Black and White Contrast Control with a Color Enlarger

RalphLambrecht

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MattKing

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RalphLambrecht said:
Imeant http://www.waybeyondmonochrome.com/WBM2/Welcome.html.look into the 'library section. if it doesn't work,I'll send you a direct link. also looking for a new host for 'darkroomagic.com.any recommendations for a reliable web hosting company?
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Hi Ralph:

I've just found it under the "Templates" link in the library section of the Way Beyond Monochrome site - but the description beside that link gives you very little in the way of hints what might be found there. Most of the "good stuff" was well labelled on your site.
 

pentaxuser

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MattKing said:
Hi Ralph:

I've just found it under the "Templates" link in the library section of the Way Beyond Monochrome site
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When I clicked onto Ralphs' link it said "not found" but when I tried Waybeyondmonochrome it did take me to the book and then the templates section but I couldn't find the exposure change corrections table for grade changes in the list of templates. Maybe your "it" isn't a reference to that particular table.

As I said I have the book so it's not a concern for me but it might be handy for others.

pentaxuser
 

pdeeh

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RalphLambrecht

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john_s said:
To reduce trial and error, I calibrated my system based on this article by Paul Butzi. Go to the link and look for the article entitled Variable Contrast Printing.

http://www.butzi.net/articles/articles.htm
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Paul knows what he is talking about, and his method works well.I show a similar method in WBM, which has the benefit of less exposure correction when changing contrast, but Paul's calibration is a bit simpler and faster.
 

tih

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RalphLambrecht said:
I show a similar method in WBM, which has the benefit of less exposure correction when changing contrast, [...].
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This got me reading WBM2 again, and I decided I'd like to have a go at another method described there, for calibrating the film development process. I've started by using a Stouffer T4x5-31 transmission guide to check the densitometer mode of my RH Designs Analyser Pro. Stouffer says the 31 steps of the guide have a .1 logarithmic density increase per step. The Analyser Pro, however, claims that they're at .15 (from #1, the thinnest one, up to around #16, where it can no longer follow the increase), when I put the guide in my L1200 enlarger, and measure the projection on the baseboard.

If I didn't have Stouffer's documentation, I'd be convinced the guide really was .15 per step, since the Analyser Pro very accurately and repeatably says so, and is able to follow up to about the 2.25 relative density that RH Designs says is its limit. I find it really hard to believe that Stouffer made a mistake, though, so something else must be going on. Has my Analyser Pro simply drifted 50% out of calibration (which seems rather incredible), or am I missing something obvious?

Edited to add: correction: the Analyser Pro hasn't drifted. Measuring a single spot while stopping down the lens shows that it's accurate.

Any ideas will be greatly appreciated!

-tih
 
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Xmas

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Tony Egan said:
x2. If you enjoy wasting paper and practicing cuss words, stick with the colour head
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yes but if you prototype on postcard size for contrast and exposure then test strip for exact exposure at final size allowing for greater enlargement you may take more time but only need to have calibrated two paper speeds and an enlargement factor

then all you need to do is dodge and burn at final size
to tell the truth my new process also includes scanning for a straight inkjet print and rescanning to mark up the print for burn and dodge times hoping this allows less paper wastage on difficult negs

I scan the marked up inkjet for records... and scrub off the gloss cause I encapsulate the ink jet in plastic
rare for me to get dodging 1st attempt and I do have a meter but like to see the silver wet paper or RC in bright light

still need cuss words most of my negs are difficult

split printing seems too complicated
 

tih

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RalphLambrecht said:
FWIIW,my Heiland Densitometer shows similar readings.CAN YOU CHECK WITH A SPOTMETER TO VERIFY if the error is with theStouffer or the Analyser?
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I didn't have much time this morning, but I managed to do a quick test, and the result is interesting. Using my Pentax Spotmeter V to measure the projected image on the enlarger baseboard, it sees a one stop difference when I move three stripes over - i.e. 0.1 log density increase per stripe. It also correctly sees a one stop change for each stop I close the aperture of the enlarger lens.

This contrasts interestingly with the Analyser Pro, which agrees with the Spotmeter when I stop down the lens, but claims to see a 0.15 log density increase per stripe, where the Spotmeter sees 0.1.

I'm trying to imagine something that could induce such an error, but so far, I've not been successful. I think I'm just going to have to do more comparison testing, and try to find a scenario where the discrepancy goes away.
 

tih

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Oops. I was too quick this morning. More careful observation, and a greater enlargement to make it easier to be precise, shows that I've got the too high contrast visible also to the Spotmeter. Richard Ross from RH Designs suspects it's a combination of flare and the Callier effect, and it seems he's right. It turns out that I can measure relative densities in 4"x5" negatives with the Analyser Pro either by projecting them through the L1200 (a condenser enlarger), measuring at the baseboard, or by carefully holding the negative in position over the Analyser's sensor, using the enlarger without a negative as a convenient light source. Measuring the projection yields a 1.5 log density difference where direct measurement of the negative shows 1.0.

