Anyone using LED lights for contact printing?

[Bronson Dugnutt]

Seems like a shorter exposure time would minimize diffraction effects at hard edges of contrast while contact printing, yielding greater sharpness.

Any before & after photos?

 

[Rolleiflexible]

Seems like a shorter exposure time would minimize diffraction effects at hard edges of contrast while contact printing, yielding greater sharpness.

Any before & after photos?

I'm going to nod and say "That sounds right," which is my reaction when Scotty warns Kirk the dilithium matrix will overload if the Enterprise enters the tachyion field.

I've not reprinted anything yet to make a direct comparison. I think part of my sense of increased sharpness may be a function of the blacks being slightly blacker, and the whites being slightly clearer, as if the longer exposure was causing some kind of veiling effect. These are just preliminary impressions.

 

[koraks]

I am curious as to whether others have found that the sharpness of their images is affected by exposure lengths -- I assume the increased resolution is a function of reduced exposure time, but if I am mistaken, someone please speak up. Here's a link to the lights, if anyone wants to investigate:

I'll bite, albeit late. I posted about it earlier here: https://www.photrio.com/forum/threa...t-experience-for-alt-process-printing.193729/
This refers to two blog posts I wrote about my recent experiences with a low-cost UV LED floodlight for alt. process printing (my application, not its intended application).
Here's the comparison against my trusty bank of UV tubes: https://tinker.koraks.nl/photography/uv-tube-vs-led-a-quick-comparison/
Conclusion: sharpness is better due to the LED light being more collimated, but the difference is marginal at best and mostly visible around the edges of the print, not so much within the image area.

I also noted that while my unit was sold as '300W', it by no means comes anywhere near that power level. It's closer (and even not quite) to your 96W unit in terms of true power rating. See here: https://tinker.koraks.nl/photography/what-a-300w-uv-floodlight-is-not/

I will continue down this path, but so far, the UV tubes are still more efficient and effective at their job than this particular unit. Mind you, this is a 395nm unit. My intent is to use these for carbon transfer, and dichromate efficiency in combination with LEDs tops out at around 385-390nm - i.e. that's where you get the most exposure for your Watt of input power (and coincidentally it's also the cheapest solution). See Calin Grier on the subject, although you'll have to buy his Gum Printing book to get to the good stuff about light sources.

Seems like a shorter exposure time would minimize diffraction effects at hard edges of contrast while contact printing, yielding greater sharpness.

Nah, don't think so. There's no reason why diffraction would be time-dependent. Look at the physics, it wouldn't make any sense. The additional sharpness is due to the more collimated nature of the light from these little LED beads compared to a bank of UV tubes.