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Re: Artisan Dreams



 Reply to:     RE>>Artisan Dreams
What I have observed is that over the "linear" (whatever that is!) 
area of operation (like normal mid-range stuff), one camera stop 
equates to about, approximately sort-of 10 IRE. But I will admit 
to not being scientific about it.

Tom Leeser, our ex-video opticals director ran a test once with a 
cameraman to this effect and I think those are the results he got. 

I invite you to ask him directly. Tom is now at Rhythm & Hues and 
can be reached at tom at rhythm.com.

-bt


----------------------------
Date: 10-11-95  3:18
To: Topazio, Bill
From: Bob Kertesz

I'd like this as well.  How does one stop equate to FootLamberts, or to IRE?

Theoretically, one stop is twice the light, so should be twice the IRE.

In practice, it's not even close.  

In video production (ie. using a lens), opening up a stop never doubles the
IRE because all that electronics (gammas, soft and hard clips, enhancement
processing etc.) all get in the way.  It is likely that the amount of light
dribbling out the back of the lens doubles when you open the iris a stop,
but that doesn't translate to a doubling of the video on the scope (when
shooting video).  Now it may well result in tickling the emulsion so that
the image on film is twice as bright, but I can't say.  Also, it's not
exactly a linear function, and doubling the light does not appear twice as
bright to the eye.

I presume it must be the same in telecine because most of y'all have those
big green tubes followed by all that endless processing.

My practical experience is that opening up a stop while shooting results in
roughly a 50% increase in IRE levels, and I would imagine it's not
dissimilar in telecine.

Your mileage may vary.

--Bob             bob at bluescreen.com


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