A time lapse video assembled in ImageJ

Steps used to create video

  1. Use time-lapse setting in camera to take a series of 300 photographs, one every 10 seconds. Set auto-exposure lock. Set camera on a tripod.
  2. Import the 300 images into Capture One (version 12.1). Edit the first image including correction for perspective and cropping. Select the 300 images, copy the edits from the first photograph to the remaining 299.
  3. Export the 300 photographs JPEG, setting long edge maximum length at 1600 pix.
  4. Read the 300 images into ImageJ (version 1.52p) using “File > Import > Image sequence”.
  5. Export the video from ImageJ using “File > Save as > AVI…“, choosing the desired number of frames per second (fps).

Equipment

Camera Olympus E-M1 Mk II and M.Zuiko 12-40 mm f:2.8 objective. Camera on tripod. Zoom objective set at 12 mm, f:5.6, 1/400 s, ISO 200.

Caveat

It is possible to create the video in camera, but I do prefer to convert from raw (ORF) and edit the images in Capture One before assembling the video.

Godox AD200 flash for UV, VIS and IR photography

[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.) Continue reading Godox AD200 flash for UV, VIS and IR photography

Oversized lens hoods and windows

I read during the 1970’s, most likely in a photography magazine, about the use of collapsible rubber lens hoods to take photographs through windows. They do work, specially if one manages to find a stiff enough one that will not collapse instantly at the first bump in the road or in the flight. Hama branded rubber lens hoods did work well for this purpose 45 years ago and those currently available from Hama also do work well. The problem is that given their size one has little room for deviations from pointing straight into the window as vignetting quickly becomes a problem. Neither can one use them with wide angle lenses. Continue reading Oversized lens hoods and windows

Measuring campaign in the Alps

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 near-infrared regions of the spectrum.

This posts contains several galleries of photographs from the site and the vegetation.

Continue reading Measuring campaign in the Alps

Most neutral density filters are not neutral

[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.

Continue reading Most neutral density filters are not neutral

Capture One to the rescue

Rescuing a technically “bad photograph” is not that difficult nowadays. This photograph was taken against all odds… through the double glassing of a dirty window on a train racing at high speed through the landscape. To make things even worse the sun was shining on the window I took the photograph through and the glass was slightly tinted green. The result out of camera was a low contrast raw image that looked like a sure discard… but was it?

Default rendering of the RAW file in Capture One 12.

Continue reading Capture One to the rescue

How small a spectrometer can be made?

[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 takes place in the sensor modules. In spite of the number of channels communication between the spectrometer and a micro-processor requires only two wires. The spectrometer supports two different communication protocols, the specialized I2C and a generic serial communication (UART).

Macro-photographs of both sides of an early prototype of a breakout board are shown below. The size of the board is 18 mm × 19 mm. (Photographs were taken as described for the UV-A sensor.)

I bought this board from a seller at Tindie for USD 50. The seller is now selling a differently shaped board, with the three modules in a triangle, and so closer to each other.