EJG
Hello and good day,
I still have an old Krokus 3, which I love because of its viewing screen with adjustable mask strips (ideal for panoramic negatives) and which I’d like to convert to LED. Does anyone have any experience with such a solution? I know there are custom-made conversion kits available, but they cost around €1,000.
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Best regards,
Ernst Jürgen
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Magirus
Hello
Since the LED emits white light, there’s no reason not to
just give it a try.
The price of the LED shouldn’t be too high;
I have an E27 12W 3000K LED in my desk lamp
which gives off plenty of light and no heat.
Regards, Bernd
Renate
It may be that the multigrade filters produce different contrasts. At 3000 K, the blue component is slightly higher. It’s a fascinating experiment, though. I’ve thought about it myself, but haven’t got round to it yet as I don’t have a suitable bulb.
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Best regards
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Renate
Wolf_XL
... the problem is likely to lie less in the spectrum of the LED bulb – and more in the evenness of the light distribution. Unlike a standard light bulb, most E27 LED bulbs either emit light in a hemispherical pattern or consist of several SMD light-emitting diodes that do not have a uniform luminance (which is why you need a special opal bulb instead of a standard one).
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So whether something like this works is likely to depend primarily on the design of the enlarger.
Magirus
The Krokus has the light source positioned above the condenser,
the E27 bulbs have a cap that acts as a diffuser (apologies for the spelling).
You’d need to test the light output to see if the exposure time remains within acceptable limits.
Regards, Bernd
Renate
I happened to buy an LED bulb with a diffuser (Osram) yesterday to use as a reading lamp. The light distribution is very even and comparable to that of an opal bulb. However, this bulb has an E14 base, so I can’t just screw it into an enlarger.
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The spectrum of this LED bulb differs from that of a traditional incandescent bulb of the same colour temperature. There is a noticeable gap in the visible blue range and in the transition to green. How this affects multi-grade paper remains to be seen. However, I won’t be testing this for the time being, as I have no need to do so.
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The brightness isn’t a problem. The 2450 lm stated in the headline is actually far too bright. That’s equivalent to more than 200 W of a conventional incandescent bulb. In my Opemus 6, I prefer a 75 W opal bulb so that the exposure times aren’t too short. An 800 lm lamp should be roughly equivalent in terms of brightness.
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I am currently considering using LED lamps to light still lifes. For this, however, colour temperatures of 4000 K or even 6000 K are of interest. For black-and-white film, this should roughly correspond to daylight. This simplifies exposure metering, as it eliminates the uncertainty caused by the lamp’s red component and the film’s red sensitivity. However, an interesting LED bulb from Osram for this purpose will not be available until November.
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Best regards
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Renate
AchimBauer
Hello Ernst Jürgen,
I’d never given your plan much thought, but I recently switched to LED bulbs at home because I managed to get some cheaply. In doing so, I discovered a problem: the bulbs are larger than standard incandescent bulbs and therefore don’t fit in all light fittings.
And what does that have to do with the enlarger?
If you’re lucky, nothing; if you’re unlucky, the interaction between the bulb and the condenser won’t work properly anymore.
…
Regards, Achim
Urnes
Ultimately, it depends on the LED lamp and its spectrum, which in turn depends on the manufacturer and the consistency of the manufacturing process.
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Everything else can be adjusted. I’ve had a look at the Krokus and seen that you can adjust the height of the lamp to match the condenser to achieve even illumination. You can also fit a diffuser plate to the filter tray. So it shouldn’t be a big problem. And it’s definitely worth giving it a go.
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Regards, Sven.
EJG
Thank you very much for all your replies. I’m looking for a suitable bulb with a colour temperature of around 4000 K. I’ll be using the diffuser.
If everything works out well, I’ll post some photos to show you.
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Best regards,
Ernst Jürgen
Wolfgg
Hello,
If the filters for variable contrast paper are to be reasonably accurate, I feel that 4000K would be too high. Here are a few spectra for comparison, showing the relative intensity across the wavelength:
40W light bulb:
[ATTACHMENT NOT FOUND]
2700K LED lamp:
[ATTACHMENT NOT FOUND]
5000K LED lamp:
[ATTACHMENT NOT FOUND]
Regards, Wolfgang
highscore
<a></a>Hi
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I might have a solution for you.
