Chapter 14
Section 4

Computer Program for Identification of Photographs


The FOTOFIND program on the disk accompanying this book starts with three questions to establish whether the unknown picture is on paper, glass, or in a group of miscellaneous bases including metals. The answer to these screening questions determines which of three groups of questions are presented to the user. The three groups contain respectively ten, eight, and nine questions, thus limiting the questions to the ones most relevant to the base material. Some questions are yes/no, while others are multiple choice; all are prompted on the screen. The operator is instructed to type "u" for "uncertain" wherever there is doubt. Details of the program are given in Appendix III; instructions on answering the questions are listed below.

Many history books choose to group photographic processes in such categories as silver and non-silver. However logical these categories may be for teachers or historians, they are not useful for an identification search. Archivists who are confronted with boxes of old photographs do not usually sort them into two piles of silver and non-silver, because there is no simple observational way to do it. This is the reason base materials were chosen as a first screen.

The program loses its ability to distinguish between types of photographs made after approximately 1900, based on simple visual observations; other types of analysis are then needed.

How to run FOTOFIND


This version of FOTOFIND runs in Microsoft DOS or Microsoft Windows 98; it will not run under MicroSoft Windows 3.x or 95. Windows 98 users can run it by several methods (UPPER or lower case may be used in the following procedures):

1) Go to the DOS command in the Programs menu, then enter the drive containing the FOTOFIND disk. The starting command is foto27

2) Reboot the system from a floppy disk containing the DOS command files, or restart the computer in the MS-DOS mode from the SHUTDOWN command in the START menu.

3) In Windows 98 desktop, enter the opening menu with the START key. Go to RUN, enter the drive followed by the file name, eg - a:foto27.exe

4) Find the program in "My Computer" on whatever drive you have installed foto27.exe, and double click on it.

In modes 3 and 4, the display should be expanded for best visibility.

foto27.exe may be installed on a hard drive in a directory such as c:\FOTOFIND\ which allows easy and quick access. It only requires about 180 kb disk space. FOTOFIND creates temporary *.dat files on its drive when it is run, for each of the base materials entered. These files are small, and can be deleted at any time to save space, without interfering with subsequent runs.

Reports can be printed either from DOS or Windows 98. The printer response time is faster under DOS than under Windows 98, and the DOS screen looks better. If printing problems are encountered on a particular machine in Windows operation, DOS operation should be satisfactory. In either case, screen displays and search times will be nearly instantaneous on most machines.

Apple machines should be able to run FOTOFIND with a suitable conversion program. At this writing we have no specific instructions on running FOTOFIND on Apple machines, nor on Windows NT or ME. Future upward compatibility, of course, cannot be predicted, which is a well known problem with archival data storage and retrieval.

Notes on answering the questions

Is the picture on paper?
Usually this is self-evident, even if the picture is framed under glass.

Is the image on glass?
One possible ambiguity is the crystoleum or Crystal photograph, which was an albumen print sealed to the underside of a convex cover glass, which is included in the listing of glass bases. Pictures framed under glass should not be confused with images printed on glass.

If both the above answers concerning bases are 'no', the program brings up the questions pertaining to miscellaneous bases.

Questions on Paper Photographs

1. Is the image a positive or negative?
Generally a self-evident question except perhaps for ambrotypes, which were made as negatives but viewed as positives. Ambrotypes were coded as positives based on their intended use.

2. Is there a baryta subcoat?
A baryta coating was used under the photosensitive layers of all commercial papers starting in the 1880's (see chapter 3). This included bromide, chloride, and chlorobromide papers such as Aristo and gaslight varieties with both gelatin and collodion emulsions. It is usually markedly whiter compared to albumen and earlier papers; also the baryta completely covers the paper fibers in highlights and shadows.

It is impractical to identify separately all of these types by the questions in FOTOFIND. Close examination is necessary, possibly augmented by chemical or physical analysis. Answering "yes" to the baryta question serves to catagorize a print to a group of commercial papers fron the 1880's on.

