Photographic Film Structure

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Shu-Wei Hsu

University of Rochester
Materials Science Graduate Program

OPT407: Electron Microscopy
Spring 2010
Final Project

Introduction
Sample preparation
Analysis Methodology
Results and Discussion
Conclusion
References
Acknowledgments

 

Introduction

As a photographic lover, it is common to take a camera with me to record what I see into rolls of films. 
Compare to digital sensor, film is a classical choice for photographer to take picture with wonderful colors and enjoy the surprise after 36 times shutter release. 
How films record images has always been very curious to me, so I decide to use microscopy to see the film structure in this project.

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Sample preparation

The samples are made from several kinds of films which I used before. Basically, they are black & white films and color films. 
They are cut by razor blade or ultramicrotome in order to have a clear cutting to see the cross section of films. 
All the samples are coated  with gold  by sputter coating to ensure conductivity. 
The TEM sample is  prepared by ultramicrotome

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Analysis Methodology

Scanning electron microscope analysis was done using a Zeiss SUPRA40-VP model SEM and  Transmission Electron Microscope analysis was done by a FEI Tecnai F20 at the Institute of Optics at the University of Rochester. 
In SEM analysis, secondary electron detector (SE2), InLens detector and backscatter electron detector (BSD) were used to collect micrographs. 
BSD detector are specially used to find out the position of silver particle in film layers. X-ray microanalysis was down using an EDAX x-ray spectrometer for compositional analysis.

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Results and Discussion

From reference, the basic films structure is noticed.
 color film layer  color film layers
figure 1. The color film cross section.
B&W cross section
figure 2. The B&W film cross section.

By using SE detector, The color film cross section could be seen.  There are several different layers in the cross section. Three record layer and base are clear and the interlayer could slightly been seen.
The image in color films is formed by dye. The silver particles are already been moved out in film processing, so there is nothing obvious under BSD.
color01    color 2     color02 color       
figure 3. color film cross section                                                                                figure 4. record layers                                                                                                  figure 5. colored layers

Pore structure    InLens
figure 6. pore structure in record layers                                                                   figure 7. InLens

In B&W films, not like color film, it only have one record layer. However, the image is formed by silver particle left in record layer, it is easy to figure out the silver particle contained in gelatin in emulsion layer.
bw se2    ir se2    ir se ag particle
figure 8. B&W film by SE2 and BSD combined                                                        figure 9. B&W film silver particle in gelatin.                                                           figure 10. silver particle in B&W film.

bw bs 1    bw bs2    bw bs3
figure 11. BSD micrograph: a layer of silver  in B&W film cross section.             figure 12.  
B&W film silver particle in gelatin by BSD.                                          figure 13. The silver record layer is only a small region in the film.

bw se bsd    mix
figure 14.
B&W film by SE2 and BSD combined  (BSD more)                                figure 15. B&W film SE2, BSD cross mix.

EDS    maping
figure 16. By EDAX, the silver layer shows a clear Ag pick.                                                                                            figure 17. Ag signal in silver layer from x-ray mapping.

tem1    tem2
figure 18. Silver particle from TEM.                                                                        figure 19. silver particle from TEM 2.

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Conclusion

The color film layers are very obvious from cross section cuted by ultramicrotome. 
However,  the bad part is there are no metal particles in color film layers, so the BSD micrograph shows nothing interesting in color film. 
In B&W film, most of the structure is base. There is only a thin region of silver in gelatin.
Using BSD detector, other part of the film turn black and only left a shinning silver layer.
By combining BSD and SE micrograph, surface detail and composition can both be seen in combined micrograph.
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References

Films & Filters <http://www.geog.ucsb.edu/~jeff/115a/lectures/films_and_filters.html>

kodak color film <http://motion.kodak.com/motion/uploadedFiles/US_plugins_acrobat_en_motion_education_kodak_color_films.pdf>

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Acknowledgments

I would like to thank Brian McIntyre for his guidence, advise and help to use SEM, TEM  and ultramicrotome. 

I  also want to thank Andreas Liapis for his assistance about sample preparation.

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