Increasing dark values to black in print

[Pieter12]

.....for the same negative... No?

Obviously

 

[GregY]

Obviously

so since that's near impossible.... why make the point? Just asking really. We're just talking among ourselves.
I think Doremus probably provided the most useful information for the OP silvercloud....

 

[Pieter12]

so since that's near impossible.... why make the point? Just asking really. We're just talking among ourselves.
I think Doremus probably provided the most useful information for the OP silvercloud....

If I were to need to make a new print on a different enlarger, it is nice to have a starting point rather than going back to zero. And this part of the discussion is not relevant to the OP anyway, since he/she is using a conventional color head.

 

[koraks]

So you have purposely compensated for the paper's sensitivity, but other LED systems might vary. Your times only work with your set-up.

Indeed, hence my comment. And it's true for any setup, in the end. Since other topologies than tungsten-based enlargers are becoming more common, I think it's relevant to take the nature of the light source into consideration.

Btw, like incandescent sources, LEDs also have commonalities, e.g. in terms of inherent efficiency of different wavelengths (innovation permitting...) The green/blue ratios I've noticed have been confirmed by others; there's some info on it here on the forum if you search for it.

 

[GregY]

If I were to need to make a new print on a different enlarger, it is nice to have a starting point rather than going back to zero. And this part of the discussion is not relevant to the OP anyway, since he/she is using a conventional color head.

Pieter, IMO it would depend on the enlarger. I have two, a Beseler 45mxt with a ZoneVI VC head, and a Durst 138 with a colour head. The two are dissimilar......as would be another that required the use of Ilford filters under the lens. When/if I change enlargers i inevitably make a new test strip rather than wasting a full sheet on a guess and a gamble.

 

[Pieter12]

Pieter, IMO it would depend on the enlarger. I have two, a Beseler 45mxt with a ZoneVI VC head, and a Durst 138 with a colour head. The two are dissimilar......as would be another that required the use of Ilford filters under the lens. When/if I change enlargers i inevitably make a new test strip rather than wasting a full sheet on a guess and a gamble.

True. It just seemed like a very large difference in having the blue/green ratio radically different from what a filtered tungsten light source might provide. I have no idea of the blue/green ratio of a cold light (fluorescent tube) would be.

Most of the LED heads I have seen are DIY and probably vary all over the place. Heiland is the only one I know of that is commercially available today. There might me others. And the old Modern Enlarger Lamp LED head produced what seemed to be very similar results to a tungsten bulb.

 

[jonmon6691]

I don't think so.

Firstly, because of how VC papers work, which shows that they don't "care" if you expose the various emulsions simultaneously or in succession.

Secondly, it can also be demonstrated empirically. Although it wasn't the focus of this post, it was a nice coincidental 'finding': https://www.photrio.com/forum/threa...-interesting-things-ive-been-learning.193908/
Check the 3rd set of curves, and compare the red one (grade 2) to the blue one (equal exposures for G5 and G0). They don't overlap precisely, but slightly altering the balance of the G0/G5 exposure will. @jonmon6691 didn't do this, but if you're interested (and bored enough) you could.

A split grade print as such is identical to a single grade print, provided they're matched for the same effective contrast grade. The advantages of split grade are therefore in other areas:
1: the ability to easily 'make' fractional grades
2: a workflow that involves a predictable number of test strips to approach a 'perfect' result
3: the possibility of selectively burning and dodging the separate exposures

Finally, I don't think @Nicholas Lindan's remark about 'woo-woo' was effectively insulting to anyone, let alone intended as such. He merely signaled that he finds split grade printing a contentious topic and that he doesn't recognize any 'magic' in it. That's not an insult; it's taking a perfectly reasonable position in a civilized debate.

LED light sources will complicate things because they don't have "perfect" color rendering indexes like incandescent bulbs which pump out broadband energy up to their black body temperature. But ultimately there are still only two emulsions on the paper, and the effect of contrast will always come down to the balance of which emulsion got more exposure than the other. That relative exposure between the two emulsions at a certain point on the paper is controlled by the spectral content of the light that hit it there. The easiest way to do this in a controlled manner is by using a tungsten lamp in the enlarger and contrast filters supplied by the paper manufacturer. But you can absolutley get the same results with LED's, it will just take some experimentation and tuning on the part of the photographer to dial things in.

Also, I couldn't leave well enough alone on that particular multigrade testing rabbit-hole, and I did end up doing more controlled testing and posted the results here not long after that first post. I was able to recreate every single grade by mixing grade 0 and grade 5 exposures.

