Re: [Cameramakers] fluorescent lamps for b/w LF cold head enlarger
I am not sure I understand the need for a full spectrum source for black and white though I agree one must consider the spectrum with more care for color work. If you are not using multi-contrast paper I would think a bluer lamp would look good and a lot of inexpensive fluorescent lamps ought to fill the bill. For multi-contrast papers you must be sure the required spectral components are there but my intuition suggests just a couple (or maybe a few!) selected lines would be sufficient) (A few might come into play if the emulsions have more than two components to gain wide contrast range.) More than likely is it that a couple well positioned lines could increase the available contrast range by avoiding overlap of the spectral responses of the low-contrast and the high contrast components. You would have to judge this by looking at the lamp data and the emulsion data. Any fluorescent lamp for which I have seen data tends to have some sharp line structure superimposed on a continuum. The phosphors are blended to yield the required spectrum for the application, almost always to give the eye the correct impression (Some blends seem to be aimed at machines which have special requirements and there are green lamps for copy machines, to give a single example.) The narrow lines come from the mercury discharge which excited the phosphors and some of this light leaks out with the extent of the leakage depending greatly on the lamp type. The total amount of light left in these lines is sometimes a lot and sometimes rather small (you should notice the width of spectral features and compare area under the curve in determining importance of the leakage.) Try to obtain the catalog from Osram for a nice set of graphs of the spectra. Some of you might also want to look at the POWER STAR HQI. This gives a pretty smooth spectrum from a concentrated source (possibly suitable for a condenser enlarger, although the source could be too big in the higher power types) There is a major problem; you cannot turn these lamps on and off very easily. When hot they start with great difficulty and the lifetime drops dramatically with short cycles. A shutter would be required. Conversely, maybe they are satisfactory for color work at high powers. The lamps can deliver massive powers (maybe 3500 watts input) with efficiency better than a hot filament lamp so the same input power is delivering more light. Bob At 01:01 20.09.02 -0400, you wrote: Hello: I am curious if anyone has ever used 'tri-phosphor' lamps for enlarging. I'm interested in an 8x10 enlarger for b/w only, on a budget. I started looking into low pressure pulsed xenon - lotta heat, and nearly obsolete, $100 for 750W lamp, $3000 for new commercial ballast/power supply, and it's not a friendly prospect - 52 V at about 18 amps plus 1 volt spike to ionize gas...so, I think I'll look into other approaches. Ansel Adams used massive array of logo-less incandescent lamps - heat again. I'm pondering either full spectrum fluorescent (linear tubes only as far as I know), or tri-phosphor complact fluorescent (3 spectral peaks spread out over visible spectrum depending on color temperature, 2700K, 3500 K, 4100K and 6500K available (CRI 82, but that may not be relevant to film). I got spectral plot of the 6500K one today because I was unfamiliar with that one, and the spikey spectrum of the tri-phoshor type does make me nervous...hence my request for others' fluorescent experience. What I'm considering is using seveal GE Biax (folded tube) 18 or 27W lamps for an 8 x 10 or 11x 14 head, each driven with a high frequency electronic ballast. Driving the lamps above 15kHz eliminates the 120 Hz (100 for 50 Hz countries) flicker and produces about 15% more lumens than line frequency. I have access to a manufacturer of small electronic ballasts (I used to work there). I am considering running them from a DC supply with individual regulators so the light output could be adjusted for each lamp. My main worry is the strong spectral peaks in this type of lamp. The intent of this lamp design is that the brain is supposed to 'fill in the spectral gap', and THINK they are full spectrum lamps. Thanks in advance for responses. Murray ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
[Cameramakers] viruses
I have checked my PC with a current virus checker and apparently all is well. I still get responses back from mail servers blocking mail from my reply-to: address allegedly containing viruses. I think this is the other side of the coin with all the messages I get with weird attachments from people who didn't send them. I think it's a variation of an Address Book virus, and not necessarily the fault of the alleged sender. Murray ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
[Cameramakers] Fluorescent replies - Bob M Panoramic AZ
Thanks Bob - I think in my case a little knowledge is dangerous - I worry more about what I do NOT know than what I do...with the hope that eventually when I know it, I'll be the first to know. And AZ (panoramic), I would like info (off list or on, whatever's appropriate) on custom lamp...I had thought about a neon place locally that makes weird custom neons. Are you talking about something similar to the 'grid lamps' Arista/o makes? Murray ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
[Cameramakers] Huw of LED fame on this list?
