Dichroic Red Safety Setting

bvy · Oct 8, 2013

My Omega C700 enlarger has a color head but the red safety filter is long gone. I wonder, is there a dichroic setting that would be safe for orthochromaitc papers? Sometimes I work without an easel, and it would be a good aid for aligning the image on the paper. Thanks.

Rick A · Oct 8, 2013

Use a red filter under the lens. Either find a C-700 filteror hand hold a red camera filter.

AgX · Oct 8, 2013

The Maximum red filtration you'd get from a colour head is by combing the Magenta and Yellow filter.

David Brown · Oct 8, 2013

http://store.khbphotografix.com/Replacement-Red-Filter-for-Omega-B600-and-C700-Enlargers.html

ic-racer · Oct 8, 2013

AgX said:
The Maximum red filtration you'd get from a colour head is by combing the Magenta and Yellow filter.

This.

pentaxuser · Oct 8, 2013

ic-racer said:
This.

Was the word "this" meant to be a link to something? By itself I cannot work out to what it refers? Any help appreciated

Thanks

pentaxuser

cliveh · Oct 8, 2013

You need to use a red filter, not a magenta/yellow/cyan combination.

AgX · Oct 8, 2013

AgX said:
The maximum red filtration you'd get from a colour head is by combining the Magenta and Yellow filter.

That would be a log. Red-density of about 1.

(a colour seperation filter goes above Dlog 3)

Gerald C Koch · Oct 8, 2013

Just buy a sheet of Rubylith and replace the red filter. This stuff is not expensive. People use it to make safelight filters.

ic-racer · Oct 8, 2013

pentaxuser said:
Was the word "this" meant to be a link to something?

Alternative to "+++" to emphasize the value of AgX's comments.

MartinP · Oct 9, 2013

Instead of putting your paper on the baseboard, or on a black card covering the baseboard, try a dark-red piece of mounting card. You can mark the required paper position in pencil (for ease of removal) at the time of framing and focussing, then easily see the marks to place your paper due to them showing up well under safelighting. No red-filter needed. Alternatively , make up a filter holder from a bit of foamboard etc. and put some rubylith in there.

AgX · Oct 9, 2013

As a side note: that "Rubilith" is hinted at Apug again and again. I first came across this designation here.
And such foil seems to be quite common at some places. Though over here one only gets such at dealers serving the printing industry.

pentaxuser · Oct 9, 2013

MartinP said:
Instead of putting your paper on the baseboard, or on a black card covering the baseboard, try a dark-red piece of mounting card. You can mark the required paper position in pencil (for ease of removal) at the time of framing and focussing, then easily see the marks to place your paper due to them showing up well under safelighting. No red-filter needed. Alternatively , make up a filter holder from a bit of foamboard etc. and put some rubylith in there.

Can you expand on this? I am unclear how a dark red piece of mounting card means that no red filter is needed? It may be that I can't work out how the red piece of card is used to act as a substitute for the red filter. Thanks

On a separate point and not related to MartinP's quote I am at a loss to understand what the relevance of a combination of Y and M giving a red colour has to the need to safely protect the paper. A combination of Y and M is used in dual filtration exposure so cannot protect the paper, can it?

I assume that AgX's post talking about log 1 was actually saying that the strength of the max red combination of Y and M isn't enough to give the kind of protection needed for paper so therefore doesn't qualify as a safety filter. Am I right?

Maybe it was only me who found the reference to Y and M giving max red confusing as an answer to whether this combo qualifies as a safety filter

pentaxuser

AgX · Oct 9, 2013

pentaxuser said:
I assume that AgX's post talking about log 1 was actually saying that the strength of the max red combination of Y and M isn't enough to give the kind of protection needed for paper so therefore doesn't qualify as a safety filter. Am I right?

Yes.

RalphLambrecht · Oct 9, 2013

bvy said:
My Omega C700 enlarger has a color head but the red safety filter is long gone. I wonder, is there a dichroic setting that would be safe for orthochromaitc papers? Sometimes I work without an easel, and it would be a good aid for aligning the image on the paper. Thanks.

there is no such combination,but you can try a max cyan setting and check if that leaves you sufficient luminance to see the image. it should protect the paperadequadtly.

cowanw · Oct 9, 2013

RalphLambrecht said:
there is no such combination,but you can try a max cyan setting and check if that leaves you sufficient luminance to see the image. it should protect the paperadequadtly.