Ah, and according to the internet (e.g. at Dead Link Removed), the average Callier coefficient is 1.4 ± 0.2.

I think I'm going to have a piece of frosted glass made, to fit in the filter drawer, turning the L1200 into a diffuser enlarger for the purpose of such measurements.
 
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tih

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Yup, guess I should have pointed that out... I had no idea the effect was this large!

For the purpose of zone system film development calibration, I guess I should divide my readings by 1.5 before typing them into your spreadsheet (unless I can manage to measure directly, with the negative resting on the Analyser Pro sensor), and then reduce the "normal gradient" from .57 to .38 on the summary page?
 

RalphLambrecht

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I'm surprised also.actually, it is difficult to measure callier accurately,especially with low densities, but your plan sounds corect to me.
 

tih

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RalphLambrecht said:
I'm surprised also.actually, it is difficult to measure callier accurately,especially with low densities, but your plan sounds corect to me.
Click to expand...

So what's the trade-off? If I customize my exposure and development to create low contrast, I'll get negatives that print well on grade 2 paper through my contrast-enhancing condenser enlarger. However, that means I'll get thin, flat negatives, that utilize less than they could of the available contrast range of their emulsions. On the other hand, if I choose to get the most out of the recording potential of the negative, I end up having to under-utilize the paper to keep the contrast down. Surely, at the extreme ends of these scenarios there's a loss of total image detail? So how far should one be willing to go in either direction? Does aiming for a negative gradient of .38 imply such a loss of image potential in the negative, that the gains of being able to print on grade 2 paper in a condenser enlarger really aren't worth it?

I've been looking for an answer in WBM2, but can't find it...

-tih
 
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tih

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Oh, and to atone for hijacking the thread: I once did a thorough calibration, following Ralph's suggestions in WBM, of the Meopta Colour 3 head for variable contrast printing with Ilford papers. I discuss it in this thread:

(there was a url link here which no longer exists)

-tih
 

wiltw

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ckpj99 said:
So here's my question: is there any difference in how yellow and magenta affect contrast? If I were to hook up the color head on my enlarger, is there a system I can use to control contrast that's better than the old just-magenta system?
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I can provide filter values from multiple sources.

From Ilford comes suggestions for different brands of dichoic heads for its paper


From Kodak, a chart for its Polymax paper


From Beseler, it lists its Dichroic head values for different brands of papers


And a general suggestion of filter values to start with


So you see that universally Yellow does figure into contrast control, mostly at the low contrast end of paper ranges, but even at the 'normal' contrast range.
 
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Sirius Glass

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Nihil Abstat said:
The sheet that comes with VC papers (at least Ilford's) gives suggested filtration settings.
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For one filter and two filter combinations for all grades. That is what I use.
 

DREW WILEY

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With a simple test strip, I can bypass everything on those charts. Unless you were reared on graded papers to begin with, none of it means anything anyway. All you need to know is what kind of light gives more contrast, and what kind less, then VISUALLY evaluate your dried-down test strip for potential adjustments. Reminds me of all these people who think they need a GPS just to cross the street, then get run over because they're staring at the damn device instead of using common sense.
 

MattKing

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I like having speed matching through dual filter adjustment, because it tends to get things close, which allows me to do a much better first test strip - one with relatively small steps.
 

DREW WILEY

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I certainly have the capability to do that, even with sophisticated feedback circuitry which is valuable for precise color printing applications. But I'd rather tinker a bit until I decide exactly what I want the print to look like, and typically print a negative more than one way. The notion of precisely previsualizing a print is more ideological than realistic. The negative should be within certain parameters, but still be flexible enough for more than one interpretation. More often than not, I'll use a VC paper just like a graded paper without any filtration at all.
 

Tony Egan

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I recently rescued a beautiful Fujimoto 45m enlarger with a colour head so I thought I would try to test my patience again with it using multigrade paper. The dual filter method certainly minimises exposure time adjustment. I used a lightmeter to measure EV in the middle of the easel, setting grade 0 as close to 5 as possible and moving up the grades from there. Attached is a photo of my measurements. I am normally working in a range of grade 1.5 to grade 3 and there is less than half a stop across that range. Using this table and dual filter controls has helped me get the first draft print a lot closer as I change grades. It is also nice to be able to occasionally switch between the Durst 138 and Fujimoto based on negative properties. I still prefer the Ilford gels but the cussing has diminished when using the colour head!
 
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