I have been testing some objectives for their UV transmission using LEDs as sources of radiation. I developed a protocol for such tests. Although used in this example to measure the spectral sensitivity of a camera sensor, the protocol can be easily adapted for the measurements of biological action spectra.
For those interested in photography “beyond the visible”, some of the filters available from Midwest Optical Technologies Inc. under the MIDOPT brand name should be very interesting. They are distributed in European countries by Stemmer AG. Both companies are specialised in the supply of machine vision equipment. What adds additional interest is that filters are supplied in very many different sizes (from M13.25 all the way to M105, mounted and unmounted, and even with mounts suitable for installation at the back of objectives with C-mount).
Many cheap extension tubes, lens adapters and lens hoods are made of aluminium and have a black anodised finish: are they always better than plastic ones? As it was revealed by the macro extension tubes comparison internal reflections can be a problem in visible light and lead to glare and low contrast. These problems are caused by a relatively small amount of visible light reflected by anodised aluminium, specially if the surface is smooth. The ribbed surface frequently used avoids specular reflections, so controlling “stars” and similar artefacts but not so much the loss of contrast due to diffuse reflection. Continue reading Black anodised aluminium in IR
An on-going Kickstarter campaign offers sophisticated pinholes for digital cameras in an assortment of different lens mounts. I ordered mine, as I am interested in ultraviolet photography and pinholes, in spite of their many limitations, allow radiation of any wavelength through. Pinholes are simply very small holes in a thin plate.