"Blackbody" light sources like tungsten filament have a continuous spectrum, but differ in specific color temperature. But fluorescents, CFL's, and LED's all produce a discontinuous spectrum with spikes and imbalances; and therefore the best color renditions of those are actually quite expensive. CRI was a traditonal manner of expressing the statistically probability of how many of a hundred representative color patches would be properly rendered relative to human vision, according to any given lightsource. This was generally in context of opposing metamerism, where certain colors act chameleon-like under different sources. Anyone who aspires to balance a colorhead to a particular batch of color paper using a standard color reference should be acutely aware of this general principle.
But serious lighting engineers, along with pigment and dye experts, nowadays think more in terms of CIE color mapping and gamut properties, hoping to close at least a few of the loopholes. But nothing will ever be perfect. In fact, inkjet colorants are a bit of a step backwards in terms of gamut. No color film or RA4 paper is perfect either; every one of has idiosyncrasies which need to be recognized. I look at my own dry color prints not only with my expensive German color matching (5000K, CRI 98) tubes, but using several other sources too - diffuse daylight outdoors, high-end LED spotlights, commercial fluorescent 5000K, warm tungsten, oddball CFL too if necessary. No different than what I did when our company paint color matchers came to me for a final assessment. Only half of it is physiological sight. The other half is psychological, with training and experience knowing
what to look for, and how to compare, and in what light, according to the real-world conditions involved.
Nothing like spending 2-300 on a single SINGLE studio light on stand, that needs a 120$ bulb..
Now you know why Natural Light photography is so popular....
Zone VI cold lights themselves operate differently, using two different overlapping grids, one blue, one green, rather than the combined blue-green light of the more powerful Aristo. Either way, one can selectively use blue versus green glass filters under the lens for split printing or related purposes.
What I have has worked for contrast control (split printing, as I noted, with yellow and blue filters), but I'm not looking forward to doing split filter on a color head. "Expose sixteen seconds on C0 Y90, then twenty seconds on C60 Y0 while dodging the base of the trunk for ten seconds and the rightmost rock another five" is a lot less simple when I have to move those dials 150 clicks between each exposure. I might find I do most of my printing with the condenser head or the cold light and save the color head for color...
That's really rather strange. A 1/2 stop drop in light is rather significant, equal to around 1 zone. Flourescent tubes usually get brighter as they warm. The Aristo I had - albeit dating from the 60's-'70s - had a heater to keep the lamp warmed up (kinda) between exposures. Does your Aristo have a second power lead for the heater?Aristo head ... the lamp gets dimmer as it heats up during the exposure.
If you have a group of people openly discussing something, eventually something characterized as "political" will arise.
There's a story that the light bulb manufacturers colluded to make the lifespan of the bulbs shorter. You've heard that, right?
Well, the LEDs in the new bulbs will work for 50000 hours or some such ridiculous number, but the second-rate electronic components that power them won't last more than 5000. They'll soon find replacements that won't last 3000 hours.
That's really rather strange. A 1/2 stop drop in light is rather significant, equal to around 1 zone. Flourescent tubes usually get brighter as they warm. The Aristo I had - albeit dating from the 60's-'70s - had a heater to keep the lamp warmed up (kinda) between exposures. Does your Aristo have a second power lead for the heater?
To measure the lamp temperature you need to have the thermocouple or RTD bonded to the glass of the tube. I'm sure the temperature of the tube is swinging more than 4C. 1/2 stop over 4C, why you have yourself a thermometer, with a DA meter you can tell your darkroom temperature to 0.1C.
Well, the LEDs in the new bulbs will work for 50000 hours or some such ridiculous number, but the second-rate electronic components that power them won't last more than 5000.
Can someone enlighten me about the terminology of the bulbs?
Was there first the incandescent bulb for the enlargers? For the enlargers made in the fifties and sixties?
I began printing in the late seventies and I still use the same bulbs for the basic condenser light heads of that period. Focomats Ic and IIc, Valoy II and Durst L1000.
There are differences in the sizes of the bulbs but they all share the E27 fittings. Over the years I have stocked up on these bulbs, generally second hand.
The ones that were hardest to find were the very large bulbs for the Durst. I have these mostly from Atlas and Durst, in 200 or 300 watt.
Second hardest to find were the 'short neck' bulbs for the Valoy II (10,4 cm long or a little smaller). These were mostly made by Osram. 75, 150 and 250 watt. Dr. Fisher makes these, but I prefer the old ones as the white opal is thicker.
Finally the 'standard' 11,5cm bulb in 75, 150 and 250 watt. I believe these are still for sale.
Sorry to be so long, in particular because I have accumulated plenty of these bulbs. The reason for asking is for the younger generations. If we'd run out of bulbs, then what?
When a manufacture quotes 50,000 hours that does not mean any given LED will last 50,000 hours. It means in a population of lamps every 50,000 hours a failure occurs. So if you have 10 LED lamps in your house expect one failure every 5000 hours. (50,000/10).
When a manufacture quotes 50,000 hours that does not mean any given LED will last 50,000 hours. It means in a population of lamps every 50,000 hours a failure occurs. So if you have 10 LED lamps in your house expect one failure every 5000 hours. (50,000/10).
The limitation the bulbs themselves have comes from the other components - particularly the capacitors -, which have a much shorter practical life.
Larry - what you don't take into account is how so many manufacturers have increasingly whored themselves out to low bidder expectations in the past three decades. This is just fact. I was a professional product buyer and saw it first hand, knew all kinds of inside stories, even had CEO's tell me to my face of their intentions. I've seen formerly highly reputable manufacturers go off that cliff one after another. If people want to categorize that as "political" due to the direction the outsourcing went, that is their prerogative. But it's also like sticking their head in the sand as a default. It has to be reckoned with; and often a lot of homework has to be done to find the jewels among the junk heap. And with that trend, there has been a tsunami of BS marketing. The threads immediately above spell out the crux of it pertaining to mass-marketed LED products : corners have been cut in quality control; and the product is only as good as its weakest link.
No, I wasn't personally involved in any of this kind of LED lighting, but did distribute high-end construction and mfg inspection LED lighting, which had either domestic or German solid wiring in every component. Real deal. Pricey too. I knew the people in charge on a first name basis. The bait and switch low bid imports might have looked the same, but failed prematurely, ridiculously quick sometimes; could be unsafe too. I make the same kind of distinction even when buying an ordinary enlarger light bulb; one needs to know where they actually come from, and what the quality control is like.
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