Understanding Split Grade Printing

The method of split grading that Ilford suggests hasn’t been mentioned so far in this thread. There is a good video by Dave Butcher on YouTube that explains it really well. Briefly, the method is to make a test strip at G2.5. The midway point between G5 and G0. Then choosing an exposure from...

www.photrio.com

 

[Craig]

I have found with split grade printing that a little yellow goes a long way, and you have a lot of yellow.

I'd start by determining what is the highlight (darkest portion of the negative) that you wish to retain detail in, and make a test strip of that spot using the yellow only. The correct exposure is when you are just starting to get detail off paperbase white. It will be a very light image. That is your yellow exposure time and filtration.

Next is determining the magenta time. Expose the entire next test strip with the yellow as determined above. Do a magenta exposure test strip on top of the yellow until you get the correct exposure. Contest should also be close to correct.

The yellow determines the overall contrast of the print and the magenta determines the overall exposure.

 

[MattKing]

Most subjects work best if you start first with determining the low contrast exposure, and then follow up by determining the high contrast exposure.
For high key subjects with mainly light or near white detail, it often works best if you start first with the high contrast exposure.
One thing I find useful when helping people learn about split grade printing is to first use the standard techniques to achieve a good straight print of a scene with a range of tones - no burning or dodging for this exercise. Record separately the individual low contrast and high contrast exposure times.
Then without changing any settings, do one print with just the low contrast exposure, for the time you recorded. Then on a separate sheet of paper do one print with just the high contrast exposure, for the time you recorded.
Then compare all three prints. You are likely to be surprised at how much of the final image on the good straight print comes from each of the two separate components.

 

[koraks]

LED light sources will complicate things because they don't have "perfect" color rendering indexes like incandescent bulbs which pump out broadband energy up to their black body temperature. But ultimately there are still only two emulsions on the paper, and the effect of contrast will always come down to the balance of which emulsion got more exposure than the other.

This is certainly true, and note that I didn't argue that LEDs somehow didn't work for this. The statement I responded to was that you need much more blue light than green. But this depends a lot on how you define 'more'. I demonstrated that it's actually not 'more electrical power' in the case of LEDs. With LEDs, it appears you need far less blue light, but this is likely mostly due to the efficiency of blue vs. green LEDs. Further complicating the issue is if you were to express the amount of light in lumens, you'd be thrown off heavily by the gigantic bias towards green light in the lumen scale, making a comparison between lumens of different colors very problematic. You'd then be left with something like mW/cm2 - and then you'd still have to think about the relationship between photon energy and wavelength.

Btw, this doesn't have much to do with color rendering indexes. That's another issue, and mostly refers to the spectrum of a white LED. That's yet another case than the one I addressed, but equally relevant since you can (and many do) replace the tungsten bulb in an enlarger with a white LED bulb. In practice, this appears to work just fine, and that's probably because the spectrum (and color rendering index) of a white LED is in fact quite well suited to B&W variable contrast printing: it tends to have a big peak in the blue area and lots of emitted power in the green band. There will generally be a difference between these power levels and those you get from a tungsten bulb, so here, again, you may find that an equally timed exposure on grade 5 + grade 0 doesn't land you at grade 2 or 2.5, which is what you typically would get with a tungsten bulb and Ilford filters.

To cut a long story short, what I remarked was as simple as "what works for a tungsten light source, does not necessarily work the same way from a practical viewpoint for other light sources". If you change out your tungsten enlarger for a LED one, don't expect the same exposure time ratios for split grade printing to still hold true. With an increasing popularity of LED light sources, this is IMO relevant to remark as a footnote to Pieter's initial statement.

 

[Nicholas Lindan]

Most subjects work best if you start first with determining the low contrast exposure, and then follow up by determining the high contrast exposure. For high key subjects with mainly light or near white detail, it often works best if you start first with the high contrast exposure.

Which test strip to make first depends on the contrast of the print.

• For prints that are average to slightly contrasty or slightly soft it doesn't matter which test strip you do first.
• For contrasty prints (low contrast negatives) the high contrast test strip should be made first.
• For soft low-contrast prints (high contrast negatives) the low contrast test strip should be made first.

This makes intuitive sense as a dominant filter will have some effect on the opposite contrast - a lot of high contrast exposure will have influence on a small amount of low contrast exposure and vice versa.

