RPS Imaging Science Group

Flew home from Budapest yesterday and had an interesting experience. Mid flight both my wife and I were reviewing photos taken on our trip using PDAs. My wife’s IPAQ, new but well used suddenly experienced a problem that required a soft reset. Most unusual but not unknown. My older but extremely proven Axim was in an even more serious plight, requiring a hard reset to recover a completely unresponsive unit. Electrical event in flight?
Thankfully both the Compact Flash cards therein and the PDAs appear undamaged. The lesson for me is to back up my images even before the flight home!

The Danube in Budapest ©Alan Hodgson

Just spent a fascinating few days in Budapest. I took my IR modified Photosmart camera with me and the weather was not disappointing with a mixture of bright sunshine, spectacular thunder clouds and the Danube in flood. I plan to put these images together for an Imaging Science / Infrared 100 entry for the next RPS Portfolio publication.

I read today in the June edition of Lyra’s Hard Copy Observer that Konica Minolta, once big in silver halide technology has finally left AgX completely. It got out of most of it in 2007 but some vestiges, such as medical and image setting products remained.
And yesterday The Times ran an article announcing the end of Kodachrome.
End of an era (again)!

The Infrared 100 celebrations now have their own web site – see http://www.infrared100.org/ 

Nick died on May 23, 2009, aged 75. As a distinguished Imaging Scientist Nick was a true role model for up and coming holographers through the 1980s. He served as a bridge between the art and science of holography, encouraging and nurturing talent in both photographic science and art. As a new entrant to Imaging Science in the 1980s I benefited from his wisdom and experience in holography that was feely and graciously shared. In his later years it was my privilege to discuss with him some of the work being shown through the Royal Photographic Society and the Institute of Physics. In latter years he had struggled with Parkinson’s disease but each time I saw him he was still sharp of mind. He will be sadly missed.

I am preparing an obituary for the Journal of the Royal Photographic Society. All contributions gratefully received.

The Journal of Imaging Science & Technology

Ink absorption into a substrate is a feature of many types of printing. Penetration of ink components can be significant over a range of time scales from the first stages of ink/media interaction to drying by absorption and evaporation. These first stages are the subject of the Institute of Physics Printing and Graphics Science “Dynamics of Printed Drops” meeting – see http://www.iop.org/activity/groups/subject/pgs/Events_archive/page_7754.html . However, it is this second stage that is the subject of this article where 2 papers in the same edition of the Journal of Imaging Science & Technology (JIST) cover aspects of ink penetration into paper.
The first paper “Studying Ink Penetration with Microscopic and Spectroscopic Techniques” (JIST 50(4), 327 – 332 (2006)) looks at water based inkjet ink penetration into uncoated papers using microscopic and spectroscopic analysis. The work uses only the HP 970 desktop printer inkset (dye based CMY inks only) and shows that internal sizing reduces the penetration of these inks. This sizing also increases print mottle which is illustrated by non-uniformity of the penetration of the cross sectional images of ink penetration.
Complementing this the work also shows the effect of internal fillers such as calcium carbonate and kaolin. These are strongly light scattering and are used for reasons of economy and to improve the reflectivity, brightness and opacity of the paper. However, the work shows that these have limited effect on ink penetration.
The second paper “Nondestructive Microscopic and Spectroscopic Methods for Depth Profiling of Ink Jet Prints” (JIST 50(4), 333 – 340 (2006)) uses a variety of non-destructive techniques that are applicable to prints in museums and collections. Again they look at aqueous inkjet prints but in this case with dye and pigment based inks on a wider variety of paper types. They make the point that pigmented inks form a thicker, compact layer on the surface of the paper while dye based inks penetrate deeper.
We hope to run Dynamics of Printed Drops again later this year – come and join us!

