Use of the blue filtration as ND filter??

[delphine]

Hello all,

Your help is so badly wanted....

I am setting up for some artwork which I have in mind which will involve a succession of very small prints. Because of the rigorous size of the enlargement needed, the enlarger head is going to be 17cm away from the easel.

I use a color head, and I don't have a dedicated ND lever. I am wondering whether I can use the cyan filtration as an ND filter.

If I do so, what is the impact on the grades when I get to use the usual magenta/yellow filtration?
Small note: I remember that the 3 filters nil each other, however I will be using in turn magenta and yellow, as opposed to conjointly, as I split grade everything (bad habit).

That would be awesome to have a couple of pointers before I start my printing session.

Thank you

Best

Delphine

 

[paul_c5x4]

How about screwing an ND filter on to the end of the enlarger lens ?

 

[Vaughn]

I don't see why not it would not work. But I do not think it would be a matter of just adding cyan (not actually "blue"). One would have the desired filter settings for the contrast one wants, then one would add to that equal amounts of Magenta, Yellow and Cyan -- the more of each, the stronger the ND. My guess is that it is not as simple as that, and it might take unequal amounts of M,Y, & C filtration to achieve a true "Neutral" Density. As an example, if one has a filter pack of 30M and 10Y, and then adds 10C to act as a ND filter, then one would actually have the contrast equivilent of 20M and 00Y -- or thereabouts. (I assume the the 10 units of cyan would neutralize the contrast affects of 10 units of M and Y.) But that's what experimenting is for!

Of course what would be a cleaner fix would be able to use a longer focal length lens on your enlarger. Then you could have the head farther from the easel and not deal with need of a ND filter.

Vaughn

 

[Ian Grant]

Delphine, you can just increase all three filters, if you add the same of each they will act as a ND filter.

An alternative is to use longer focal length enlarger lens, so if you were shooting 35mm use an 80mm lens, but I guess you'll use 120.

Ian

 

[paul_c5x4]

As an example, if one has a filter pack of 30M and 10Y, and then adds 10C to act as a ND filter, then one would actually have the contrast equivilent of 20M and 00Y -- or thereabouts. (I assume the the 10 units of cyan would neutralize the contrast affects of 10 units of M and Y.)

That is the way I understand the effects of dialling cyan to gain neutral density. But if Delphine is doing split density printing, this could/would reduce her min/max contrasts. For example, dial in 130M to get grade 5, add 50C and 50Y for ND. The net result would be 80M and give grade 4 (assuming Ilford VC papers).

 

[delphine]

wow, I just popped out to get some croissants, and you guys have already chimed in.

Vaughn - point taken, blue is actually cyan. I wish I could edit the thread's title.
I see your point about the ratio of the 3 filtrations for them to nil each other.

To all - Yes I am printing off 120, and I am using my longest focal, so the head is the farthest away I can.

Paulc_5x4: I have some ND filters but they are different filtration diameter. May be I could try to cellotape one, somehow, could this do the trick?

 

[cowanw]

I am under the impression paper is that with the Magenta Yellow system of grading the paper is sensitive to blue/green and the removal of blue/green only means that less "Actinic" light is getting to the paper.So yes Cyan can be used as a neutral filter.
If the paper is not equally sensitive to the blue and the green then some finetuning to either Magenta or yellow may be required.

 

[erikg]

That is how it works when printing on color materials, I don't see why it wouldn't work for black and white. I remember doing this for small prints at the lab.

 

[polyglot]

B&W paper is sensitive to blue and green light only, with the blue producing more contrast. Adding cyan filtration only cuts out red, therefore it should have no effect either on your exposure time or your contrast. It will theoretically provide no ND effect at all. I haven't tried it myself, but there will shortly be people in this thread who have and are very emphatic that it does nothing at all.

If you dial in some of all three colours (CMY) then you will get ND effects but that's only because you've dialed in both M and Y, the C has no effect. Y attenuates B (high contrast layer) and M attenuates G (low contrast layer), so if you dial in both in equal amounts, you remain at grade 2 but slower. Obtaining an extreme grade may be difficult because if you're dialing in both Y and M then the colour ratio you can achieve is clearly reduced compared to dialing in just one.

Edit: a screw-in ND filter seems the best option. If it's too small/large then use step-up/down rings as necessary. And if you're printing tiny, you should be able to stop the lens down a very long way as the diffraction effects won't be visible on such a small print.

 

[phfitz]

You can make ND filter material from B&W film in dilute developer in room light and install above the neg stage to block the light. This will leave full adjustment for split grade printing. Just mix your regular developer 1-4 with water to dilute.

