Dichroic Calibration - Worth It?

bvy · Dec 27, 2012

I've been making more prints lately trying to get better contrast -- i.e. the darkest blacks possible without bringing down the highlights. I'm not interested in dodging and burning at this point. The literature suggests that a grade 2 or 3 filter will cover most printing needs, but my results with these always seem to be flat. As such, I find myself using the grade 5 filter more often than not. I thought grade 5 was for slightly more advanced techniques -- like spilt-grade printing -- and not really to be used by itself. Even so, I'm not completely satisfied with my grade 5 prints.

So I've done some more reading and came across some threads and this link about calibrating your enlarger's color head for variable contrast printing:
http://www.butzi.net/articles/vcce.htm

It sounds promising -- I expose for the highlights, and then make adjustments to increase the contrast (blacks) while holding the highlights constant (casually speaking). I have an Omega C760 with dichroic head, but I don't have a light meter or step wedge transparency to run the tests. Before I go down this path and buy "more stuff," I'm wondering if anyone can speak to this process. Does it live up to its promise? Is it worth the effort? I understand the concept and I like the idea, but I want to hear that it holds up in practice and isn't just another academic exercise.

Thanks.

(I'm using the Ilford multigrade filters with Ilford MGIV RC paper. I'm using the white light setting of my dichroic enlarger and holding the filters under the lens. My paper developer is Ilford PQ 1:9, 60 seconds.)

chriscrawfordphoto · Dec 27, 2012

It would be easier for you to produce negatives that print well on grade 2. Develop them longer and you won't need to use grade 5.

cliveh · Dec 27, 2012

chriscrawfordphoto said:
It would be easier for you to produce negatives that print well on grade 2. Develop them longer and you won't need to use grade 5.

I would agree with this post and go further by saying that you should (where possible) produce negatives that require no filtration, given your film development procedure and enlarger type/set up.

pentaxuser · Dec 27, 2012

Ilford filters give the full range of contrasts without the need to calibrate a dichroic head. Based on what you have said dichroic calibration is not the answer to your problem. Do what Chris Crawford has suggested initially.

If that doesn't solve your problem then it is even possible that your personal film speed is wrong i.e. it is possible to develop longer and still not have good negs that will give a fine print on grades 2-3. Your exposure based on a correct film speed has to be correct.

However first things first. Develop for longer and see what does does

pentaxuser

MattKing · Dec 27, 2012

The suggestions above are good. Here are a couple of other things to think about:

1) it would be prudent to check your enlarger's light source. If, for example, the bulb is wrong or there is some cyan filtration that is not moving out of the way when you use the white light setting, there may be too much green light hitting the paper and therefore reducing the contrast;
2) light sources with dichroic filters are really nice to use, so if you have one that is working well, you may appreciate the flexibility it offers. You don't really need to calibrate the source, unless you are trying to match previous work. What you need to do is use the Ilford link above to get a reasonable idea of the range, and then become familiar with how it performs, so you can use it reliably in the future. The numbers themselves don't matter, it is the correlation between the settings and how you perceive the results;
3) it is possible that your desire for high contrast relates mostly to how you see the prints - you may prefer something like the "soot and chalk" look as compared to something with fine tonal gradation. If that is the case, you will need both contrastier negatives and high contrast enlargement filters/settings. I looked at the one enlargement you posted in the APUG gallery and its contrast looks fairly normal. Does it look low in contrast to you?

bvy · Dec 27, 2012

Thanks everyone. Develop longer as in push a stop? For this session, the negative is Tri-X 400 from my Olympus XA4, developed in D76 1:1 for 9:45. Fresh everything.

I also use the dialed in filtration, and I have the equivalents from the insert that ships with the paper. (I'm using the Kodak line.) I did some tests a while back and found that the results from the physical filters versus the dialed in filtrations weren't always the same. Maybe my filters are faded (?); anyway, it was a casual test.

Here are some examples. I like the shadow detail in the top print (grade 2 dialed in) but the blacks aren't very black. The bottom print has blacker blacks and good contrast but the shadow detail is gone.

cliveh · Dec 27, 2012

bvy said:
Thanks everyone. Develop longer as in push a stop? For this session, the negative is Tri-X 400 from my Olympus XA4, developed in D76 1:1 for 9:45. Fresh everything.View attachment 61764

Try 12.5 minutes.

Rafal Lukawiecki · Dec 27, 2012

Michael R 1974 said:
If you find yourself always needing high contrast filters, first do some darkroom tests for things like safelight fog or enlarger light leaks, make sure your filters aren't faded, etc. If everything checks out and your paper and developer are fresh, then you're simply not getting enough contrast in your negatives. Try increasing negative development time. Monitor temperatures. Make sure you are agitating enough etc.

