Atelier Bonryu(E)
ultraviolet photography
Laboratory: Ultraviolet Photography
Taking Ultraviolet Photographs - Focusing
An ultraviolet(UV) photograph can be taken in the similar way as described in the pages of the infrared (IR) photographs. Different points from usual photographing are usage of the visible light blocking filter and necessity of a tripod because shutter speed is slow when an unconverted camera is used. For the serious UV photography a lens dedicated for the UV light is necessary to reduce absorption of the light through the lens but a conventional lens used for the visible light photography can be still used for the UV photography. I usually take UV photographs by using a conventional lens. There are also difference of sensitivity to the UV light among different cameras. On this point I have not sufficient data yet.
When taking a photograph focusing is very important. To take the invisible light photographs I use two point-and-shoot cameras(unconverted), Olympus Camedia -5060, Olympus mu digital 800, two dSLR (unconverted), Olympus E-300, Olympus E-510, and a converted dSLR, Olympus E-620. As for the two point-and-shoot cameras the AF function works satisfactory but as for the two dSLRs it doesn't. In the page of the IR photography the result of a very rough measurement of the sensitivity for the IR photography is described. Though E-300 is most sensitive to the IR light the AF function does not work for the IR light. Therefore, only the high sensitivity is not sufficient for focusing a camera by using the AF function. If the AF function does not work and focusing by a live-view screen cannot be used (E-510 has a live-view screen but E-300 does not have it) it is necessary to focus the camera before setting the visible light blocking filter and then setting the filter and take a photograph. In this case it is very important to focus the camera according to the empirically obtained data because the focal lengths of the visible, the IR, and the UV lights are different. In order to take a photograph in good focus it is important to carry out this correction of focal distance due to the wavelength which depends on individual lens with different designing. By making the f-value as large as possible to realize deep field depth a resulting photograph becomes sharper.