Is Huw of LED enlarger fame on this list? Murray ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
[Cameramakers] Re: Scanner now camera
Hell Ken, You wrote First, the sensor needs to be directly behind the lens , on the centerline. My scans were dark at each end with a circle in the center. So you will see by looking at: http://www.rit.edu/~andpph/photoforum.html But this does not show your picture. Can you please provide the complete URL? Brian Swale ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
Re: [Cameramakers] Fluorescent replies - Bob M Panoramic AZ
At 03:19 PM 9/21/2002 -0400, you wrote: Thanks Bob - I think in my case a little knowledge is dangerous - I worry more about what I do NOT know than what I do...with the hope that eventually when I know it, I'll be the first to know. And AZ (panoramic), I would like info (off list or on, whatever's appropriate) on custom lamp...I had thought about a neon place locally that makes weird custom neons. Are you talking about something similar to the 'grid lamps' Arista/o makes? Murray * Enlarger lamp instructions. I have had several lamps made for my panoramic enlargers at neon shops. I had a green/blue set made for variable contrast. It was a pain in the butt to use without a fancy computer timer so I didn't use it except for extreme contrast situations where I only needed green or blue. I have a picture of a lamp for a 2 x 7-1/2 inch format here: http://www.panoramacamera.us/enl_lamp1.jpg Use 9mm dia. tubing with cold white phosphor. Make a full size pattern of the lamp. Explain to the glass maker that they have to bend the tubing in a flat zig zag that covers whatever format you need. The bends and cathode/anode should be on the outside of the format size. The distance between each length of tube is the same as the diameter. The cathode/anode should bend upwards slightly from the face (or even more to save space). Beg for a used sign transformer that will give you enough zap. They know what sizes. I have a 9000V, 30ma transformer on a lamp with four linear feet of glass which is pretty hot. Use black foam-core (best) or 1/4 in. ply. for the housing and mount the grounded transformer on the wall out of the way. Don't have it where it can be accidently touched. Regular zip cord appliance wire is OK for connections but keep it away from metal and you! Wood or foam-core is an OK insulator but not UL approved. Get a set of bananna plugs at Radio Shack for the connections. To protect the lamp mount it on a piece of 1/16 clear plex with light wire thru pairs of holes in the plex or use clear tape or dabs of silicone calk. I used 1/8 in. milk (skim!) white plex for a diffuser with the glass about a half inch away. The sign co. may have this. An alternative is clear plex with layers of frosted mylar or tracing paper. Use white cardboard on top and sides of the lamp for a reflector. When the lamp is on the individual runs should not show. It may take some testing and adjusting. Even Aristo and Ilford lamps can need some adjustment for uneven lighting. The shutter assembly is easier to make than explain. It's design is from an ancient Omega 8 x 10 enlarger with old style fluorescent lamps that remained on at all times (modern enlarger lamps use a pre-heated cathode system). It can be made any number of ways. Any small motor (like from a hair dryer) will do. The shutter is mounted below the lens. How this is done will of course depend on your enlarger. Mount a pivoting shutter (paddle shaped mat board) to the motor armature axle. I used a motor with a small cooling fan and cut away all but one blade of the fan and tape the shutter to the remaining blade. Use a thin rubber band and a bumper stop to cause the baffle to return closed when the power is shut off. It takes a bit of trial-and-error but once you see it working it is obvious what to do. Fasten a piece of soft foam material to the bumper to absorb the momentum of the returning shutter. The motor is connected to the enlarger lamp outlet of the darkroom timer (remember this is a switch - half the circuit - and can switch low voltage DC motors too). The lens shutter should swiftly rotate completely open (about 100 degrees) when you punch the timer, and close completely without bouncing. It is a contraption and may require a bit of tape and bubblegum to work the way you like it. Once it is adjusted it will be trouble free. AZ Maker of Lookaround panoramic camera. http://www.panoramacamera.us or keyword.com lookaround ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
