Re: [Rollei] Incident v. reflective

[Bob Shell <bob >]

Funny, I just got Jerry's response to Dirk-Roger, but never got D-R's
original note.  Anyway this below is addressed to both:


on 4/12/02 5:34 PM, Jerry Lehrer at jerryleh   wrote:

> RUGers
> 
> Well, I see that Dork-Roger has not read or understood
> Ansel Adams or Minor Whites books on the Zone System.
> 

Jerry, unless that's an accident I find making fun of someone's
name very rude.

> All this self-abuse type of testing means naught without an
> appreciation of the Zone System.  (Yes, the theories of the
> Zone System CAN be used for color transparencies).
> 

You don't need to know anything about Zone System, per se, just some basic
notions of sensitometry.

>> 
>> Bob, now I am getting more confused and more crazy......
>> 
>> I have a new "Non Kodak Grey Card" from "Bildwand". The benefit of that is
>> that it is made of plastics and is washable. The Sun fading resistance is
>> given with 7-8 on the "Blauwollskala" (translated: blue wool scale)
>> whatever that means. The reflectance is specified to be 17.68 % without
>> giving tolerances.
>> I made now, just a few minutes ago the followign test:
>> 

Throw that thing away and get a real Kodak Gray Card.  The plastic ones I
have seen have a surface that is too shiny and it messes up their
reflectance.

>> 
>> My questions: Where is the reason for the discrepancy between the Gossen
>> and the camera world?
>> 

The Gossen is broken?

>> And Bob: What is the reason to give half a stop more? Which types of meters
>> are calibrated to 12.5 %? Could it be that the camera meters are calibrated
>> to 12.5 % and the Gossen meters to 18 %?

All meters are supposed to be factory calibrated to 12.5% reflectance, the
international standard.  Last time I did some work with them Gossen was
using this same standard.

>> I thought, the idea of the grey card ist just to measure it and to expose
>> like the measurement on it.
>> 

No.  The Gray Card is just a standardized reference.  You could use a white
card or a black card so long as you made the proper compensation.  The
compensation for an 18% card is half a stop.

>> 
>> Look at my measured values for the 6008!!!  Here, the discrepancy to the
>> Gossen world is one stop.
>> 

I'd trust the Rollei.

Bob

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