near-infrared radiation – Photo rumblings and whispers

NIR-pass filters

Pedro J. Aphalo 2021-02-01 2021-02-01Equipment, Photography, Techniques 0

All the near-infrared (NIR) long-pass filters described in this post are absorptive glass filters and sold for special photography effects. All modern photography digital cameras have internal UVIR-cut filters. Use of these filters requires special film, special digital cameras or modified DSLR or DML cameras. Some filters can be used with unmodified digital cameras with very long exposure times. Few normal camera objectives are designed to work well in NIR. Two problems are common: 1) focus shift which needs special attention when focusing is done in visible light (e.g. not using an EVF or live-view from the camera sensor, 2)…

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…

‘Black anodised aluminium in IR’ post updated

Pedro J. Aphalo 2018-08-05 2018-08-05Equipment, Photography, Techniques 0

I have updated the post ‘Black anodised aluminium in IR‘ after using the Tenenal special camera paint (black deep mat) and repeating some of the tests.

Pinholes in NIR and UVA

Pedro J. Aphalo 2018-04-28 2018-06-18Equipment, Photography, Techniques 0

Using the E-M1 converted to full spectrum with the Pinhole Pro objectives is possible. Using a 58 mm NIR filter (Hoya R72) attached to the front of the 11 mm Pinhole Pro S11 worked fine, with no increase in vignetting. Using the StraightEdgeU 52 mm or Baader U-filter 2″ with a step-down ring blocked the corners of the image completely. The original 26 mm Pinhole Pro suffers a lot less from vignetting and can be used with these filters of smaller diameter than the front thread of the lens without problem.