[argyllcms] Re: CCT of a Speedlight
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 10 Jul 2021 10:46:02 -0700
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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