Split-Grade Dodging

albada · Feb 26, 2021

I know how split-grade burning works: Because its surroundings are darker than the object being burned, burning with green (00 filter) reduces telltale halos because green affects dark areas less than blue.

But what about dodging? Let's assume that the dark area to be lightened has much lighter surroundings. To avoid putting a halo in those surroundings, would I dodge only the blue (5 filter) exposure? This rule assumes that blue affects lighter areas less than green.

If both rules above are true, then both burned and dodged areas will have lower contrast because their green/blue ratios are higher (because burning adds green, and dodging removes blue).

Or do I have this all wrong?
Mark Overton

Sirius Glass · Feb 26, 2021

I dodge and burn with both filters, one at a time, whenever necessary. Do not over think it.

Huub · Feb 27, 2021

Indeed, except that dodging with a blue or a #5 filter will increase local contrast. I often use a #5 filter for dodging to increase shadow detail and at the same time maintain the deep blacks in the area.

Nicholas Lindan · Feb 27, 2021

Here there be worms...

I think split grade dodging depends on multiple factors:

Are you dodging highlights or shadows?
Do you want to move the contrast of the dodged area up or down?
What is the contrast of the base print?
What is the current phase of the moon?

More than that I can not think about now -- the coffee hasn't yet arrived at my brain. The same questions also apply to split grade burning but seem easier to get one's head around.

Split grade burning (burning with a #00 or #5/blue or green) can be done without split-grading the base print; you can still make the base print with a #3 1/2, filter and burn with a #5, as an example.

Split grade dodging, which to tell the truth I haven't put much thought into, does give a theoretical leg up for split-grade base printing. You can't very well give a #2 dodge to a print made with a #3 1/2 filter.

I have a feeling, though, that the question can get awfully sticky awfully fast. So, as practice always precedes theory, I'd just give it a try and spend a day in the darkroom figuring out what you can. Putting theory before practice often results in everyone's underwear getting into a knot: endless argument without any resolution.

mrosenlof · Feb 27, 2021

it's going to vary with *how* you want the dodged portion to be in the end. You may want to split your dodging with the same ratio of low:high as you have for the rest of the print area.

distributed · Feb 27, 2021

If both rules above are true, then both burned and dodged areas will have lower contrast because their green/blue ratios are higher (because burning adds green, and dodging removes blue).

As a direct answer to your question, if you limit yourself to burning with green and dodging the blue exposure, you are correct. Both manipulations will lower contrast.

You can of course also burn blue and dodge the green exposure. These also have their uses, the latter e.g. to make some highlighty-but-slightly-darker features stand out better - less muddy - against its darker neighbors. These manipulations increase local contrast.

The advice given to the possibility of split grade burning without splitgrading the print (@Nicholas Lindan) and reducing the base exposure to the non-dodged minimum and viewing the rest a burning (@michael_r) are good techniques to have in one's workflow toolkit.

I have a love-hate relationship to dodging when splitgrading. If you have a shadow gone too dark or a highlight too grey in bright and dark surroundings, respectively, splitgrade dodging works great. If you want to just dodge at the effective grade, say because a part of the image in the shade should be brightenes as a whole, splitgrade dodges make this more difficult than it would be with just one filter.

MattKing · Feb 27, 2021

distributed said:
The advice given to the possibility of split grade burning without splitgrading the print (@Nicholas Lindan) and reducing the base exposure to the non-dodged minimum and viewing the rest a burning (@michael_r) are good techniques to have in one's workflow toolkit.

+1

albada · Feb 28, 2021

distributed said:
The advice given to the possibility of split grade burning without splitgrading the print (@Nicholas Lindan) and reducing the base exposure to the non-dodged minimum and viewing the rest a burning (@michael_r) are good techniques to have in one's workflow toolkit.

I'm asking because I've built an Arduino-based LED-controller that is also a timer, and I'm trying to write its software to handle burning/dodging both easily and flexibly. Dodging is the more difficult case.
I'm thinking of adding a Tool-Time feature to the timer which computes the time you should use the dodge/burn tool, relative to the base exposure, in units of time-stops or percent. Time-stops is log2(seconds), and they behave like f-stops or EV numbers. Here's how I envision the controller handling common cases. In all cases below, the tool-time was set to 6 seconds:

Case 1: 20 second exposure (4.3 time-stops) supplemented by a 6 second (.4 time-stops) burn.
1. Expose for 6 seconds, burned.
2. The controller turns LEDs off for one second, which tells you to remove the burn tool.
3. The controller exposes for 20 seconds.

Case 2: Normal (non-split) dodge: 4.7 stops total (26 sec), dodged for .4 stops (6 sec).
1. Expose for 6 seconds, dodged.
2. The controller turns LEDs off for one second, which tells you to remove the dodging tool.
3. The controller exposes for 20 seconds.

