Split-Grade Dodging

[MattKing]

Should I translate this to magenta and yellow so I can figure out what means?

magenta is the usable blue plus red (which has no effect on the results).
yellow is the usable green plus red (which has no effect on the results).
So go right ahead .

 

[grain elevator]

I would suggest you spend the next three years printing without any contrast control and then spend another three years experimenting with contrast filters and then perhaps try split grade printing.

I don't understand why you recommend taking short cuts. No way anyone could become a decent printer in under five years of working without contrast controls, and of course without a darkroom timer (plug in and out to control time).

 

[MattKing]

I believe the last two posts come from the "success through suffering" school of thought.

 

[Sirius Glass]

I would suggest you spend the next three years printing without any contrast control and then spend another three years experimenting with contrast filters and then perhaps try split grade printing.

TRANSLATION: I want you to have so much trouble printing that you will give up on darkroom work and give me everything you have.

 

[Pieter12]

TRANSLATION: I want you to have so much trouble printing that you will give up on darkroom work and give me everything you have.

Or I had a hard time learning, you should too.

 

[Sirius Glass]

Or I had a hard time learning, you should too.

I cut the learning curve shorter by going to workshops and learning from experts.

 

[Pieter12]

I cut the learning curve shorter by going to workshops and learning from experts.

Well, I had to learn to read German to understand the Agfa data sheets, walk 15 miles barefoot in the snow to an unheated darkroom where I ground my own chemicals and had a hand-cranked enlarger.

 

[Sirius Glass]

Well, I had to learn to read German to understand the Agfa data sheets, walk 15 miles barefoot in the snow to an unheated darkroom where I ground my own chemicals and had a hand-cranked enlarger.

Well I walked 50 Km both ways on ice and snow with barb wire wrapped around bare feet in a blizzard and it was uphill in both directions so I could save 5 cents by not using the coal fired trolleybuses.

 

[MattKing]

Or I used an Ilford Multigrade 500 or 600 light sources, or one of the growing number of blue and green light sources, and achieved better results, with greater simplicity.
You are so early to mid 20th century Sirius!

 

[albada]

I think Mark should have kept the incandescent lamp, and a set of Ilford Multigrade filters, and also not bothered with the “min-max” split grade.

That's about what I'm doing, but using LEDs and a home-built controller. Last night, I was teaching myself how to dodge -- two dodges on the same negative. Here are the straight print (left) and my dodges (right):

The dodges were to (1) bring out the detail in the ugly grille, and (2) lift the wheel out of distracting blackness. All this was simple work in grade 2, with no split grade yet. I'm learning the basics. "Success through suffering", eh?

As an aside, I can't decide if that grille is an angry mouth or Dearth Vader's mask. That disgusting grille is why I took this picture. And look at that evil eye (headlight)! I'd be embarrassed to drive it. And people actually pay money for these. Weird.
Mark Overton

 

[albada]

Did you achieve high contrast with the blue LED? In my head I had to add untraviolet LEDs to get high contrast. So my head has Red, Green, Blue, and UV lights.

That makes four or five of us on Photrio who are building LED-heads and controllers.

Yes, I have achieved the same grade 5 that Ilford's filters provide. To achieve that, I used "Royal Blue" with a wavelength of 450 nm, purchased from here: https://www.ledsupply.com/leds/cree-xlamp-xt-e-royal-blue-leds
Using Stouffer step-wedges, I cannot see any difference between Ilford's grade 5 and what these LEDs yield. I made an exact copy of Mal Paso's final light-head here: https://www.photrio.com/forum/threads/led-split-printing-enlarger-lamphouse.173834/
Note that his final design has no LEDs in the middle; he got better uniformity by removing them. So my head has 5 LEDs of each color (15 total), all in a circle around the perimeter. I'm running them with Mean Well LDD-700L drivers that get their PWM pulses from the Arduino. This design works well.

Your table reminds me of the grade table in my controller, which allows you to change grades without affecting exposure-time. It maintains a selected tone, which is shadow, mid-tone, or skin-tone. The software interpolates between table entries, thus offering you fractional grades. I find this smart-grade-change feature very handy, and I used it last night to switch from grade 2 to 5 while preserving mid-tones. You're welcome to the source-code if interested.

 

[grain elevator]

I believe the last two posts come from the "success through suffering" school of thought.

Or I had a hard time learning, you should too.

