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Photo Forum / Film Photography / Darkroom / January 2005Light Spot On B&W Paper - Enlarger? Fix? Bulb?
Yesterday, while printing, I noticed a diffuse light spot about 1-2" in diameter on some of my 5X7 prints, almost as if I'd dodged. I checked the neg it's clean. I scanned the neg to look at it -- it's clean. I tried printing other negs -- same spot. So I immediately started to look at the condenser head (MX45). I recently changed the bulb (150Watt) in the head after it blew. The old bulb was frosted, the new bulb is frosted but also has some writing from the manufacturer on the top (Soft White, 150W, Sylvannia etc.) can this writing create light spots on my prints? The old bulb had no writing but also no other information about who made it. I'm currently disassembling and cleaning the head anyway, I noticed even though there was little or no dust it was a bit "filmy". Thx. Enlarger bulbs aren't household bulbs. I will go buy an enlarger bulb today. Thx. And thanks to all who answered. > Enlarger bulbs aren't household bulbs. > Yesterday, while printing, I noticed a diffuse light spot about 1-2" in > diameter on some of my 5X7 prints, almost as if I'd dodged. <snip> > printing other negs -- same spot. So I immediately started to look at the > condenser head (MX45). I recently changed the bulb (150Watt) in the head > after it blew. The old bulb was frosted, the new bulb is frosted but also > has some writing from the manufacturer on the top (Soft White, 150W, You need an enlarger light bulb. Enlarger lightbulbs have much better frosting than regular frosted lightbulbs as well as having no writing at the top. Any photo store which has any darkroom supplies will have the PH211 (75W) and PH212 (150W) bulbs which are the ones you want. In an emergency, you can use a standard lightbulb and cover the top of the condenser with a piece of vegetable parchment or vellum, but the proper lightbulbs are much better, only cost a few dollars, and will last around 60 hours of enlarger use. Peter.  Signaturepirwin@ktb.net >> Yesterday, while printing, I noticed a diffuse light spot about 1-2" in >> diameter on some of my 5X7 prints, almost as if I'd dodged. >You need an enlarger light bulb. Enlarger lightbulbs have much better >frosting than regular frosted lightbulbs as well as having no writing >at the top. Any photo store which has any darkroom supplies will have >the PH211 (75W) and PH212 (150W) bulbs which are the ones you want. I ran into this a couple of years back, my daughter had been using the darkroom and when the enlarger bulb blew, she just replaced it with a 60W household bulb from our kitchen drawer. Took me an embarassingly long time to figure out why my prints were not coming out right. Had she replaced the bulb with the same wattage as the original bulb, it would have taken even longer! It may well be the bulb. If not, then look at your neg. Is there a dark spot (probably from a crinkle while the film was being wound on the developing reel) on it in the same place where the light spot is appearing on your print. Usually these will show up as diffuse (rather than sharp-edged) light spots. > > [quoted text clipped - 19 lines] >she replaced the bulb with the same wattage as the original bulb, it >would have taken even longer! Enlarger lightbulbs cost about 10X as much as ordinary light bulbs of the same wattage. They presumably have some properties, like better frosting, more stable light output over their lifetime, and perhaps more carefully centered filament, that differ from ordinary bulbs. In reality you may find that all you need to do is take a piece of steel wool and scrub the writing off the top of the bulb. I suspect that "soft white" instead of merely frosted, may be pretty good, and may be essentially indistinguishable from the official bulbs. RJF > Enlarger lightbulbs cost about 10X as much as ordinary light bulbs > of the same wattage. They presumably have some properties, like > better frosting .... Enlarger bulbs are made from opal glass (or something just like it) applied to the outside surface of an unfrosted bulb, the coating is thick and is not very transmissive. A paint coating will let through longer wavelengths and attenuate the shorter, unlike opal glass. As a result: o the filament doesn't create a hot-spot when it is viewed through the frosting as happens with household bulbs -- using a household bulb results in uneven illumination with a hot spot in the middle and darkening at the edge of the bulb; o the light bounces around inside the bulb more than it penetrates the opal coating thus making the bulb into an Ulbricht integrating sphere resulting in very even illumination. Additionally: o The GE 'Meatball' is printed on the neck of the bulb; o The bulbs are always the small household size irrespective of wattage, keeping the optics of the enlarger constant. A condenser lamp house 'images' the end of the bulb onto the back of the enlarging lens. The imaging is _very_ out of focus but as the light bulb has, supposedly, no features to it, it is like taking a picture of the sky: it looks the same no matter where you focus the lens. The downside is the bulb runs very hot for the lumens produced. I don't know that GE produces enlarger bulbs anymore. The very low sales volume for a non-standard light bulb is what raises the price, 10x is 'almost' reasonable. SignatureNicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. Remove spaces etc. to reply: n o lindan at net com dot com psst.. want to buy an f-stop timer? nolindan.com/da/fstop/ > Yesterday, while printing, I noticed a diffuse light spot about 1-2" in > diameter on some of my 5X7 prints, almost as if I'd dodged. I checked the [quoted text clipped - 7 lines] > currently disassembling and cleaning the head anyway, I noticed even though > there was little or no dust it was a bit "filmy". Thx. Off hand, I might suspect some fixer carry-over to the un exposed paper. If you are not _very_ careful, it is very easy to a=have this happen - as I have personally experienced. Good luck, dr bob. Check the condenser (if it is a condenser enlarger). If they are dirty, spots _will_ show up. > g from the manufactu How to I check for spots on the condensor apparatus? I was thinking I'd put a neg into the carrier, focus, then remove the neg and print a black 5X7 and see where the spots show up? Is there another way? > Check the condenser (if it is a condenser enlarger). If they are dirty, > spots _will_ show up. > > > g from the manufactu > How to I check for spots on the condensor apparatus? I was thinking I'd put > a neg into the carrier, focus, then remove the neg and print a black 5X7 and > see where the spots show up? Is there another way? I sort of doubt it is your bulb, but I could be wrong. From what you describe, it sounds like dirty condensers. The condensers are thick glass things that focus the light from the bulb evenly onto the negative. They will be above the negative carrier. You should be able to remove them in order to clean. I have to do this frequently in both my Beseler 23C and my Omega DII because my room is rather dusty. What kind of enlarger do you have? If you have a diffusion enlarger, there are no condensers. It's a Beseler 45MXII. I have both a condensor head and a dichro head. I gingerly disassembled and cleaned the condensor elements. Big heavy suckers. I used lens cleaner and microfiber clothes. They came out spotless. They were definately filmy from who knows what -- humidity and dirty air? It's second hand equipment. The first time I've had to clean them. Buffed up real nice though. Carefully reassembled. Took my time. Things look a lot better, plus an official PH211 75 Watt bulb. The lower wattage I think is more my speed rather than the 150Watt which was driving me to stop my enlarger lens way way down. Thx for the reply. > > How to I check for spots on the condensor apparatus? I was thinking I'd put > > a neg into the carrier, focus, then remove the neg and print a black 5X7 and [quoted text clipped - 10 lines] > What kind of enlarger do you have? If you have a diffusion enlarger, > there are no condensers. > How to I check for spots on the condensor apparatus? I was thinking I'd put > a neg into the carrier, focus, then remove the neg and print a black 5X7 and > see where the spots show up? Is there another way? By moving all the knobs and putting in the right lens (and that's all I remember) it is possible to get a sharp image of the condenser dirt. -- Nicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. Remove spaces etc. to reply: n o lindan at net com dot com psst.. want to buy an f-stop timer? nolindan.com/da/fstop/ |
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