Film Speed Testing for IR Film

[thefizz]

With the help of fellow Apuger Michael McClellan and his Densitometer, I have worked out personal film speeds for some standard B&W films.

Can the same zone 1 test be done for IR films even though they will be recording IR light when opaque filters are used. I do not have a meter suitable for IR light so I usually meter without filter and then apply the filter factor. This has worked out pretty good so far.

Should I shoot the test through the filter and do the densitometer readings as normal?

Peter

 

[Roger Hicks]

Dear Peter,

Speed tests are a bit meaningless with IR films -- IR reflectivity varies too much -- so the best bet is simply to expose generously. Fortunately B+W photography is incredibly forgiving, so it makes no sense to look for more precision than is (a) needed and (b) available.

Cheers,

Roger (www.rogerandfrances.com)

 

[Gerald Koch]

You need to use the film manufacturer's recommendations, as meters are useless, and then bracket your exposures. Experience with a particular film is very important.

 

[thefizz]

Thanks Roger & Gerald, I expected it might be a waste of time and film so I will continue as before.

Peter

 

[rbarker]

Although I don't shoot IR on a regular basis, I would agree that speed testing IR film is only marginally useful. The amount of IR light present varies with both time of day and season. So, about the best you can do is to arrive at a starting point for wide bracketing, adjusting for time of day and year for your general location - for a specific film and filter combo, of course.

 

[Markok765]

I heard for hie, industrial\street set meter at 400 and them add filter factor. for anything that has a lot of plants\trees set at 1600 because those reflect more IR

 

[Helen B]

If you are really serious about IR then you can modify a spotmeter to respond in a similar way to a particular film/filter combination. I have a Pentax Digital modified to match HIE with an 87 - I followed the method set out in Photo Techniques a while back - but hardly ever bother to use it for pictorial work because I can get close enough with TTL metering.

There was a Dead Link Removed discussing the use of IR film under different sources of illumination and the consequent problems with exposure determination.

Best,
Helen