I second Michael's recommendation to check your safelight. Please consider using the Kodak test, and not a "coin test" or its variants. It will only take 10 minutes.

Unsafe safelight that does not fog paper will reduce contrast and it will force you to use excessively hard contrast filtration, in addition to causing other issues with print-to-print consistency. Second to that would be checking your enlarger for significant light leaks.

I would say that 4 our 5 darkrooms which I have visited had unsafe safelights. All the other suggestions, which you got, are pretty good too.

cliveh · Dec 27, 2012

Rafal Lukawiecki said:
I second Michael's recommendation to check your safelight. Please consider using the Kodak test, and not a "coin test" or its variants. It will only take 10 minutes.

Unsafe safelight that does not fog paper will reduce contrast and it will force you to use excessively hard contrast filtration, in addition to causing other issues with print-to-print consistency. Second to that would be checking your enlarger for significant light leaks.

I would say that 4 our 5 darkrooms which I have visited had unsafe safelights. All the other suggestions, which you got, are pretty good too.

If you don't have a densitometer, what's wrong with the coin test?

Rafal Lukawiecki · Dec 27, 2012

cliveh said:
If you don't have a densitometer, what's wrong with the coin test?

I don't think you need a densitometer for the Kodak test—the results should be fairly visible across the pre-exposed areas.

The issue with the coin test is that it does not subject the paper to a pre-exposure under the enlarger. The only exposure the paper gets is the safelight exposure. This way, you are testing the safelight exposure on a sheet of paper that has not crossed the boundary of its inertia. A positive outcome of a coin test is always a positive indication that safelight is not safe, but it will often produce a false negative, in my experience, with safelights that are only slightly unsafe, for example with old safelight filters, some LEDs, and so on. They will not fog the paper, but they will depress contrast just as a pre-exposure of the paper would do, which could be the reason OP is not getting the desired contrast.

MattKing · Dec 27, 2012

cliveh said:
If you don't have a densitometer, what's wrong with the coin test?

I expect that Rafal is referring to tests which don't involve a slight pre-exposure of the paper when he mentions a "coin test". You can replace the cardboard in the Kodak test with coins and achieve the same result.

EDIT: he beat me to it!

Rafal Lukawiecki · Dec 27, 2012

MattKing said:
I expect that Rafal is referring to tests which don't involve a slight pre-exposure of the paper when he mentions a "coin test". You can replace the cardboard in the Kodak test with coins and achieve the same result.

That is exactly what I meant, Matt. Thank you for pointing this out, as I should have made it clearer that I was only concerned about safelight tests that skip that important pre-exposure step, which carries the paper over the threshold.

PS. Also, the cool part about the Kodak safelight test procedure is that it checks both the pre-exposure before and after the safelight exposure, which can yield different results, contrary to intuition. Whoever came up with the test put a lot of thought into a few simple steps.

cliveh · Dec 27, 2012

I understand the wisdom of what Rafal refers in terms of the inertia exposure, but as Matt points out this can still be done with any opaque material after initial exposure. However, I understand where Rafel is coming from and respect this point of view.

Gerald C Koch · Dec 27, 2012

Multi-contrast papers are designed to produce a grade 2 or 2.5 without any filtration.. If you cannot then you need to develop longer. The problem seems to be with your processing and not with your enlarger.

Rafal Lukawiecki · Dec 27, 2012

cliveh said:
I understand the wisdom of what Rafal refers in terms of the inertia exposure, but as Matt points out this can still be done with any opaque material after initial exposure. However, I understand where Rafel is coming from and respect this point of view.

Thank you, Clive, from now on, every time someone asks about safelight tests, I will make sure to be precise in pointing out the matter of the necessary pre-exposure while mentioning a coin test.

May I just add, that it does make a difference to the outcome of the test when the safelight exposure is made after as opposed to before the enlarger exposure that produces the light tone. The Kodak test takes that into account, but I suppose one could modify a coin test to use two rows of coins and to make two enlarger exposures. It is just that I have never seen a coin test comprehensively include all of those important details, while the Kodak test includes them, and it is concise.

cliveh · Dec 27, 2012

Rafal Lukawiecki said:
Thank you, Clive, from now on, every time someone asks about safelight tests, I will make sure to be precise in pointing out the matter of the necessary pre-exposure while mentioning a coin test.

May I just add, that it does make a difference to the outcome of the test when the safelight exposure is made after as opposed to before the enlarger exposure that produces the light tone. The Kodak test takes that into account, but I suppose one could modify a coin test to use two rows of coins and to make two enlarger exposures. It is just that I have never seen a coin test comprehensively include all of those important details, while the Kodak test includes them, and it is concise.