Case 3: Split-grade dodge of green: 4.7 stops total (26 sec), green dodged for .4 stops (6 sec).
1. Expose with blue for 26 seconds.
2. Expose with green for 6 seconds, dodged.
3. The controller turns LEDs off for one second, which tells you to remove the dodging tool.
4. The controller exposes with green for 20 seconds.

The third case (split-grade dodge) is the most complex, and brings up a question: Can this tool-time feature be simplified or made more useful in some way? Is this the way you perform split-grade dodges?

Mal Paso · Mar 13, 2021

I find myself dodging green the most. There is much less effect in adjacent lighter areas and I usually want to increase contrast in the shadows, not just lighten.

I'm still running the LEDs on a single channel timer with switches. I printed for years with a hotrodded Time-O-Lite and time dodge and burn in my head. Old habits. LOL

When I lived in Escondido the selection of timers was limited. I crammed a 120V solenoid into a Time-O-Lite to hit the start button which was mechanical, you couldn't use a switch. Dual footswitches on the floor, one started the timer, the other focus/burn. Single multigrade printing back then with 6" filters in frames in a rack.

distributed · Mar 13, 2021

Case 3: Split-grade dodge of green: 4.7 stops total (26 sec), green dodged for .4 stops (6 sec).
1. Expose with blue for 26 seconds.
2. Expose with green for 6 seconds, dodged.
3. The controller turns LEDs off for one second, which tells you to remove the dodging tool.
4. The controller exposes with green for 20 seconds.

The third case (split-grade dodge) is the most complex, and brings up a question: Can this tool-time feature be simplified or made more useful in some way? Is this the way you perform split-grade dodges?

From a user point of view, the described 4 step sequence seems simple enough and I could imagine myself working with it. If you want to dodge both blue and green with a similar scheme, I suppose you will add a pause between blue base exposure and green dodging exposure so you know when to bring the green dodge tool into position.

A possible addition to this scheme is to lead into the dodge with a short red LED exposure. I have just built this but haven't got to try it out. My red LED is safe with Ilford MGRC, but due to bad experience with red LED safelights and Foma MG paper I think it won't work for Foma.

I think these workflow questions are very personal and you are unlikely to get a great deal of advice, however it is possible that you will get a lot of reports of how other people are working! One issue is that you, especially with a microcontroller, can build a great variety of workflows that are hard to lay out comprehensively and that commenters used to one type of timer or controller maybe did not conceive.

Trying to bridge the gap between comments on workflow and just stating what I do myself: For my own controller I haven't yet built a dodging feature, because I can't quite figure out how I should start. I have a stopgap solution, though, in that I use my computer (which provides the user interface in my setup) to act as a 120 bpm metronome. This allows me to easily manually time dodges in half second increments, which is typically enough. My original idea is to make a dialog that allows me to specify multiple dodges and have the program arrange the dodges in a timeline. If the individual dodges add up to more than the total exposure time, some of the dodges will need to be combined. This is not hard to program, but harder to present cleanly in a user interface and I suspect I might easily lose track of where I am in the dodging sequence. Some day I might give it a try, optimally with red exposure between the dodges to allow myself to position my tools. I have a hunch, however, that I might be totally fine with the metronome and prefer it to the programmed dodging because I can do the dodges in one fluid process, it feels a bit like playing an instrument.

When I lived in Escondido the selection of timers was limited. I crammed a 120V solenoid into a Time-O-Lite to hit the start button which was mechanical, you couldn't use a switch. Dual footswitches on the floor, one started the timer, the other focus/burn. Single multigrade printing back then with 6" filters in frames in a rack.

I love your approach, a very creative way of using the equipment you already have

radiant · Mar 13, 2021

distributed said:
For my own controller I haven't yet built a dodging feature, because I can't quite figure out how I should start.

I have implemented one to my darkroom timer and you know the address where to ask for code It was quite mind-bogging at first.

albada · Mar 14, 2021

Thanks for the recent replies to this thread. In response, I will add the following feature to my LED controller:

If you press the Start button twice within 1/2 second, it will begin the exposure with 8 or 10 seconds of red-only, giving you time to position a burn/dodge tool.
It also has a Manual button which simply turns on the LEDs so you can do anything you want, such as multiple burns. I'll add the same double-press-gives-red feature to that as well.

Also, I only put a Burn feature in the controller, because a dodge can be thought of as a burn where the main exposure time is that of the dodged area, and the remaining exposure can be regarded as a large-area burn. michael_r pointed that out in posting #5 above. That's fine for one dodge, but if you have multiple dodges, you'll have to do them during a single long exposure, the old fashioned way, or split the exposure into several short exposures, changing tools between them and double-pressing Start each time to give you some red-time to position each tool. Unless you can think of a simpler way to do this...

