D.I.Y. Under the Lens Safe Filter for Enlarger.

[BobUK]

I have found a few people on various forums asking about what filter to use as a red swing filter under the enlarger lens.
Nobody appears to name an actual filter and brand.
So I am raising the topic again.

I use an old 4x5 camera body with the Intrepid light source for enlarging 4x5 negatives.
I can easily fabricate a swing holder for an under the lens filter.

I already have a few old scuffed red filters. Perfectly serviceable for the job in hand, but not for actual use on a camera.

What I cannot find is any relevant data for Cokin and Hoya Red filters.

Can anyone point me in the right direction for the data, or actually name a camera filter that worked for them?

Thank you.

 

[glbeas]

The swing filters Ive seen have been cheap plastic, guess at a 25 red. Its just there to help position the paper so as long as its big enough to block any white light spilling around it you have nothing to worry about. Not rocket science. Try out what you have and see.
You might want to look at the under lens contrast filter sets with a holder, they sometimes have a red filter in the set.

 

[Ian C]

Although I don’t have a data sheet, the original red safe placement filter is either a Kodak Wratten #25 (old Kodak designation is “A”—same filter), or something very close to it. This was initiated long ago when all enlarging papers were orthochromatic—essentially blind to red light.

The problem is that almost all B&W enlarging paper is now variable contrast and requires an amber Kodak OC or the equivalent Ilford 902 “brown” filter.

The filter chosen should match the safe spectral range of the emulsion in use. A red filter isn’t actually safe with modern variable contrast paper emulsions.

Of course, people still used red safe placement filters on enlargers with modern paper. So long as the intensity isn’t too great, nor the exposure too long, not enough light reaches the emulsion to cause fogging. Ideally, you’d want something equivalent to a Kodak OC filter for modern variable contrast papers.

https://www.kodak.com/content/products-brochures/Film/KODAK-Safelight-Filter-OC.pdf

As a matter of practicality, the safe placement filter is not required. I own several enlargers that are equipped with the original red filters. I never use them. All that’s needed is a paper holding easel and an upside-down scrap sheet the same size as the print you want to make. Use this for focusing and composing. Switch off the enlarger lamp. Place the paper in the easel and expose. That’s all there is too it.

The original purpose of the safe placement filter was when a user wanted to make the occasional oversize print for which the proper easel was not at hand. The filter allowed positioning the paper into the projection, the lamp switched off, the filter removed, and the exposure made.

 

[koraks]

A red filter isn’t actually safe with modern variable contrast paper emulsions.

Ideally, you’d want something equivalent to a Kodak OC filter for modern variable contrast papers.

I'm sorry, but I think you've got it backwards. Ideally you'd use something that blocks everything in the range the used paper is sensitive to, and this implies it depends on the paper. On this, we agree. However, a Kodak OC filter cuts off at around 550nm and e.g. Fomaspeed has a sensitivity reaching to approximately this point. It's a well-known problem that Foma papers do NOT work with certain 'orange' safelight filters.

A safe choice is in fact a red filter, i.e. something that blocks everything from ca. 600nm and upwards, since there's no B&W enlarging paper (in current production) with sensitivity extending that far. A good candidate is the mentioned Kodak Wratten #25, but a simple piece of Rubylith should do the trick just the same.

For most papers and brief exposures, the Kodak OC filter may work OK as well. The advantage of something in the orange range is that the human eye is more sensitive to that bandwidth and thus it takes a lot less light to see what's going on. A projected red image is very difficult to see.

Overall, I've never found a safelight filter on an enlarger to be of much use at all. The only potential benefit I can think of is with burning & dodging, but I find a simple piece of cardboard and a footswitch are at least as effective: just hold the cardboard under the lens, use the footswitch to turn on the light and the projected image on the cardboard will show you where to burn & dodge.

 

[RalphLambrecht]

I'm sorry, but I think you've got it backwards. Ideally you'd use something that blocks everything in the range the used paper is sensitive to, and this implies it depends on the paper. On this, we agree. However, a Kodak OC filter cuts off at around 550nm and e.g. Fomaspeed has a sensitivity reaching to approximately this point. It's a well-known problem that Foma papers do NOT work with certain 'orange' safelight filters.

A safe choice is in fact a red filter, i.e. something that blocks everything from ca. 600nm and upwards, since there's no B&W enlarging paper (in current production) with sensitivity extending that far. A good candidate is the mentioned Kodak Wratten #25, but a simple piece of Rubylith should do the trick just the same.

