Ilford 500h and 500C

Dear darkroom friends,


I’ve been working with an Ilford 500H head and the 500C pad, diving deep into the magical world of split grade printing. Along the way, I discovered two more Ilford gems: the Power Dial and the CP500. Both seem to allow control over the green filter’s intensity—which would be absolutely amazing, especially since I’m printing negatives with densities up to 1.00 in key highlight areas. Every nuance matters.





The 500C pad lets you adjust the green filter intensity from 1 to 6, but it doesn’t really specify what percentage or grade each step corresponds to. I’ve been running contrast tests, spending hours and going through sheets of paper, but haven’t quite landed on consistent results yet. Hence, the research.





I’m wondering—has anyone here developed a method to properly test these filters? Or maybe swapped out the pad for one that allows finer control over filter increments? I’ve also started exploring F-stop printing, which feels like another beautiful rabbit hole worth getting lost in.


Any wisdom, experiences or even curious guesses are more than welcome. This craft is just so much richer when we explore it together!

Rmaydana said:

the Power Dial and the CP500

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I'm not familiar with the Power Dial. What is it?
By "CP500", do you mean the 500P probe that can be used for baseboard measurements? If so, it's a nice toy, but IMO not of all that much added value.

Rmaydana said:

negatives with densities up to 1.00 in key highlight areas

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So those are really very thin negatives? 1.0logD is quite thin for highlights.

Rmaydana said:

The 500C pad lets you adjust the green filter intensity from 1 to 6

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The 500 system works by altering the ratio between green and blue. It doesn't just adjust the green intensity. It adjusts both green and blue at the same time.

Rmaydana said:

haven’t quite landed on consistent results yet

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Please show what you've got and what kind of consistency problem you think you see.

Rmaydana said:

The 500C pad lets you adjust the green filter intensity from 1 to 6,

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Not sure which pad/controller you're referring to. The one I had allowed the grade to be set in half steps IIRC. I always found that perfectly adequate.

Rmaydana said:

Or maybe swapped out the pad for one that allows finer control over filter increments?

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Why would you need this? You mentioned split grade printing earlier. This gives you control over fractional grades that's virtually unlimited, even if your filters can only be set to the highest and the lowest contrast with nothing in-between.

I have a feeling you've started to dig a hole for yourself without really knowing why you'd want to do this, and you're now in the process of falling into that hole.

PS: I've used a 500 system for several years. I found it to be perfectly consistent and straightforward to use. I'm surprised you're running into trouble with it; it's literally as easy as setting the grade and the time and press the button. For split grade, you can set two (or even more) grade/time combinations if you want, although I never used that option much.

1- I had this note saved a long time ago, and honestly, I can’t remember if it’s accurate or just a mistake I jotted down. I’ve always seen the 500C and the CPM units used with the 500H head.

2- Now, here’s something that really caught my attention—when working with low-density negatives, I’m able to get good contrast just by boosting the blue filter. It’s subtle, but real.

3- On the back of the pad, there are 7 program settings—from 1 (least amount of green) to 7 (strongest green intensity). I’m wondering if anyone here has tried calibrating using those program settings?

4- With low densities (around 1.00), I’ve noticed you don’t need much green light to pull detail in the highlights—the bright zones. That’s what I’m curious about: just how much impact do those 7 rear programs have?

5- Also, when someone mentions IIRC—is that referring to grade 2½?

6- I have to say, Ilford’s components for the enlarger are incredibly consistent. I’m just a bit restless… curious, I guess. It’s part of the journey—trying to understand how those 7 programs really behave. And if I don’t see meaningful differences or improvements, I’ll probably go back to program 1—it’s served me well for over 5 years.

IIRC = "If I Recall Correctly"
And, IIRC, the programs are/were ways of calibrating for different paper types.
One thing to be cautious of is the fact that over their history, there were a few relatively minor - and some not so minor - changes to the models, and the accompanying documentation changed accordingly. It can be difficult to ensure any documentation you find matches the unit you have exactly.

koraks said:

I have a feeling you've started to dig a hole for yourself without really knowing why you'd want to do this, and you're now in the process of falling into that hole.

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Exactly - Ilford's own documentation is pretty clear about what the 500 system can and can't do. It was intended for churning out high productivity lab work, not necessarily fine-art. The two most useful features are the push-button grade selection and the metronome tone - and neither of those are really worth the premium that some want for these units today.

koraks said:

The 500 system works by altering the ratio between green and blue. It doesn't just adjust the green intensity. It adjusts both green and blue at the same time.

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I think what is being referred to is the ability to adjust the green 'normal' relative intensity against a nominally fixed blue intensity. Never had any need to mess with that with years of working with 500 heads (other than switching to the 500HLZ channels for running a modded MG400). I think it mainly had to do with the probe and adjusting the intended 'G2' within the mid-tone exposure constant that the probe works to (I'd need to go and dig in the manual for this). Either way, 0 & 5 don't change on any of the program shifts.

Rmaydana said:

With low densities (around 1.00), I’ve noticed you don’t need much green light to pull detail in the highlights—the bright zones. That’s what I’m curious about: just how much impact do those 7 rear programs have?

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What you're finding out is that negs with highlights that aren't overdeveloped are much easier to burn in, especially with a lower grade (think sensitometrically, based on the curve shapes at 00 and 5 and how much energy is required on a flatter vs steeper gradient to make a visible change). That's all. No magic in either split-grade or F-stop printing (other than the latter being a reasonable way of understanding how to quickly adjust exposure times without making needlessly small increments). Process controls (and understanding exposure-to-process relationships) rather than mystical time-wasting test-exposure patent-medicines is the way forward.