Filter Factor Chart
Exposure compensation for coloured filters in black and white photography. Select a filter to see the adjustment needed.
Calculate filter compensation
Enter your base exposure and select a filter
Seconds, m:ss or a fraction such as 1/125
Complete filter reference
Filter factors and their effects on black and white film
| Filter | Factor | Stops | Effect |
|---|---|---|---|
| Yellow (No. 8/K2) | 2× | +1 | Moderate sky contrast, reduced haze |
| Deep yellow (No. 15) | 2.5× | +1.3 | Strong sky contrast, good for landscapes |
| Orange (No. 21) | 4×* | +2 | Strong sky darkening, dramatic clouds, reduced haze |
| Red (No. 25) | 8× | +3 | Near-infrared effect, black skies, stark white clouds |
| Deep red (No. 29) | 16× | +4 | Extreme contrast, infrared-like, technical use |
| Yellow-green (No. 11/X1) | 4× | +2 | Strong foliage separation, darker skies than yellow |
| Green (No. 58) | 6× | +2.6 | Maximum foliage brightness, deep tonal separation |
| Blue (No. 47) | 6× | +2.6 | Increased haze, lighter skies, mist enhancement |
| Polariser | 2.5× | +1.3 | Reduced reflections, deeper skies (1.5-2 stops typical) |
| UV/Haze | 1×* | +0 | No exposure change, reduces UV haze, lens protection |
Important: Factors are approximate
Filter factors vary significantly based on several factors:
- Film type: Panchromatic films (most modern B&W) respond differently than orthochromatic films (like Ilford Ortho Plus)
- Film brand: Each emulsion has unique spectral sensitivity — Tri-X responds differently to red than HP5+
- Light source: Tungsten vs daylight vs fluorescent all affect filter compensation
- Filter brand: Two "Yellow K2" filters from different manufacturers may vary by 0.3–0.5 stops
Factors without an asterisk are Kodak's published daylight factors for TRI-X 400 (Kodak F-4017, Wratten gelatin filters); No. 29 is Kodak's figure for TRI-X 320 sheet film. Factors marked * come from Fujifilm's Acros II datasheet (daylight); other charts give about 3 for the No. 21 orange. Other films differ: always check your film's datasheet and bracket important shots.
Understanding filter factors
Coloured filters work by absorbing some wavelengths of light while passing others. In black and white photography, this changes how different colours render as grey tones:
- Filters lighten their own colour and darken complementary colours
- Yellow/Orange/Red progressively darken blue skies and increase contrast
- Green lightens foliage and improves outdoor skin tones
- Blue increases haze and atmosphere, lightens skies
The filter factor tells you how much to increase exposure. A 2× factor means double the exposure (open up 1 stop), while 8× means 8 times (open up 3 stops).
Panchromatic vs Orthochromatic
Panchromatic films (Tri-X, HP5+, T-Max, Delta, etc.) are sensitive to all visible colours including red. The factors above are calibrated for these films.
Orthochromatic films (Ilford Ortho Plus, Rollei Ortho 25) are insensitive to red light. Red filters have no useful effect, and orange filters will have drastically reduced effect. Yellow and green filters work normally.
Track your filter usage and exposures with Silverlog
Coming soon