Doremus Scudder · Mar 14, 2021

Thinking about this a bit more...

The only time I really "split-grade dodge" is when I really need to change the contrast of an area. Sometimes I'll dodge the sky during the base exposure made at a middle contrast grade (say I'm printing with a #2 filter or whatever). I'll dodge it for half or even more of the base exposure time and then burn back with the #5 filter.

Or, the opposite, I'll dodge a contrasty area and then burn back with the #00 filter (actually, I don't use filters, but a color head, so insert max. yellow for #00 and max. magenta for #5; I'll even use a Wratten #47 blue filter to eek out a bit more contrast if needed.)

As implied above, I don't make my base exposures with split-grade technique, but start with an intermediate contrast setting. Burning is then done later with the extremes to adjust contrast in certain areas. I find this method a lot faster than making the two-contrast-setting ring-around test sheet needed for determining base exposure and contrast using the split-grade method.

I will, however, decide on my base exposure and contrast with a view to how I'm going to burn later; e.g., I'll start with a less-contrasty setting and then burn up the areas that need more contrast with the #5 setting or vice-versa. Also, I'll "underexpose" my base exposure since I plan on adding more exposure to all areas with burning, but with different filtration for different areas. That way, I can do most, if not all of the contrast tweaking with burning and keep the dodging to a minimum.

Best,

Doremus

cliveh · Mar 14, 2021

albada said:
I know how split-grade burning works: Because its surroundings are darker than the object being burned, burning with green (00 filter) reduces telltale halos because green affects dark areas less than blue.

But what about dodging? Let's assume that the dark area to be lightened has much lighter surroundings. To avoid putting a halo in those surroundings, would I dodge only the blue (5 filter) exposure? This rule assumes that blue affects lighter areas less than green.

If both rules above are true, then both burned and dodged areas will have lower contrast because their green/blue ratios are higher (because burning adds green, and dodging removes blue).

Or do I have this all wrong?
Mark Overton

May I ask how long you have been printing?

albada · Mar 14, 2021

cliveh said:
May I ask how long you have been printing?

About six months. I am a newbie.

A co-worker gave me an enlarger, and I quickly learned that LEDs are easier to work with than tungsten, and that sucked me into this LED-controller black ho..., I mean, project. I know that I know only the basics, so I'm learning from experienced folks in this thread.

albada · Mar 14, 2021

michael_r said:
Mark, what was it that led you to conclude LEDs are easier to work with than incandescent? I’m curious because to me it seems like the opposite is true (from a design perspective).

A good question. As I was learning to print with tungsten, I faced the following disadvantages of tungsten:

The need to frequently change contrast filters. That was a hassle, and the filters themselves experience wear in such handling.
I know that frequently turning a tungsten bulb on and off shortens its life, so I always felt under pressure to minimize the number of turn-ons.
Heat. If the bulb is left on a while for composing and focusing and pondering, it gets hot up there, which can warp negatives.
Finite life. I knew the bulb would eventually burn out, and that when it did, replacements are not widely available.
Condenser heads show scratches and dust more readily than diffusion.

LEDs suffer none of those disadvantages. But commercial LED-heads are costly, forcing me to make my own head (I copied Mal Paso's design here: https://www.photrio.com/forum/threads/led-split-printing-enlarger-lamphouse.173834/), and my own controller. I started with a reasonably simple analog controller, but I wanted better accuracy and range of illumination, and I wanted more accurate short-exposure timing than my Gra-Lab 300, which pushed me into building an Arduino-based controller/timer.

MattKing · Mar 14, 2021

Some of the disadvantages of "tungsten" you refer to aren't as important as you might think.
My enlargers with either tungsten or halogen bulbs tend to last years between bulb changes.
I've been working with halogen bulbs and dichroic filters (in either colour heads, or variable contrast heads) for years.

distributed · Mar 15, 2021

Mark, what was it that led you to conclude LEDs are easier to work with than incandescent? I’m curious because to me it seems like the opposite is true (from a design perspective).

I'll take the liberty of also answering the question! The short story is that I had access to a Heiland spligrade head (halogen lamp/dichroic filters) in a communal darkroom, liked the comfort and realized I could build something similar at home with my skills using LEDs.

If you want electronic or automatic control over contrast and you have a "traditional" light source like halogen, you need filters and an electromechanical system to move them in and out of place. I think this qualifies as complex and is definitely outside of the range of my skills. Even ignoring grade control, I would need to switch either high voltages (compared to digital electronics) or high currents, which is within my skill set but I will avoid it if possible.

