I have been asked the following question;

“What emissivity setting should I enter in my camera when carrying out a CM survey?”

Of course this is a bit subjective, and can be an individual choice, but there are a few different options that people normally use. I have to say that if we need a true temperature, then we MUST have the correct emissivity.

Option 1: Leave it set at 1.

Some people like to leave it set at 1, and work with apparent temperature only. This is not a bad option, and is probably true to say that it is correct when working qualitatively.

Option 2: Leave it set to 0.5. People that use this argue that it shows the worst case scenario, and therefore helps to err on the side of caution. Of course, it assumes that you should not be trying to measure the temperature of something with an emissivity less than 0.5, this is normally correct.

Option 3: Leave it set high, say 0.95. I think that this is the best option. When working out in the field, we are obviously not going to come across black bodies, nor should we normally be trying to measure anything with a low emissivity. 0.95 is about the highest emissivity that we are normally going to come across. So most normal objects that we are going to come across will have an emissivity less that 0.95. Therefore if we can consider the temperature to be the “at least” value, and stick to measurement from non-metals, we won’t end up in too much trouble.


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