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For a century from the invention of the Kodak camera the best way to get an image was the photograph. Chemical photography has never been the cheapest and easiest way to get an image on paper but it can be a fast, eliable method of producing fine grained images.

One obvious method to build a printer is to use a cathode ray screen of the kind used for monitors and TVs, and then capture this photographically.
Specialist devices of this kind used to be quite popular in scientific labs and the graphical trades. For instance many older oscilloscopes and other instrumentation screens can have a special Polaroid camera mounted on them. Before the advent of cheap A to D converters and inkjet printers this was common laboratory practice.

Computer printing direct to photographic material has some applications:

Photographic reproduction is an obvious application. Inkjets at 1200 or even 5400 dpi on specially treated paper look superficially like photographs and most people are satisfied with them as "snaps". Inkjets don't have a greyscale, the image tends to fade and smear - so even if the image originated in a digital camera a traditional chemical photograph may be preferred.

Cinematic production is a related use. Making a movie is an expensive exercise so digital editing and animation are increasingly used. Some animations originate entirely in computers and need so many to produce the high resolution output that the collection is known as a  "render-farm". Because film gives such high resolution it is still the preferred distribution medium.

"COM" or Computer to Microfilm used to be a major application in the 1960s and 70s. Before networks of terminals and PCs were available microfilm seemed a practical route to office automation. Although the mass market has turned to disk and tape storage COM may still be the best way to keep important records. More on this below.

Photographic printers are not common but not entirely unknown.

Typesetting

Typesetting has been one role. Traditionally typesetting for letterpress is laborious. Wooden and metal sorts are assembled by hand into lines and then bound tightly into formes which are complete pages. The raised print on the forme is inked and used to produce the page. The process requires skill, is labour intensive and since publishing has often been a city centre activity it is expensive. Letterpress is still used for some special jobs. At the end of the 19th Century the introduction of the Linotype and Monotype machines enabled a machine operator to do the job ten times faster. these machines cast type in hot metal, so they were obviously large and expensive.

Printing methods have generally changed to offset lithography where the plates can be produced photographically - either etched or treated to provide an ink-receptive surface. A page can simply be made by cut and paste techniques and then photographed using a "copy" or "process" camera onto a full sized negative film which is then developed and placed on the lithographic plate under a powerful light.

The paste-up can contain typewriting or even handwriting but these won't give the kind of highly legible kerned and very even lines of text people often want.

PhotoTypesetting

Phototypesetting machines produce the text using a spool of photographic material in a light-tight canister.

Early phototypesetting machines only created one line or column of type. The long galleys produced were cut and pasted onto layout boards and the negative made by a process camera

In later machines the full negative for the print process is made in the phototypsetter

Phototypesetting can be done mechanically, electronically or using a laser printer mechanism.

Mechanical phototypsetting is obsolete but the machines were extraordinary.

In the mechanical phototypesetter preformed characters on a film are projected one at a time onto the typesetting surface. Characters were arranged around a glass disk or drum that was otherwise blacked out. The photographic material in it's canister could roll in front of the imaging point. In each character position a strobe of light projected the character onto the negative forming the image. since the disk or drum rotated at high speed and the strobe selected the character the process could be rapid.

The disk or drum would only have one or two fonts, so a page with mixed fonts would mean changing it. To vary the font size the lense could swap or the carriage could move back and forth, projecting a larger or smaller image. Later machines were more flexible. For bold type like newspaper headlines there were special devices.

 
CRT typeseters did much the same thing but raster scanned each character image onto the face of a cathode ray tube and then projected that onto the medium. In simple machines the image to be projected was held on film and scanned into the electronics as needed. In more advanced machines the character images were held in computer memory and fonts could be loaded from a floppy disk.

Forming the image on a CRT and focussing it onto the film gave more flexibility which could be exploited by mini-computers. Typesetting programs like Unix "troff" were developed to control these machines.

Phototypesetting now tends to be based on optical mechanisms like those used in laser printers - indeed laser printer copy can be good enough for use by a process camera.  

