Photo Filter – technical question

DR
Posted By
Douglas_Rhiner
Aug 9, 2004
Views
260
Replies
7
Status
Closed
Question:

How did the Photoshop team come to the color combinations to create the various preset filter colors in the Photo Filter dialogue in CS?
I.e.: for the Cooling Filter (80) a color mix of L(45),A(18),B(-123) Is there some formula/guideline?

What spurs this line of questioning is my INSANE desire to be able to create SPECIFIC filter colors to combat SPECIFIC color problems. Yes there could be "easier" workarounds but I’m dealing with very specific and targeted color problems.

I’ve put out a question to other forums that goes like this;

"I’m seeking information regarding color temperature compensation post-production.

I.e. if I take a picture in uncontrollable lighting conditions, gels can’t be used, but know the color temperature of the film and take a color temperature reading during the shoot, is there a formula or guidelines as to how to compensate for the off color temp. of the lighting so as to "match" the temp. of the lighting to the temp. of the film?"

The above question is a bit general, but it was intended to hpefully find a formula for microreciprocal degrees(Mired) shift.

ANY help on this subject owuld be greatly appreciated!

-Doug
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CC
Chris_Cox
Aug 10, 2004
Measurements of several real filters (concluding that there is no standard because they vary too much across brands), then extrapolating to get a saturated color.

In uncontrolled lighting conditions, you’re probably hosed.

If you get different light temperatures in the same scene (or worse, mixture of light types) it’s near impossible to correct.

If you’ve got a single light type and temperature (like the sun) – then ACR can do a really good job of correction.
AW
Allen_Wicks
Aug 11, 2004
Shoot digitally and save RAW… 🙂
Z
Zeb
Aug 11, 2004
Use a grey card or colour chart in some of the photographs.
AS
Ann_Shelbourne
Aug 11, 2004
If you get Kodak’s handbook on Filters, you can look this up.

Accurate calculations for which CC filter that you need for light of a particular, and measured, Color temperature in relation to a particular film stock are based on "Mired Shifts".

Photoshop’s Photo filters emulate a few of Kodak’s extensive range of Wratten Filters.

When exposing daylight film under tungsten lighting you would use one of the bluish filters such as the 80A.
When exposing Artificial light film under daylight lighting you would use one of the orangey filters such as one from the the 85 group.

You just have to use your best judgement when using Photoshop’s filters on uncorrected original shots.

And if you originally shot under mixed light sources, you will just have to correct surface by surface—if you can.

The colored Photoshop Photo Filters do not work in the same way as their real world counterparts which are used for tone-correction on black and white film.
CC
Chris_Cox
Aug 12, 2004
Ann – Kodak’s measurements aren’t very accurate. I’ve got the book.
P
progress
Aug 12, 2004
unfortunately its very rare to have a single light type, because of the effect of irradance from other objects…

had hoped when i heard about the feature that it would do a little more than dump colour into the shot and would hold white points whilst handling the warming/cooling of the shot but retaining correct colour balance in shadows.

think i should know by now that often filters proclaiming to do wonderful things in one trick are false prophets…
TL
Tim_Lookingbill
Aug 12, 2004
Stanly Kubrick neutrals in 2001 and Ridley Scott’s Alien as apposed to the bluish shadow filter foggy’s in James Cameron’s treatment and now prevalent in all action flicks like Resident Evil.

I can’t stand it and I have an aversion to movies that use it for dramatic affect. I’ll be glad when they stop using it.

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