TAKO. INTERNET SEIT 1996.
Olympus-OM

[OM] Re: SLIDE DUPLICATING - 5000ºK LIGHTBOXES w ith OLYMPUS E-1

Subject: [OM] Re: SLIDE DUPLICATING - 5000ºK LIGHTBOXES w ith OLYMPUS E-1
From: "Jay Drew" <dreaded@xxxxxxxxxxx>
Date: Tue, 28 Aug 2007 07:58:11 -0700
>> According to my Minolta color meter (which could probably use 
>> a calibration) my Gagne Porta-Trace puts out 5000K to 5250K 
>> depending on where you measure it from.  But as Wayne points 
>> out there is a green factor to be accounted for.
>> 
>> This particular flourescent source would need a 10M filter.
>> 
>> Of course this is from a guy who is color deficent in 
>> Red/Green and can use all the artifical help he can get.
>> 
>> Jay - Who's non-calibrated meter is probably more accurate 
>> than the owner's rods and cones.
>> 

>Most colour temperature meters make 2 measurements through a red and a blue
>filter and the ratio of these 2 measurements is used to infer the colour
>temperature.  This will obviously generate some value for colour temperature
>for any light source, however it will only be meaningful if the light source
>has the spectrum of a black body radiator (e.g. sunlight, tungsten lights).
>I'm not even sure if it will be accurate for flash.
>
>...Wayne

This particular meter, a Minolta Color II, does have 3 cells, so that's how it
got the value to indicate this light box would need a 10M filter.  And this
meter can't handle flash, it needs a longer duration light source.  

But now for a digital neophyte question.  I see cameras that have multiple white
balance settings.  So if you select fluorescent, does it do some adjustment for
the green spike?  For that matter when you select a custom white balance, does
it adjust for RGB or just Red and Blue?

And back to the original purpose.  If the E1's white balance CAN compensate for
the green spike, couldn't Dave illuminate a white paper with a light box, lock
the compensation for that then use that source to light up the IT8.7 slide?  Or
am I missing something here?

Jay

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