Relative Film Sizes
Cameras:
- Large: Sinar 4x5 and Antique Kodak 5x7
- Medium: Pentax 6x7II, Hasselblad 6x6cm
- Small: Canon EOS 35mm
Dynamic Range
Photographic Papers have less dynamic range than film, and significantly lower resolution. An image with high contrast can be quite difficult to print in a conventional darkroom.
However, modern film scanners have excellent dynamic range (DR). For scanners DR is a number between 1 and 4. Scanners are also optimized for highlights (DMAX) as opposed to shadows (DMIN).
Commercial Drum Scanners have DR=3.9 (outstanding). My Nikon Coolscan has DR=3.6 (excellent). My Microtek i900 has DR=3.2 (better than most papers), and performs extremely well in highlight areas (DMAX=4.2). The Nikon is for small format. Microtek is for medium/large format.
Topics in Photography
For the moment, I have a few topics of interest. Film formats and the concept of film latitude or dynamic range. From time to time, new topics will be added.
Film Formats
Film formats can be a little confusing, with just dimensions, so I created an illustration at left. We find some gems of wisdom in the old school of photography. For example, if you want better print quality, use a bigger negative. The largest film format I use is 5x7 inches, negatives large enough for a seven-foot mural.Since film area is really the matter at hand, it's useful to multiply film dimensions.
- 5x7 is 35 square inches
- 4x5 is 20 square inches
- 6x7cm is 6.2 square inches
- 35mm is 1.4 square inches
To cloud this tidy picture, there are at least 12 commonly used film formats. These are just the formats I use. Medium format is about 4 times the size of small format, and large format is 3 to 5 times the size of medium format. 6x6cm square format is not shown; it's a little smaller than 6x7cm. My Hasselblad uses the square 6x6cm format, which can easily be cropped.
Film Latitude
Our eyes are amazingly sensitive. We can see differences in brightness with a ratio of 1:50,000! What we can see won't fit on film, and one challenge of photography is fitting our contrasty world inside the narrower range of film. In photographer's lingo, the range of brightness for human vision is about 15 "stops". This term is derived from the aperture scale on lenses, where opening the aperture by one f-stop doubles the amount of light striking the film. Since this is an exponential scale, dynamic range improves dramatically as we move towards the top of the scale.
The illustration should be helpful. It shows the latitude of various films in stops. If you look at the scale on the left side, this will give you a contrast ratio. Black and white film is as good as it gets in photography with 11 stops of film latitude. This is a contrast ratio of 1:2048, though the range for tones and texture will be shorter. Black and white film also has outstanding resolution. This level of performance explains why black and photography is so popular among artists, myself included.
Color film, also has pretty good latitude, about 7 stops. Many subjects that could be photographed in black and white cannot be rendered on color film. The highlights will be pure white, or the shadows pure black. In high contrast scenes, we simply run out of road. There is still wide freedom in choosing and composing subjects, but photographers must be aware of limitations.
At the lower end of the scale we find transparency films. Typically, slides have about 3.5 stops of film latitude. This is very short latitude, but transparency film seduces many artists just the same. Transparencies have superb resolution and color saturation. A transparency is also a finished product, but can be used to make cibachrome prints, or scanned digital images. Photographers who shoot transparency film know the limitations, and compose images in ways that reduce contrast. Artificial light can be used to raise the values of shadows. Telephoto lenses have a narrower angle of view, allowing greater selectivity in composition. An overcast day is a good day for shooting slides. I sometimes shoot transparencies in the rain, keeping my camera dry under an umbrella.
Like transparencies, digital has short dynamic range (latitude), and very poor resolution. "Megapixels" is a term meaning millions of pixels. Developed film has billions of grains of metallic silver, a thousand times the resolving power of digital. With low resolution and poor dynamic range, you might be wondering how images of such low quality can be visually effective. It's a trick done with colors. Digital has a palette of millions of colors, more than enough to satisfy our color perception. Digital images are a close cousin to your computer monitor, but a distant relative of film.