Understanding Split Grade Printing

[David Lingham]

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 that test strip. Divide it in half and make a test print using both G5 and G0, giving half the exposure to G5 and half to G0. Assess this print, adjust accordingly and plan any dodging and burning. Then make a final print.

I tend to avoid going straight to split grading, instead I usually start a print with a G2.5 step test, unless the negative would obviously appear to need another grade. From this initial test strip my method of printing is to establish the correct contrast grade I want in the print with a second strip, either up or down from the G2.5 test.

When making the final print I will burn highlights at a lower grade either with G1 or G0, plus any flashing if needed.

Which is more of a multi grade workflow, but it works for me.

Also starting at my initial G2.5 test strip I have the option to use the full split grading method of G5 and G0, on occasions when I think that be the way to go.

 

[Pieter12]

I wonder if those of you using blue/green filters know if there is a significant difference in exposure times vs yellow/magenta? I have been using yellow/magenta for many years now, all my exposure records are for that combination and I am considering an LED head that uses blue/green light.

 

[Sirius Glass]

But what if you are using a colour head enlarger, or a condenser, or diffuser with multigrade paper?

My colorhead has a diffuser.

 

[Patrick Robert James]

I wonder if those of you using blue/green filters know if there is a significant difference in exposure times vs yellow/magenta? I have been using yellow/magenta for many years now, all my exposure records are for that combination and I am considering an LED head that uses blue/green light.

I don't think there is an exact answer to your question. There is a difference with my Focomat when using a grade 5 filter vs a 47b. The 47b needs more exposure. I know there is a difference between a 47 and a 47b, but I don't recall offhand what that is right now. Maybe a 47 would be the same. I've never compared the yellow/green difference if there is one. Hope that helps a little.

 

[Ethan Brossard]

I wonder if those of you using blue/green filters know if there is a significant difference in exposure times vs yellow/magenta? I have been using yellow/magenta for many years now, all my exposure records are for that combination and I am considering an LED head that uses blue/green light.

There are many different blues and greens in the world of LEDs, and all will print differently. I think there were even a few different CMY filtration scales used by different enlargers. In my experience with LED heads, and from what I've read about other LED heads, the best results are obtained with 450nm blue LEDs, and 530nm green LEDs. 450nm blue and 530nm green should give a greater range of contrasts than Ilford multigrade filters, and I'd imagine they're comperable to yellow and magenta filtration as well. Pure blue and pure green won't be the same as full yellow and full magenta filtration, but you should be able to calibrate settings using a mix of them to match yellow and magenta in order to keep using your filtration ratios.

 

[oxcanary]

Here is my method. I take a reading with a calibrated Ilford exposure meter which will give me the same time overall - with minor aperture adjustment. I then look at the negative and guess the time split between grade 00 and grade five. Make a print ( double the time for grade five) then assess it. Sometimes right first time, majority require a second tweaked print, sometimes with dodging and/ or burning to taste.

 

[albada]

Here is my method. I take a reading with a calibrated Ilford exposure meter which will give me the same time overall - with minor aperture adjustment. I then look at the negative and guess the time split between grade 00 and grade five. Make a print ( double the time for grade five) then assess it. Sometimes right first time, majority require a second tweaked print, sometimes with dodging and/ or burning to taste.

Could you provide more details about your method? It sounds like you guess one time (or two?) for 00 and 5, and then you mention doubling the 5-time.

 

[Pieter12]

Here is my method. I take a reading with a calibrated Ilford exposure meter which will give me the same time overall - with minor aperture adjustment. I then look at the negative and guess the time split between grade 00 and grade five. Make a print ( double the time for grade five) then assess it. Sometimes right first time, majority require a second tweaked print, sometimes with dodging and/ or burning to taste.

I am not sure of this, but I don't think the total time for split-grade printing is the same as single-grade. Since with split-grade printing you are always using a #5 filter (that takes more time) while if the end result is less than grade 4, just printing with a single filter would take less time overall.

 

[jonmon6691]

This discussion inspired me to do a bit of a study on split grades using a step wedge and some excel kung-fu

I started by bracketing "all" the mixtures of Grade 0 and Grade 5 since I wanted to see if there was a difference between split grade vs an intermediate grade.

