ultraviolet radiation – Photo rumblings and whispers

UV-cut filters

Pedro J. Aphalo 2020-06-12 2020-06-17Equipment, Photography, Techniques 0

As described in the post UVIR-cut filters both absorptive filters and interference filters are sold as UV-blocking filters. All modern photography digital cameras have internal UVIR-cut filters and most modern objectives transmit little UV-radiation. There are some exceptions, most if not all Olympus cameras are sensitive to long-wave UV-A radiation and a few modern objectives also transmit long UV-A radiation. Many filters sold as UV-filters do not differ from those sold as clear protection filters enough to matter. However, a few UV-filters do absorb in the whole UV-band and even into the visible violet band. Their effect might make a…

UVIR-cut filters

Pedro J. Aphalo 2020-06-11 2020-06-17Equipment, Photography, Techniques 0

Filters can block radiation either by reflection or absorption. Absorptive filters are usually made of glass containing various metal ions while cheaper plastic filters tend to be coloured with organic dyes. There is a third type of absorptive filter, which are rare nowadays that consist of a coloured gelatine layer in-between two glass sheets. Most high-quality absorptive filters sold for photographic use are made of solid glass and absorptive. In the case of square filters plastic is more common than for smaller circular filters. The current perfected version of the gelatine-between glass filters is Tiffen’s “core technology”. With absorptive filters…

Godox AD200 flash for UV, VIS and IR photography

Pedro J. Aphalo 2019-07-14 2019-07-18Equipment, Mehods, Photography, Techniques 0

[Updated 2019-07-18] Godox sells a medium-power flash called AD200 with interchangeable heads and several accessories like light modifiers and remote wireless triggers with TTL exposure metering and high speed synchronization capabilities. This gives a lot of flexibility in its use. After a few separate purchases I now own the AD200 and the H200, H200J and H200R heads, an Xpro-O TTL Wireless Flash Trigger, and several light modifiers, all of them branded Godox. (The same flash and accessories are also available under other brand names.)

Digital UVA-photography with M43 equipment

Pedro J. Aphalo 2019-07-14 2019-07-14Equipment, Photography, Techniques 0

How far can we go, with off-the-shelf equipment One question which I have been pondering for some time is: do I need to have a digital camera converted to full-spectrum for UVA photography? and are there any modern objectives that are good accidental UVA-objectives? This is not a question of cost alone. Although a converted camera can be used for VIS photography, obtaining good colour reproduction requires effort. A suitable filter is used on the objective to replace the one removed from the image sensor unit during conversion. As it is not possible to find a perfect match to the…

Measuring campaign in the Alps

Pedro J. Aphalo 2019-06-19 2020-12-19Lichens, Photographs, Plants, UV-induced fluorescence 0

I joined a field measuring campaign organized by my collaborator T. Matthew Robson with the participation of José Ignacio García Plazaola and Beatriz Fernández-Marín from the University of the Basque-Country (see Matt’s CanSEE and my SenPEP blogs for information on our research). We spent the last week of May the at 2100 m a.s.l. in the Alps at the Jardin Botanique du Lautaret measuring solar radiation and the responses of plants to it. I did some measurements of solar radiation but spent most of the time photographing plants and lichens to record their optical properties in the ultraviolet-A, visible and…

Most neutral density filters are not neutral

Pedro J. Aphalo 2019-05-11 2019-07-18Equipment, Mehods, Photography 0

[Updated 2019-07-17] A neutral density (ND) filter is a “grey” filter, a filter that transmits equal fractions of the incident radiation at all wavelengths. A perfectly neutral filter over a broad range of wavelengths is an idealized concept, and one very difficult to implement in practice. There are different approaches to making filters approximating colour neutrality. We here compare the spectral transmittance of of ND filters of three different types available for use on camera lenses and explain why the use of some of them can introduce strong colour casts in the photographs we take with them.

Photographs of flowers: VIS vs. UV-A

Pedro J. Aphalo 2018-09-09 2018-10-15Photographs, Photography, Plants 0

Visible vs. UV-A false-colour

How small can a UV-B plus UV-A sensor be made?

Pedro J. Aphalo 2018-08-08 2019-02-13Mehods, Photography 0

[updated 2019-02-13] [I will update this post again after testing the sensor] Rather recently Vishay announced a miniature sensor under the name VEML6075 with two channels nominally centred at 365 and 330 nm. The peak width at half maximum is 20 nm. So, in practice it is a sensor measuring two regions within the UV-A band with the tail of one of the two channels extending into the UV-B. It is not a sensor capable of separately measuring the UV-B and UV-A bands. However, under sunlight it collects enough information to obtain a reasonable estimate for the UV Index (see…