speed-matching a dichroic head

[Doc W]

There are several methods out there for calibrating a dichroic head for b&w so that when one changes contrast, one does not need to change exposure. For those of you with colour heads, how do you do this, or if you don't, how to you adjust for changes in exposure (other than just trial and error)?

 

[Sirius Glass]

I do not worry about it. When I change to a higher contrast filter where the exposure time is going to change, I just bump up the time and then a little trial and error. The Ilford data sheets has a note about the change in exposure versus grade.

 

[DREW WILEY]

I don't even think about it. Once you change contrast, something will change about the "feel" of the image anyway. So I just pull another test strip if
needed. But ultimately, I need to see a fully toned and dried print when fresh eyes on a later date to assess what I like or don't like about it. That last
mile always seems the longest. All that automated "grade" stuff means zero to me. Just complicates matters.

 

[RobC]

http://www.waybeyondmonochrome.com/WBM2/TOC_files/CntrstCtrlClrEnlargersEd2.pdf

However, it never quite works out how you think it will.

in order for so called speedmatching to work you must be able to very accurately pick the speed matched density in your work print to know that is the tone that wont change when you change contrast. Numerous reasons why it doesn't quite work.
Fact is you can't do that accurately by eye in the darkroom with the safe lights on. Its a subjective assessment not absolute objective assesssment.
Fact is that the speed match negative density might not even exist in the negative or print.
Fact is paper speed match point moves as paper ages and its contrast changes. And this change can be a large amount for old paper. So you never know exactly what the speed point tone is anyway.
Fact is different brands of papers have different speed points and Y+M values would need to be calibrated for each paper.
Fact is that when you make any contrast adjustment both highlight and shadow contrast will change. Maybe only a small amount in the highlights if speed point is in highlights but there is nearly always a small time adjustment required if you're being picky about getting the perfect print.
It ain't an exact science so I wouldn't waste your time on trying to calibrate an enlarger head if the grades are already reasonably close as shown by below step wedge test. It would be a time wasting exercise which wouldn't gain you anything in reality.
On the other hand if they are significantly different then its worth addressing.

Having said that, its reassuring to know that your enlarger Y+M values are more or less speed matched. To do that get a stouffer transmission step wedge, 1/3 stop steps are best and produce some pints with it to find out how well the grade settings are speed matched.

Print the step wedge at softest grade first so all steps from end to end print on paper and range from paper max black to white. Then using same time and no other adjustments, increase contrast a grade at a time and print again.
Then line up the print steps from each grade print and in theory if your Y+M values are good you will find one step of the wedge which prints same tone for every grade.
Assuming there is one step where all grades are close then you will know if its a mid tone or a highlight tone and thats about the best you can do.
Now when you print normal negs you can make an assessment of what the speed point tone is in your work print but you'll never be able to judge it really accurately in the darkroom with a neg projecting onto baseboard so its all ball park assessment to get to where you want to be by intuition rather than numbers.

OR

You can get a set of ilford filters and use those. They are acurrately speed match on Ilford MGIV papers on approx paper density of 0.3 which is a highlight. But rumour is that MGIV Classic FB has different speed point which I haven't tested for yet.

what make and model of enlarger head do you have?

 

[RalphLambrecht]

There are several methods out there for calibrating a dichroic head for b&w so that when one changes contrast, one does not need to change exposure. For those of you with colour heads, how do you do this, or if you don't, how to you adjust for changes in exposure (other than just trial and error)?

part of my calibration procedure takes care of the speed matching;Yes, I change the base exposure every time I change contrast.the rest is taken care of by f/stop timing.works well for me;I'm doing it for years.I made myself a simple table on how to change the base exposure when changing contrast.If you send me a private email to rlambrec@ymail.com,I'll send you a copy of my procedure.Alternatively,it's written up in 'Way Beyond Monochrome'

 

[RalphLambrecht]

http://www.waybeyondmonochrome.com/WBM2/TOC_files/CntrstCtrlClrEnlargersEd2.pdf

However, it never quite works out how you think it will.

in order for so called speedmatching to work you must be able to very accurately pick the speed matched density in your work print to know that is the tone that wont change when you change contrast. Numerous reasons why it doesn't quite work.
Fact is you can't do that accurately by eye in the darkroom with the safe lights on. Its a subjective assessment not absolute objective assesssment.
Fact is that the speed match negative density might not even exist in the negative or print.
Fact is paper speed match point moves as paper ages and its contrast changes. And this change can be a large amount for old paper. So you never know exactly what the speed point tone is anyway.
Fact is different brands of papers have different speed points and Y+M values would need to be calibrated for each paper.
Fact is that when you make any contrast adjustment both highlight and shadow contrast will change. Maybe only a small amount in the highlights if speed point is in highlights but there is nearly always a small time adjustment required if you're being picky about getting the perfect print.
It ain't an exact science so I wouldn't waste your time on trying to calibrate an enlarger head if the grades are already reasonably close as shown by below step wedge test. It would be a time wasting exercise which wouldn't gain you anything in reality.
On the other hand if they are significantly different then its worth addressing.

