[argyllcms] Re: CCT of a Speedlight
- From: Jack Hogan <jack.hogan77@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sun, 11 Jul 2021 08:15:49 +0200
2) Reportage. <
This is an interesting question, I often wonder about this in Landscape
situations with natural illuminants: given such a setting, is there a
practical way to estimate the white balance that the Human Visual System is
applying internally? E.g. take a picture of a gray card placed where the
eye would be from the approximate direction that the eye is looking at?
On Sat, Jul 10, 2021 at 7:46 PM Ben Goren <ben@xxxxxxxxxxxxxxxx> wrote:
On Jul 10, 2021, at 9:59 AM, ternaryd <ternaryd@xxxxxxxxx> wrote:
Does this mean that the CCT of a
typical flash is actually that cool?
I’ve found CCT to not be all that useful in photography. Its best use is
in marketing of consumer household lightbulbs, where it gives an
easy-to-understand expression of what sort of “look" / “mood” the light
will create.
Two light sources with radically different emissive spectra can have the
same CCT. A fun experiment would be to find (or construct) such a pair and
set them up in side-by-side viewing booths. The neutral patches of a
ColorChecker would look “close enough” the same as likely wouldn’t make a
practical difference, but the rest of the patches would be radically
different. You could have some fun, covering and then revealing the colored
patches. I imagine an exhibit like this can probably be found in a science
museum somewhere.
There are three broad approaches to color in photography that pretty much
everything can be classified into:
1) Colorimetrically accurate representation, such as with fine art
reproduction. You need a fairly smooth illuminant with no significant
spikes nor dips in its spectra; then, the math works well to translate
(using ICC profiling) everything to D50. Good studio flashes are moderately
spiky, but still smooth enough for this to work well. Consumer compact
fluorescent bulbs aren’t. “Hot” lights (plain ol’ tungsten bulbs) are
superlative, provided you can get enough light on the subject without
starting a fire.
2) Reportage. A photographer at a concert wants to capture the mood of the
light as a faithful rendition of the experience of being there. In this
setting, white balance becomes all but meaningless. If the performer is
wearing a giant 18% gray card but standing under a purple spotlight, you
technically “should” balance the color such that the performer’s outfit is
gray. But nobody at the concert saw the outfit as gray; everybody saw it as
purple. (A good approach is to tell the rendering pipeline that the scene
was shot under the same illuminant as your working space (probably D50,
maybe D65).)
3) “Pleasing” color. Many, many photographers aim for “pleasing” color.
There’s some overlap, but a lot of this comes down to style and personal
preference. Typical is to control the light to something in the ballpark of
the photographer’s vision and then creatively apply whatever tools are
available in development to align the photograph with the vision. Note
that, if the light is fully controlled such that the scene as viewed is as
desired, a colorimetric workflow might work best — but it’s typically only
skilled and experienced product and fashion photographers who can control
the light this well.
So…you probably don’t need to worry about the CCT value of your flash.
(For that matter…unless it’s a studio flash on the level of an Alien Bees
Einstein or above, the CCT will change with output power.) If it ever
becomes significant…you’ll know that it has and why.
b&
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