visible radiation – Photo rumblings and whispers

Small Fill/Video LED lights revisited

Pedro J. Aphalo 2022-10-15 2022-10-16Photography 0

Four years ago I wrote a post comparing the Sunwayfoto Fill Light FL96 and the Aputure Amaran AL-M9 mini LED light. They are both still available new. Sunwayfoto has released a few variations on the original model, the FL96 C with batteries with increased capacity and faster chargin through USB-C, and in the case of the FL120, slightly higher light output and power-bank function. A few days ago I bought an Elgato Key Light Mini, and decided to run a new and more thorough comparison between these the three commercial LED light sources that I own. In part because I…

Hemispherical time-lapse under a tree

Pedro J. Aphalo 2020-09-29 2020-09-29Landscape, Plants, Techniques 0

In two earlier posts titled “Lens adapter with filter drawer” and “Lens adapters: flange-to-flange distance” I discussed how crucial it is to achieve the exact effective flange-to-flange distance when dealing with adapted objectives with a very short focal distance. I also described how I shimmed an adapter to achieve this. Recently I had an opportunity to use the Sigma 4.5mm 1:2.8 circular fisheye objective in Nikon AF mount adapted to my Olympus E-M1 Mk II camera to create a time-lapse video. I captured 500 images, with a pause of 1 s between them. Total time was a bit over 10…

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.)

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.

How small a spectrometer can be made?

Pedro J. Aphalo 2019-02-13 2019-02-13Equipment, Photography 0

[I will update this post after testing the sensor] In a recent post I described a miniature two-channel UV-A sensor with digital interface. Here I will describe a miniature and low cost spectrometer, type AS7265X from ams. It does not used a grating as monochromator, but instead each of the 18 channels has a different interference filter deposited directly on the silicon chip. The FWHM is 20 nm, and the wavelength range from 410 nm to 940 nm. The spectrometer consists in three separate sensor units working together. The interface is digital, and temperature compensation and analogue to digital conversion…