Having said that, its reassuring to know that your enlarger Y+M values are more or less speed matched. To do that get a stouffer transmission step wedge, 1/3 stop steps are best and produce some pints with it to find out how well the grade settings are speed matched.

Print the step wedge at softest grade first so all steps from end to end print on paper. Then using same time and no other adjustments, increase contrast a grade at a time and print again.
Then line up the print steps from each grade print and in theory if your Y+M values are good you will find one step of the wedge which prints same tone for every grade.
Assuming there is one step where all grades are close then you will know if its a mid tone or a highlight tone and thats about the best you can do.
Now when you print normal negs you can make an assessment of what the speed point tone is in your work print but you'll never be able to judge it really accurately in the darkroom with a neg projecting onto baseboard so its all ball park assessment to get to where you want to be by intuition rather than numbers.

OR

You can get a set of ilford filters and use those. They are acurrately speed match on Ilford MGIV papers on approx paper density of 0.3 which is a highlight. But rumour is that MGIV Classic FB has different speed point which I haven't tested for yet.

what make and model of enlarger head do you have?

speed-matched filters are a myth and actually quite impossible.However a contrast calibrated color head with a speed-matching table works well

 

[nworth]

However you do it, the answers will only be approximate. But that is all you want; you will trim the final exposure as you go along. The technique I have observed is to choose the yellow filtration for the lowest contrast and then decrease yellow and add magenta to maintain constant exposure as you increase contrast. The yellow plus magenta results in neutral density as far as the paper goes. Papers probably vary in their green vs. blue sensitivities, so the answer may not always be the same for different papers. I found the following somewhere (long forgotten) which is supposed to duplicate the Kodak Polycontrast filters:
.
1 25Y
1-1/2 12Y + 9M
2 4Y + 21M
2-1/2 7Y + 40M
3 10Y + 70M
3-1/2 20Y + 140M

This sort of works. It is certainly not exact. Ilford publishes a list of suggested filtrations that are not corrected. They are much different. They seem to work pretty well, but the exposure adjustments are significant. I sometimes use a corrected light meter to measure before and after light and make adjustments.Here are the Ilford settings:

0 80Y 1/2 55Y
1 30Y 1-1/2 15Y
2 0 2-1/2 25M
3 40M 3-1/2 65M
4 100M 4-1/2 150M
5 200M

I suppose you could measure the blue and green densities of an actual filter set and convert them to dichro settings. I've never tried it.

 

[RobC]

Durst have some enlargers which go from 0-170 and others which go 0-130 units. Kodak go 0-200 so you can't use kodak figures on enlargers which don't have 0-200 of filtration. You must use correct numbers for kodak or durst or whoever depending on which units your head is using.
And people fiddle with enalrgers and many old ones have had filters replaced with wrong ones etc etc so its definitely worth doing the step wedge test first to determine how close or not your filters are matched to what you would expect. And then decide whether further action/calibration is actually required.

 

[MartinP]

I'd suggest that if you need to match a print-grade for some reason, then use the Multigrade filters - either in a filter drawer, or under-lens. In general use, just pick a soft/hard/middling contrast appropriate to the negative and then start thinking harder or softer than that.

It can be very instructive to make a ring-a-round of density and contrast with a few dozen exposures. Try that out quickly and easily with a card mask, printing four up on an 8x10" sheet of RC paper. That reduces the total processing time to a quarter of what it would be if you printed each small example on a separate piece of paper.

