UV photography requires a UV-pass filter (for UV-only photography) and a visible-spectrum-pass filter (also called a UV/IR cut or blocking filter). Photographs are taken with each of these filters using a full-spectrum camera.
Available UV filters (empirical imaging has no affiliation with these companies):
| Baader Venus-U filter | This is the standard filter which has been used for many years. It has excellent IR blocking, and the transmission is in a suitable range. It can also be easily paired with the Baader UV/IR blocking filter for photography in the visible region. One downside is that the thread sizes are standard for astronomical instruments, but not cameras. |
| Andrea “U” | The specifications of this filter are excellent, and it uses a more standard thread size than the Baader filters. |
| Kolari Vision UV Photography Filter | The specification of this filter sounds ok (though with fairly low maximum transmission of 50% at 365nm), and decent sounding IR suppression. But they haven’t published a full transmission profile. We haven’t tested it though. The colour-correcting UV/IR cut filter from the same supplier sounds ideal for getting a more sensible colour in the visible-range than the above Baader UV/IR cut filter. |
Full-spectrum cameras are far more sensitivity to near infrared than UV light, and many bandpass filters have second harmonic leakage (e.g. a filter designed to transmit UV light around 350nm, will often transmit at double this wavelength, around 700nm, where the camera is far more sensitive). Most artificial and natural light sources also produce more near-infrared than UV light. The result is that a low-quality UV filter will actually just be showing you infrared instead! Always be very careful to test your filters to ensure that can’t detect near IR. An easy (but not entirely fool-proof) test is to point an infrared TV remote control at the camera with the UV filter and ensure you can’t see the flashing IR source).
Visible filters
Historically most labs use the Baader UV/IR cut filter. However, this transmits everything between 400-700nm with a very sharp spectral transmission switch at these wavelengths. Given the sensitivity of sensors to near-infrared, this can result in the red sensitivity shifting to longer-wavelengths than is always ideal. So if possible, we recommend retaining the UV/IR cut filter that came with the camera. For APS-c and full-frame cameras this rectangular filter is often big enough to use with lenses such as the Nikkor EL 80mm. This filter restores the camera’s sensitivity in the nearly the same visible range as the manufacturers’ specification. it has a gradient in the red transmission that shifts red sensitivity to a narrower and shorter-wavelength peak. Kolari Vision also offer these “hot mirror” filters in various sizes e.g. here (we have not tested these filters and are not affiliated in anyway way).