For all the gory detail see pages 3-7 of http://www.darkroomautomation.com/support/appnotesgmeasured.pdf

 

[snusmumriken]

Which test strip to make first depends on the contrast of the print.

• For prints that are average to slightly contrasty or slightly soft it doesn't matter which test strip you do first.
• For contrasty prints (low contrast negatives) the high contrast test strip should be made first.
• For soft low-contrast prints (high contrast negatives) the low contrast test strip should be made first.

This makes intuitive sense as a dominant filter will have some effect on the opposite contrast - a lot of high contrast exposure will have influence on a small amount of low contrast exposure and vice versa.

For all the gory detail see pages 3-7 of http://www.darkroomautomation.com/support/appnotesgmeasured.pdf

That attachment is an interesting read, thanks for sharing it.

Under ‘Cons’ of split-grade, you list “No direct control over the midtones where the visual interest lies”. Is your point that by fixing shadow and highlight densities as darkest black and lightest grey, you just let the mud-tones (pun intended) fall where they will? And isn’t that also the case with conventional printing?

 

[Nicholas Lindan]

That attachment is an interesting read, thanks for sharing it.

Under ‘Cons’ of split-grade, you list “No direct control over the midtones where the visual interest lies”. Is your point that by fixing shadow and highlight densities as darkest black and lightest grey, you just let the mud-tones (pun intended) fall where they will? And isn’t that also the case with conventional printing?

Ye olde conventional printing holds the midtones (ZV, 18% grey) constant as you change grades. So first you would find the ZV exposure with a test strip. A second teststrip can then determine the right filter to get the desired highlights or shadows (not both). The final highlight/shadow tweaking is done with dodging and burning.

Split grade starts at getting the highlights and shadows correct with a test strip for each. The midtones fall where they may and are adjusted with dodging and burning.

Both systems can only determine the exposure(s) for 2 out of the 3 main tones (highlights, midtones, shadows) in an image. Usually the remaining tone is acceptable, but if not it is time to get out the dodgers and burning cards. This limitation can't be worked around as there are only two controls available to hit three points.

The RH Designs and Darkroom Automation systems let you pick two tones to determine both contrast and exposure. Both these systems are geared to using fixed grade printing filters. The Darkroom Automation system does accomodate split grade in the above referenced application note http://www.darkroomautomation.com/support/appnotesgmeasured.pdf

 

[Sirius Glass]

That attachment is an interesting read, thanks for sharing it.

Under ‘Cons’ of split-grade, you list “No direct control over the midtones where the visual interest lies”. Is your point that by fixing shadow and highlight densities as darkest black and lightest grey, you just let the mud-tones (pun intended) fall where they will? And isn’t that also the case with conventional printing?

One can set the mid tones with the magenta filter and if deeper blacks are needed, burn those in.

 

[cliveh]

I'm surprised that so many people on this thread jump in with contrast control, before exploring print exposure control.

 

[Sirius Glass]

I'm surprised that so many people on this thread jump in with contrast control, before exploring print exposure control.

Split grade printing starts with exposure control.

 

[snusmumriken]

Ye olde conventional printing holds the midtones (ZV, 18% grey) constant as you change grades. So first you would find the ZV exposure with a test strip. A second teststrip can then determine the right filter to get the desired highlights or shadows (not both). The final highlight/shadow tweaking is done with dodging and burning.

Split grade starts at getting the highlights and shadows correct with a test strip for each. The midtones fall where they may and are adjusted with dodging and burning.

Both systems can only determine the exposure(s) for 2 out of the 3 main tones (highlights, midtones, shadows) in an image. Usually the remaining tone is acceptable, but if not it is time to get out the dodgers and burning cards. This limitation can't be worked around as there are only two controls available to hit three points.

The RH Designs and Darkroom Automation systems let you pick two tones to determine both contrast and exposure. Both these systems are geared to using fixed grade printing filters. The Darkroom Automation system does accomodate split grade in the above referenced application note http://www.darkroomautomation.com/support/appnotesgmeasured.pdf

OK, thanks, it is much as I thought. My approach using the graded filters is actually similar to what you describe for split-grade: test strip aimed to determine exposure for highlights, followed by a couple of tests at that exposure to nail the blacks by varying contrast grade. Then tweaking both variables and dodging/burning as necessary. Do my print aims to exploit the full tonal range of the paper.

