Today I received a “K&F Canon EOS-M4/3 PRO” adapter (bought from https://www.kentfaith.com/). This is a new design advertised as being of high precision. I was specially interested as this is one of the very few or maybe the only series of relatively low cost adapters with a non-reflective black interior finish. This is is important to prevent reflections that otherwise degrade image contrast or create flare and ghost images. Please see Black anodised aluminium in IR and Commlite products: how I wasted my money. Continue reading Lens adapters: flange-to-flange distance
I here describe my experience with the DEO-TECH OWL EF/MFT lens adapter. The adapter is available mainly through astronomy web stores and seems to be currently distributed by Optolong. It is also available on special order at B&H photo video and possibly other large shops. Development of the adapter was initially funded through Kickstart crowd funding.
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 difference in high UV environments such as high elevation mountains and snow in sunny weather. On the other hand, most photographers us UV-filters to protect their objectives. For such use the most important considerations are well polished and parallel surfaces and control of reflections to prevent flare and ghosting. Only photography using film and older objectives benefits significantly from the haze-cutting effect of UV and skylight filters. Continue reading UV-cut filters
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 the angle at which the light impings on them affects the path length so that absorbance increases when the angle of incidence is shallow. This effect is small enough to be rarely noticeable in photographs.
Steps used to create video
- 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.
- 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.
- Export the 300 photographs JPEG, setting long edge maximum length at 1600 pix.
- Read the 300 images into ImageJ (version 1.52p) using “File > Import > Image sequence”.
- Export the video from ImageJ using “File > Save as > AVI…“, choosing the desired number of frames per second (fps).
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.
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.
[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
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 filter removed, one or more colour profiles of the camera need to be created and applied instead of the one used automatically by the camera and/or raw file converters. So, in many cases, for best results one would need to carry two different cameras to any field trip. In addition a conversion voids the camera manufacturer’s warranty and even access to official service facilities. Continue reading Digital UVA-photography with M43 equipment
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
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.
[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.