Rafal, you make a very good point, as I had not thought about applying the coin test to before and after. Exposure inertia is an important factor that I overlooked. Thanks.

bvy · Dec 27, 2012

MattKing said:
3) it is possible that your desire for high contrast relates mostly to how you see the prints - you may prefer something like the "soot and chalk" look as compared to something with fine tonal gradation. If that is the case, you will need both contrastier negatives and high contrast enlargement filters/settings. I looked at the one enlargement you posted in the APUG gallery and its contrast looks fairly normal. Does it look low in contrast to you?

Thanks Matt. It's funny because I was trying to decrease contrast with that print. I printed that one using a grade 1.5 filter for 5 seconds. Same film/paper and development, but a few things are different since I created that print:
1. Different camera (Yashica T5 there)
2. Different enlarger (I was using the Omega B600 then -- condenser head)
3. Same safelight but I actually pointed it up at the ceiling until recently. Now it points down and provides more light.

About the safelight, it's an old Premier Safelight fitted with Kodak OC filter. I don't have a densitometer, but I'll check out the links and try to run a test.

ic-racer · Dec 27, 2012

I'm not interested in dodging and burning at this point.

Unless you are totally in control of your scene's illumination, you will likely need dodging and burning.

The literature suggests that a grade 2 or 3 filter will cover most printing needs, but my results with these always seem to be flat.

Don't trust "the literature"

As such, I find myself using the grade 5 filter more often than not.

Increase negative development by 25%

I thought grade 5 was for slightly more advanced techniques -- like spilt-grade printing -- and not really to be used by itself.

You thought wrong.

Even so, I'm not completely satisfied with my grade 5 prints.

See above (Increase negative development by 25% and use dodging and burning).

So I've done some more reading and came across some threads and this link about calibrating your enlarger's color head for variable contrast printing:
http://www.butzi.net/articles/vcce.htm

That is a good technique, but Ilford already did it for you if you use Ilford papers (see the chart they put in with all their paper packaging). Realize what is going on with the 'calibration.' It allows you to change contrast and keep your exposure for middle grays constant. It does not make your final prints look any different, it just saves some steps getting the exposure correct.

nworth · Dec 27, 2012

The article is excellent, and it gives a good methodology for doing an approximate calibration. Since enlargers vary and dichro filters age, it may be quite worthwhile if you do much printing. An important part of this calibration is the introduction of neutral density to keep exposure times for the various contrast grades approximately the same. Most people just use the Ilford suggestions and go from there. But the Ilford suggestions do not include neutral density, so you have to adjust the exposure for every change in contrast. There are a set of suggestions from Kodak out there that do include neutral density. Many people like to make small adjustments in filtration (usually by changing the magenta) to get the contrast just right, but these small adjustments (up to a third of a grade) usually don't affect exposure that much. Finally, it should be noted that VC papers vary a lot, and a given filtration will not give the same contrast on two different kinds of paper. The differences can be enormous. The calibration technique assumes you print (at least mostly) on one kind of paper. If you switch papers, you can use the grades established for your favorite paper as a point of departure for the new paper, but it probably will not behave in quite the same way. Finally, nothing has been said about the correspondence between density ranges and paper grades. There are some differences between manufacturers here as well, despite some more or less standards. Here is a table from an old Kodak B/W Photographic Papers pamphlet (G-1, 9-71GX):

Grade Paper Log Exposure Range Negative Density Range
0 1.40 to 1.70 1.40 or higher
1 1.15 to 1.40 1.20 to 1.40
2 0.95 to 1.15 1.00 to 1.20
3 0.80 to 0.95 0.80 to 1.00
4 0.65 to 0.80 0.60 to 0.80
5 0.50 to 0.65 0.60 or lower

RalphLambrecht · Dec 27, 2012

yes, worth it, very much so. you will be able to fine-tune contrast like a master printer. i typically adjust contrst to 1/8gradefor a fine-art pint made for sale. try it and enjoy the power!

