Durst La 1200, CLS450 head, too bright!

[athens01]

Sorry to keep harping on it, but were talking about amounts of light not wave length or color of light. If adding equal part magenta and yellow are "neutral" why would paper companies list suggested filtration for specific filters for color head enlargers be a combination of yellow and magenta? If adding equal parts yellow and magenta were neutral then a print at 10 yellow, 50 magenta would be the same as a print at 40 magenta. Or 100 yellow and 50 magenta would be a 50 yellow. Obviously having filter combinations of magenta and yellow is what makes the filter, not what cancels
it.

[Renato Tonelli]

Maybe the head on your L1200 is different from mine. In addition to the YMC filters, mine also has a Neutral Density filter setting. Maybe the earlier color heads don't have this feature? The lamphouse is is so bright that without the ND setting, my exposures would be 10 scs. or less.

Adding equal parts Y & M or Cyan seems counter intuitive to me but it's late and I may not be thinking straight.

[ChrisN]

Thanks for the ideas, everyone. Yes, the diffuser I am missing is the one in the top of the mixing box - that ebay listing is for one in the bottom. But that does raise the possibility that the one I have in the bottom might be the optional less-dense one.

I visited a local plastics supplier today who was able to supply me with a 90mm x 90mm x 3mm piece of frosted perspex at nil cost. I've fitted that, and installed a 200w bulb to replace the usual 250w. Between the two I've now got a 30 second exposure at the same other settings. That's usable, but I still need to dial it back a few stops. I might be able to fit a second layer of frosted perspex beneath the first.

[ic-racer]

I stand to be corrected but I am sure that adding cyan filtration must reduce the amount of light reaching the negative regardless of the sensitivity of the paper.

Think of it (cyan) as using a dimmer safelight bulb. You can tell the difference but your paper can't

[athens01]

Adding equal parts cyan magenta and yellow is subtracting "white" light from the source, but the color of the light is still "white" You can see it when you dial it in. Start with equal amounts of yellow and magenta and dial in the same amount of cyan. The color goes back to that without any filtration, but it's not as bright. The paper may not "see" red, but in equal parts the light is white as if the bulb had no filtration at all, but it is dimmer. I'll explain more when I'm not
using a freakin' phone to reply.

[ChrisN]

Still playing with this. I substituted a 2-stop ND filter for the top diffuser, and it was worse - very short exposure needed again. I'll try for another layer of the diffuser perspex under the top piece.

The discussion about the colour filtering is very interesting, but I'd rather not play with the filtration settings at this stage as I'm trying to use the suggested settings I found somewhere on the 'net, per the attached snapshot. Once I've settled in a bit with the enlarger I'll feel more confident.

[ic-racer]

Yes that scale looks like the one from the Ilford paper insert. I use that one with my CLS2000 and it works perfect.

? Why did you replace the diffuser with the ND filter? Can't you use both together?

[ChrisN]

Yes that scale looks like the one from the Ilford paper insert. I use that one with my CLS2000 and it works perfect.

? Why did you replace the diffuser with the ND filter? Can't you use both together?

To see if it would work! And no, the two combine to too great a thickness. But there is room to add another layer under the top plate if the piece is cut to the correct size.

[Tony Lakin]

Think of it (cyan) as using a dimmer safelight bulb. You can tell the difference but your paper can't

"By balancing the yellow and magenta dichroic filtration with a color enlarger head, you can achieve a full range of evenly spaced contrast grades and incremental grades with VC papers. With a careful balance of yellow and magenta, it is possible to speed-match the filtration. Cyan can also be used as ND filtration to help speed-match filtration".

From "The variable contrast printing manual" by Steve Anchell.

[ic-racer]

"By balancing the yellow and magenta dichroic filtration with a color enlarger head, you can achieve a full range of evenly spaced contrast grades and incremental grades with VC papers. With a careful balance of yellow and magenta, it is possible to speed-match the filtration. Cyan can also be used as ND filtration to help speed-match filtration".

From "The variable contrast printing manual" by Steve Anchell.

Ilford MG paper is sensitive to bright red light. So technically that is correct. But in general, any 'anti-cyan' light is not going to have much effect (if any) on the paper's exposure.

I use "primary Red" Rosco for my 'safe filter' under the enlarger lens. When I dial in cyan with that 'safe filter' in place the image, expectedly goes black. But, technically that Rosco filter is not perfectly safe (as Ilford's data indicate and as I have found out from trials).
Ten minutes and a step wedge and one can see if it (cyan) does anything to a print under your own conditions.