Apparently it wasn't obviously that my post was ironic. In fact I first thought so was the post I replied to, but I could see nothing that would have prompted it. The basics of darkroom printing, which to me include stuff like split grade, aren't hard at all. Anyone who can cook and bake something edible can do it. But then again, a surprising number of people can't do that. I'd encourage anyone to try everything as soon as you feel the need.

 

[Nicholas Lindan]

...the grade table in my controller, which allows you to change grades without affecting exposure-time. It maintains a selected tone, which is shadow, mid-tone, or skin-tone.

There is a method for split grade that takes the black/deep shadow / white/specular highlight meter readings and comes up with the right blue and green exposures. Paper characterization for split grade is easy as compared to characterizing a paper for 12 contrast grades.

Inputting the meter readings for black and white points, with a few stored paper constants, should allow your head to come up with the right contrast and exposure.

http://www.darkroomautomation.com/support/appnotesgmeasured.pdf

 

[MattKing]

Apparently it wasn't obviously that my post was ironic.

It was, so I added some more!

 

[grain elevator]

It was, so I added some more!

Well... sorry I broke rank. I'd have expected something along the lines of "back in the day, we didn't have no stinkin electric light enlargers, we used gas light and nitrate film would sometimes go up in flames" from an experienced forum member like yourself

 

[MattKing]

Well... sorry I broke rank. I'd have expected something along the lines of "back in the day, we didn't have no stinkin electric light enlargers, we used gas light and nitrate film would sometimes go up in flames" from an experienced forum member like yourself

The only response that I think is appropriate to this, is one given by the US historian, author and biographer (of Abraham Lincoln, among others) when asked the question: "What was it like to meet Lincoln?"
Her answer: "How old do you think I am?"

 

[grain elevator]

The only response that I think is appropriate to this, is one given by the US historian, author and biographer (of Abraham Lincoln, among others) when asked the question: "What was it like to meet Lincoln?"
Her answer: "How old do you think I am?"

I expected an exaggeration, Matt, I know there was electricity in the 1930s in Canada!

 

[MattKing]

I expected an exaggeration, Matt, I know there was electricity in the 1930s in Canada!

Well, I've heard that there was some

 

[kenh]

distributed:
With my blue LED's I was only about to get down to about R100 .. big disappointment as the LED's were not replaceable .. so that is why I stuffed in the UV lights .. and now I can get down to R50 like it should be.

Pieter 12:

I have not seen any UV shift issue yet. However I did not look for it specifically. My lens requires me to stop down to about f/6.3 to obtain a uniform lighting .. otherwise the corners get cut. But I will keep an eye for this as I would expect most lenses to have issues when working out of the visible spectrum.

Nicholas Lindar:

My second generation unit was able to scan over the image and record the minimum and maximum values and then I used a set of graphs that would translate the readings from the light meter to exposure times. In general it worked well. Occasionally there would be a negative taken of something that had too much contrast, and the system would then result in a print that failed to have sufficient punch to it. It would have shadows and highlights .. but because the range was stretched out the final print looked odd, without enough punch, muddy.
For this reason I am making a more elaborate system that will assist more in the burning and dodging to obtain more "local" contrast control.

It has been a longer project as I keep adding more items or getting side tracked, like making a print densmeter to assist in calibration which gives me a graph like this:

 

[Mal Paso]

The Problem with tungsten bulbs is 95% of the output is Heat, only 5% is light. A big part of the Beseler condenser system is IR Heat Absorbing Glass. LEDs are close to 50/50, heat/light. Good diffusers eat light. Light output has always limited diffusion heads. On some of the cold light heads you can see the tubes through thin negatives. They used sandblasted glass instead of flashed opal to keep the light output up. The LED head I built is about 35 watts of printing light that acts like 350 watts without the heat. I have 1/2 inch of opal diffuser in the light path. I was dreaming of this 50 years ago while putting flashed opal glass on top of the negative carrier to get the look I wanted. I also think it makes split grade printing a lot easier.

 

[Nicholas Lindan]

Occasionally there would be a negative taken of something that had too much contrast, and the system would then result in a print that failed to have sufficient punch to it. It would have shadows and highlights .. but because the range was stretched out the final print looked odd, without enough punch, muddy.

Ah, yes.

VC paper has a problem with low contrast grades that results in an HD curve with a flat spots. Areas of the image in the midtones and the shadows lose detail and turn into grey clouds - this may be what you are seeing.

