MIDOPT filters

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).

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Black anodised aluminium in IR

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