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RE: [APML] RG200 characteristics. Was: New Images From Last week
Good Morning,
I have tried hypered LE400 and E200 Blended before. I like the grain reduction
on the LE400 with the E200, but the M27 image seems a little too red...
Please see:
http://home.stny.rr.com/apilato/m27.html and
http://home.stny.rr.com/apilato/m51.htm
Tony P.
Binghamton NY
www.darkstarimages.com
> Philp,
>
> I'm still pretty new at this (mostly just shooting some film and reading and
> learning from you guys), but would it be possible to composite a good OIII
> film (e.g., NHG) with a good Ha film (e.g., E200) and then correct the
> colors in the final product. I've been toying with idea of trying this (it
> might be easier than getting Kodak and Fugi together), but I don't know if
> it would be worth the effort. Any thoughts? Thanks again to you and others
> who are willing to share their knowledge here.
>
> Frank
>
> -----Original Message-----
> From: Philip Perkins [mailto:philip@astrocruise.com]
> Sent: Thursday, October 18, 2001 8:02 PM
> To: astro-photo@seds.org
> Subject: Re: [APML] RG200 characteristics. Was: New Images From Last
> weekend
>
>
> Hello Bert,
>
> I think I understand what you are saying. In the case of 656.3nm it's only
> quantity that matters, because the whole of that spike can only fall in the
> red (cyan forming) layer. It can only evoke a response in the red
> layer. But in the case of the 500.7nm spike it is more complicated because
> that does not fall right in the middle of one of the colour forming
> layers. In fact it falls almost exactly mid way between the blue and green
> layer. So if the film is responding correctly, that 500.7nm spike should
> produce a colour that is mid way between green and blue (sort of 'aqua
> marine' or whatever you want to call it:-) but if you look at that curve
> for RG 200 again...
> http://www.kodak.com/global/en/consumer/products/pdf/e42.pdf
> .... you can see something wierd - that 500.7nm spike will produce a
> response that is almost wholly in the green with very little blue. It will
> produce a predominantly green colour, and when green is mixed with red
> (656.3nm) it produces a colour that veers towards the yellow (minus blue) -
> in other words Ha regions that are orangey-red. That's simply wrong and is
> very typical of Kodak films. If the 500.7nm spike produced the correct
> blue-green colour then, when mixed with the red, it would de-saturate it,
> producing a pinkish red. That is correct, and it is the colour that we see
> from tri-colour work, both CCD and film.
>
> So it is not just a case of quantity with the 500.7nm spike - you can't
> simply add up green and blue, and because the total is OK, say that the
> response is correct. In this case it's also the quality that's critical -
> the _relative_ quantity of green and blue response. And as mentioned
> above, they should be about equal.
>
> OTOH Fuji films often have a good OIII response and in the case of NHG II
> 800 it is terrific. See here (scroll down the
> page): http://www.astrocruise.com/xppfvnhg.htm But just as if to deny the
> astrophotographer his perfect film, these films often have a weak Ha
> response, as is the case with NHG II 800. The exact opposite of the Kodak
> problem! If only Kodak and Fuji could get together... there is no doubt
> whatsoever that technology exists to produce an astro film with perfect
> characteristics.
>
> (Much of the above owes nothing to me and everything to Chuck - I hope I
> have it reasonably correct)
>
> --Philip
>
>
> At 14:21 18/10/01 -0700, you wrote:
> >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
> > >
> >
> >
> >
> >-- APML Archives at <http://astro.umsystem.edu/apml/> ---
> > Unsubscribe at <majordomo@seds.org>
>
> Philip Perkins - philip@astrocruise.com
> Wiltshire UK & Luberon France
> Astrocruise - http://www.astrocruise.com
>
>
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