Infrared Exposure

Correct infrared exposure needs to be determined by the amount of infrared light rather than visible spectrum light. This creates some new concerns which do not exist for films only sensitive in the visible region of the spectrum.

Film Speeds for Daylight Exposure of B&W Infrared Film

The following table describes "equivalent ISO exposure speeds" for Kodak HS Infrared and Konica 750 in daylight. These values should be considered starting points for doing your own testing. Time of day, time of year and weather conditions strongly effect infrared exposure conditions. These numbers are valid for April through September, and from 10 am through 2 pm in clear bright sun conditions. Other conditions will require an increase in exposure. Open shade on a bright sun day may require opening up one additional stop or halving the effective film speed listed here.


Wratten Number Kodak HS IR Konica 750 Comment
None
80
32
 Strong visual spectrum sensitivity
25
50
10
 Includes red portion of visual spectrum
25 Meter
400
80
 Filtered exposure meter readings (test!)
29
50
10
 Limited exposure meter use (ISO x 3, test!)
70
50
10
 Limited visual spectrum
89B
40
8
 Minimal visual spectrum
88A
25
4
 Opaque to visible spectrum
87
25
2
 Marginal with Konica 750 - limited spectrum
87C
10
NR
 Not recommended for Konica 750


Film Speeds for Tungsten Exposure of B&W Infrared Film

The following table describes "equivalent ISO exposure speeds" for Kodak HS Infrared and Konica 750 in 3200 or 3400 Kelvin tungsten lighting. Due to the more consistent infrared output of tungsten lighting results should also be more consistent than for daylight exposure. Testing is still a good idea for critical work. Infrared output of tungsten may vary with increased bulb usage.

Wratten Number Kodak HS IR Konica 750 Comment
None
200
50
 Strong visual spectrum sensitivity
25
125
30
 Includes red portion of visual spectrum
25 Meter
1600
320
 Filtered exposure meter readings (TEST!)
29
125
20
 Limited exposure meter use (ISO x 3, TEST!)
70
125
30
 Limited visual spectrum
89B
125
30
 Minimal visual spectrum
88A
64
20
 Opaque to visible spectrum
87
64
20
 Marginal with Konica 750 - limited spectrum
87C
25
NR
 Not recommended for Konica 750


Reciprocity Data for B&W Infrared Films

The following reciprocity data is provided as a starting place for testing (Konica 750 reciprocity data is estimated). Exposure times are in seconds.

Exposure Time Kodak HS IR Konica 750
1/1000
None
None
1/100
None
None
1/10
None
None
1
0.5 stops
None
10
1.0 stops
0.5 stops
100
2.5 stops
1.0 stops
1000
3.5 stops
2.5 stops


Exposure Speed Data for Ektachrome Color Infrared Film

The following exposure speed data is from Eastman Kodak data sheets. Exposure times are in seconds.

Illumination Type Recommended Filter Meter Setting
Daylight
Wratten #12
100
Tungsten Light
(3200K or 3400K)
Wratten #12
+CC50C (cyan)
50

For critical work a Corning Glass Filter CS #3966 (1-59) plus a CC20C (cyan) filter can be combined with a Wratten #12 filter. The same meter setting of 50 will apply in this case.


Reciprocity Data for Ektachrome Color Infrared Film

The following reciprocity data is provided as a starting place for testing data (from Eastman Kodak data sheets). Exposure times are in seconds and include filter factor compensation.

Exposure Time Additional Filtering Increased Exposure
1/1000
None
None
1/100
None
None
1/10
1.0 stop
+CC20B (blue)


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Spectral Sensitivity of Color Infrared Film
Contents
Spectral Selectivity
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Ultraviolet

C1997 by Ed Scott - <dotted.dog@worldnet.att.net>
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