I bought the Sony 20mm F2.8 E-mount pancake lens mainly to test it for its capability in shooting UV and Insect-D-sight, as it is small, light, fairly wide-angle and a native E-mount lens with autofocus. I previously owned the Sony 16mm F2.8 lens, but sold it even though it transmits UV reasonably well as I did not like the image quality. I was hoping this lens could perform similarly well in UV transmission but with better IQ. For this test, I used my friend’s NEX-5N.
I used the Baader U filter to shoot the UV images. These images were shot indoors using my Quantum X2D for light source. Settings for these were ISO 200 F11 1/80 secs. I have included both processed from RAW as well as out-of-camera jpeg images for comparison. The last studio shot was taken with the NEX-5N and Coastal Optics 60mm F4 APO for comparison – as you can see, the colour is much richer due to the exceptional UV-transmission of the Coastal Optics. But the 20mm F2.8 lens is able to capture the UV-pattern of these flowers.
Outdoor UV images were taken mounted on my Giottos YTL-8354 tripod. Do note that these were taken late in the evening when the sun was no longer shining.
IDS2e images were shot handheld using autofocus with higher ISOs to reduce image blur. Although images were shot with in-camera custom white balance, unfortunately this information in the RAW file is lost when the image is loaded into Capture One Pro. Hence the white balance still needed to be adjusted in Capture One Pro.
The question I had before was whether the Sony 20mm F2.8 transmits sufficient UV to be useful for UV-imaging and the answer is yes. But as with modern lenses, it does not transmit very deep into UV, unlike the Kuribayashi 35mm F3.5, the Novoflex Noflexar 35mm F3.5 or the 35mm F3.5 enlarger lenses.
It would be nice to do a direct comparison with the Sony 16mm F2.8 lens, but as I no longer own one (and neither does my friend) I am unable to compare the transmission between the two. But certainly this lens is an alternative wide-angle lens which can autofocus in UV and IDS2e, is fairly sharp even wide open and will be useful for shooting wide-angle Insect-D-Sight videos
when autofocusing is required. (where manual focusing with focus peaking works the best).
Equipment: Sony NEX-5N, Sony 20mm F2.8 E-mount lens, Baader U filter, IDS2e filter, Quantum X2D, Nightsearcher UV torch.