I’m finding ultraviolet photography to be one of the biggest challenges I’ve come across in the photographic process in years. Such a huge learning curve.
Due to the short bandwidth of ultraviolet light, the reflective transmittance doesn’t seem to travel as far as visible light, plus this also causes a focus shift issue as photographing in infrared does.
With the sensitivity of the converted camera, I have been able to pick up the ultraviolet spectrum at a decent iso (around 800 – 1600 as opposed to 200 – 400) and live view permits achieving a fine focus if I take the time to really review and adjust before I shoot.
More of the problem seems to be in the lenses. Glass, air space and the cement used to join elements in a lens all interfere with the UV transmission. True UV transmission lenses (made with quartz-fluorite elements instead of glass) are still manufactured and a few older ones can be found second hand but these are way beyond my price range at an approximate cost of $3000US and up.
Fortunately ultravioletphotgraphy.com has a list of true and “accidental” lenses for ultraviolet photography work. I managed to pick up one of the Steinheil 50mm Cassarits recently and imediately noticed a difference. While not a spectacular shot, it is the first time I’ve been able to achieve focus on any subject farther away than about six inches.
This was shot midday 1/4 second, f8, iso 1600 using a Hoya U360 and S8612 bringing it to around a 360-365nm light source. The Steinheil triplets have been tested to have a cutoff of around 320nm. I am looking forward to testing this lens (as well as an older Cassarit 100mm) with a Hoya U340 to see if I can achieve a deeper UV cutoff point.
Learning Ultraviolet Photography is proving to be such a challenge it reminds me of when I first picked up a camera. How wonderful to be able to shoot 35 photos and not find a single keeper. Reminds me of the film days. I’m finding that trying to imagine how an image will appear, when the focus is using non visible light, has many variables that can affect the outcome.
One of course is the light source. If you don’t have full sun cover, using a dedicated light for a specific bandwidth or a full spectrum flash is essential. Next is choosing quality filters that absorb all light not wanted to affect the image. Also, I’m finding that the lens choice is just as important as the light source itself. Very few lenses are truly dedicated UV lenses made from quartz rather than glass, so the challenge is finding “accidental” lenses that permit good UV transmission.
Below is a basic test I used to determine which of my older lenses would permit the best UV transmission in the 360-365nm bandwidth. I used a pinhole cover with a dedicated Hoya U360 and BG40 filter stack to eliminate all light in the visible and IR range. I used a white plastic as the background and focused a dedicated 365nm light on it. White balance was done on the background. Exposure time was 15 sec and iso 1600. All phtos were post processed with the same settings.
All lenses tested were set to f4 and the rear of the lens was set at 2 1/2 inches from the background. Lenses tested were the Lensbaby Sweet 35 and Edge 80 optics, the Lensbaby Twist 60 and Selective Focus optics, an El-Nikkor 50/4 and Meyer Optik Domiplan 50/2.8 and Helios 44M 58/2. The Domiplan is supposed to transmit down to 345nm from other test located on ultravioletphotography.com (great reference site). The El-Nikkor is also supposed to be a good transmitter. The clearer the light through the lens itself signifies better UV transmission, purple signifies the worst.
From my basic, non-scientific test I was suprised to see the Lensbaby Soft Focus optic seems to perform as well as the Domiplan and both the Lensbaby and Zeniton 35mm lenses performed well. The Zeniton 135 performed poorly, even though it is the same optical construction (4 element / 4 groups) as the Zeniton 35.