Last Updated 99/07/29 1300PST
by Martin W. Baumgarten © July 1999
Take a given cartridge of Super 8mm film, expose it normally of a given continous tone daylight scene, perhaps with someone in it....fairly closeup...seated or standing...holding a color card or gray card....(have you ever seen Laboratory test photos? That would give you an idea....go to your local 1-hour lab and ask to see what their control photo looks like), and then just film the entire cartridge. Whenever you need a "visual control strip," you just pull off some film from the end of the film....thru the cartridge gate opening...first wind the takeup core counterclockwise to break the ratchet inside....then you'll be able to pull off, say 6 inches or so of film (in the dark of course!), and place that into an empty 35mm film canister...the Kodak type which are light tight! Process just this piece of film....in a one reel Nikkor type tank and then see how well it looks...if it looks too dark...increase your time...if it looks too light...decrease your time...and apply these First Developer time corrections to your actual film process then. You can even splice one of these onto the end of a roll of film and process one with your actual film to see how the processing is doing. Place the remainder of the exposed cartridge into a ziplock bag, evacuate as much air as possible, and place into the freezer. Whenever you need a "control strip," just remove it from the freezer......open the bag...in the darkroom, and remove yourself a length of film from the cartridge....returning the cartridge to the ziplock bag and freezer as rapidly as possible. If after one-year you haven't used it all up....dispose of it and start with a fresh cartridge of film and make yourself another batch of control strips.
Now, if you want to have more professional control over your processing, film your control strips of a scene (which would be easier to film a photograph so you can alternate quickly) for a few frames, then film an 18% gray card, then the scene again...and so on. By using copy lights and metering carefully you can set all this up on a table top somewhere, and easily alternate between the two. Do this for the entire test cartridge. Then no matter what length of film you need to remove from the cartridge as your control strip....you'll always have both the scene representation in the film segment as well as a correctly exposed 18% gray card. Make sure your exposures are definitely correct, and use a handheld light meter of known accuracy to help pinpoint the exposure and/or double check your Super 8 camera's light meter. Do the same for this control test cartridge....placing it into an airtight ziplock bag with as much air evacuated as possible.
If you don't have your own densitometer, you can usually go to your local 1-hour photo lab (when they're not busy of course!) and ask the technician if he or she would be so kind as to read out the optical density only on the frames which have the 18% gray card filling the frame. Have them read out a few of them for optimum results and then you can average them numbers together. The ideal target is .80 optical density...however...you can live with the range of .70 to .90. Your scene representation in the film will also help provide you with a visual indication of how light or dark the film is. For films that are too light, say .50 density, then you should DECREASE your First Developer time by about 20%...or 1 minute if using 6 minutes as your time...for example; it could've been that there was another variable, too high a temperature...and that increased the developer activity. Try to be consistant and use the same processing temperature each time you process films. Then the only other variables will be the chemistry activity (state of wear) and your First Developer time. For films that are too dark, INCREASE the First Developer time.....for example if the optical density is 1.00, Increase the time by 1 minute based on the same earlier example.
Processing control on PUSHed films: this applies very much the same as above......however, you would have to shoot a test control film that is 1-Stop underexposed intentionally. Then whenever you process the control strip....you should still get an approximate .80 optical density reading on the 18% gray card frames....and the scene representation should look normal as well. In pushed films..often the contrast increases, so try not to let the lack of some tones in the image throw you off into thinking that the image might be too light. That's why it's good to have the 18% Gray Card frames in the control strips as well....since you can read these out.
For extremely technical processing control and to see how a given film was processed etc, you can shoot a series of exposures of an 18% gray card, beginning with 5-Stops under-exposed, and either in half-stop increments (if possible) or full-stop increments. This can be done at the beginning of a given film or anywhere in the film...since you're only going to use up a tiny bit of film for all this: 20 to 40 frames. Shoot each increment at least twice using the single-frame feature of your Super 8mm camera, that way..if one has a dirt mark or scratch on it...you have a backup frame next to it. You can probably get someone at a laboratory to read and plot this out...make sure you tell them it's B&W reversal film, since reversal films are plotted out differently from negative films. You can also do this for color film...but since all three Primary Colors have to be plotted (Red, Blue & Green), it does get more involved.
Once the strips have been read out, you can or a technician can determine what type of correction should be made to the processing of your own films. Also, you can tell if a lab has processing problems....or if the film you're using is old and has lost effective filmspeed and contrast, and by how much. Your local library should have some books on the technical end of photography which covers control strips and plotting, and you only need to familarize yourself with the basic elements of this..unless you want to delve deeper into it.
Hope this helps.
Best wishes,
Martin Baumgarten, Plattsburgh Photographic Services