To save time and money, it's important to get the greatest number of usable images on a roll of infrared film as possible. Metering for a correct exposure on infrared film becomes, at best, a guess with no way of evaluating near-infrared light. To solve this problem, some people have converted visible light meters costing 100's of dollars. Others have converted digital cameras for infrared imaging costing even more, but that route lacks the "blooming" effect which only film can provide.

The IRM 750 is a simple and effective infrared light meter that really works, for less than $100.

Using this meter along with a user-supplied digital multi-meter/volt meter will have you shooting more correctly exposed frames than ever before on every roll.

If you do not already have a suitable digital multi-meter, then you will need to purchase one. The multi-meter should be able to read 0-1 volts in .001 increments. Most if not all digital meters have an mV scale that will work with the IRM 750. Specific models include:

Radio Shack:
#220-813 digital multi meter
#220-811 digital multi meter
#220-812 digital multi meter

General Electric:
#GE2524 digital multi meter

These meters cost as little as $15.99 and can be purchased from suppliers such as Radio Shack, Wal-Mart or most hardware stores. A connector cable will be provided with the IRM 750. The multi-meter must have standard "banana jack" type female plugs. All meters listed will work with the connector provided.

CALIBRATION PROCEDURE

This procedure must be accomplished for each different film type/developer combination. Items you will need for calibration include:

• Infrared film
• IR filter
• IRM 750 meter
• Digital multi-meter or volt meter
• Camera with built-in light meter (or handheld meter)
• Pen and pad for note taking

It is vitally important to keep accurate detailed notes. Your new IR light meter will be used to gather information, and you will take and record measurements to develop a system of exposure.

First, select a site to do your test. A local park works perfectly for this. Pick a day that is sunny with scattered clouds and plan on shooting multiple sites at different times of the day. Record your information on 4x6 flip index cards. It's small and durable. You can also keep developing information in the cards so that all your information is in one location.

Your first test roll of film will have many bracketed exposures. After selecting a suitable site, set up your camera loaded with film and compose the image. Set your camera's exposure controls to the recommended starting point provided by the manufacture. Because of the design of the IR meter head, try to aim the meter the exact same way each time a reading is taken. Keep in mind that the meter acts a little like a very wide angle spot meter. I placed my meter head on the same spot on my camera aimed at the central part of the scene each time it was used. This provides some form of consistency. Another technique for taking readings that might be more accurate and useful is averaging. Record the highest and lowest values for the scene and average the two. Just remember to use the same technique that was used during the calibration while shooting film in the future.

Take meter readings with both the IR meter and your camera's built-in light meter (or a separate hand-held meter). Shoot 4-5 stops over and under the starting point exposure. Record your information for each frame you shoot. A blank sample form is included for you to copy and use. Do this for several different subjects, sky conditions, and times of day. After finishing your roll, process as soon as possible.

Consistent processing is vital in the success of the calibration procedure. Again, keep accurate notes on chemical mixing, times, temperatures, solution volumes used and film handling technique. After processing your roll, let fully dry for evaluation later.

Evaluate the processed negatives and pick out the best exposures on the roll. Match each acceptable frame with the recorded exposure info from your exposure record. You may want to print a few properly exposed frames to see if they are acceptable. Once you have developed a "cheat sheet" of sorts, repeat the procedure with another roll of film using the basic exposure information from your cheat sheet. You will not have to bracket as much as the first roll. 3-4 half stops should be adequate. This will refine the information further to produce an exposure chart that can be applied in the field.

Keep in mind that this is not 100% foolproof and some bracketing will still be required to produce the "look" you want. It will, however, provide you with an exposure system which should produce a greater number of usable images on each roll of IR film. On my first try after only one test roll of film, I was able to produce 12 properly exposed frames out of 15 with no bracketing.

Instructions provided by Mike Lubiarz