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Because after a 150 W projector bulb supposedly blew, I simply fitted an E27 LED bulb from Ikea that I had lying around and carried on.
I didn’t give the colour temperature a second thought. :spudnikdizzy:? Because my results are still good. :spudnikshooter:?
But the insert filters no longer warp from the heat!
However – negative – the exposure time has become significantly longer.
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So, on the spur of the moment, I fitted five bulbs into the Krokus 3 using a homemade new E27 socket holder, and three additional switches allow me to switch any number of bulbs on or off.
And lo and behold, the light output is, if I want it to be, even greater than with the single bulb.
Very little heat build-up, no warped filters! :spudnikcoinflip:?
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So, provided you’re not all thumbs, a modification like this is quick to do. :spudniklifter:?
Once I’d gathered all the materials, it took me about 3–4 hours to put it all together.
mattes
If you’re only interested in enlarging images, I’d advise against it, as the whole process is too time-consuming. By converting the device, you’ll simply be able to do what you could do with it before: make enlargements.
Of course, things look a bit different if you’re driven by curiosity and a playful spirit. As already hinted at, there are many interesting solutions to consider. I could well imagine an LED panel where you can switch off or dim the individual LEDs. Essentially, dodging and burning with the lighting unit.
But I’d rather just take photos and spend my time on that.
Opal bulbs are still available (e.g. FOTOIMPEX Shop) and it’s not a bad idea to buy them if needed, so that demand helps keep them in stock. Apparently, some colleagues keep a small stock of bulbs so they’re not left in the dark.
Matthias
highscore
Hi again
Yes, I was feeling quite playful.
But above all, the Krokus, with its 150W, fried the filter foils.
(Contrary to what I’d thought, my Opal bulb hadn’t died; I’d just had a broken cable in the supply line.)
But since I had to dismantle the Krokus anyway to change the cable, I decided to invest about 60 in the conversion.
Having to buy new filters once is definitely much more expensive!
(I’d still have to buy new ones anyway)
Now I can switch different numbers on or off.
According to the packaging, the LED lights are also supposed to be dimmable.
However, I haven’t installed a dimming function.
After all, I have 600, 1200, 1800, 2400 or 3000 lumens at my disposal.
And, above all, no more cylindrical filters!
With 35mm, I often use only the middle three lamps.
However, with 6 x 7, I often use all 5 together.
Rolf-Werner
Looking at the layout of the lights, I wonder if you’ll manage to achieve even lighting. I’d leave the one in the middle on all the time, but if you only switch on one of the others, won’t you end up with a spot that’s too bright in one corner?
Rolf
highscore
Good point, Rolf
I haven’t been entirely happy with the position of the middle one either.
However, the results speak in favour of this configuration
I always switch the opposite ones in the pair. The middle one on its own
There have also been negative results when I switch the middle one off
However, due to the huge diffuser, the effects on the lighting are very minor
It doesn’t immediately create a visible shadow zone or anything like that
It’s all very subtle
You can have a slightly positive influence on the need for adjustment
mattes
I wasn’t aware that the Krokus got so hot; I’m only familiar with the Meopta models, and I’ve never had any problems with them. Of course they get warm, but that didn’t affect the filter foils.
I think your solution is brilliant – can you vary the distance of the lighting?
As LEDs are also available as G4 bulbs, you could fit a relatively large number of lights onto a round plate; even light distribution can be achieved using a diffuser and adjusting the distance.
Definitely a very interesting idea.
Matthias
highscore
Hi
I can still adjust the height quite easily, but I’ve hardly any leeway when it comes to the sides.
However, I could have used E14 sockets as well. That would have given me a bit more leeway.
But as I’ve already said, I’m happy with my results;
with G4 LEDs, I’d have concerns about the ‘light colour’.
But I’m sure there are real experts here on the forum who can answer that question.
My gut feeling makes me a bit wary of them, though.
