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On Nov 27, 2009, at 20:51, Tom Kershaw wrote:

Ralph,

Thanks for explaining how you arrived at the figures. I don't possess a densitometer so would be making comparisons against the R2110 reflective wedge.

How is the second edition of the book coming along?

Regards,

Tom

Ralph W. Lambrecht wrote:
Tom

I picked eleven evenly distributed points across the filtration values to get the smoothest curve possible, but don't take that too seriously. Spread them out any way you like.

Nevertheless, here is what I did:

I made two series of prints from the lowest to the highest filter setting, one for magenta and one for yellow only. Then I determined the log exposure range for all test prints and got the curves in fig.1, ranging from 0.6 to 1.6 log exp range. I picked the filter values for every 0.1 log exp exp range increase, and that's how I got the eleven values, but these test input values have little influence on the test results. They just assure a smooth test curve.






Regards




Ralph W. Lambrecht


http://www.darkroomagic.com



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On Nov 27, 2009, at 14:39, Tom Kershaw wrote:

Claudio,

I'm currently using dual filtration from the ILFORD Multigrade data sheet, not from real-world testing. Figure 1 of the 'Contrast Control with Color Enlargers' chapter in 'Way Beyond Monochrome' gives 'Test settings' to make eleven prints from a projection step wedge as follows:

Test 1. Y 130, M 0
Test 2. Y 110, M 2
Test 3. Y 95, M 4
Test 4. Y 80, M 8
Test 5. Y 65, M 12
Test 6. Y 50, M 20
Test 7. Y 35, M 30
Test 8. Y 20, M 50
Test 9. Y 10, M 70
Test 10. Y 4, M 95
Test 11. Y 0, M 130

The prints from the step wedge are then assessed with either a densitometer or a reflective step wedge, and graphed to provide the data on contrast and exposure performance. In the case of 'Way Beyond Monchrome' the end point in filtration terms is then given for the test paper (Kodak Polymax), e.g. 'ISO Grade 2' is given as Y 59, M 15. So the multiplication factor I applied is for the starting point of testing e.g. Y 65*1.54 = 100.1, M 12*1.54 = 18.48.

Tom

Claudio Bonavolta wrote:
----- Message d'origine -----
De: Tom Kershaw <tom@xxxxxxxxxxxxxx <mailto:tom@xxxxxxxxxxxxxx >>
Date: Thu, 26 Nov 2009 19:35:55 +0000
Sujet: [pure-silver] Calibrating a colour enlarger to ISO paper grades wrt Way Beyond Monochrome À: pure-silver@xxxxxxxxxxxxx <mailto:pure-silver@xxxxxxxxxxxxx >


I suspect this message may be best directed towards Ralph W. Lambrecht. Reading through the calibrating chapter in 'Way Beyond Monochrome' I noticed the suggested filtration values given for a Durst max. 130 unit enlarger are not symmetrical across yellow and magenta. i.e. the step progressions between each value are not numerically equivalent; is this correct, and how variable are these values relatively across different manufacturers of enlargers? For my DeVere 5108 model I applied a multiplication factor of 1.54, i.e. 130 becomes 200.2 units as the filtration values go upto '200'.


Tom


It's rare to have a symmetry or constant progression in the values of yellow and magenta with a color head when used for BW multigrade paper.

Another example with my Focomat V35 (YMC filters go up to 200) with simple filtering:
00 Y200 2.24
0 Y90 2.24
0.5 Y65 2
1 Y50 1.78
1.5 Y25 1.41
2 ---- 1
2.5 M20 1.41
3 M40 1.78
3.5 M65 2.24
4 M100 2.82
4.5 M140 3.16
5 M200 3.16
Column 1: grade with Ilford Multigrade IV Fiber
Column 2: filtration
Column 3: exposure compensation (ref. density of 0.60)
Here too, you can see there is no symmetry and no linear progression either.

The factor you applied based on Ralph's own enlarger values may or may not be correct. If you want a progressive scale of contrasts, you've better to test it with a step wedge. Keep in mind these filters values are not really standardized, there are some big groups where results are similar, but, for precise work, you must fine-tune your enlarger. And because filters may fade with time you have to re-do it from time to time.

Note also that you may have simple filtering, i.e. using a single filter at a time but this requires time compensation, or double-filtering, i.e. using a mix of yellow and magenta as to keep constant exposure, or split-grade filtering, i.e. 2 different exposures done with either full magenta or full yellow.

Claudio Bonavolta
http://www.bonavolta.ch
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