Question about cold light and vc filters

[Tim k]

I am thinking that the filters on my D6 Super Chromega head may have faded over the years. I also have one of those little pancake cold light heads with the fluorescent tube, that I would like to use, but I dont really want to use graded paper. I do like the quiet of the cold head, as my Chromega sounds much like a 747 taking off.

My question is; If I pick up some vc filters, can I just lay them on top of the negative? With the cold head, there is no obvious place to put them in. Or should they go under the lens?

Thanks guys

[ic-racer]

In general dichroic filters don't fade. If you have a step wedge, you can test you maximum CCY and maximum CCM and see what you get.

If you put the VC filters between the light and the negative, make sure they are far enough from the negative so the dust on them won't be in focus (probably greater than one inch). Probably easier to just put them under the lens.

I use Dichroic filters for VC printing and also use a coldlight with Ilford under the lens VC filters. Both ways of doing it work fine.

[Tim k]

Thanks,
Sounds like under would be a lot simpler. Need to do some shopping.

[John Powers]

Tim K,
I have a Durst 138S, 8x10 conversion with 12x12 Aristo Cold Light Head with split grade filter holders underneath the lens. The conversion was done by Michael Mutmansky. The holders use six inch Ilford filters cut down to about five inches.

Michael was delayed in completing the filter holders. For about six months I used a simple one gallon alcohol can cut out so it fastened to the lens. The filter could be slid in from the front. The filtered light went through a hole in the bottom to the paper. The filter holders were an elegant replacement for this mess of scrap metal that had worked well.

This allows me to use filtered light, even split grade, for 8x10 enlargements or as a filtered light source for either 8x10 or 7x17 contact prints. The whole system is silent unless I make a mistake and swear at it.

If you are a subscriber to APUG.org you can see two images in my (jp80874) gallery. If not PM me your email address and I can send you pictures. I just did my Sunday morning five mile hike with the dogs and I am too tired to learn how to post pictures here.

John

[Mark Sampson]

The old 'flying-saucer' type cold-light heads have several serious problems. 1) the spectral transmission of most fluorescent tubes doesn't match VC paper, making the use of contrast filters questionable at best. 2) on/off time for the fluors makes accurate exposure time difficult. 3) is the fact of the lamps' varying output with temperature (the achille's heel of old-style coldlights), again making consistent print exposures difficult.
In short, I think using the dichro filters in a Super-Chromega head is an effective and painless way to control contrast on VC papers.
I think the flying-saucers are a complete waste of time; you could possibly get one to work, at a large cost of time, paper, and aggravation. I've worked with more 4x5 Super-Chromega enlargers than I can count, and none of them have ever resembled a "747 taking off". The fan should be relatively quiet; if it isn't, consider replacing it. If you truly can't tolerate the sound, disconnect the fan and do short exposures. We did that with one, once, in attempt to reduce vibration at high mags; but there was no improvement in the prints and we didn't burn up the head either. It was quieter... just not a big deal in a darkroom with water running in the sink and a couple of roller-transport print processors nearby.

[Tim k]

Mark,
Very good points. Honestly I exaggerated a "little" bit about how loud it is, but still, I just cant wait to turn it off.

It just seems so peaceful in the darkroom. Except for that fan. Perhaps I should look into doing something about the fan. I had read somewhere about an external exhaust fan, that would pull air out through a flex duct system, and that sounded like a good idea.

[Mark Sampson]

Tim, I take your point; but really, the fan isn't needed unless you're doing very long exposures (minutes) or are cranking out dozens of 5x7s and 8x10s like a commercial lab. Disconnect it (or put a switch in) and see. The convenience and effectiveness of dichro filters and a light source of the proper color are hard to exaggerate. In my darkroom, I have a 4x5 Super-Chromega dichroic next to my old Omega D-II with a stabilized Zone VI cold light and under-the-lens Kodak filters. Guess which one gets the use?

[Chuck Pere]

I would think that the cold light would be a step backwards. With the color head you have almost infinite easy control over contrast. With the filters you will have to make two exposures through two filters to get at contrasts in between. And some times you need that. I suppose you might get better contrast extremes with filters but you can always use them with the color head for those cases.

[John Powers]

.... 2) on/off time for the fluors makes accurate exposure time difficult. ..

You can control this aspect with the RH Designs stop clock vario designed with a probe into the light area for consistent exposure. See their web site for details and explanation.
http://www.rhdesigns.co.uk/darkroom/...ock_vario.html
John

Pictures sent. Sorry Tim. I see now that you are in AZ. I am afraid you probably can't drop in for a look see in downtown Bath, OH.

[jeroldharter]

What is a flying saucer cold light?