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Judging colour filtration
This is not always easy and I have always used a 230V 75W blue bulb in an angle-pois lamp to get a close-as-I-can judgement of what looks right. However I have found a company called BLT Direct (nowt to do with sandwiches!) from whom I have just bought a 13.5W (75W equivalent) LED bulb with a large Edison screw base. The best bit being the colour temperature is stated on the box as being 6500 degrees Kelvin - in other words the same as noon daylight on a sunny day.
The old blue tungsten bulb was around 5000 degrees Kelvin and in comparison quite warm. I am going to try it out this afternoon to see if it does make it easier. I have always had trouble with a Cyan cast with the blue bulb letting too much red through. so hopefully that is a thing of the past. What did surprise me though was how weighty the bulb was compared to an ordinary tungsten one. They are not cheap - aroung £7 but could save money though not wasting paper. The contact number for BLT Direct is 01473 716418 or 559501 Their website is bltdirect.com Last edited by John King; 20th December 2016 at 11:28 AM. |
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John your findings would be of interest to me, please post them.
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"Tea is surely the king of all drinks. It helps against the cold, it helps against the heat,against discomfort and sickness, against weariness and weakness". Heinrich Harrer. |
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13.5w (75w tungsten equivalent) LED Bulb
I have just thought of another use for these bulbs and that is in B&W enlargers that take screw base bulbs The one I have bought is roughly the same size as a normal tungsten bulb so if it fits, the lamphouse will run a lot cooler than a normal enlarger bulb. It has a pure white opalescent glass envelope too so you cannot see the light source. There is no writing on the glass itself, the specifications are all on the base so I cannot see why it should not work
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First Impressions.
Norm.
I have just printed a 12x16 from an old negative that I have been unable to get anything satisfactory from before. Under the new LED bulb The 1st test print showed it was way, way too yellow and the Kodak printing filters indicated I needed 20 units of yellow to be added. (LPL7700 colour head) The 2nd test print was just about right, but still a tiny bit green. I removed 2.5 units of magenta, then printed the full size print without doing another test and it is almost perfect! Far better than I have ever had before from this negative. The paper was Kodak RA4 The subject was part of a limestone pavement, close to Ribblehead viaduct and the limestone is a natural pale grey - almost a dirty white and this has reproduced exactly as I would have liked it to be. The background is also as I would have expected with back lit reeds and coarse grass showing the light with exactly the correct shade of yellowish green. I have learned one thing, the bulb may have an equivalent output equal to 75w but it is so much whiter, and looks much brighter. If you look at the bulb you loose your night vision for quite a while when you shut the room light off again. Overall, this has to be the best darkroom accessory I have bought this year. Last edited by John King; 20th December 2016 at 02:45 PM. |
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Quote:
__________________
"Tea is surely the king of all drinks. It helps against the cold, it helps against the heat,against discomfort and sickness, against weariness and weakness". Heinrich Harrer. |
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A good find, John, and frankly that is not a bad price in my opinion. I had an old incandescent tungsten blue 100W lamp from Nova Darkroom in my darkroom. It never seemed to be particularly "daylight " looking to me. In reality I imagine that getting a noon-day look from any tungsten filament is a near impossibility even with the blue glass surround.
It eventually burned out so now have a normal clear tungsten 100W filament bulb as I use the filament to gauge the state of my film developer. If an exposed developed and fixed leader, held up to the bulb reduces the glow from the filament enough to see the filament wire as an orange line then the developer is still good to go. However a 6500K LED might be the way to go for print inspection, even B&W prints. My only concern would be whether a 75W equivalent in the ceiling would give enough light and secondly I have noticed that while an LED bulb I have elsewhere is "instant" when switched on it does seem to take a couple of seconds to "die" when switched off but getting more paper out of its box for the next print probably takes at least that long anyway so in reality this may not be a problem. Mike |
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bulbs
I have a craft/hobby daylight blue coloured bulb in my darkroom for viewing prints both colour and black and white. The "sad" 6500k daylight bulb sounds like a better option. I have a candelarboro light fitting in my darkroom that holds 3 bulbs I put three blue craft bulbs in it all the bulbs shone with a different intensity. I chose the brightest. That being said once the print is hung on the wall it can be viewed under a wide variety of changing light (cool morning or warm evening daylight then later in the day tungsten light). Using a constant light source in the darkroom to judge your prints is a good idea. If you know what lighting your print is going to be viewed under for example, in a gallery you may want to print to match that lighting. No one print will look its best in all the various lighting conditions we encounter. Seasonally adjusted daylight bulbs 6500k temperature in the house maybe a good idea for me because I do hate the dull grey overcast light that is prevalent throughout the winter months. Thumbs up! SAD bulbs for me in the darkroom and in the house, will it make me less grumpy, only time will tell
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"Tea is surely the king of all drinks. It helps against the cold, it helps against the heat,against discomfort and sickness, against weariness and weakness". Heinrich Harrer. |
#8
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LED Bulbs
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Ceiling fitment
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I can assure you the light goes out without any discernable delay - it is a win-win device all round |
#10
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Another print.
Since doing the past one, I did another, again on a difficult negative and I got the colour right again with a couple of test strips - the only thing is when I dried it off, I saw the damn negative is unsharp, but it is still good practise.
Originally, I had been trying to get the grass in the picture to look green(ish) but now I find out that the grass has a coating of frost and is in fact white! No wonder I was having colour balance difficulties! |
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