Direct To Plate

Direct to Plate systems expose and treat the offset litho plates directly using a normally a semiconductor laser and a polygon mirror to scan the image. The plates are large - typically A0 to make the best use of the width of a web offset machine so a direct to plate machine is essentially a giant laser printer with a plate developing process instead of the normal drum, toner and fuser.
 

Photographic Printers

Honeywell made a printer that could output directly from cathode ray tube onto a roll of photosensitive paper. This weird printer was popular in training departments where it could be used to directly capture what a student had done from screen to page - or at least to a photograph. The mechanism had a conventional CRT but most of the face was masked out - only one line was visible. The roll of film advanced a step at a time across a lense focussing the one-line image. There seem to have been several advantages to doing this, rather than generating a screen image and just capturing that:
 

CRT images aren't very stable, they jitter sligtly from frame to frame. Just exposing one line is more stable

Ordinary CRTs can't actually "image" a page. In the 1980s 640x480 VGA standard barely displays half a page of text and the result is crude. The 640 pixels on the screen are a poor representation of  the 2,400 print resolution of a printed page. Even with special quality mono tubes, phosphor granularity, scattering in the face glass and reflections in the lense path degrade the image.

The line can be scanned down any length of film, rather than just producing rectangular CRT-shaped images. So using a line output and moving the film gives flexibility in page-length.

If the same idea were done today presumably the CRT could be replaced by something like a laser scanner or the LED array from a printer. However these printers weren't cheap - a price of over £2,500 and the fixed epair price from the one specialist in Britain was of over £500. Operation was costly too. The paper medium was an instant use type - some sort of polaroid (I think).

In some ways it is surprising that photo-chemical technology didn't become one of the major bases for computer printers. Photographs give a high resolution image in a form people find very acceptable. Computer imagery often involves full page cover so the photographic process isn't particularly inefficient or expensive. However by the time high resolution laser or LED light sources that might haver been used in a photo-printer were becomming available there might have been a perception that photography was "old technology". Technically it would be possible to make a little colour printer at about the same cost as a scanner (under £100) however it never happened. The inconvenience of getting films developed was not great but in an age used to instant action it may have been unacceptable.

Photographic media are now being displaced from their conventional markets by inkjet printers. Inkjets are probably cheaper than photographic "snaps" but the big advantage is that the user gets instant gratification.

Microfilm

Microfilm was popular before computer terminals were commonplace. In the 1960s some large organisations tried to shift the greater part of their paperwork onto microfilm in a move reminiscent of today’s interest in workflow systems. Microfilm promised space savings over paper which combined with computer indexing would potentially make paperwork obsolete! The dream of a paperless office has a long history.

Microfilm is an interesting counterpart to today's trends in electronics - make things cheaper by making them smaller. Ordinary paper is cheap to make but the argument is that it is expensive and clumsy to store and that microfilm can help solve that problem.

All that is really needed to make microfilms are a camera and a developing laboratory - both simple home equipment. Anyone who has tried to photograph a document even using a digital camera with a viewfinder will know that this doesn't work very well. Commercial operations use planetary cameras (a camera fixed on a pole) and have fast, efficient developing machines.

The "media" used can be conventional roll film
16mm film is suited to capturing A4 pages
35mm captures maps and plans well.

There are also special media
Microfiche - flat plates of 105mm material - may be easier to store at high densities.
 
Aperture cards are a combination of a Hollerith punch-card with a 35mm film mounted in it.

The counterpart to the camera is the viewer. Viewers are just a lamp, a lense assembly, a mirror and a translucent screen so they need not be very expensive.

Unlike domestic photography a microfilm is often kept in it's negative form and might never be printed out. White writing on a black page means less reflection and glare when the film is placed in a reader.

Computer output to Microfilm (COM) used to be popular and there seem to have been several competing suppliers in the 1960s.
 
 
 
One of the problems with microfilm has always been it's centralising tendency. All the cameras and equipment used to be special models with prices aimed at corporates. This in turn produced a centralising tendency. Even mid-scale operations like city councils and small banks can't afford the equipment and specialist knowledge. Every document has to be indexed and sent to a central agency.

