Hi all,
Is there a way to find the corresponding HEX number for a Wratten number? IE what is the HEX color of a 81A filter?
Cheers
Peter
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Hi all,
Is there a way to find the corresponding HEX number for a Wratten number? IE what is the HEX color of a 81A filter?
Cheers
Peter
I don't think there is a simple way to translate them. Filters are subtractive, while the RGB hexadecimal codes for colors displayed on your monitor or similar are an additive color system. What you actually see is dependent on the properties of the light source in both cases.
Additionally, many Wratten filters would not be easily described as sums of CMY or RGB color compensating filters.
81 amber warming series versus 82 cooling series of filters are classified as LB (light balancing) filters. But progressive pure CMY as well as RGB filters are classified under their CC density designations. To complicate things a little bit further, there are somewhat different variations and gradations of the precise definition of these items between older Wratten gel specifications and current filter manufacturers as well as different colorhead gradations. I sometimes have to tangle with the issue because I use true additive RGB colorheads, and can approximate an interpretation between such systems using a good color temp meter, which shows not only Kelvin temp, but LB and CC correction values too; but fine-tuning the results requires densitometry and careful visual evaluation afterwards. I also have some sophisticated instrumentation, but that's not going to be of much help discussing here because it's so specialized.
But it is helpful to get an old copy of Kodak Publication B-3, Kodak Filters for Scientific and Technical Uses. This gives spectrograms and transmission values for every one of the Wratten series, which once included a far bigger selection. But again, what counts is the specific filters you intend to use today, which might differ somewhat from old Wratten specs. I can go to my own filter case and pull out six variations of what an 81A supposedly is, and every one of them is somewhat different in hue by design; quality control issues are a secondary factor, as is fading in old Wratten gel filters.
So I too would recommend placing the priority on practical visually-confirming end results, and not on hypothetical formulas that can't realistically factor in all the subtle variables.
Wratten is simply Kodak’s designation for correction filters that they used after buying Wratten. Most European manufacturers like Heliopan, B+W, Rollei, LInhof, etc. use/used the decamired system for color correction filters. Warming being red and cooling being blue.Quote:
Originally Posted by reddesert
All color films have a mired value as do all color sources. By subtracting one from the other you know which decamired filter you need to correct a given scene.
Unlike wratten filters decamired filters are additive. A KR1.5 and a KR3 make a KR4.5 value. Wratten filters can not do this. An 81A and an 81B do not make an 81C.
Kodak Filters pub B-3 lists CIE x and y for each filter except infrared and near infrared
CIE mapping is still just approximate relative to all the potential variables. There's simply no substitute for fine-tuning any intended end result with a trained eye. I've spent a helluva lot of enough time with very expensive spectrophotometers to learn that lesson. They do save time, but rarely give you a hole in one. And again let me emphasize that Wratten gels are kind of behind the times for todays applications, where coated glass filters might differ somewhat. Hoya, for example, can provide their own specs on demand from their industrial division.
Bob described one difference in conventions. But KR filters also differ from 81 series in being slightly more pink or salmon color;
and then there are other brands like Singh-Ray that once extended that characteristic even a little more. It does make a difference in specific situations, with specific films, but would be an awfully subtle thing to try to quantify. CC filters don't really come in subtle increments. Anything approaching or below cc 05 is likely to be somewhat inaccurately labeled. Continuously variable colorheads can do it more accurately; but an additive RGB head is going to perform somewhat differently from a CMY head no matter how you adjust the settings. I'm curious what you are actually trying to achieve or match.
Thanks for the feedback folks. I use (probably more often than not) a 81A filter when shooting slides... However, there are situations when Id rather not. So out of convenience it would be nice to just be able to 'apply the filter' when post processing. My eye isn't that trained so a matching number would save me a lot of time.
Such corrections are always going to be better if applied at the time of the shot rather than afterwards, and more conveniently done. In the case of chrome film, it's largely a matter of taste. But technically and theoretically, 81 series filters are used to warm up cool or overcast scenes to the rated color balance of the film.
Unlike color neg film, with slides it's very easy to evaluate your results over a good light box.
If it's just one warming/cooling adjustment rather than a general specification for many Wratten filters ... I am not a Photoshop guru, but Photoshop may have an approximation to this adjustment for common filters built in. Look at the second section, "Photo Filter" here: https://helpx.adobe.com/photoshop/us...djustment.html
I agree, usually it is better to apply corrections beforehand. I guess the easiest might be, if you don't do it beforehand, is to adjust the Kelvin. I use PhotoLine instead of PhotoShop and there are no filter presets there :-)