*From*: Matthieu DUBAIL <matthieu.dubail@xxxxxxxxx>*To*: argyllcms@xxxxxxxxxxxxx*Date*: Fri, 11 Feb 2011 14:32:40 +0100

> > It has very limited accuracy, due to the spectrometer sampling rate. > That's what I tought. Do you know if an Eye-One has a better sampling rate? Appart from that, the -h high rez is a pretty badass feature for testing light sources. It seems to me that the brightness measured by the instrument will depend > on the distance to the flash. That distance should be in your formula > somewhere. > So somewhere there should be a target of a given number of Lux seconds > to get proper illumination at a given distance, f number and ISO 100 > sensitivity. > > If you measure the actual flash output, you should then be able to use > the distance scaling to compute the guide number. Actually Ngn is the distance. So there should be a simple multiplication factor of the whole formula. > Typically there is a factor of pi to convert between cd and Lux (due to > the assumption of 180 degree angle). What exactly is the constant k's units > ? > You need to get the units to match. > I reread the whole paper, pointing out several aspects that doesn't seam very clear. I made several jpg of this reading as attached files. I'm really stucked on this calculation. Damn...

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**References**:**[argyllcms] Spotread -f and flash Guide Number calculation problem,***From:*Matthieu DUBAIL

**[argyllcms] Re: Spotread -f and flash Guide Number calculation problem,***From:*Graeme Gill

**[argyllcms] Re: Spotread -f and flash Guide Number calculation problem,***From:*Matthieu DUBAIL

**[argyllcms] Re: Spotread -f and flash Guide Number calculation problem,***From:*Graeme Gill

- » [argyllcms] Spotread -f and flash Guide Number calculation problem, - Matthieu DUBAIL
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Matthieu DUBAIL
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Matthieu DUBAIL
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Graeme Gill
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Matthieu DUBAIL
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Matthieu DUBAIL
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Iliah Borg
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Graeme Gill
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Matthieu DUBAIL
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Iliah Borg
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Matthieu DUBAIL
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Matthieu DUBAIL
- » [argyllcms] Re: Spotread -f and flash Guide Number calculation problem, - Matthieu DUBAIL