LED UV 365nm 2X2 inch size 50 watts , Does it cover A4

LED UV 365nm 2X2 inch size 50 watts , Does it cover Kallitype or Van Dyke A4 ? How far it must be placed ?

Does it look like the one above? Does yours have a lens mounted over it? Without a lens you probably get even coverage at around 50cm, but you'll have to experiment. With a lens, it depends on the lens angle. 365nm 50W is fine for kallitype & Van Dyke; you'll get fairly fast printing speeds.

koraks said:

Does it look like the one above? Does yours have a lens mounted over it? Without a lens you probably get even coverage at around 50cm, but you'll have to experiment. With a lens, it depends on the lens angle. 365nm 50W is fine for kallitype & Van Dyke; you'll get fairly fast printing speeds.

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Hello Koraks , it looks like your photograph but no lens.
At alternative photography list , they said distance should be 10 centimeters and they said 50 watts so weak. They advised me to buy 16 of them and make a grid 4X4 and use it. One unit goes 28 dollars and 16 makes 438 dollars.

Author of Kallitype book , Don advised me to use daylight - north side - and not to use direct sunlight. I have no idea , how many minutes does the print should stay under daylight.

Mustafa Umut Sarac said:

they said distance should be 10 centimeters and they said 50 watts so weak.

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They must be thinking of a different kind of LED. Both of the things I quoted above are wrong. 10cm is much too close for this LED to cover A4 size and you really only need one for perfectly reasonable exposure times. An array of 16 of these LEDs is totally insane and overkill for making A4-sized prints. If you find the printing times too long with a single LED, you can either upgrade to a single 100W LED and cut the exposure time in half, and possibly use 2 to 4 of these to also gain 1-2 stops.

Btw, I use the same type of LED all the time; mine are 100W which is one stop faster than your 50W.

Daylight is fine but honestly, this type of LED that you have is perfect for this purpose as well and much easier to control consistently than daylight, which of course cannot be controlled at all.

Keep in mind that with this LED you need a heatsink and a fan and also a constant current power supply. If you have not already purchased it, I would recommend getting the 100W version of the LED which is generally only slightly more expensive than the 50W version but twice as fast.
Also, if you only want to do kallitype, van Dyke, cyanotype etc, the much cheaper 395nm LEDs will be fine, too. The power supply and heatsink are the same.

Hello Koraks , Thank you very much for clarifying the issue. I read at 50 watts LED source selling website , its directly connects to 220 volts. How many minutes does it take to print a van dyke or kallitype print and do I need really a fan and heatsink for for example 20 minutes exposure ? We will not constantly print , one in one hour may be ?

Mustafa Umut Sarac said:

its directly connects to 220 volts.

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Okay, then it's not exactly the type of LED I posted. Can you link to the website please?

Thanks; that clarifies.
The issue with such LEDs is that the 50W nominal power is generally much higher than the real (RMS) power they effectively run at. I expect this LED to effectively dissipate around 20-25W RMS, based on my experience with LED systems with similar power supply arrangements.
It does require a heatsink also for exposures of just a few minutes. A unit like this heats up within a few seconds and will burn out in under a minute if no heatsink is mounted.

I personally would consider other options instead. The simplest solution for your application would be a home-made exposure box using UV LED strips and a generic 12V or 24V DC adapter. This is easy to build, affordable and works well for the purpose. The LED strips generally have adhesive tape so you can easily stick them onto a surface of your choice. You can use 395nm LEDs for kallitype and Van Dyke, which saves you some money compared to the more expensive 365nm LEDs. If you use LED strips, you don't need to worry about a heat sink or fans. You just need the LED strips and a suitable power supply. You may need to solder several strips together. This is not very difficult to do.

Raghu Kuvempunagar said:

Ultraviole Projektör

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RMS power output can be expected to be around 40W or so. It will work as shown in the video with printing times comparable (within an order of magnitude) to UV-BL tubes.

Hello Koraks,

I dont have access to strip uv leds , heatsink and wind maker. If I make the my attachment work for 40 seconds and wait to be cooled and then expose again for 40 seconds.. Do you see this method plausible ? How many minutes does it take to cool and how many minutes does all expose take for kallitype and van dyke seperately ?

Thank you very much,

Umut

Mustafa Umut Sarac said:

Do you see this method plausible ?

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No, you'll likely kill the LED. It should not be run without a heatsink for longer than 2-3 seconds.
Also, 40 seconds will likely be too short for a Van Dyke/kallitype exposure with the light source you linked to for an A4-sized print. It'll be a couple of minutes; I estimate 5 or so, could be up to 10 if real power output is lower than anticipated.