Mehods – Photo rumblings and whispers

Broad band VIS+NIR LEDs

Pedro J. Aphalo 2021-10-25 2021-10-27Equipment, Mehods, Photography 0

Broadbands LED based on a blue LED and “phosphors” have appeared in the market. One example is type SMB1N-BB450 from Roithner LaserTechnik (Vienna, Austria). The primary LED has a peak of emission at 450 nm and the spectrum as a whole covers the range 400 nm to 1000 nm. Except for the prominent blue peak the spectrum is rather flat, making it useful light source for VIS and specially NIR imaging and spectrometry. This LED type seems useful for photography as well as for its intended use is spectrometry. Emission is rather weak and efficiency rather low, emitting 0.3W of…

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.)

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 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…

Camera objectives for UV photography

Pedro J. Aphalo 2018-04-23 2021-11-25Equipment, Mehods, Photography 0

I have been testing some objectives for their UV transmission using LEDs as sources of radiation. I developed a protocol for such tests. Although used in this example to measure the spectral sensitivity of a camera sensor, the protocol can be easily adapted for the measurements of biological action spectra.

PWM-dimming of RGB LEDs

Pedro J. Aphalo 2017-10-23 2018-10-15Mehods, Photography 0

Here I have tested a single individual lamp, of a single brand and type. From the ubiquity of identical or very similar lamps sold under different brand names by numerous sellers in eBay and Aliexpress, this seems to be a “typical” or popular type. The intention is for it to serve as an example of one specific technology for adjustment of the light output of LED lamps. This is not a comparative review.

Macro extension tubes (description)

Pedro J. Aphalo 2017-09-06 2018-06-18Mehods, Photography 0

This is the first of three instalments on the comparison of three sets of macro extension tubes for MFT cameras: Macro extension tubes (description), Macro extension tubes (glare), and Macro extension tubes (lens mount).