I don't think so. Paper is blue green sensitive.
cyan lets blue green through; it is minus red. it will thoroughly expose your paper. There seems to be some confusion between a red filter and minus red in this thread.

MartinP · Oct 10, 2013

For Pentaxuser, above.

Most enlarger baseboards are white or grey or woodgrain. If you place the paper on that surface and expose it then you will probably have a fair bit of light spillage, even with masking in the neg-stage - the usual answer would be to put a piece of black card on the baseboard to kill the diffuse reflections. If you have a piece of black card on the baseboard then you cannot easily make alignment marks which will be visible under safelight, which in turn implies that you swing a red filter in to the light path so that you can see what will fall on your paper whilst it is in position and the enlarger is on. Great, except that filters fade or may not be present on a colour enlarger.

Using a dark-red card on the baseboard means that you can use the back of an old print (same size as the paper you are using of course) to decide your paper position, then make soft-pencil marks to show where you want your paper to go for the exposure. Alternatively, use a larger piece of dark-red card with the paper-size drawn on it directly, and move the whole thing around for alignment. Because the card is dark-red it appears light in colour under the safelight and the alignment marks show up clearly, plus any white-light from the exposure bouncing off the dark-red card will have much less affect on the exposure you have made.

That took longer to write than to use the method for an exposure. If you have curly paper then you might be stuck, though you can tape the corners down, use magnets on the base board of a dismantled old easel etc. etc. though this will need some trimming. If the paper is not flat it's probably more practical to use an easel and trim it down afterwards - but if you want to make large prints only infrequently then using the paper without a large and expensive easel can be an economic and practical choice, even if you have to trim a few millimeters to lose the corner marks from tape etc.

DREW WILEY · Oct 10, 2013

Conventional subtractive colorheads won't deliver a very deep red effect by mixing Y and M. And being subtractive, there is going to be a bit
of residual white light contamination left over ... so certainly risky trying to do this for safelight purposes. But it was common to use a swing-away filter holder beneath the lens which would hold a very deep red tricolor filter like a 29. Or you could just screw a glass one on to the enlarging lens threads.

pentaxuser · Oct 10, 2013

Thanks Michael 1974. That was in fact what I had presumed to be AgX's point and he confirmed this but always nice to get confirmation from another user

MartinP Thanks for your reply. Most easels like the Paterson, the Durst Comask etc seem to be white and yet I haven't noticed a problem of light spillage with a neg in the neg carrier but a dark red paper might help and I understand why it has advantages over a black paper. However by itself a red paper on the base board doesn't for instance substitute for a safety filter which can be swung across when you need to get a dodger in position or need to place a cut-out in position for more complicated dodging

I now understand, I think, the function of your red card but on balance, I still think that a functioning red safety filter under the enlarger lens has advantages.

pentaxuser

MartinP · Oct 10, 2013

That's right, they have different functionality. For the OP's original question though, a bit of dark-red matt board will be easier to arrange than scratch-building a red swing-filter

Doremus Scudder · Oct 11, 2013

Get an under-the-lens swing-away filter holder and some ruby-lith or the like, or find an alternative way to position your paper.

How about just using some blue painters tape to mark where the corners of the print should go? Position these with white enlarger light and with a wide-open aperture. Then dial-in your filtration, stop down and position your paper. Or, get some sheet steel and magnetic strips to hold your paper (used in conjunction with the red filter, this is your best non-easel solution IMO).

Best,

Doremus

bvy · Oct 11, 2013

Lots of good ideas here. Thanks to all for chiming in. Sounds like the dichroic filters will allow too much light through at any setting for this to be a workable alternative to a true red filter. I might pick-up some red posterboard and try the aforementioned idea regarding marking and positioning.

Curious, though, why Ralph Lambrecht suggested maximum cyan as an option. Given that orthochomatic paper is blue-green sensitive, I (and others obviously) wouldn't have thought that would work. But he's written extensively on analog photography, so he must know something I don't.

Dichroic Red Safety Setting

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