About Bluefire® Police film:    Resolution of image detail    Microstructure and acutance    35mm vs. larger negatives

Pictorial photography:     Exposure    Processing instructions 

High contrast photography:     Exposure and  Processing

Bluefire films are of a type of film for which there are no ANSI or ISO speed rating standards, so we have arrived at our Exposure Index values through evaluation of sensitometric step wedges and subjective evaluation. The recommendations here are specific to the combination of Bluefire Police film and Bluefire HR developer.

You can also process Bluefire Police films in soft-working document-film developers, such as POTA (available from Photographer's Formulary), Kodak Technidol, Formulary TD-3, Spur Nanospeed and Docuspeed, and Labor Partner Docufine LC and HC. When you use these developers, film speed and image characteristics will not be the same as processing in Bluefire HR, and you will need to test and establish your own ratings.

Bluefire Police is a panchromatic black and white film, which is sensitive to the entire visible spectrum. All the colors of the scene are recorded as a more or less natural-appearing shade of gray. Its grain is so fine that it is not apparent even at extremes of enlargement. It can resolve detail beyond the resolution limits of most commercially-available lenses. 

This makes it an ideal film for surveillance at a distance with a telephoto lens, where positive identification of individuals requires extreme enlargement of small portions of the negative. This was the film's original commercial purpose.

But it also results in a beautiful gray scale and pictorial qualities that are noticeably different from what most photographers are used to, and which some photographers will come to prefer.

With any film, including Bluefire Police, your results are influenced by the camera and lenses you use, how accurately and carefully you expose the image, on your processing technique, and on your printing equipment and technique. You should test any new film with your equipment before using it for photographing important one-time events or transient subjects.

Resolution of image detail

The Bluefire Police film and developer combination is capable of ultra-high resolution, on the order of several hundred line pairs per millimeter. A properly exposed and processed 35mm Bluefire Police negative can, in theory, be enlarged to as much as 100x without losing image detail to grain. However at that degree of enlargement, your lens will no longer be resolving image detail. The practical maximum enlargement is a function of the maximum resolution of your optics, generally no more than about 40x (although experimental enlargements to 67x have been made). Enlarging a 35mm negative to 40x gives a maximum print of about 3 by 4.5 feet (a little less than 1m x 1.5m).

However, it is unrealistic to expect to be able make those kinds of enlargements routinely. Image sharpness is affected by the resolution limits of the entire optical system, including mechanical issues like camera shake during exposure, and film flatness. You are at the mercy of the lenses in your darkroom or film scanner; the accuracy of your exposure, the care you exercise in the darkroom, and more. 

For those reasons, you will find that your film is not the limiting factor in the size of enlargement you want to make. The limiting factor is your equipment and technique. 

Microstructure and acutance

All films, including the apparently grainless Bluefire Police, have granular structure and properties. Although the grain of Bluefire Police is not normally visible, even at extreme enlargement, it does interact with the recommended developer and create exaggerated light-dark transitions on a microscopic scale. While the individual transitions are invisible to a viewer, in mass they make image details more clearly defined. Without this microstructure, technically know as acutance, the grainless image would appear unnaturally soft.

Bluefire Police derives its unique image qualities from this combination of invisible grain and pronounced acutance. The recommended Bluefire HR developer, when used according to instructions, acts as a high-acutance developer and shows the film's acutance to advantage.

35mm versus larger negatives

The general rule is that larger negatives enlarge better than small. If you use 35mm Bluefire Police products correctly, you will be able to make substantial enlargements that approach the image quality of medium- and large-format negatives. Certain subjects, and certain lighting conditions, will lend themselves to this. However, 35mm Bluefire Police should not be considered a substitute for larger negatives. Instead, you should use Bluefire Police 35mm film as a way of extending the expressive range of your 35mm equipment.

Pictorial photography:

Exposure

We recommend exposing at EI 80 and processing in Bluefire HR developer using a specific time and agitation technique outlined below. EI 80 is the minimum exposure that yields good negatives which print well on grade 2 paper, in our experience. When photographing subjects that do not have strong highlights and where shadow detail is the most important part of the image, you should give more exposure. When you want to preserve highlight detail, give less exposure.

The undeveloped image on all exposed films, including Bluefire Police, degrades with time. Protect your unexposed and exposed film from heat and humidity. Process your exposed film promptly.

Development

The most consistent, and consistently satisfactory, negatives will result from processing for 12 minutes in Bluefire HR developer at 20 degrees (68 degrees F) with continuous agitation using a Jobo processing system or something similar.

If you prefer intermittent agitation, process in Bluefire HR developer for 15 minutes on a spiral reel in a steel or plastic tank at 20 to 21 degrees (68 to 70 F). Maintain uniform temperatures in all solutions throughout the processing cycle, including washing.

You will have the best results using a tank large enough to hold your film plus at least one empty spiral reel on top. The empty space above your film allows good solution flow during agitation.

Agitation during development:

You are unlikely to be successful using ordinary agitation techniques. The following technique is recommended if you choose to use intermittent agitation rather than continuous agitation.

Agitate gently and continuously for the first minute. If your negatives show uneven densities in areas of uniform image area, like sky, increase this to 90 seconds.

Then agitate for about five seconds at the beginning of each subsequent minute.

During this first phase, uniform development is occurring. The next phase is designed to bring out the film's acutance.

At the end of five minutes, agitate less frequently. We recommend five seconds of agitation, every three minutes, with the tank sitting undisturbed between cycles.

The agitation we recommend is to pick the tank up and shake it at a medium speed, about one up-down movement per second, for five seconds, taking care to not cause excessive splashing.

Stop bath

Follow the recommendations of your stop bath manufacturer. If you use a plain water bath, fill the tank twice, agitating continuously for 30 seconds with each filling.

Fixer

Follow the recommendations of the manufacturer of your fixer. Bluefire Police requires less fixing time than most other films because its emulsion layer is so thin. It is good practice to test a scrap of film in your fixer in daylight, so you can time how long it takes to clear. Fixing will be complete in 1.5 times as long as the clearing time. Bluefire Police is generally fully fixed in as little as 90 seconds with ordinary ammonium thiosulfate rapid fixers.

Wash

Running water wash is not recommended if it can be avoided, since it wastes water. Instead, we recommend the following:

Fill the tank with fresh water. Agitate gently. After 30 seconds, drain the water. This flushes surface chemicals from the film.

Fill again and and let the film sit undisturbed for 30 seconds. This allows fixer to diffuse from the emulsion. Then drain.

Repeat six more times, without agitation, so your film has been in eight changes of water over the course of about five or six minutes total cycle time.

Dry

Rinse the film in a wetting agent according to the manufacturer's directions. Hang it vertically to dry undisturbed at room temperature in a dust-free place. Do not wipe or touch the wet emulsion layer. Do not use forced air or heat. Allow the wetting agent to do its work.

Drying time depends on relative humidity (five minutes in Calgary, which has a dry climate). Bluefire Police is generally dry in about half the time of ordinary films, due to its extremely thin emulsion.

Note: the film has a magenta anti-halation undercoat that washes out during processing. It will color your stop bath and fixer, and you will probably see it in your wash water. It has no effect and can be ignored.

High contrast photography:

Expose at EI 100 and process in a high-contrast developer according to the manufacturer's instructions.

See the Pictorial instructions above regarding specific instructions for fixing, washing and drying.