 

[RobC]

speed-matched filters are a myth and actually quite impossible.However a contrast calibrated color head with a speed-matching table works well

I wouldn't disagree but there are a few caveats associated with it.
Yes its nice to have evenly spaced contrast grades becasue it makes contrast adjustment produce more predictable changes from grade to grade.
Your paper needs to be tested originally with a known level of contrast so its always best to test using new and fresh paper as its contrast will change over time. And then you always need to print with new or fairly fresh paper.
Then you need to know the speed point so you can at least make an approximation to it when judging what contrast change will do in advance.
Then you need to have your adjusment table which requires some significant testing to arrive at unless you're saying it works for all papers which I would be sceptical about.
So there's a lot of up front calibration and testing to be done.
And where does that get you? Well it will probably work for you if you've done all the testing and setup.
But on the hand if you have done just the basic setup of printing a stouffer step wedge to verify that your grades a re reasonably well speed matched and spaced then it really then comes down to havng good quality negs with the right density to print easily. If you have that then all the printing calibration and numbers game shouldn't be necessary.

It all comes down to how much printing you do. Someone who prints frequently will be get to know their materials and equipment and be able to do it instinctively in short time. Someone who is just learning and/or prints infrequently maybe struggling and looks for shortcuts which lead them down the numbers path without realising it can be mind numbing to print by numbers and can stifle creativity as you become dependant of the system.

 

[ic-racer]

Try the insert that comes with the paper, try the suggestions in the color head user's manual. You can make your own table without much trouble also. (there was a url link here which no longer exists)

 

[Doc W]

what make and model of enlarger head do you have?

Rob, I have a Devere 504 with the dichroic head (Kodak system 00200). I just went through Butzi's procedure with a 31 step Stouffer and it seems to work ok. I am still doing a bit of checking. Some of the numbers don't make any sense to me which is why I was curious as to who used what method.

 

[Doc W]

I am quite surprised at the range of responses and even more surprised by the idea that speed-matching is not possible! In addition to the Butzi method, I am going to try some of the published combinations and do a comparison.

So far, the most interesting thing I have found is that Ilford Classic FB seems to have a really wide and subtle range at the lowest contrast.

 

[Doremus Scudder]

I am quite surprised at the range of responses and even more surprised by the idea that speed-matching is not possible! In addition to the Butzi method, I am going to try some of the published combinations and do a comparison.

So far, the most interesting thing I have found is that Ilford Classic FB seems to have a really wide and subtle range at the lowest contrast.

Speed matching certainly is possible, but, as Rob points out, not simple since the "speed point" is an arbitrary print density (hence so many different values...) and may or may not even appear in all prints. Like Drew, I just dial in more or less contrast and make a new test strip. I like to make big jumps at first and then zero in on my desired contrast, so if I have a flat print, I'll add a bunch of magenta, do a new test strip and make a work print to evaluate. I can then estimate where in the gap the next print should likely be, so I'll dial that in and then make a new test strip. After that, changes in filtration will be more minute, so I'll guesstimate a change in exposure when I tweak the filtration. All this time I'm refining dodging, burning, bleaching, developer, etc. so I'm really not wasting paper. I don't think speed matching would really speed things up for me.

Best,

Doremus

 

[DREW WILEY]

The Durst colorhead I just finished rewiring and refurbishing has two scales, CC values for the color of each filter per se, and the alleged equivalent
density at that setting, which obviously compounds when using more than one filter. So you can reasonably calculate the effective neutral density
factor. I won't bother.

 

[RobC]

So far, the most interesting thing I have found is that Ilford Classic FB seems to have a really wide and subtle range at the lowest contrast.

Ilford papers are known for this as they go right down to grade 00 and many printers like this if they are really wanting very fine control of soft highlights.

 

[RobC]

even more surprised by the idea that speed-matching is not possible!

Speed matching is there but you just can't get at it reliably or accurately enough to make it worth it. All you need to know is that there is a ball park tone in the mid or highlight region of your prvious work print that will remain at fairly close tone and then use your experience to assess how much time and/or contrast you need to adjust by.
Its getting that experience and judgement which is the learnt skill of it. Some people just never get it or are too impatient whilst others work at it and print often enough that it becomes second nature. Being a perfectionist who doesn't give up easily helps a lot.

 

[Gerald C Koch]

Matching can be done by using the third primary color. Usually yellow and magenta are used to determine contrast. Yellow, magenta and cyan make a neutral density filter when used in equal amounts.

 

[RalphLambrecht]

Speed matching certainly is possible, but, as Rob points out, not simple since the "speed point" is an arbitrary print density (hence so many different values...) and may or may not even appear in all prints. Like Drew, I just dial in more or less contrast and make a new test strip. I like to make big jumps at first and then zero in on my desired contrast, so if I have a flat print, I'll add a bunch of magenta, do a new test strip and make a work print to evaluate. I can then estimate where in the gap the next print should likely be, so I'll dial that in and then make a new test strip. After that, changes in filtration will be more minute, so I'll guesstimate a change in exposure when I tweak the filtration. All this time I'm refining dodging, burning, bleaching, developer, etc. so I'm really not wasting paper. I don't think speed matching would really speed things up for me.

