The Finer Points of Color Correction
By: Lionel Armstrong
Many times when we shoot with color film we get an image that has a blue or orange cast because the lighting was not standard photographic daylight. A correction can be made with a filter. The most common problem is when we shoot indoors with daylight balanced film and we get a dark orange cast to our pictures. Most of the time an 80A Blue filter will correct for the orange tone and leave a bit of warmth to the image. Another common problem is when we shoot outdoors on an overcast day and we get a blue cast over our images. Correcting this with a light warming filter such as the 81B or 81C will give your subject the proper color balance.
*Here is a secret that many people don't know: When your subject is in the shade on a suuny day and only lit by a clear blue sky, use an 85A or 85B filter to correct for the excess blue. Any areas in your image that are in direct sunlight will take on a bright orange color as well!
No filter 85B = Cokin P30
To get an accurate balancing of the light source to your film you can use the Mired System to calculate which filter or combination of filters you need to get "perfect color".
Find the mired number for your light source and film and then subtract the light source number from that of your film and the result is the amount ( positve or negative ) of correction needed. You can then determine which filter will give the desired color shift. Sometimes you might need to use 2 filters to get a more accurate balancing. Just add the mireds together ( paying attention to + or - ) to get the combined value.
An example would be if you are using Daylight color film and the room light is from regular 100 Watt lightbulbs. The calculation of 182-345=( -163 ) shows that you need a correction of negative 163 mireds. By adding the mireds of the 80A and 82B filters ( -131 )+( -32 )=( -163 ) we get the exact amount of correction to achieve a balance with the daylight film. If you want to also have a slight warm or cool cast to your image, you can also calculate this as well.
When using TTL metering, you will not need to make any adjustment of the exposure that is given by the camera. When using a handheld meter you will need to calculate the adjustment in exposure to compensate for the filter.
Sometimes when you are using color print film the lab will correct for a color cast during printing but if you are using slide film you must make the adjustment to avoid the blue or orange cast. Slide film is very fussy about color balance and exposure!
Remember that POSITIVE mireds are orange and NEGATIVE mireds are blue!
The tables below give the mired values for the balancing filters as well as for light sources.
Light Balancing Filters Table
| Kodak Number |
Color | Cokin Number |
Mireds | f-stop Adjustment |
Common Use |
| 86 | +242 | ||||
| 85A | 029 | +141 | 1 | ||
| 85B | 030 | +131 | 2/3 | Using 3200K Tungsten film in Daylight | |
| 85 | +112 | 2/3 | Using 3400K Tungsten film in Daylight | ||
| 85C | 031 | +81 | 1/3 | Using blue photoflood lamps with 3400K Tungsten film | |
| 86B | +67 | ||||
| 81EF | 037 | +52 | 2/3 | Using Daylight film on day of light overcast | |
| 81D | 035 | +42 | 2/3 | ||
| 81C | 028 | +35 | 1/3 | Using Daylight film on day of heavy overcast | |
| 81B | 027 | +27 | 1/3 | Using Daylight film on day of heavy overcast | |
| 86C | +24 | ||||
| 81A | 026 | +18 | 1/3 | Using 3400K photo lamps with 3200K Tungsten film or Using electronic flash with Daylight film | |
| 81 | +9 | 1/3 | |||
| 82 | -10 | 1/3 | |||
| 82A | 023 | -21 | 1/3 | Using 3200K photo lamps with 3400K Tungsten film or Direct sunlight with Daylight film | |
| 78C | -24 | Using blue photoflood lamps with Daylight film | |||
| 82B | 024 | -32 | 2/3 | ||
| 82C | 025 | -45 | 2/3 | ||
| 80D | -56 | 1 | |||
| 78B | -67 | ||||
| 80C | 022 | -81 | 1 | ||
| 80B | 021 | -112 | 2 | Using 3400K photo lamps with Daylight film | |
| 80A | 020 | -131 | 2+1/3 | Using 3200K Tungsten lamps with Daylight film | |
| 78AA | -196 | ||||
| 78 | -242 |
Color Temperatures Table
| Source | Color Temperature (K) |
Mired |
| Setting Sun | 1500 to 2000 | 667 to 500 |
| Burning Candle | 1800 | 556 |
| Household Tungsten Lamps: | ||
| 40 Watt | 2600 | 385 |
| 75 Watt | 2800 | 357 |
| 100 Watt | 2900 | 345 |
| 200 Watt | 3000 | 333 |
| 3200K Photo Lamps | 3200 | 313 |
| 3200K Color Film | 3200 | 313 |
| 3400K Photo Lamps | 3400 | 294 |
| 3400K Color Film | 3400 | 294 |
| Clear Aluminum-Filled Flash Bulbs | 3800 | 263 |
| Clear Zirconium-Filled Flash Bulbs | 4200 | 238 |
| Blue Photoflood Lamps | 4800 | 208 |
| Direct Sunlight | 5000 | 200 |
| Theatrical Arc Lamps | 5000 | 200 |
| Standard Photographic Daylight | 5500 | 182 |
| Daylight Color Film | 5500 | 182 |
| Blue Flash Bulbs | 5500 | 182 |
| Electronic Flash | 6000 | 167 |
| Sky - Heavy Overcast | 6500 | 154 |
| Sky - Light Overcast | 7500 | 133 |
| Sky - Hazy Blue | 9000 | 111 |
| Sky - Clear | 12000 to 20000 | 83 to 50 |