 

[delphine]

Et Voila !!

Well, I have sorted out the ND issue and it works very well, not without a sweat I have to say.

I got the idea to replace the cyan filtration by a piece of base fog neg ( iPhone snap: http://twitpic.com/fyyd0 ). As I unscrewed the holders of the cyan filtration, I dropped the cyan filtration in the head which proved a bit of an exercise to get back as I had to dismantle the head and had started the enterprise perched on top of a swirly rolly stool ... I pass on the details and how the heavy beard easel flew across the room. Somehow the enlarger and I survived, I did not even blow the bulb. Eventually I got hold of the little b***r (<--- read cyan filtration), intact still and not broken. I tried to fit in my little piece of neg, but it proved too challenging without removing the whole of the filtration system. So I dismantled the back of the head to inventory how many circlips I'd have to mess around with and how likely I was have an operational head after I am done.
Somehow, lost in my thoughts, the obvious surfaced up as there was a holder with magnifying glass in between the bulb and the filtration system, so rather than fitting in the neg in the holder of the cyan filtration, I fitted it in front of the magnifying lens.
It works wonders... no change to the grade and filtration when using magenta/yellow, and I gained several f stops.

When I am more chilled and more prepared to unscrew the filtration mechanism, I'll attempt to fit in properly the mini patch in the cyan filtration holder, then it will be all honky dory.

Thank you all for your input.

Best

Delphine

 

[keithwms]

Why not cut down your light source rather than putting a filter over the lens. Maybe you could make yourself a pinhole in aluminum foil and put it over the enlarger bulb.....

Anyway, sounds like you found a solution.

 

[fschifano]

You're making things too hard on yourself. There's no need to dismantle your enlarger's lamphouse. Get some of this Dead Link Removed, cut it to size and simply slip it under the lamphouse above the negative. The link points to the 1/2 stop density material, and there are stronger ones available. You can stack them if you like. I use 'em a lot and they work a treat. Cheap too.

 

[JBrunner]

If you are using variable contrast B&W paper and controlling contrast with yellow and magenta settings, you can increase cyan to reduce the exposure. No need to stick gels in the light path or disassemble the head, or jump through any other hoops. Just twist the dial and see.

 

[paul_c5x4]

I had to dismantle the head and had started the enterprise perched on top of a swirly rolly stool ...

Please use a solid stool or a stepladder rather than a pile of books or a wibbly-wobbly chair. We really, really don't want to be pushing you round the Dales in a wheelchair.

 

[delphine]

Please use a solid stool or a stepladder rather than a pile of books or a wibbly-wobbly chair. We really, really don't want to be pushing you round the Dales in a wheelchair.

Now that would be a sight, Dee in a wheelchair, a pie in hand... I am sure that the perspective would make more than one grin in a silly manner.

To all, thank you for the good ideas given... yes, with retrospect, I regret a bit having taken the cyan filter off. Will use something else than the stool to put it back

 

[cowanw]

Polyglot, not only are you correct in theory but in the real world as well.
I am in the darkroom for the first time since this thread and was using the Number 2 kodak settings for Ilford papers. I dialed in an extra 40 cyan and then an extra 150 cyan. The most change was perhaps a half grade higher in contrast. No change in times and certainly no ND effect.
Thanks you for setting me straight.

B&W paper is sensitive to blue and green light only, with the blue producing more contrast. Adding cyan filtration only cuts out red, therefore it should have no effect either on your exposure time or your contrast. It will theoretically provide no ND effect at all. I haven't tried it myself, but there will shortly be people in this thread who have and are very emphatic that it does nothing at all.

If you dial in some of all three colours (CMY) then you will get ND effects but that's only because you've dialed in both M and Y, the C has no effect. Y attenuates B (high contrast layer) and M attenuates G (low contrast layer), so if you dial in both in equal amounts, you remain at grade 2 but slower. Obtaining an extreme grade may be difficult because if you're dialing in both Y and M then the colour ratio you can achieve is clearly reduced compared to dialing in just one.

Edit: a screw-in ND filter seems the best option. If it's too small/large then use step-up/down rings as necessary. And if you're printing tiny, you should be able to stop the lens down a very long way as the diffraction effects won't be visible on such a small print.

 

[polyglot]

Depending on how your cyan filter is constructed (i.e. exactly what its cutoff frequency is and how steep it is), it's possible the cyan will lose a little bit of the longest green wavelengths, hence your increased contrast.

Still, nice to know that it is as it was explained to me.