What bugs me is the difficulty of controlling mid-tone separation. Of course one can choose to ‘fix’ two less extreme grey values, and I guess that amounts to mid-tone control. Unfortunately I hate having to do much dodging and burning. Wishing for the moon, I guess.

 

[Nicholas Lindan]

What bugs me is the difficulty of controlling mid-tone separation.

That's where the RH Designs and Darkroom Automation systems come in.

 

[cliveh]

Split grade printing starts with exposure control.

Oh, I must have missed that bit.

 

[snusmumriken]

That's where the RH Designs and Darkroom Automation systems come in.

You tryin’ to sell me something?. It may happen - give me time.

 

[Nicholas Lindan]

You tryin’ to sell me something?. It may happen - give me time.

If you are in the UK you will need to get an RH Designs system. Darkroom Automation only makes the timer for 120 power and US/Canadian safety standards. A 220 volt timer can be special ordered but it is not ideal.

 

[Doremus Scudder]

Ye olde conventional printing holds the midtones (ZV, 18% grey) constant as you change grades. So first you would find the ZV exposure with a test strip. A second teststrip can then determine the right filter to get the desired highlights or shadows (not both). The final highlight/shadow tweaking is done with dodging and burning. ...

Not how I worked (and still work with graded and VC papers). The approach I always found most successful was the on the OP cited in his first post, "Expose for the highlights and control the shadows with contrast." That meant guesstimating the correct paper grade, making a test strip, finding the best highlight exposure, making a test print (or another, larger, test strip) to check paper grade. If the contrast needed tweaking, repeat the same procedure on a different contrast paper. So, I am, indeed, finding the right filtration to get both the desired highlights and shadows. I think most good printers of the past worked this way as well.

FWIW, I generally work this way with VC paper too; guesstimate the contrast needed, make a test strip, find exposure based on highlight rendering, make a print, tweak contrast with filtration, either adjusting exposure by guess or making another test strip, if the contrast change is great. I end up with base exposure and base filtration (e.g., f/11, 18 seconds, 45M - or whatever). Split grade techniques for the base exposure do this with two exposures; I don't. There's absolutely no difference; the paper doesn't care if it gets its green and blue components together all at once or separately in two doses. Then, I'll switch to max M or max Y for burning. The only times I really rely on the two-exposure approach to make the base exposure are the rare occasions when I need to dodge at max M or Max Y.

Best,

Doremus

 

[Nicholas Lindan]

"Expose for the highlights and control the shadows with contrast."

That works if you are printing at softer grades with contrasty negatives.

However, if printing at harder grades then the shadow/magenta part of the exposure will affect the highlights and so the shadow exposure determination comes first, then the highlights are controlled with contrast.

The middle-first approach has the advantage that the paper exposure for ZV doesn't change if the contrast filtration is changed and after it is determined then either shadows or highlights (or any other important tone) can be used to peg the contrast.

There are many ways of getting to the same end, and they are all compromises at some point.

 

[Doremus Scudder]

That works if you are printing at softer grades with contrasty negatives.

However, if printing at harder grades then the shadow/magenta part of the exposure will affect the highlights and so the shadow exposure determination comes first, then the highlights are controlled with contrast.

The middle-first approach has the advantage that the paper exposure for ZV doesn't change if the contrast filtration is changed and after it is determined then either shadows or highlights (or any other important tone) can be used to peg the contrast.

There are many ways of getting to the same end, and they are all compromises at some point.

Certainly, there are more ways than one to skin the proverbial cat. That said, basing your print exposure on the least-dense areas of the print has merit because that's where the small changes in exposure make the most difference. Of course, if one is using a lot of magenta exposure and split-grade printing with separate exposures for magenta and yellow, the magenta exposure will affect the highlights and it may end up being easier to start with the high-contrast exposure. Even so, the final print needs the highlights to be right, so it gets worked out in the exposure/contrast testing stage.

However, if one uses an intermediate filtration, even when working with soft negatives, the single, overall exposure gives both blue and green components at once, so determining a base exposure based on the highlights is still more precise.

The whole "middle-first" approach is predicated on using a set of speed-matched filter values à la Ilford. In theory, one could speed-match filtration to any print value. It certainly works to base exposure on whatever print value you like and then adjust contrast to get the other values to fall where they are pleasing. My reason for advocating for using the high values of the print to determine a base exposure is that it is easier to zero in on the correct exposure since the highlights show small changes in exposure more readily than mid-tones or shadows.

It really depends on how one like to work.

Best,

Doremus