Here's starting with Grade 5, then progressively adding more Grade 0 on top for each print (Blue is the start)

Here's the opposite, starting with Grade 0 then adding more and more Grade 5 on top this time

Then I printed each grade on its own and tried to pick one of the lines from above to see if there was a match

Grade 1

Grade 2

Grade 3

Grade 4

This may be obvious to other folks but I was short of surprised to see that there was no difference between split grade or intermediate filters, at least for the base exposure (dodging/burning is a different story).


Note that I'm using a Beseler 23Ciii with a variable contrast head, not sure if this would be somehow different with individual filters.

 

[jonmon6691]

Also I thought this was really interesting, look how the grade 2 print rides on top of the grade 0 curve then as grade 5 crosses, it switches over and rides on top of that. It's kind of like your green sensitive emulsion is in control of the highlights and the blue sensitive is in control of the shadows. Seems to me like this isn't ideal since your contrast index is always going to have this curve to it. Not sure if the classic graded papers had this characteristic but seems to me like potential reason someone might prefer them. At least if that had more linear responses for each grade

 

[Pieter12]

No big news here. The point of split grade printing is you don’t have to determine the grade to use. Plus the obvious dodging and burning advantage.

 

[albada]

Thanks for posting those graphs. I made similar measurements to use inside my DIY LED-head controller. It can compute green and blue exposure (i.e., 00 and 5) based on only one test-strip. To do that, I had to put curves like yours inside the controller's memory for the type of paper in use. That exercise helps us to understand the paper. Your observation of green controlling highlights is both perceptive and accurate.

 

[snusmumriken]

Also I thought this was really interesting, look how the grade 2 print rides on top of the grade 0 curve then as grade 5 crosses, it switches over and rides on top of that. It's kind of like your green sensitive emulsion is in control of the highlights and the blue sensitive is in control of the shadows. Seems to me like this isn't ideal since your contrast index is always going to have this curve to it. Not sure if the classic graded papers had this characteristic but seems to me like potential reason someone might prefer them. At least if that had more linear responses for each grade

View attachment 315334

Would this still be true if you were using yellow through magenta filters? I don't think you mentioned which paper you used here, but officially the difference between the three emulsion layers in Ilford MG is indeed how sensitive they are to green light; they are all sensitive to blue (source here). Yet the filters for Ilford MG are yellow-ish through to magenta-ish. Why?
(Strange that in the source linked above, the 3 under-lens filters pictured are all the same colour!)

Cost was (is?) typically the reason for sticking to fixed-grade papers with a single emulsion. However, you could end up with boxes of rarely-used brands/grades/warmth/surface that had passed their best-by date, so for low-output photographers like me it was a false economy.

Thanks for posting these graphs. Although the underlying facts are familiar, it's still interesting to see. I presume the units are milliseconds on the horizontal axis? How have you measured density?

 

[koraks]

This may be obvious to other folks but I was short of surprised to see that there was no difference between split grade or intermediate filters, at least for the base exposure (dodging/burning is a different story).

Goes to show how insanely useful this kind of testing is, and your effort in posting these charts on here. 'We' may know these things already, but at least whenever I try to look for good data to understand what's really going on, I mostly draw a blank. There's a few good writings online, but most curves they show are brushed up and reinterpreted. Still useful, but raw data is sometimes even nicer.

Not sure if the classic graded papers had this characteristic but seems to me like potential reason someone might prefer them.

AFAIK you're not alone in this. I think you hit upon exactly the reason why some people still prefer graded papers over VC.

 

[jonmon6691]

Would this still be true if you were using yellow through magenta filters? I don't think you mentioned which paper you used here, but officially the difference between the three emulsion layers in Ilford MG is indeed how sensitive they are to green light; they are all sensitive to blue (source here). Yet the filters for Ilford MG are yellow-ish through to magenta-ish. Why?
(Strange that in the source linked above, the 3 under-lens filters pictured are all the same colour!)