3. Is the image faded?
Fading is a lightening effect, not to be confused with staining or spotting. It is difficult to evaluate without a comparison with the original appearance, yet it can be an important descriptor. Here are some clues:

Platinotypes have a long tonal range and soft shadows, but are not faded because of their stable chemistry. On the other hand, calotypes usually have low contrast because they are faded. Albumen prints are nearly always faded; their color has been variously described as brownish, rose, sepia, and yellow. Their faded yellow color is almost unique: a yellow print is likely to be an albumen, but not all albumens are yellow. Among the types that are never faded are carbon, carbro, gum, and all inked prints such as collotypes. Note that these images do not fade, although the paper base may have become brown or yellowed. Cyanotype images are stable and they were coded as not faded, but they have a short tonal range and both highlights and shadows may be distinctly blue. It may be due to original overexposure or contaminated chemicals in the processing, which causes a gradual increase in blue density over the years. However, cyanotypes will fade if they are stored in contact with buffered archival paper.

In general, prints made late in the 19th century are less likely to be faded than earlier ones, and their highlights will be whiter because of baryta undercoating. Silver bromide and chloride prints, except certain POP papers such as Aristo, did not contain excess silver nitrate as early salt prints did. If bromide prints faded, the cause was usually insufficient fixing or washing, which showed up as uneven spotting and fading. Many prints were toned gold or sepia to improve stability, producing a brownish color.

4. Is the image color black, brown, blue, gray, yellow, purple, or "u"?
The above remarks on fading should first be reviewed, along with Chapter 10. Color can be an important clue, but it is difficult to describe colors verbally. Some of the carbon processes included pigments or dyes: the Autotype Company advertised more than fifty colors. Most dyes were unsaturated, or pastel. Sepia and brown are similar, and brown was coded as the descriptor. The ink used in collotypes was generally black, but colors were used in intaglio printing. Cyanotypes are uniquely blue or blue-black, and most platinotypes are a distinctive silver gray or neutral black that was called gray rather than silver to avoid confusion with Daguerreotypes and brown platinotypes. In case of doubt about the color of any print, type "u" for the first run, then try running with other answers.

5. Is the surface glossy, matte, matte fibers, or glossy shadows only?
"Glossy" includes smooth, which is a minor variation. Matte surfaces were made by adding cornstarch to the emulsion, or by mechanical stippling, which can be observed microscopically. Both glossy and matte are emulsion-coated overall, usually with a baryta undercoat that hides the fibers. "Matte fibers" means that the paper fibers are exposed over the entire surface. "Glossy shadows only" refers primarily to gum and carbon processes; the shadows are coated with gelatin but the highlights show exposed paper fibers where the gelatin was washed away during development. These surface types can usually be identified with a hand magnifier or with a microscope and illumination at grazing angle, concentrating on differences between shadows and highlights. Some emulsion reticulation patterns look almost like fibers: a microscope is needed. Gelatin emulsions coated by photographers were sometimes so thin that fibers are visible; adjustment of the microscope light will show small areas of sheen between the fibers. This is also true of albumen paper, which had no baryta undercoat: the fibers are visible but not exposed, so the descriptor is "glossy".

6. Are the shadows heavily tarnished?
Many silver processes show this effect to some degree, but it is so pronounced with gaslight papers and nitrate negatives that it is a fairly reliable identifier. It is also known as bronzing, silvering, or mirroring, and is caused by deposition of metallic silver on the surface by processing residues or storage environment.

7. Is the picture glued to an embossed card mount?
Although many paper photographs were mounted on cardboard, this question refers to cartes-de-visite, cabinet cards, and others with specific dimensions listed in Chapter 9. These mounts were usually printed with the photographer's name or studio on front or back, sometimes with advertising messages, and with decorative borders; they have a manufactured look. Processes include albumen, aristo, and chlorobromide papers, and some carbon and Woodburytypes. Tintypes were often mounted on small cards behind a thin paper cutout, and this is included as a tintype descriptor; it is easily distinguished from other card mounts.