For most papers and brief exposures, the Kodak OC filter may work OK as well. The advantage of something in the orange range is that the human eye is more sensitive to that bandwidth and thus it takes a lot less light to see what's going on. A projected red image is very difficult to see.

Overall, I've never found a safelight filter on an enlarger to be of much use at all. The only potential benefit I can think of is with burning & dodging, but I find a simple piece of cardboard and a footswitch are at least as effective: just hold the cardboard under the lens, use the footswitch to turn on the light and the projected image on the cardboard will show you where to burn & dodge.

I agree with Koraks, red is 'safer' than OC. For many papers, OC is sufficent but some require red, which is safe for all. In all cases, light intensity plays a role; keep as dim as possible foryour print highlights to be as brilliant as possible.

 

[Ian C]

Regarding Post # 4:

Apparently, I’ve been confused for a long time. When I began darkroom enlarging in April 1987 I consulted a knowledgeable friend, Paul, from Brussels. He advised me to forego graded papers for the modern variable contrast papers. Initially, all I used was Kodak Polycontrast II as did Paul. He gave me a single printing lesson in his darkroom that year. His Kodak safelight was equipped with an OC filter, which he told me was the correct filter for VC papers. He mentioned that “in the old days” we used red safelight filters, but those were intended for orthochromatic papers that by then were falling out of favor.

I equipped my rudimentary darkroom with a complete outfit cheaply: A like-new Omega B66XL & Dichroic B color head, 50 mm f/4 EL Nikkor, Kodak safelight, two timers, trays, tongs, film tank and reels, and so forth that I had bought from a fellow who no longer did darkroom work. The entire kit was $200, a great bargain then.

When I bought my first package of Kodak paper, the instruction booklet in the box read:

“Use a Kodak OC Safelight Filter (light amber) in a suitable safelight lamp with a 15-watt bulb at least 1.2 meters (4 feet) from the paper. Minimize safelight exposure to avoid unwanted quality changes. Be especially careful if you use other types of safelights.”

Later, I used VC papers by Ilford, Oriental, Agfa. The instructions with each indicated the same safelight information. None of these (to the best of my recollection) mentioned the use of a red filter. Eventually, I tried a package of Foma. Its instructions indicated that it required a red safelight filter, which I obtained for that paper.

Over the following decades, I acquired many books on darkroom enlarging. None of them mentioned using a red safelight for anything other than orthochromatic materials. Some commented that using a red filter with VC papers might fog them.

I consulted Kodak and Ilford information on websites and found them to be in agreement with respect to filters for VC papers. Although Kodak hasn’t made B&W papers since about 2004. Its safelight recommendations are still available.

Burred in a long string of paragraphs on page 1 in Publication K-4, October 2006, there is a comment that I hadn’t previously noted:

“For example, a red safelight filter often has less effect on photographic papers than the amber filter listed in the table. However, most workers find that they can judge print density or perform other functions better under an amber light. (So, although it is a slight compromise in protecting the paper from fogging, an amber filter improves working conditions.)”

A table of Kodak Safelight Filters and the appropriate materials for which they’re intended is given on page 2. There are 3 different red filters listed: 1, 1A, and 2. None of these are recommended for non-orthochromatic papers. I wish that Kodak had been more specific. With the information that a red filter was permissible with VC and other non-orthochromatic materials. The darkroom books that I consulted seemed to imply that modern papers MUST be used with the Kodak OC or Ilford 902 safelight filters.

https://www.kodak.com/content/products-brochures/Film/KODAK-A-Guide-to-Darkroom-Illumination-K-4.pdf

After reading Post #4, some following comments, and doing further Internet research, I think I now have a better understanding of the situation. My apologies for my misstatements of post #3.

 

[Doremus Scudder]

Red filters like the #25 pass only red light. Amber OC safelights pass red and a bit of yellow/green, i.e., more of the spectrum. Amber filters are preferred because it makes the darkroom brighter while still being safe for most papers because it passes light to which the eye is more sensitive (that's the yellow/green part). So for the same measured low light level, things appear brighter.

The problem is that amber safelights are not safe with all papers. Some VC papers have sensitivity to the yellow/green part of the spectrum that amber fillers pass (Foma papers are a prime example). For those, you need red.

The main point though is that red is safe for everything else as well.

Best

Doremus

 

[snusmumriken]

If the Ilford one I have is pristine (I think it is, will check), do you want it?

 

[koraks]

@Ian C no worries, I'm glad you shared your thorough research & memories on the matter!