Thanks yeah I forgot to mention this was all on Ilford MGRC Deluxe Glossy (aka Gen 5). Actually I have wondered why the filters are warm tones, but the contrast head projects distinctly purple/green light. I might have to grab a set of those filters and do this again to see if there's a difference...

Thanks for posting these graphs. Although the underlying facts are familiar, it's still interesting to see. I presume the units are milliseconds on the horizontal axis? How have you measured density?

Actually this data came from my Epson V700, I scanned the step wedge prints and pulled the pixel values from the raw tif and did log(216/pixel) to get the density. So the x axis is pixels and that's why you can see the steps of the step wedge. Its a Stouffer T2115 so every two steps is a full stop of additional exposure, or alternatively, every 6 steps is roughly +1 relative log exposure which is the units you usually see on these charts

 

[MattKing]

Actually I have wondered why the filters are warm tones, but the contrast head projects distinctly purple/green light.

The contrast filters are designed for a subtractive system which uses a full spectrum source (tungsten or halogen bulb) and a yellow filter to decrease blue light, and a magenta filter to decrease green light. With either filter, lots of red light comes through.
Your Beseler variable contrast head may not transmit as much red light. If it were an Ilford 600 or (in most cases) 500 Multigrade head, you wouldn't see any red light - just blue and green.
And I don't know if this applies to you, but many people who see blue light think that it is actually purple.

 

[koraks]

Yet the filters for Ilford MG are yellow-ish through to magenta-ish. Why?

Yellow = minus blue, so passes blue + green (and red). An MG yellow is basically a low-pass filter.
Magenta = minus green, so passes blue (and red), but no green. The magenta filter is a notch filter.

If the 'why' was not so much a technical question but one about usability: the additional red being passed makes burning & dodging easier although it doesn't contribute to the actual exposure (well, not significantly in any case).

 

[MattKing]

Yellow = minus blue, so passes blue + green (and red).

I think you mean Yellow = minus blue, so passes green (and red) and a lower to no amount of blue.

 

[koraks]

Yeah, sorry...brainfart...evidently yellow passes green + red, blocks blue. Thanks for spotting it!

 

[Pieter12]

All the graphs are nice and really won't help much when printing, since you print negatives of actual scenes and not step wedges. Now go make some prints.

 

[jonmon6691]

All the graphs are nice and really won't help much when printing, since you print negatives of actual scenes and not step wedges. Now go make some prints.

This sentiment shows up over and over and over again in these types of threads. I totally disagree that they aren't helpful. Because understanding the medium means being able to more fully express creative vision without fumbling around wishing you could just get your visualization on the paper.

No one is saying this is what photographic materials are FOR. But when you have a question eating away at you, you can either throw up your and say it's unknowable magic. Or you can figure it out and understand it.

Edit: And on top of all that, I'm one of the weirdos that really enjoys the time spent on projects like this, I get a lot of satisfaction from it and I definitely don't consider it wasted time. The opportunity to do this kind of stuff is part of the draw to analog photography for me and I suspect many others.

 

[snusmumriken]

Thanks for explaining about the filters, guys. Makes perfect sense.

 

[koraks]

All the graphs are nice and really won't help much when printing

LOL.
Process control just happens.
Now go waste some paper.

 

[Pieter12]

This sentiment shows up over and over and over again in these types of threads. I totally disagree that they aren't helpful. Because understanding the medium means being able to more fully express creative vision without fumbling around wishing you could just get your visualization on the paper.

No one is saying this is what photographic materials are FOR. But when you have a question eating away at you, you can either throw up your and say it's unknowable magic. Or you can figure it out and understand it.

Edit: And on top of all that, I'm one of the weirdos that really enjoys the time spent on projects like this, I get a lot of satisfaction from it and I definitely don't consider it wasted time. The opportunity to do this kind of stuff is part of the draw to analog photography for me and I suspect many others.

OK. Lead me through how you would use this information to make a split-grade print.

 

[MattKing]

These sorts of discussions - process control, yes or no - make a lot more sense if we add something like:
- "for me, the graphs don't help me print better", or
- "for me, it helps to understand exactly what is happening when I go to print".
I know and appreciate the photography of people of both types, as well as a fair number who are somewhere in between.