8. Is there a screen pattern?
The commonest example is the geometrical dot pattern in screened newspaper halftones, a positive indication of an inked print. Other screen patterns are random dots and reticulated line patterns, all examples of ink prints: see Chapter 5. These patterns are coarser than photographic grain and can be seen under low magnification.

9. Are paper fibers visible in highlights only?
Emulsion-coated papers that did not have a baryta undercoat reveal paper fibers through the translucent coating. It is visible only in highlights because shadows are opaque. Careful lighting and magnification may be necessary. A clue is the color of highlights: baryta retained its whiteness better than most uncoated papers, which have usually yellowed in a century.

10. Is the picture retouched to look like a painting?
Many early portraits were tinted to some degree, but in some "crayon" prints the retouching essentially obscured the underlying image. Both colored tints and charcoal were used. Sometimes the silver image was chemically weakened or removed to foster the impression of a free-hand drawing or painting. See Appendix II.

Questions on Glass Photographs

1. Is the image a positive or negative?
It is often necessary to use lighting at various angles to minimize reflections.

2. Is the picture in a hinged case?
This question refers to the distinctive cases of ambrotypes, Daguerreotypes, and tintypes. These cases originally had hinged covers and glass over the picture; the covers are sometimes missing today. Metal lockets on chains are not identifiers of any particular photographic process.

3. Is the picture magnetic?
All tintypes are magnetic, and some transferotypes may also be: see Chapter 9. A weak magnet is adequate for testing; a magnetic compass can sometimes be used.

4. Do the highlights show silver reflections?
This is a property unique to Daguerreotypes; it is a specular or mirror reflection. Tarnish and reflections from the cover glass can hinder the observation, but the tarnish (usually occurring in a diffuse zone around the edge) helps distinguish Daguerreotypes from ambrotypes and tintypes.

5. Is the image reflection tinted, milky, or dark?
The difference in reflection color is most visible in the image shadows; see Chapter 6.

6. Is the transmission color brown, black, or tinted?
Daylight viewing is preferred.

7. Is the glass flat, curved, or milky?
Milky refers to opal glass, not to be confused with the reflection in question. Curved means part of a spherical surface, convex to the viewer.

8. Is the edge coating even or uneven?
This refers mostly to wet-plate collodion negatives: hand coating was uneven at the edges. Ambrotypes are cased and their edges are not visible without dismantling; the same is true of bound lantern slides. The descriptor is based on what is normally visible to the viewer without taking things apart.

Questions on Metal, Cased, or Other Types of Photos

1. Is the picture a positive or negative?
Rarely a problem with most subject matter in adequate light.

2. Is the picture in a hinged case?
See comments in number 2 under glass photographs.

3. Is the image on a flexible transparent base?
This question refers to what is now called "film". It does not include translucent bases such as paper negatives (waxed, oiled, or plain), which are coded under "paper" and "negative."

4. Is the picture fixed to a card mount?
Some Gem tintypes were mounted in tiny brass frames that were crimped to a card mount. Other tintypes were mounted on cards behind a thin paper cutout. Many pictures were simply glued to cardboard, either plain or decorated. Plain cardboard is not a helpful clue, but decorations are fairly well documented; see Chapter 8.

5. Is the picture magnetic?
See comments in number 3 under Glass Photographs. Glass is not magnetic, but cased tintypes sometimes resembled ambrotypes, and the magnetic test is simple and definite.

6. Do the highlights show silver reflections?
See comments in number 4 under Glass Photographs.

7. Is the picture printed on fabric?
Several processes were printed on different kinds of fabrics. Most are fragile and rare.

8. Is the picture printed on leather?
The leather was sometimes lacquered to resemble japanning, and is fragile and rare.

9. Is the picture printed on metal?
The commonest example was the tintype, but transferotypes were made on many metals. Some were non-magnetic, such as copper and brass.