First ... Contact Calumet. Their catalogs had an extensive list of enlarging and projection lamps for a wide variety of equipment. I'd be surprised if they did NOT carry the proper "bulb" - at a lower price than original equipment.
Next - I'll apologize in advance for the forthcoming rant. If anyone cares to stick with "but everyone KNOWS", just scroll on down...
For Pete's sake. gang. Give the lens manufacturers a little credit for intelligence. Their designers have long recognized the sensitivity out there to the results of their products. ALL the major manufacturers pay particular attention to resolution, definition, contrast and distortion over any reasonable conditions of use.
There is a major reason why lenses are limited as far as maximum and minimum aperture.... their use beyond the limits available will result in a reduction of image quality. I've read that "enlarging lenses should not be used at their smaller apertures because of diffraction." For crying out loud, gang, there is a reason for a minimum aperture - and that is that beyond that limit - actually quite a bit beyond that limit - there will be a noticeable decrease in quality, but as long as one stays somewhere within the available range, diffraction will NOT be a problem.
Give the Optical Engineers a little credit ... They KNOW what they are doing... and if they did not, they wouldn't last ten minutes at Rodenstock or Schneider, or Fujinon, Nikon, Elgeet, Wollensak...
There would be an interesting exercise -- If anyone believes that the image quality would be materially degraded at the extremes of the aperture choice, they could make test prints, hopefully LARGE ones to magnify quality differences, from wide open through "optimum middle" to extreme closed, paying close attention to focus and reciprocity-influenced exposure - then mix them up and compare the results.
I have not done this ... I have much more confidence in the reputation of the major enlarging lens manufacturers and their designers to justify the work involved.
Is there an "optimal" aperture in lens design? Yes, definitely .. it is part of the Design Specifications, but enlarging lenses (and I'll include all the rest) do not "fall off a cliff" at other apertures.
Ed Sukach, FFP.
I've not done this over the whole range, and I didn't pay much attention to reciprocity effects, but I have done it over a few f-stops. There are definite and visible differences with my 4-element 50mm lenses (Nikon el-Nikkor f/4, Durst Neotaron f/2.8, and Industar-96U f/3.5), with f/8 seeming best of the apertures I tested with all of them. My 6-element Nikon el-Nikkor f/2.8 shows much less in the way of differences across apertures. Testing across the entire range, I don't know how noticeable those differences would be.
Originally Posted by Ed Sukach
Ed. Only veering away slightly from your statement, I hope, but is there any truth in the statement in the F Schultz article on the Colourstar 3000 that when choosing an aperture for exposure it is important to aim for between 5-10 secs. Frances says: shorter exposures may be "hot" (colour balance affected? Unfortunately Frances doesn't elaborate) because of the warming and cooling of the lamp; longer exposures may run into problems with reciprocity failure"
Checking the manual itself, it recommends between 4-10 secs but only mentions reciprocity failure as the reason for this and not lamp heating and cooling. It does go on to say that another channel can be calibrated for printing accurately at 30...80 secs. So its clearly a problem that can be overcome should long exposures be needed.
If short "hot" exposures are an issue and long exposures also unless a channel has been calibrated for it then it may be that while f2.8 or f4 might be OK print resolution- quality wise, both would result in too short exposures and equally f16 may cause reciprocity problems.
So very big or very small apertures are not a problem in terms of resolution but in terms of exposure.
If all, some, none of this is true in practice for colour work, what applies to B&W?
Originally Posted by Nick Zentena
the enlarger bulbs are MUCH more expensive, and not available in Russia - so 50W gain just doesn't seem to be an adequate solution. So household mains halogen lamps in parabolic reflectors, fitting directly to my colour head and available freely, are just way easier
My Fuji CSD690 uses the same big lightbox with a movable white frame for 135 film (with smaller aperture). I get the same relatively long times with both formats (today I've printed something for my friend from 135 film, and the exposure was around 25 seconds on f/4, 80M filtration and 13*18cm print format).
The lightbox is not dirty inside, it's built in a funny yet good way: the light enters it through a slightly matted heat filter from its SIDE, not top, then the foam white walls reflect it to three (!!!) center filters. These are just plates of glass with some kind of dot pattern printed on them with white enamel, denser in centre, more loose to the edges. Finally the mixed and levelled light reaches a bottom plate of light box, made from thick opal plastic. So no wonder that this box eats away PLENTY of light - but it makes the remainder very good-behaving, soft and perfectly even. I don't know why Fuji engineers have decided to make it that way, really - but it works That's probably the way the enlarger was engineered Again, even with 200W of power (both focusing and printing lamps on), I can't say I get the whole additional stop of light, judging by the test exposures...
