As I have just done a test on M42 lenses comparing their UV-transmission, I thought I would also do a test of a few different brands of 35mm F3.5 enlarger lenses (both new and older casing designs) using the same setup, to see if there is much variation in their UV-transmission.
I chose to compare these 5 lenses: Aico (old casing), Aico (new casing), Beslar (new casing), Spiratone (old casing) & Soligor (old casing) lenses. I do have many more different brands, but I don’t expect there will be that much difference (other than sample variation) & certainly not too noticeable in real life UV-imaging. Just be aware that the camera body remained at the same place as for the M42 lens test, and hence the front of the enlarger lenses was a good 8-10cm further from the subject than the M42 lenses.
Camera: Olympus E-PL5
UV-pass filter: Baader U, 330AF20 bandpass filters
Settings: All lenses set to F8 for the Baader U (1/80 secs, 1/4 power Quantum X2D, ISO 200) & F5.6 for the 330AF20 (1/80 secs, full power Quantum X2D, ISO 200). Focusing was done for Baader U shot using Nightsearcher UV torch & remained unchanged for the 330AF20 shot.
Processing: All images were shot in RAW. All Baader U & 330AF20 shots were boosted by 1.0 EV in Capture One Pro. This is more to show the difference in UV-transmission. No other adjustments were made (except for white balancing).
White balance: All images had white balance adjusted by clicking on the sintered PTFE in the background in Capture One Pro (I shot a separate 1/16 Quantum X2D power image for each lens for white balancing, except the Spiratone image where for some reason I did not have a 1/16 shot).
Anyway, here are the results.
There may be slightly better transmission with the Spiratone old lens, compared to the others (but it comes with T2 threads instead of M39 so may not fit fully into a normal M42 helicoid). Otherwise all the 35mm F3.5 enlarger lenses all perform similarly well, and you would be hard pressed to tell them apart; there will be sample to sample variation, but in the real world, it should not make much difference when doing UV-imaging.
I include an image of the Spectrosil 2000 filter I bought which has anti-reflective coating (248-400nm) for the UV range. I will leave you to draw your own conclusions about the ideal lens coating for UV-imaging.
In this case, all the 35mm F3.5 enlarger lenses look very similar (lens coating and construction) except for the actual brand i.e. they are clearly all rebadged versions of the same lens bought from the same manufacturer (although Spiratone seem to have gone for T2 mount rather than M39).
Equipment: Olympus E-PL5, various 35mm F3.5 enlarger lenses, Baader U, 330AF20 filter, Nightsearcher UV Torch, Quantum X2D