i saw this in another section, thought i would repost here. i am curious to hear from Doug of CI hopefully and other technical specialists on this technique vs. color correction in C1 etc.
From iPhone...
If your goal is the highest possible quality then correct by lens filter wheneve practical. Keep in mind the lens filter cuts light and therefore makes it harder to focus/compose/hand-hold; sometimes it's just not practical. Also there are many situations in which you don't want to "correct" away warmth; a neutral sunset kinds misses the point!
You shoot landscape so tungsten doesn't come up for you very often, but I'm going to use tungsten as my main example because it's where the question most commonly comes up with our clients.
Setting the white balance away from the sensor's native daylight range inherently means pushing one channel and pulling another. So if your light source is warm (low kelvin; e.g. Tungstun) and you want to produce neutral tones in the final image then without a lens filter you will be pushing the blue channel and therefore increasing blue channel noise and decreasing it's shadow detail while decreasing highlight detail on red subjects (which makes for terrible skin tones).
The extent to which this meaningfully reduce image quality depends on
1) how much you are shifting the white balance (e.g. 500 or 2000 degrees)
2) the dynamic range of your system
3) how well exposed and what ISO the image (which establishes the baseline of noise)
4) whether your camera has a profile specific to the light source e.g. Phase produces a tungsten color profile (not the same as a tungsten white balance) for each of its digital backs.
So a modern digital back can "recover" from uncorrected tungstun light much better than a entry level dSLR.
This is why it's often said that digital backs deal with mixed lighting much better than other options; with more fidelity per pixel more dramtic local color changes can be made without introducing excessive noise.
Doug
Captureintegration.com