Re: [APML] RG200 characteristics. Was: New Images From Last weekend

["bert katzung" <katzung1@home.com>]

Hi Philip and list members:
Your comment about the RG200 spectral sensitivity reminded me of a question
I've been meaning to ask: simply, how to interpret these film sensitivity
curves? For example, for the OIII line (I assume we're talking about the one
at 500.7 nm) and RG 200 , it looks like the sensitivity in the
magenta-forming layer is about 1.7 (log values) and the sensitivity in the
yellow forming layer is about 0.9. If we scan an RG200 negative exposed to
500.7 nm, will it not report a negative-of-green color there of about 2.6
units (sum of 1.6 + 0.9)? So the O III green should register partly in the
magenta-forming layer and partly in the yellow-forming layer. The sum of the
two would be equal to (or better than)  the sensitivity of the cyan-forming
layer  to H-alpha light at 656.3 (about 2.4 units).
Or am I missing something fundamental here?
Bert

Bert Katzung
katzung1@home.com
www.astronomy-images.com

----- Original Message -----
From: "Philip Perkins" <philip@astrocruise.com>
To: <astro-photo@seds.org>
Sent: Thursday, October 18, 2001 10:54 AM
Subject: Re: [APML] New Images From Last weekend


> Michael,
>
> Great shots and well processed.
>
> RG 200 looks very encouraging.  I checked the sensitivity curves which are
> here:
>
> http://www.kodak.com/global/en/consumer/products/pdf/e42.pdf
>
> These curves are very typical for a Kodak colour negative film.  In fact
> they are very close indeed to a lower sensitivity version of PJM-2, PJ400,
> and LE400.  This means some good things and some bad things.  The Ha
> response is very good, which is typical, but the OIII response is very
> poor, which is also typical.  However the OIII response is no worse than
> the 'PJM-2 genre' and your results show that it improves dramatically upon
> hypering (the IC 405 colour looks pretty decent).  The spec says that no
> exposure adjustment is needed for exposures of up to 10 seconds which is a
> sign of good reciprocity characteristics (same as other films in the
'PJM-2
> genre').
>
> This looks to me like a finer grained version of 'PJM-2 genre' films like
> PJ400, LE400, etc, and it looks to me like the OIII response might improve
> even further with hypering than those films.
>
> --Philip
>



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