Paleonet: Orthochromatic images

enrico bonino e_bonino at
Wed Mar 23 11:35:26 GMT 2011

Dear all

I'm searching for a method that allow to acquire images with a digital camera (Fujifilm filmpix S2Pro) that can emulate the old Orthochromatic films.

Orthochromatic films block the red wavelength and are sensitive to blue and green only, giving a great contrast when red colors are present in the image. 

These films are used in Xiangguang & Bergström  (1997), Arthropods of the Lower Cambrian Chengjiang fauna, southwest China, in Fossils & Strata n°45, to improve the contrast of some lower Cambrian Chengjiang arthropods.
This methods don't need the immersion of the sample in Toluene or Xylene alcohols, and it is very useful when the matrix (and this is the case) is soft, like marls and clays.

Chengjiang fossils are generally covered by a thin Iron oxide layer, and this technique allow to increase the contrast between the gray-yellow matrix and the reddish fossil.

Looking at some filters that have the same spectral  behavior, I've found that the cyan Kodak Wratten gelatine filters 44 and 44A ( and for the transmittance curve) are able to give the nearly same result of the old and practically unavailable orthochromatic films. 

There is someone that has developed similar techniques and digital image processing methods to increase the contrast using peculiar filters?

Thank you,

Enrico Bonino

Enrico Bonino Dr.
GIS Specialist - Geologist at KEYOBS SA, Liège, Belgium
Museum Curator at the Back to the Past Museum, Cancun, Mexico
skype: enrico_bonino
...and some of my dioramas at FossiliVeraciand Paleonet

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