{"id":8918,"date":"2012-08-20T20:47:34","date_gmt":"2012-08-21T02:47:34","guid":{"rendered":"http:\/\/jbhphoto.com\/blog\/?p=8918"},"modified":"2023-07-16T21:06:56","modified_gmt":"2023-07-17T03:06:56","slug":"thomas-duplex-super-safelight-filters","status":"publish","type":"post","link":"https:\/\/www.jbhphoto.com\/blog\/2012\/08\/20\/thomas-duplex-super-safelight-filters\/","title":{"rendered":"THOMAS DUPLEX SUPER SAFELIGHT FILTERS"},"content":{"rendered":"

\"\"Seems the last couple of times I have tested the darkroom safelight I have had to cut down the illumination.\u00a0 That should be a clue that the filters are fading and it is time to replace them.\u00a0 We use a Thomas Duplex Super Safelight that I rebuilt many years ago.\u00a0 Since we have a small\u00a0 darkroom I knew I needed to attenuate the light.\u00a0 My original safelight was modified when I rebuilt it and the 35 watt lamp was replaced with a 18 watt lamp.\u00a0 Note:\u00a0 You have to replace the ballast and start capacitor if you change the lamp wattage.\u00a0 Wasn\u2019t that big a problem seeing how the original ballast was no good.\u00a0 I purchase the safelight many years ago not working for little to nothing.<\/strong><\/h4>\n

So, now I needed to replace the filters.\u00a0 Since I am only interested in B&W, work that simplifies things for sure.\u00a0 All I need to find is the correct filter and then I can assemble my own replacement.\u00a0 I have plenty of scrap glass, and tape.<\/p>\n

With a little research on the Internet I discovered that the hard part had already been done.\u00a0 Seems a Rosco #19 \u201cFire\u201d<\/a><\/span> filter has the necessary bandwidth to filter out the annoying green and blue spikes in the low pressure sodium lamp spectrum.\u00a0 And, seems that others had proven this the best way possible. . . they tested it in their own darkroom.<\/p>\n

All I needed was to order some filter material.\u00a0 Rosco filters are the industry standard for stage and film production and readily available.\u00a0 That was way too easy.\u00a0 The thing that I was still toying with was how to adjust the light output.\u00a0 It finally came to me.\u00a0 Why not put the #19 filter in the body position and then add a Neutral Density filter to the vane?\u00a0 Yep, that would do it.\u00a0 So I ordered a sheet of Rosco #19 filter and a sheet of 0.30 ND.<\/strong><\/h4>\n

We have a lot of scrap glass around.\u00a0 I cut new glass to fit the body and vanes using TruVue Conservation Grade UV<\/a><\/span> glass.\u00a0 Thought it wouldn\u2019t hurt to add even more filtration.\u00a0 I also found out why the factory uses tissue paper.\u00a0 Without it, the filter material does not look that great against the glass and I could see that if any moisture were to condense in there, it could be bad for the filter.\u00a0 \u00a0I really didn\u2019t want to use tissue paper and I had a roll of Gila<\/a><\/span> frosted window film from another project.\u00a0 This stuff is a self-adhesive plastic material used to frost windows.\u00a0 It was exactly what I needed to put a smooth textured surface on the inside of the glass to keep the filter from sticking.\u00a0 It also works well to diffuse the light.<\/p>\n

One of my favorite tapes is the aluminum HVAC ducting tape.\u00a0 It is lightproof, sticks and stays in place.\u00a0 Slit a few pieces of tape, peel the backing and it will hold the filter sandwich in place with ease.<\/p>\n

I placed the #19 filter in the body and 0.30 ND in the vanes.\u00a0 My first test showed there was still too much light.\u00a0 I was testing at my closest point to the safelight for the worst case situation.\u00a0 I ended up adding a second layer of 0.30 which made for 0.60 ND, which is two full stops attenuation.\u00a0 But remember, I was testing with the most sensitive VC paper we use at a very close proximity to the safelight.\u00a0 Always test for the very worst case scenario.\u00a0 <\/strong><\/h4>\n

Once finished, I found that the darkroom is much brighter than before. \u00a0This proves that the filters do fade.\u00a0 Now we are back in business.\u00a0 \u00a0With the vanes fully closed all VC and standard papers are safe.\u00a0 I like to print on Azo, which allows me to open the vanes for even more light. <\/strong><\/h4>\n

I will test again in a year or so and if I need new filters they are easily replaced.\u00a0 I have plenty of material, the Rosco filter comes in a 24 x 24 inch square.\u00a0 Enough for several more safelight filters, if and when they are needed. <\/strong><\/h4>\n

JB<\/strong><\/h4>\n","protected":false},"excerpt":{"rendered":"

Seems the last couple of times I have tested the darkroom safelight I have had to cut down the illumination.\u00a0 That should be a clue that the filters are fading and it is time to replace them.\u00a0 We use a Thomas Duplex Super Safelight that I rebuilt many years ago.\u00a0 Since we have a small\u00a0Continue reading →<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[5,10,12,9],"tags":[15,16,18,126,121,38],"class_list":["post-8918","post","type-post","status-publish","format-standard","hentry","category-darkroom","category-diy","category-how-to","category-photography","tag-darkroom-2","tag-film-photography","tag-jb-susan-harlin","tag-thomas-duplex-super-safelight","tag-thomas-safelight-filters","tag-vc-paper","no-thumb"],"jetpack_publicize_connections":[],"yoast_head":"\nTHOMAS DUPLEX SUPER SAFELIGHT FILTERS<\/title>\n<meta name=\"description\" content=\"DIY filters for Thomas Duplex Super Safelight\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.jbhphoto.com\/blog\/2012\/08\/20\/thomas-duplex-super-safelight-filters\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"THOMAS DUPLEX SUPER SAFELIGHT FILTERS\" \/>\n<meta property=\"og:description\" content=\"DIY filters for Thomas Duplex Super Safelight\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.jbhphoto.com\/blog\/2012\/08\/20\/thomas-duplex-super-safelight-filters\/\" \/>\n<meta property=\"og:site_name\" content=\"jbhphoto.com Blog\" \/>\n<meta property=\"article:published_time\" content=\"2012-08-21T02:47:34+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2023-07-17T03:06:56+00:00\" \/>\n<meta property=\"og:image\" 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