Reference the paper curve for MGIV RC here - http://www.darkroomautomation.com/support/mgivrchd.jpg
Note how the curves for grades 00 - 1 1/2 have a minor saddle at ~0.6 OD and pronounced saddle at ~1.4 OD. The reasons for this behavior are explained in http://www.darkroomautomation.com/support/appnotevcworkings.pdf

 

[distributed]

@kenh An ISO(R) of 100, wow! That makes it sound like your blue LED has considerable green component, but I digress into speculation. What kind of LEDs do you have? How did you build your reflection densitometer?

@Nicholas Lindan I would like to take the oppportunity and thank you for the information you have published about multigrade papers on your website. Your writings are among the most detailed on the topic that I have found to date. After months of wondering whether and, if yes, how, I should convert my enlarger to LED illumination, "THE WORKINGS OF VARIABLE CONTRAST PAPERSAND LOCAL GAMMA" has given me the impetus to go ahead and try. The data and analysis contained gave me a good idea for a few key points to look out for!

 

[cowanw]

Ah, yes.

VC paper has a problem with low contrast grades that results in an HD curve with a flat spots. Areas of the image in the midtones and the shadows lose detail and turn into grey clouds - this may be what you are seeing.

Reference the paper curve for MGIV RC here - http://www.darkroomautomation.com/support/mgivrchd.jpg
Note how the curves for grades 00 - 1 1/2 have a minor saddle at ~0.6 OD and pronounced saddle at ~1.4 OD. The reasons for this behavior are explained in http://www.darkroomautomation.com/support/appnotevcworkings.pdf

Was that fixed in the new MGRC?

 

[Nicholas Lindan]

Was that [the saddle-shaped HD curves] fixed in the new MGRC?

Ilford seems to say so. I haven't tested it. I ordered a box of MGV (or whatever it is that Ilford is calling it) for finding out but I have to get the darkroom sorted first.

 

[kenh]

Ah, yes.

VC paper has a problem with low contrast grades that results in an HD curve with a flat spots. Areas of the image in the midtones and the shadows lose detail and turn into grey clouds - this may be what you are seeing.

Reference the paper curve for MGIV RC here - http://www.darkroomautomation.com/support/mgivrchd.jpg
Note how the curves for grades 00 - 1 1/2 have a minor saddle at ~0.6 OD and pronounced saddle at ~1.4 OD. The reasons for this behavior are explained in http://www.darkroomautomation.com/support/appnotevcworkings.pdf

@kenh An ISO(R) of 100, wow! That makes it sound like your blue LED has considerable green component, but I digress into speculation. What kind of LEDs do you have? How did you build your reflection densitometer?

@Nicholas Lindan I would like to take the oppportunity and thank you for the information you have published about multigrade papers on your website. Your writings are among the most detailed on the topic that I have found to date. After months of wondering whether and, if yes, how, I should convert my enlarger to LED illumination, "THE WORKINGS OF VARIABLE CONTRAST PAPERSAND LOCAL GAMMA" has given me the impetus to go ahead and try. The data and analysis contained gave me a good idea for a few key points to look out for!

Nicholas Lindan:

Wow, that is the best information I have ever seen about variable contrast papers and how they work. I learned a lot, and I appreciate the time it took to learn and write it up in a way that is easy to understand.

After reading it, I became a bit discouraged, noting the first derivative clearly shows how poor the HD curve is with the low contrast grades. Wish it was far better.
​

distributed:

Yes, R100 is obviously showing that the LED's have the wrong spectrum. The LED's I chose are called neopixels, and they are actually three LED's in one package that is controlled via a digital input signal. The LED's can be attenuated and selected using the digital signal. They are actually meant for display signs and such. Which probably explains why they have so much Green in the blue. I selected this set of neopixels because I can adjust the brilliance of each of the 64 LED's separately. I had read a bit about other people using LED's and having to work pretty hard to get the illumination even. So this seemed like a pretty good solution. I have actually tuned them so that the image on the easel is pretty even. So that part was a success. So now you can understand why I can't just swap out one blue LED for another. That is why I had to add UV LED's (probably could have used royal blue LED's and that would have made life much easier).

The UV LED's were difficult to put in and get the illumination even. First I had to worry about blocking the neopixels, so the UV LED's had to be placed in odd locations. Second I had to tune the system with various resistors to get the illumination even. And to make it even worse, my light sensor is deliberately designed to not respond to the UV light. So in order to evaluate it, I had to put a fluorescent material over my light sensor to see what was going on.

See the picture of the neopixels here

​