Compare this to using blue/green LEDs. I can switch low voltages, e.g. 12 V, and low currents, e.g. way less than 1 A, with a logic level transistor directly attached to a microcontroller. This gives me direct control over both exposure and contrast with only simple electronics and no electromechanical components. My background is in electrical and software engineering, thus I was able to draw on my professional skills to modify my hobby equipment. In summary, in order to make my dichroic enlarger into a system approaching Heiland exposure comfort, for little monetary cost, using LEDs instead of traditional light sources was simple and within my skill set, hence the choice.

kenh · Mar 22, 2021

This thread is interesting.

I am also making an Arduino based controller for my home made LED head. I also have a light sensor that I can run around on the easel to analyze the contrast in the negative. This is actually my third generation version, the earlier versions were all analog based. Adding a microprocessor opens up a lot of flexibility.

Yes, adding Green will lower the contrast, and dodging Blue will also lower the contrast. Both methods will also alter the exposure so the area should be lighter or darker as well.

It looks a bit like this:

So, in your question dodging blue with green unaltered or burning green with blue unaltered both will lower contrast. But they will also have the side effect of changing the overall density of the area.

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.

distributed · Mar 22, 2021

@kenh I would be very interested in reading about your setup. You have been hard at work at this. Third time's the charm, they say!

I agree about microcontrollers adding a lot of flexibility. I took a next step as well by having only the sensor measurement and precise timing controlled by a microcontroller, the user interface is run on a PC.

I plan to write up an article about my design and will post the link here when I get around to it

Depending a bit on measurement series I found that my blue LEDs deliver an ISO(R) of 54-58 with Ilford MGRC. This is a bit short of the published number of 50 ISO(R) for a grade 5 filter. How far do you get with your blue LED and what's your range with the UV?

Bill Burk · Mar 22, 2021

albada said:
I'm asking because I've built an Arduino-based LED-controller that is also a timer, and I'm trying to write its software to handle burning/dodging both easily and flexibly. Dodging is the more difficult case.
I'm thinking of adding a Tool-Time feature to the timer which computes the time you should use the dodge/burn tool, relative to the base exposure, in units of time-stops or percent. Time-stops is log2(seconds), and they behave like f-stops or EV numbers. Here's how I envision the controller handling common cases. In all cases below, the tool-time was set to 6 seconds:

Case 1: 20 second exposure (4.3 time-stops) supplemented by a 6 second (.4 time-stops) burn.
1. Expose for 6 seconds, burned.
2. The controller turns LEDs off for one second, which tells you to remove the burn tool.
3. The controller exposes for 20 seconds.

Case 2: Normal (non-split) dodge: 4.7 stops total (26 sec), dodged for .4 stops (6 sec).
1. Expose for 6 seconds, dodged.
2. The controller turns LEDs off for one second, which tells you to remove the dodging tool.
3. The controller exposes for 20 seconds.

Case 3: Split-grade dodge of green: 4.7 stops total (26 sec), green dodged for .4 stops (6 sec).
1. Expose with blue for 26 seconds.
2. Expose with green for 6 seconds, dodged.
3. The controller turns LEDs off for one second, which tells you to remove the dodging tool.
4. The controller exposes with green for 20 seconds.

The third case (split-grade dodge) is the most complex, and brings up a question: Can this tool-time feature be simplified or made more useful in some way? Is this the way you perform split-grade dodges?

Quite simply find delta-E for the tone in question for the filter color (least noticeable difference) and use that to base the dodge burn times in that filter.

Make dodge burn units in terms of noticeable difference and if you stay within 2 units you won’t usually have a halo.

I make it sound simple but I don’t know if anyone made a system or offers instructions already...

Bill Burk · Mar 22, 2021

You probably have to burn shadows with green because the blue has already reached dMax and the green is the only layer with anything left to expose.

cliveh · Mar 22, 2021

albada said:
About six months. I am a newbie.

A co-worker gave me an enlarger, and I quickly learned that LEDs are easier to work with than tungsten, and that sucked me into this LED-controller black ho..., I mean, project. I know that I know only the basics, so I'm learning from experienced folks in this thread.

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.

Pieter12 · Mar 22, 2021

kenh said:
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.

Are you experiencing any of the UV-induced focus shift that Ctein describes in his book, Post Exposure?

Sirius Glass · Mar 22, 2021

kenh said:
This thread is interesting.

I am also making an Arduino based controller for my home made LED head. I also have a light sensor that I can run around on the easel to analyze the contrast in the negative. This is actually my third generation version, the earlier versions were all analog based. Adding a microprocessor opens up a lot of flexibility.

Yes, adding Green will lower the contrast, and dodging Blue will also lower the contrast. Both methods will also alter the exposure so the area should be lighter or darker as well.

It looks a bit like this:

View attachment 270242

So, in your question dodging blue with green unaltered or burning green with blue unaltered both will lower contrast. But they will also have the side effect of changing the overall density of the area.

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.

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

Split-Grade Dodging

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