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

Photographs through windows

When travelling by train, bus or aeroplane we frequently see views that would make great photographs. In this post I display a selection of pictures I have taken through windows while travelling in Finland between May and October 2017.  I also explain some tricks-of-the-trade that hide or attenuate the effects of the optical imperfections of windows. Continue reading Photographs through windows

High dynamic range

High dynamic range (HDR) is used to refer to photographs which have captured a broader range of luminosity values than what is usual. In most contexts it implies a higher dynamic range than a digital camera sensor can detect between saturation and its noise floor. How can this be achieved? By combining several images so that different parts of the scene come for images taken with different exposure settings. In other words exposure bracketing followed by digital processing to merge the images. If you do not know what is the meaning of bracketing in photography please first read my earlier post on the subject. Continue reading High dynamic range

PWM-dimming of RGB LEDs


Here I have tested a single individual lamp, of a single brand and type. From the ubiquity of identical or very similar lamps sold under different brand names by numerous sellers in eBay and Aliexpress, this seems to be a “typical” or popular type. The intention is for it to serve as an example of one specific technology for adjustment of the light output of LED lamps. This is not a comparative review. Continue reading PWM-dimming of RGB LEDs

Dimming of LEDs

If you are interested in photography, and take photographs under illumination from LEDs, you need to be aware of how the dimming of LED lamps works. LEDs are becoming very popular, and dimmers are quite frequently used to adjust the light level. This applies to households, offices, commercial spaces, and the now ubiquitous special LED lamps sold for studio and on location video and photography. Continue reading Dimming of LEDs

Fluorescence of glass filters

Until very recently I was not aware that optical glass filters can fluoresce when exposed to ultraviolet radiation. In this short post I use two filters from Heliopan that I own as examples of this. However, many other filters, and even the glass elements in some camera lenses can also fluoresce. Continue reading Fluorescence of glass filters