Cinematography Mailing List - CML

Mired Shift For Coral Filters

A little question.

I try to know if there is a coral filter which make the same mired shift made by a regular 85 filter. I was told that is the coral #5, but I would like another opinion. Is it #5 from Tiffen or another brand?

For each strength from the coral filters, is there a given mired shift?

Please help me with this little problem. I can't actually verify this with a color temperature meter and the filters, for the moment.

That's why I am asking you.

Thank  you.

Thomas Cousin

The Tiffen Coral filters and the Schneider Coral filters are color effect filters and are not graded for color correction.

The original Harrison and Harrison Coral filters are correction filters and a "#5" Harrison is often considered the equivalent of an 85. The mired shift of a Coral #5 is actually 150 points and a #4 is 130 points. There is also a Harrison blue series for correction and both correlate directly to mired shifts.

Tiffen makes what are called Decamired Filters, which are graded and numbered according to their color and decamired shift, ie. R1.5, R3, R6, R12, B1.5, B3, B6, B12. In this system the R12 is equivalent to a +120 mired shift.

Hope that helps.

Best Regards,

Anders Uhl
The DoP Shop
9 West 14th Street
Huntington, NY 11746

Tom Cousin wrote :

>"...if there is a coral filter which make the same mired shift made by a >regular 85 filter."

Anders provided some good information. I'll add here a list of Tiffen Corals and their (nominal) mired shift values:

Coral 1/8 -47
Coral 1/4 -62
Coral 1/2 -70
Coral 1 -86
Coral 2 -106
Coral 3 -133
Coral 4 -144
Coral 5 -169
Coral 6 -195
Coral 7 -234
Coral 8 -298

The visual color of our Coral 5 comes closest to that of the 85B; our Coral 3 is closest in appearance to the density of the 85. In both cases, though, the actual mired shifts of the Corals are somewhat greater than the equivalent visual values would indicate. The Coral 3 is almost the same mired shift as the 85B; the Coral 2 is very close to the 85.

The differences in color vs. mired shift relate to the fact that our Corals were not designed to have the same spectral distribution as the 85- they were to allow for a varied range of densities that closely followed the visual differences in sunlight throughout the day.

Ira Tiffen
The Tiffen Company
Hauppauge, NY 11788


A History of the Coral and Blue Light Corrector Discs :

In 1938 the coral, or coralite and blue, or bluelite filters as they were called then, were developed by Harrison in conjunction with the Harrison visual color meter to compensate for the different colors of light such as daylight, late afternoon, photoflood, tungsten, etc., used in color photography.

To arrive at the steps of coral density, a long coral wedge was made with mechanical marks on the edge like a ruler so that by sliding the wedge in front of a camera and taking pictures in short intervals, the pictures that showed a color difference was considered a step and this density of color measured to make a filter number - originally from C-1 to C-8. The color filters compensated for excess blue from the film balance and the blue filters compensated for an excess of red from the film balance according to arbitrary readings on a visual color meter.

Later when the series was calibrated in degrees Kelvin, and correlated to a visual color temperature meter - reading in both degrees Kelvin and the filter number, the series was extended to from C-1/8 to C-14.

Since they have been the most complete range of color temperature filters available, over the years they have been used in combination with many different color temperature meters for color temperature correction.

Recently however, with the advent of giving pictures a warm or old time look, they have been used for that purpose since the range of the same color enables the same warming effects on different color balance films.

For example : a tungsten 3200K balanced film with 3200K light would only need the light C-1/2 to C-4 range to warm up the picture - whereas the same film on exteriors would need a C-6 to C-9 to add the same amount of color as the C-5 would be needed to match the film to daylight. The only way the same amount of color can be added consistently therefore, is to measure the color temperature of the light for film balance, as a light; bluer than the film balance, a 3200K film in daylight for example, can offset several steps of coral just to balance the film and not add any warming effect at all.

The Harrison light corrector disc chart shows the light balance for each film in degrees Kelvin and what filters to use if it is not in balance.

With the light balanced for the film being used, the coral filters will add the same amount of color each time - and this amount is up to the judgment of the photographer, as it is an artistic amount rather than a scientific amount - the C-1/2 to C-5 being a medium color range for films that are light balanced, and the C-6 to C-9 for special heavy effects, or to color balance the film and then add color.

Best regards,

William Harrison
Harrison & Harrison Optical Engineers, Inc.

I once worked with a Cameraman many years ago, (geez I find myself saying that more and more lately,) who would decide upon a color temperature he wanted to work at. 2800 or 4200 or whatever effect he wanted to produce. He had a huge assortment of Coral and CC Blue filters.

For exterior work, he then would take his color temp meter and apply the appropriate filters to achieve the desired temp. As the sun changed throughout the day, he would adjust the filters to maintain the consistent Kelvin temp. Pretty ingenious, but lugging around the hundreds of filters got to be a bit of a pain (literally).

Ed Colman - SuperDailies
Cinematographer Supervised Video Dailies

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