The idea of microfilm as a general office tool has retreated, its place taken by ubiquitous desktop computers with disk storage. Microfilm is still used by libraries for archiving newspapers and old papers. Record offices also hold their archives on microfilm - sometimes they are legally obliged to do so.

 

Disks, Tapes and Archives

Computers have taken over from microfilm because:
desktop PCs are mass produced in such quantity that despite their complexity they are less costly than readers.

It is much easier to share information with a computer than it is with film.
Computer storage on disk and tape can take less space than film
Magnetic media have some very attractive properties.

Storage density is one, the domains of a hard disk can be 50 nanometers wide - about a tenth the size of a light beam. Microfilm and every optical device (even blue-ray DVD) hits a limit at the wavelength of light. In principle microfilm on rolls or fiches could stack very densely, but in practice it tends to have special dockets and racks that take much less space than paper, but rather more than the equivalent in disks.

Easy availablity is another - a hard disk can handle about a hundred queries per second and the server can queue overload peaks. Paper and microfilm serve just one user at a time and response times are in minutes.

Replicability is another. One of the processes accessing a disk can be replication to another disk - or a pair of them on different continents if disaster recovery is an issue.

Curiously, most computer media have poor survival prospects. The same Moore's Law progress that delivers cheap digital video cameras means expensive old 9-track tape is obsolete. Some of the disks and tapes used in the 1980's are already entirely obsolete, all the equipment able to read them has been trashed. Manufacturing a cartridge tape reader or adjusting a floppy disk drive to deal with a weird format are non-trivial (ie expensive) exercises.
Floppy disk drives are an anachronism themselves. Some of the tapes and disks made just 20 years ago are now unreadable. Unfortunately magnetic media are not permanent. On disks the magnetised domains tend to progressively weaken. On tapes, domains from overlying parts of the medium can imprint on another creating an unreadable mush. If old media are not periodically efreshed they will become useless. Without the transports the media cannot be refreshed.

Microfilm Archives

Microfilm is still sometimes used to provide an audit trail, for engineering diagrams and for records that must survive. For instance:

Britain's "Green Goddess" military fire engines remained in service from 1953 to 2004, some are still available. A sixty year service life might be exceptional (through desireable) for domestic equipment but there is often no great reason to replace industrial and military machines.

Power stations often have a design life of 25-50 years and an actual service life of 75 years. Nuclear plants are obliged by law to keep records. One of the concerns with digital media (disks and tapes) is that they decay unpredictably. Film media is likely to remain readable in the indefinite future.

Urban infrastructure often survives for a century or more - there are electricity cables 80 years old, gas mains older still and the basic sewerage and water system for most British towns was constructed in the 1850s.

Records like Births, marriages and deaths, Land registry, Parliamentary proceedings and so forth are now expected to have an indefinite of even infinite life.

These real economic needs for long term preservation of records are supplemented by another - a general desire to preserve something of the past. Some people take the attitude that "history is bunk", rather more think "those who forget the past are in danger of repeating it".

Documents with legal status may have a better audit trail on film then they can in a computer. In principle a record in a computer system might change without any evidence trail. A microfilm might be altered and re-copied - but there will be tell-tale signs.
 

Microfilm Lifetimes

Microfilm and microfiche are photographic film - polyester backing with silver halide dye in a hard gelatin coat. The life will vary with the exact composition of the material but several hundred years is thought feasible. Cellulose nitrate backing was used until the 1950s but it decays and the decay product is explosive. Polyester is much more stable, however in warm damp conditions fungal growths will destroy the gelatin. Films with diazo dies have a life of just 20 years.

The image is reduced from the original 25 times or more but the image emains immediately comprehensible and can be seen under a magnifying glass. Special readers with an optical path and a translucent screen are convenient but not essential. A single technician can build a microfilm reader should it ever happen that there are non left. It is unlikely that a small team of technicans could build a 9-track tape drive, and quite likely that the data would be unreadable.

Microfilm Capture

Material for microfilm is often conventionally printed on paper then photographed using a planetary camera. If there are only small volumes of material this solution will be sensible - the paper record has a day to day use and the microfilm or fiche goes into the archive.