My safelighting does not fog the VC paper even after half-an-hour exposure, so it's not a problem too. Really, the prints come out with a very good sharpness and gradation, with no trace of fog, so I think the machine should just work that way
And the lenses give the same excellent sharpness and contrast at both their maximum apertures (2.8 and 5.6 resp.) and stopped down to 1-2 stops. No focus shift or distortion. It looks like some stopping is more important to Tessar-type enlaring lenses - with 6-lens Fujinons and Rodagons the maximum aperture can be used for work, unless someone wants to tilt the easel a bit to correct the convergence, needing bigger DOF in printing.
Cheers, and thanks for your advices - Zhenya
Originally Posted by Ed Sukach
believe me or not, but neither Calumet nor Don's Bulbs carry THAT kind of bulbs They were probably a Japanese specialty sometimes...
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The warming and cooling of the bulb is relevant, since for a certain period of time after turning the lamp on and off, the bulb will have lower color temperature than expected for constant operation. The duration of this "glow" is independent from the exposure time, and hence the effect varies with exposure time, and is the greatest at short exposure times.
Originally Posted by pentaxuser
This is why some enlargers have a shutter. The shutter is only released after the warm-up of the bulb and closed immediately after the exposure is finished.
The effect is probably not that important for a b/w enlargement because there is no color balance issue with b/w enlargements. Only if you use variable contrast paper, the contrast may be slightly affected.
It is hard to make any statement about the relevance of reciprocity failure during printing. You would have to consult the data sheet of the paper in question. Some data sheets have graphs for reciprocity failure. If the manufacturer does not provide this information (they should), you could just make a test on your own.
If you're not taking your camera...there's no reason to travel. --APUG member bgilwee
This is interesting. It is difficult enough to get information about the color temperature of the various enlarger lamps ... at any time after their initial incandescence ... I have never seen a time sensitive study of color temperature.
If the minimum parameters are limited to 5 - 10 seconds or so - I am not familiar with the ColorStar's response time - I have never really paid attention to that charactersic - it should be possible to burn the lamp for one or two minutes and get some information about any color shift.
I'll try it, as soon as I get the chance. Right now I have an active exhibition taking up a great deal of my time.
There is always the possibility of density changes of the various color layers in the paper due to reciprocity effects. I'll study that as well.
It is always possible to calibrate a channel in the ColorStar using a different time than the recommended five seconds - I have done that with as much as twenty seconds --- I have noticed an overall density reciprocity change (slight) requiring a "n" setting of .05, but I haven't noticed a shift in color balance.
You have piqued my curiosity. Stay tuned.
Ed Sukach, FFP.
I've investigated the effect of long exposure times on color balance, due to bulb heating.
Using my Omega D5500 - an "EYA" lamp; 82V, 200 Watts, 3300 K color temperature - I've "balanced" the image from a grey card negative, using one of my three (3) ColorStar 3000 Analysers (long story - more later). Setting the exposure time to the maximum available on the D5500's controller, 99.9 seconds, I observed, carefully, the ColorStar's balance indication array over that exposure time. Multiple observations indicate *NO* change - none wahtsoever - in color balance... or exposure.
It should be noted that this is a "modern" enlarger configuration: a halogen lamp with a regulated power supply; fan cooled with an (expensive) "heat glass" IR filter immediately ahead of the lamp. All that may be vastly different from the uncooled, no fan or heat glass, systems of older enlargers.
Additionally, I've watched, carefully, color balance "drift" over a six or seven HOUR enlarging session - the greatest change I've seen is 1 (ONE) CC (magenta).
Reciprocity of color paper, with its multiple color layers (I imagine each layer has its own charateristics) is something else again.
That is next on my "curiosity" schedule.
Ed Sukach, FFP.
Same arrangement, save for a fourth ND, on my now
Originally Posted by eumenius
shelved Meopta. I found by your same test that the
bottom diffuser was too thick in center and caused
the "graying" to lighten as center was neared.
If I could find a condenser head for that Meopta I might
be able to use it. I've a mind to sell it but who wants an
enlarger that vignettes and towards center at that? Dan
that's so strange to hear that about Meopta - I always considered their quality to be quite good, at least their older stuff is made very well. I've got Magnifax II condenser enlarger, as well as Opemus - both are quite good, but they should be older than your machine. Ah well, let's think that your specimen was built by Soviet workers who received some training at Meopta factory
Perhaps the scheme with side illumination of lightbox was thought to be better in terms of field evenness, but the overall complexity of these lightboxes and reduced light output made them unpopular. And I can imagine how much has it costed for Fuji to build it, three center filters inside!
Though my Fuji is a bit on a dim side, it gives beautiful and perfect prints - and I'm quite happy with it, after all my work wih it
Originally Posted by dancqu