The image stability of modern photo print materials is getting very high. As a result, getting valid testing regimes that do not take years to demonstrate failure is difficult. The current tests for predicting the stability of colour photographic images are based on an adaptation of the Arrhenius method. This test methodology is important enough to warrant a standard in its own right – ISO 18924 “Imaging materials — Test method for Arrhenius-type predictions” – see http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=28495 .
Although this method is based on sound chemistry, the validity of its application to predicting
changes of photographic images rests on empirical confirmation. History is on our side – many chromogenic colour products yield image fading and staining in both accelerated and non-accelerated dark ageing tests that are in good agreement with the Arrhenius relationship.
However, we may be lulled into a false sense of security on this as some more modern products show significant deviation from this ideal behaviour. Some exhibit atypical staining at elevated temperatures; others abnormal image degradation, colour balance and saturation.
In particular, some photographic materials can undergo dramatic changes at relative humidities above 60 % owing to changes in the physical properties of gelatine and other binder materials. Lower maximum relative humidities may need to be tested for some of the more humidity-sensitive inkjet materials because of phase changes such as melting point or glass transition temperature.
Maybe Arrhenius has had his day!

ISO technical Committee 42 (Photography) has a good number of standards currently under development – see http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_ics_browse.htm?ICS1=37&ICS2=040&ICS3=20&development=on . A number of these pertain to image permanence and I am now project leader for a new standard – ISO 18936 “Imaging materials — Processed colour photographs — Methods for measuring thermal stability”.  This document covers the methods and procedures for measuring the long-term, dark storage stability of colour photographs.

The length of time that photographs are kept can vary from a few days to many hundreds of years. Often the ultimate use of a photograph may not be known at the outset. Knowledge of the useful life of colour photographs is important to many users, especially since stability requirements often vary depending upon the application. For museums and archives, and photographers in general an understanding of the behaviour of these materials under various storage and display conditions is essential if they are to be preserved in good condition for long periods of time.
The three main factors that influence storage behaviour are the temperature and relative humidity of the air that has access to the photograph, as well as atmospheric pollutants to which the photograph is exposed. High temperature, particularly in combination with high relative humidity, will accelerate the chemical reactions that can lead to degradation of one or more of the image colorants.
Low temperature, low-humidity storage, on the other hand, can greatly prolong the life of photographic colour images, for typical materials. Other potential causes of image degradation are micro organisms, and insects.
A draft of this standard is currently out for ballot. As project leader and UK Technical Expert I welcome your opinion. If you feel you have some input to this standard leave me a comment!

BS ISO 10505:2009 “Photography — Root mean square granularity of photographic
films — Method of measurement” is now available – see http://www.iso.org/iso/catalogue_detail.htm?csnumber=50747. This standard brings the measurement of RMS granularity of film up to date. It pertains to the measurement of monochrome and colour film granularity so it does not cover the perceived graininess of prints directly.
The standard contains a good explanation of the workings of a microdensitometer and the hazards associated with partial coherence in these optics. The work also puts these measurements on a sound statistical footing.
The standard has been a long time in coming but a worthy addition to an Imaging Science library!

The Journal of Imaging Science & Technology

Just finished reading an interesting paper on this topic, “Contrast-Gain-Based Visual Tone Mapping for Digital Photo Prints” in Journal of Imaging Science & Technology 50(5), 458-468 (2006) – see http://www.imaging.org/pubs/jist/index.cfm . The aim of this work is to investigate algorithms that produce more “professional” looking prints from digital cameras. The work investigates various tone mapping algorithms to do this.
The paper starts by contrasting spatially invariant and spatially variant tone mapping algorithms. The spatially invariant version uses a single tone reproduction curve over the whole print. In an analogue photographic analogy this is like making a straight print on graded paper. Spatially variant tone mapping is more complex but potentially more powerful. Here the tone reproduction operator changes with the spatial position of the pixels in an image. In our photo printing analogy this is like dodging, burning and masking a print onto variable contrast paper. Taking this to the digital conclusion we can dodge burn and mask every pixel over multiple paper grades to create flexible tone mapping. This gets around some of the issues with the processing of portrait images where single tone reproduction can cause contrast loss against a uniform background.
This work very sensibly leverages the experience of professional photographers who use selective lighting to better image a subject. They seek to emulate this experience in the digital domain. The pictures used to illustrate the paper suggest that this has been successful.
In addition to implementing this technique in photo printing there is the potential to integrate this into the camera software. Of course this is also a potential nightmare if, like me you take pictures of “odd” objects such as bright stars on a dark background. Another reason to move to RAW images!