Best,

Doremus

speed matching is only possible for one shade of gray but it is not possible for an entire monochrome image as some filter manufacturers claim or suggest.The best you can do is speed match for a known highlight density and adjust the shadows with contrast. overall speed matching is impossible.

 

[Doremus Scudder]

That's what I was trying to say, Ralph: you can only match one shade of grey in a print and even that's somewhat arbitrary. Then, the values on either side of the "speed point" will expand or contract with changing contrast.

I, too, like to key off the highlights, i.e., least dense part of the print, but don't bother with trying to speed match filtration.

Best,

Doremus

 

[RalphLambrecht]

That's what I was trying to say, Ralph: you can only match one shade of grey in a print and even that's somewhat arbitrary. Then, the values on either side of the "speed point" will expand or contract with changing contrast.

I, too, like to key off the highlights, i.e., least dense part of the print, but don't bother with trying to speed match filtration.

Best,

Doremus

I think ,we are in full agreement here.

 

[Doc W]

I am surprised that so many of you don't bother to try to speed-match the dichroic head. It seems to me that speed matching is a good way to avoid using a lot of paper but maybe I need to start a thread on how to do a proper test strip when changing contrast. I am very open to tips on that. I HATE wasting paper.

In any case, I went through Paul Butzi's procedure (http://www.butzi.net/articles/vcce.htm) and it looks like it worked ok. I made the test strips as he suggests and put the data into a spreadsheet to get the final magenta/yellow combinations. I then made test strips of these combinations, and lo and behold, these test strips line up beautifully. It is easy to see the number of steps decreasing as the contrast goes up, while the speed remains pretty much the same (the high grey value used for calculation stays in the same place with no exposure adjustment).

But here is something I don't quite understand. Just for the hell of it, I checked each one of these M/Y combinations with my Ilford EM-10 comparator, just to see if there was any need for fine adjustment. I found that the light intensity actually increased as the contrast went up. That would lead me to conclude that there is more light being projected as the magenta goes up and the yellow goes down. That would suggest a change in exposure, would it not? But as I said, the test strips lined up fine. I am a little confused. Btw, I used the EM-10 with the safelight off.

(sorry, I can't get this table to line up properly)
Devere 504
Ilford Classic FB

15M 175Y EM10=9
15M 135Y EM10=9
4M 84Y EM10=9
4M 44Y EM10=9
33M 33Y EM10=9
51M 11Y EM10=10
87M 7Y EM10=11
120M 0Y EM10=11
167M 7Y EM10=12

 

[MattKing]

The EM-10 has a colour sensitivity response that may make it unsuitable for this sort of test.

It is important, however, to understand how variable contrast paper works. Some people think the two (or three) different components of the emulsion - the green sensitive and blue sensitive components - have different contrasts. Actually they have similar contrast responses, but different sensitivities, with the blue (high contrast) sensitive component being more sensitive.

Your head starts with white light, and then subtracts different components to adjust contrast. The magenta filtration reduces the green component. The yellow filtration reduces the blue component. As you add magenta filtration you are reducing the relative amount of green in the light. The blue sensitive components build density faster than the green sensitive components, so the print density builds in the shadow areas, increasing the final contrast.

My light source is a Multigrade 400 head and it is sort of speed matched. I still do test prints.

 

[john_s]

For one approach, have a look at:

http://www.butzi.net/articles/articles.htm

and go to the article on variable contrast printing.

I have used a version of this for my two-tube VCL4500 and have found the results useful. It might look complicated but it's worth rolling up your sleeves and going for it.

Edit: oops, I had missed the reference to Paul Butzi's article in a couple of posts above.

 

[RalphLambrecht]

For one approach, have a look at:

http://www.butzi.net/articles/articles.htm

and go to the article on variable contrast printing.

I have used a version of this for my two-tube VCL4500 and have found the results useful. It might look complicated but it's worth rolling up your sleeves and going for it.

Edit: oops, I had missed the reference to Paul Butzi's article in a couple of posts above.

Butzi's approach takes the least amount of work to get close.My approach will get you closer but takes a lot more work initially.None work perfect except for starting with a new test strip every time you change contrast,which a concerned printer would do anyway;there is no shortcut to perfection.