Printing to paper then microfilm may be less satisfactory if there is a lot of material. There are also some cases where the infomation is originating from an unconventional digital device like a land-imaging satellite and cannot sensibly print on paper - there is just too much information for any conventional printing technique.

In these cases direct computer output to microfilm "COM" is used.

Computer Output Microfilm Recorders

Computer Output Microfilm Recorders (COM) are optical output / camera devices for direct output to film. Photochemical film
The market for these devices is quite small - Fortune 500 coprorates, government departments, libraries and archives - and bureaus serving those markets.

The first such device seems to have been the Stromberg-Carlson 4020 equipped with a Charactron tube (http://wps.com/projects/Charactron/index.html) (http://stinet.dtic.mil). The charactron was a curious cathode ray tube which produced alphanumeric characters on a screen using a small metal "stencil" to shape the electron beam.
 
Three broad methods have been used for COM:

CRT exposure - one problem has been that until recently common CRTs could not produce an image of anything like the quality seen on a piece of A4 paper - hence the weird line-at-a-time scanning techniques mentioned above. An A4 short-side at just 300 dpi is 2,400 pixels. To get an image the correct size for 16mm film either a large CRT must be focussed by lenses, or a smaller screen with a very fine grain phosphor and a fine beam is needed. Either way, specialist Cathode Ray Tubes and lense assemblies are expensive items.

Laser exposure is more promising. Basically the imager replaces the drum or belt of a laser printer with a photographic film. The laser beam has to be finely focussed onto the film so again there are light losses and reflections to deal with.

Electron beam recording writes on silver halide film directly with a fine electron beam. Its basically an aplication of the kind of electron-beam lithography machine that can be used in certain stages of chip-making. Image Graphics are the only users of this technology so far as is known.  The electron beam in their equipment can be focussed down to 4 micron's diameter and still provide a 256 step grey-scale, which the other technologies cannot. The beam can also expose a whole width of film up to 105mm fiche width in one operation which gives it applications in recording satellite imagery and RGB separation masters.

With a general shift to digital storage in data processing COM doesn't seem as common as it once was. New markets have emerged, however, notably a small but interesting one for motion picture film recorders.

Like other technical industries the movies have been going digital - so much so that digital animation has become standard practice. Movie distributors have also tried digital distribution of material but so far people haven't been entirely happy with it - a film frame translates to an awful lot of data. In data delivery terms the current generation of affordable Internet connections don't match up to a courier with a couple of cans of film.

Output from a rendering farm needs to be mixed with conventional images that can be scanned in and then output to film.

Manufacturers include:

some of the usual computer printer makers: Canon, Panasonic, Fujitsu and Konica Minolta.

some specialising in the microfilm industry. Image Graphics Inc (www.igraph.com), Anacomp, Eastman Kodak and Bell+Howell

Devices such as the Data Graphix Datamaster II

Continental DataGraphics - Known as CDG and part of Boeing

Konica Minolta DR1600

Kodak Digital Science Document Archive Writer

Kodak 3000DSV Scanner-Printer

generally take 16mm film or 105mm fiche rolls.
The equipment can have contact development built in.

Computer Input Microfilm (CIM) is the other end of the process.
Scanning microfilm images into computer data has been a trend recently - the storage density and easy access to hard disks makes them superior to microfilm in some ways.

Microfilm storage of images and data can make sense because of it's low risk, stable nature.

Scanning microfilm images back into computer form overcomes some of the issues microfilm storage raises. The scanner can automatically find the right image, or produce thumbnails of them. An image selected is converted almost instantly to digital form and then provided wherever needed over the computer network - or via fax or e-mail.

Tertiary storage using tapes or DVD is frequently used on computer networks. The potential advantage of placing such storage on microfilm is that most of the space saving of digital systems are realised, but there is less isk that some fundamental failure in hardware or - more damagingly - in the human management of the system will destroy data.

Notes

ProQuest

Founded as University Microfilms in 1938 (and subsequently named Xerox University Microfilms, University Microfilms International, UMI, Bell & Howell Information and Learning

Lithography

Print houses generally have specialist machines to produce lithographic plates. 

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© Graham Huskinson 2010