Tuesday, 24 March 2015

Thermal Eclipse

Many thanks to Dr Chris Lavers of the University of Plymouth for sending over unusual views of last week's partial solar eclipse. Here's an example ...

This was taken in the south west of England with a FLIR 320 by 240 pixel E320 thermal imaging camera. This camera covers a range of 7.5 to 13 µm, which includes a substantial atmospheric window around 10 µm.

Tuesday, 10 March 2015

Four Simon Marsden prints for auction at Sotheby's

Prints of four of the late Sir Simon Marsden's infrared photographs are included in Sotheby's 2015 Made in Britain auction. This takes place on the morning of March 25th.

Simon Marsden: Dunnottar Castle, Scotland

The four, in two lots, are his famous shot of Moydrum Castle in Ireland, as shown in the Infrared 100 exhibition in 2010, together with an atmospheric view of Dunnottar Castle in Scotland (above) and shots of Whitby Abbey and a gargoyle at Toddington Manor in Gloucestershire. Estimates for the two lots are both between £1,500 and £2,500.

In the same auction last year there was a lot of four of his prints, which exceeded their top estimate to fetch £4,375.

Like Minor White, Ansel Adams and others, Simon saw the print as (to quote Adams) 'the performance' where the negative is 'the score'. This places a great importance on the printing process, especially when the photographer does the printing (as did Simon). Whether this analogy means that no-one else can legitimately print a photographer's negatives is a difficult point, since following the musical theme it would mean that we should discount Sir John Eliot Gardiner's performances of a Beethoven symphony simply because only Beethoven himself could conduct it (other great conductors are available). But I'm just being devil's advocate ... sadly Simon will print no more and this is a chance to own the authentic manifestation of his vision. There are very few prints of Simon's work around and it's likely that there will be no more prints made. Plus, I am always delighted when people take artistic infrared photography seriously.


Lot 107, Moydrum and Castles, sold for £1750 while, sadly, the other lot didn't sell.

Friday, 6 March 2015

Infrared and tissue penetration

A recent article in New Scientist caught my eye. My drug-filled nanospheres heal at the speed of light reports work by a team led by Professor Adah Almutairi at the University of California, San Diego.

Her work explains that by making use of near infrared's ability to penetrate skin and tissue, it is possible to use a laser of the appropriate wavelength to trigger a polymer nanotube to break down and, if it's carrying a drug, to release it. Since the light can be tightly targeted it would be possible to therefore tightly target a release site for the drug. There are other mechanisms for triggering release, such as the temperature of inflammation or even sunlight on the skin. This latter has the neat prospect of a sunscreen that activates when you get into the sun.

While the NS article is very recent, I found a paper from 2011 by Almutairi's team that explains the concept:

Low Power, Biologically Benign NIR Light Triggers Polymer Disassembly Fomina et al
Macromolecules, 2011, 44 (21), pp 8590–8597

You can see the abstract or buy the paper from ACS Publications.

One interesting thing, for me, is the statement at the top of the abstract that "Near infrared (NIR) irradiation can penetrate up to 10cm deep into tissues". Admittedly, from a photographic point of view you need to remember that the IR has to penetrate the tissue and then get back out again, but I believe the figure of 'a few millimetres' has been a good rule of thumb for years. A figure of between one and two cm has been cited from a paper by Gao et al, In vivo cancer targeting and imaging with semiconductor quantum dots from 2004.

So I decided to see what Lou Gibson had to say on the matter in his third edition of Clark 'Photography by Infrared' in 1978. He quotes Balderry and Ewald, in a 1924 paper called 'Life Energy in Theraputics' as saying that sunlight can penetrate up to 25 cm into the body. So that 10cm seems quite reasonable.

Photographically, however, a near infrared photograph will often show veins under the skin, and will almost always give people a 5-o'clock shadow (even some women). This is also, as I've pointed out before, the cause of the alabaster look you can see in infrared portraits. I'll leave you with this image of Jude (a lady with whom I used to work) demonstrating the infrared look, with the added 'bonus' of 35mm infrared film grain.

Tuesday, 3 March 2015

More on visual sensitivity to IR

Following on from the experiment to extend human vision into the near infrared (part of my previous post) I found related papers in the Journal of the Optical Society of America and Acta Physica Polonica.

The first from OSA:

Visual sensitivity of the eye to infrared laser radiation
David H.Sliney, Robert T Wangemann, James K Franks (all U.S. Army Environmental Hygiene Agency, Aberdeen Proving Ground, Maryland) and Myron L Wolbarsht (Duke University Eye Center, Durham, North Carolina)

JOSA, Vol 66, Issue 4, pp. 339-341 (1976)

You can find the paper online (membership/paywall) on the Optics Infobase

The abstract reads:
The foveal sensitivity to several near-infrared laser wavelengths was measured. It was found that the eye could respond to radiation at wavelengths at least as far as 1064 nm. A continuous 1064 nm laser source appeared red, but a 1060 nm pulsed laser source appeared green, which suggests the presence of second harmonic generation in the retina.

Similarly, but more recent and with open access is ...

Perception of the Laser Radiation for the Near Infrared Range
D. Kecika, J. Kasprzaka, (both Department and Ophthalmology Clinic, I Medicine Faculty, Medical University of Warsaw) and A. Zając (Institute of Optoelectronics, Military University of Technology, Warsaw)

ACTA PHYSICA POLONICA A, Vol 120, No 4, pp 686-687

This paper is available as a PDF.

This abstract reads:
During the diagnostic research done by means of optical devices equipped with radiation sources from the near infrared range the phenomena indicating the perception possibility of this range by a human eye were observed. In this contribution the initial results of the research of this phenomenon were presented. Sources of radiation applied in laser polarimeters (785 nm) and devices designed for optical coherent tomography (820, 850 nm) were taken into particular consideration. Perception tests with the use of a laser diode generating at the wavelength of 940 nm were also carried out. It was stated that the radiation from the range examined can be recorded by a human eye giving a colour sensation — in practice independently of the wavelength of the radiation beam falling into a retina.
I suspect this kind of experiment with lasers falls into the don't try this at home category but it demonstrates that the usual limits quoted for human visual sensitivity are not necessarily the only ones.

There's some interesting notes about this also in the Wikipedia entry on light.

The final word may have to go to a paper I found in the Proceedings of the National Academy of Sciences of the United States of America (PNAS vol 111 no 50) with (sorry) too many authors to list (let's just say Palczewska et al) and with the title Human infrared vision is triggered by two-photon chromophore isomerization. Almost totally out of my area of expertise but if you have the knowledge then you can access the paper (paywall) via this link. I'll leave it to the report's authors to have the final word ... quoted from their 'significance'.
This study resolves a long-standing question about the ability of humans to perceive near infrared radiation (IR) and identifies a mechanism driving human IR vision.