I promised another member I'd stop posting while sober as I tend to write books--sorry in advance...
There are variations of color temperature expressed by different filters--both optical (lens) filters and digital filters. In my film days, I noticed that B+W filters warming series (81 A,B,C etc) have an amber color cast. Pentax warming filters labeled "cloudy" have a more rosey color somewhat like a darkened skylight filter color. I shot everything through the highly preferable Pentax cloudy filters. I've since compared Tiffen, Hoya, Kalt, B+W, Heliopan and Pentax warming filters, and they all have their own signature color cast.
Digital software from one company to another seems to have similar variation. Though I don't have the thorough comparison notes, nor the experience that I have with glass filters. Not everybody warms a scene the same way. So you'll probably want to compare exactly what different software does for you.
Note that the in-camera white balance does not set a fixed color temperature. I tested this thinking if I use the in-camera "cloudy" setting or "daylight" setting or whatever that the setting would produce a definite color cast determined by the processor and external filters affixed to the lens should have no impact---WRONG! When I add my beloved Pentax Cloudy filter to images shot at the daylight white balance setting, low and behold, there is a warming effect. Cloudy white balance with Cloudy filter and the warming effect is amplified quite noticeably above and beyond the in-camera warming alone. The double cloudy effect is not good and I'm struggling with this issue since every piece of glass I own, including Hasselblad Xpan lenses all are equipped with Pentax Cloudy filters.
I've just started playing with the 5000K white balance setting which is the theoretical "neutral" point. Last weekend I was trying to get accurate color rendering of light pink wild blueberry blossoms and the only white balance setting that retained the subtle variations in pink colors was the 5000K setting. Now that would theoretically eliminate the effect of external filter colors, but I haven't tested yet...
To wrap this book up...there are actually three different filtering methods--optical which are traditional glass or resin filters; in-camera both for white balance and for special effects; and post processed filtering. All have their place and just like the outdated "debate" of film vs digital, it just doesn't matter. Use what works for you!
Last edited by Ron Boggs; 06-03-2008 at 07:12 AM.
Reason: wording