Photographic Terminology

There are always some photographic terms that I use, but don't necessarily know enough about to teach. Or there things I've written to help the understanding of others and I put it here to help anyone. I've made this page to remind myself of some of those terms. Worst thing about it is, that after I've written something down I have no problem remembering it. Oh well...

By the way, if you have problems with my definitions, please tell me; no one is perfect after all! I may either understand something incorrectly, understand it correctly but written it down incorrectly, or written so poorly that it is not understood correctly. Most likely, you can't understand what I've written because it is written poorly :(

Bokeh

Bokeh is a term from Japanese photography. Bokeh refers to the quality of the out-of-focus areas in a photo - whether they are pleasantly smooth or whether they are distractingly coarse, etc. A mirror lens causes "donut" shaped bokeh which reflects that catadiotropic nature of the lens. Bokeh is very important for uses such as portraiture, where you don't want the out-of-focus background to take attention away from the subject.

C-41

C-41 is the name of the standard color film and the process used to develop it. All C-41 films use the exact same chemicals and process for development.

Chromogenic Film

A chromogenic film is a B&W film which is processed in C-41 color chemistry. The resulting negative is dye-based instead of silver based. This reduces the grain effect quite a bit, which is both good and bad. Bad in that you no longer have grain as a characteristic of the photo. Good in the sense that grain size in enlargements isn't as much of an issue.

ISO

ASA

Film Speed

Designates the speed of the film, which is how sensitive that particular film is to light. An ISO number which is 2x as great specifies a film that is twice as sensitive to light, or requires half the exposure. Conversely, an ISO number which is (1/2)x the amount specifies a film which is half as sensitive to light, or requires twice the exposure. Film speed is supposed to be rated so that you get good shadow density in negatives. However, manufacturer's often rate the film at a different (aka higher) speed for marketting purposes. This typically causes a loss of contrast in slides, negatives, or the resulting print. Due to this ploy it is often best to rate the film speed yourself. One example of this is Kodak Royal Gold 1000; reports from individuals indicate that a realistic rating for this film is 800 speed -- which vastly improves it's use in real life. See Exposure Index for more info.

E-6

Ektachrome

E-6 is the chemical process used to process slides. Though originally designed for Kodak products, everyone makes E-6 slide films which process in E-6 chemistry. It is possible to process E-6 at home, unlike Kodachrome.

EI

Exposure Index

Film Speed designates how sensitive a film is specified to be. EI or Exposure Index specifies the speed at which you are rating the film. In the film speed example, my comment suggests exposing Kodak Royal Gold 1000 at an EI of 800. Note that using an EI different from the film speed will have side effects ... By using an EI different from the recommended value there is something to take into consideration when development occurs. If normal development is used you will essentially be performing push or pull processing on the film you exposed! On the other hand, if you adjust the development process to match the EI you exposed the film at, then everything is as expected. This is a more significant issue with color (C-41) process films than B&W, as temperatures and times for C-41 are strict, compared to the changes you can make to B&W processing. Of course, if you send the B&W off to a lab for standard processing, you will be affected the same way.

After writing this I realize my grasp of the cumulative effects is not complete and that I need to study this further.

EV

Exposure Value

Exposure Value can simply be thought of as an amount of light. EV 0 is less light, EV19 is more light. Each increase by one in EV is a doubling of the amount of light. EV is often expressed as a combination of shutter speed, aperture, and film speed. I believe the EV standard is for 100 speed film, but I'm uncertain of what changing film speed does to EV -- after all, the amount of light hasn't changed! With film speed ISO 100, EV0 corresponds to a shutter speed of 1 second and an aperture of f/1.0. You can vary shutter speed and aperture inversely with each other, and the EV will remain constant. I could say that EV = aperture * shutter_speed. Any combination of aperture and shutter speeds that results in the same EV means that their is that much light.

Kodachrome

K-XX

Kodachrome is the other transparency process. The processing of it is complicated and can involve dangerous chemicals. Kodak is the only company which processed Kodachrome films. The flip side of Kodachrome is that the slide has a very long lifetime compared to E-6 slide films. An archival life of 30 years is not uncommon for Kodachrome slides. The estimate of E-6 life is 6 years or so; however that may be longer now due to better materials, chemistry, and processes.

PC

No, not personal computer. Rather the ubiquitous PC connector used for connecting flash equipment. The name PC comes from the two shutter companies which started using this -- Prontor and Compur.

Pulling

Pull Procesing

Pulling refers to over-exposing film, compared to it's film speed. Typically this is done when you need a slower film and you have a faster film. A typical example of why you would want to do this is when you have a fast lens, a bright day, and need low shutter speeds for some reason. Certainly a ND (neutral density) filter would be the right thing to use, but who has one when they need it? So, you underexpose the film, typically by cranking a lower ISO speed into the film speed dial. When the film is developed you compensate for the over exposed film by under-developing it. Typically this is done by reducing development time or temperature. This stops the development before it's time is complete, and instead of blowing out the negative, a somewhat reasonable negative will be the result.

If you are using roll film, typically you are stuck pushing or pulling the entire roll, instead of individual LF negatives. With modern color print film you can often do pull or push processing at printing time by printing darker or lighter. This is due to the wide exposure latitude of modern C-41 process films.

Pushing

Push Processing

Pushing is the reverse of pulling. Instead of over-exposing the negative you under-expose it. This would be done when you need a faster film than you have. For example, the light is too dim, the glass is too slow, or you need a faster shutter speed. You over-expose the film by selecting a higher ISO speed on the camera's film speed selector. At development time the under-exposure is compensated for by over-developing the negative. This is done by increasing development time and or process temperature. Instead of the negative being very thin, this pulls every little bit of light out of the emulsion, and you will have something instead of nothing.

If you are using roll film, typically you are stuck pushing or pulling the entire roll, instead of individual LF negatives. With modern color print film you can often do pull or push processing at printing time by printing darker or lighter. This is due to the wide exposure latitude of modern C-41 process films.

RA-4

RA-4 is the process currently used to process color printing paper. It replaces the older EP-2 process; I believe the transition period was in the early 1990s.