[argyllcms] Re: Feature request (and an implied question)

  • From: "Gerhard Fürnkranz" <nospam456@xxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 26 Jul 2010 18:01:36 +0200

-------- Original-Nachricht --------
> Datum: Sat, 24 Jul 2010 12:10:04 -0700
> Von: Ben Goren <ben@xxxxxxxxxxxxxxxx>
> An: argyllcms@xxxxxxxxxxxxx
> Betreff: [argyllcms] Feature request (and an implied question)

> spotread -a -v already shows ambient light levels in lux. Would it be
> possible to also show light levels in EV units?
> The conversion (for ISO 100) is:
>      EV = log2(lux / 2.5)
>     lux = 2.5 * 2**EV
> The implied question, of course, is, ``Does it make sense to calibrate a
> lightmeter by making it match the measurements made by Argyll with an i1 Pro
> in ambient mode?'' I can't imagine why not, but...

One issue to consider is that readings from different light meters are only 
comparable if they have the same directional characteristics. I think the i1 
has a light measurement head with a cosine response, while many light meters 
intended for photographic purpuses have different directional characteristics 
(e.g. hemispherical), see also http://en.wikipedia.org/wiki/Light_meter


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