cliveh · Dec 27, 2012

nworth said:
The article is excellent, and it gives a good methodology for doing an approximate calibration. Since enlargers vary and dichro filters age, it may be quite worthwhile if you do much printing. An important part of this calibration is the introduction of neutral density to keep exposure times for the various contrast grades approximately the same. Most people just use the Ilford suggestions and go from there. But the Ilford suggestions do not include neutral density, so you have to adjust the exposure for every change in contrast. There are a set of suggestions from Kodak out there that do include neutral density. Many people like to make small adjustments in filtration (usually by changing the magenta) to get the contrast just right, but these small adjustments (up to a third of a grade) usually don't affect exposure that much. Finally, it should be noted that VC papers vary a lot, and a given filtration will not give the same contrast on two different kinds of paper. The differences can be enormous. The calibration technique assumes you print (at least mostly) on one kind of paper. If you switch papers, you can use the grades established for your favorite paper as a point of departure for the new paper, but it probably will not behave in quite the same way. Finally, nothing has been said about the correspondence between density ranges and paper grades. There are some differences between manufacturers here as well, despite some more or less standards. Here is a table from an old Kodak B/W Photographic Papers pamphlet (G-1, 9-71GX):

Grade Paper Log Exposure Range Negative Density Range
0 1.40 to 1.70 1.40 or higher
1 1.15 to 1.40 1.20 to 1.40
2 0.95 to 1.15 1.00 to 1.20
3 0.80 to 0.95 0.80 to 1.00
4 0.65 to 0.80 0.60 to 0.80
5 0.50 to 0.65 0.60 or lower

Perhaps we should just look at the picture to assess it?

Bill Burk · Dec 27, 2012

bvy,

You got a lot of good advice, I see nothing to contradict...

Your shot of the wheel in the garage, it looks like that might be a flat scene in the first place. If you could have known at the time to develop for approximately 12:30 minutes it would have helped this shot. Other scenes, in full sun, may print at Grade 2 with 9:45 minutes of development.

You develop the print for 1:00 minutes. I used to develop prints for 1:30 minutes, but lately I develop them for 3:00 minutes (Ilford Galerie in Dektol 1:2). Longer print developing will deepen the blacks.

The safelight test, as has been explained, is better if you print a photograph in the test. Then you see how degraded the highlights become if your safelights are not safe. The Kodak test was a still-life Siamese cat sculpture with polished silver pots and pans. When you see the shine next to the dull thud, it is convincing evidence that a little unsafe light is bad for prints.

BMbikerider · Dec 28, 2012

bvy said:
Thanks everyone. Develop longer as in push a stop? For this session, the negative is Tri-X 400 from my Olympus XA4, developed in D76 1:1 for 9:45. Fresh everything.

I also use the dialed in filtration, and I have the equivalents from the insert that ships with the paper. (I'm using the Kodak line.) I did some tests a while back and found that the results from the physical filters versus the dialed in filtrations weren't always the same. Maybe my filters are faded (?); anyway, it was a casual test.

Here are some examples. I like the shadow detail in the top print (grade 2 dialed in) but the blacks aren't very black. The bottom print has blacker blacks and good contrast but the shadow detail is gone.

View attachment 61764

As far as I am aware and have seen nothing that disproves it, dichroic filters do not fade! According to the latest times for D76 at 1-1 at 68Deg is the times you are using. Is your camera meter accurate? Is the film speed adjusted right?

If you are not happy using Ilford Multigrade, change your paper to the Kentmere version. It is made by Ilford after a company buy-out a couple of years ago and it is at least 1 grade harder and at least twice as fast. (Also about 20% cheaper in UK too!) I gave up Ilford MG a long while back because of similar problems to yourself. with no filtration you are supposed to get Grade 2, I estimate comparing it against a non multigrade paper it is about 1 grade softer.

bvy · Dec 28, 2012

Bill Burk said:
You develop the print for 1:00 minutes. I used to develop prints for 1:30 minutes, but lately I develop them for 3:00 minutes (Ilford Galerie in Dektol 1:2). Longer print developing will deepen the blacks.

My own experience with this paper/developer combination is one of diminshing returns after the first minute. Still, I might experiment to see how the highlights are affected relative to the shadows after the first minute.

BMbikerider said:
As far as I am aware and have seen nothing that disproves it, dichroic filters do not fade!

You mean the dichroic filters in the color head, I think. I'm talking about the multigrade filters that I'm holding under the lens. They could be fading or faded. One thing I didn't consider is that a dialed-in filtration and a physical filter give the same constrast but at different exposure times. Anyway, I'd like to get away from the filters altogether, which is why I thought the calibration would be worthwhile.

I have a new supply of paper arriving today. I'm going to test my safelight to make sure it's safe. Run some more tests...

pentaxuser · Dec 28, 2012

If you are set on using a dichroic head then have a look at Ralph Lambrecht's site "Darkroom Magic". He very helpfully gives correction exposure factors when you need to change contrast grades. I have never found the Ilford or anyone else's dual filtration to give a constant exposure when changing grades although the exposure differences are relatively small over say half a grade say grade 2 to 2.5 but beyond this the exposure difference is enough to give a different print from the one you'll get if you stick to the same exposure

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