There are so many different 35mm F3.5 lenses available out there. Even within the same stable of lenses in a company, you can see different designs which were clearly bought from different manufacturers and then rebadged. Some companies are well known for doing this, such as Prinzgalaxy and Soligor. I thought it was time for another comparison test.For this test, I have assembled some of the lenses from these brands that I own, to see if I could come up with any conclusions. As you can see they all have different looking front elements, filter thread size, lens casing and even lens coating. But the Soligor KA and 9xxxxx series look fairly similar (and also have 46mm filter threads).
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 shots were boosted by 1.0 EV in Capture One Pro, while the 330AF20 shots were boosted by 2.0 EV in Capture One Pro (except for Prinzgalaxy 7xxxx Kuribayashi clone which was only boosted by 1.0 EV). The increased exposure is to boost the overall image to show the difference in UV-transmission, as some are under and others over-exposed. 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).
Anyway, here are the results. I have included Novoflex Noflexar 35mm F3.5 lens as my reference lens:
I was surprised to see that the Soligor KA lens did fairly well with the 330AF20 filter, so is also a viable 35mm F3.5 lens for UV-imaging; just goes to show that unless you do a controlled test, sometimes it is difficult to make assumptions about lens performance.
The poorest performers were the Prinzgalaxy 1xxxx and the Soligor auto Mxxxx lenses, which did not transmit as deep into UV as the rest of the lenses. But they are all capable of capturing the UV-pattern of the Rudbeckia, and once correctly adjusted for exposure and white balanced it would be fairly difficult to tell them apart.
So, as you can see – it is not so much the brand that is important, as each brand could have many versions of the same focal length lens (bought from different manufacturers). Hence care has to be taken to look at the specific design/appearance, to ensure that the colour of the lens coating, the casing of the lens and the serial numbers are actually the same as the recommended lenses; do not just consider one lens characteristic on its own e.g. serial number alone, as you could just be wasting your money if the lens looks completely different in other ways.
BTW, the Spectrosil 2000 filter I bought and cut to size (pictured below) has anti-reflective coating (248-400nm) in the UV range. Look at the colour of the coating, and I shall leave you to come to your own conclusion. But I do have to stress that I also own lenses with this coloured coating with poor UV-transmission, which illustrates the point that there are other factors (lens design, glass used) which determine the overall UV-transmission.
Equipment: Olympus E-PL5, various 35mm F3.5 M42 lenses, Baader U, 330AF20 filter, Nightsearcher UV torch, Quantum X2D