Re: Colorsync-users Digest, Vol 2, Issue 504 -capture and printing noise
Re: Colorsync-users Digest, Vol 2, Issue 504 -capture and printing noise
- Subject: Re: Colorsync-users Digest, Vol 2, Issue 504 -capture and printing noise
- From: "Stefan Steib" <email@hidden>
- Date: Tue, 20 Dec 2005 10:54:06 +0100
David (and list)
I´m kind of astonished about the answers you got here. I would have expected
at least someone of the Cameraback manufacturerers
to jump in, but they didn´t. Soooo.......... here we go:
Forget about the cameraback as a photographic equipment. Try to think of it
as a sensor to waves and as a signal to noise amplifier.
When you put a daylight spectrum of lets say 6000 kelvin at this sensor, all
the 3 wavelenghts of red , green and blue are
giving energy to the sensor in an equal relationship. This is the
relationship the sensor is manufactured for and calibrated to.
If you use flash or HMI lighting this will stay roughly the same. Every one
of the 3 channels is amplified in a signal to noise ratio
which he was build specified for.
Now- if you use Tungsten Lighting, no matter how bright it is (and thats
something that looks completely different for your eyes because our brain
compensates the difference) the spectrum of the used light is completely
shifted into the red, lacking most of the emission in the blue,
nearly the same applies to the green channel. After a whitebalance the
cameraback now acts as a channel amplifier and has to increase
x-times of signal to noise ratio of the blue channel so that it reaches
equal dense channel information as with a daylight spectrum.
while this may not be as much apparent while shooting with 100 ASA(though
its exactly the same effect), at 400 ASA this is intensified by a factor of
16 !
Means when your red channel has a signal to noise factor of lets say 1:100,
the green already goes down to 1:12 ,the blue is down to 1:6.
Now you can imagine that actually you shoot your cameraback at 1600 ASA in
the Blue channel......................no wonder there is noise!
The only way to get over this is to use a blue compensation filter for
tungsten.............well nothing new, as with film this was exactly the
same.
Anybody remembers these funny pieces of rolled plastic that were put into
cameras....................<GGG> ???
I would propose to the list members, to remember what you all have learned
in theory(?), back in those (good?) old days....................
Greetings from Munich
Stefan Steib
Gabelsbergerstr.48d
D-80333 München
tel.: +49 89 520 59 305
fax: +49 89 520 55 778
www.digitalfoto-trainer.de
Message: 1
Date: Mon, 19 Dec 2005 13:03:26 -0800
From: email@hidden
Subject: digital capture and printing - noise
All -
Looking at digital capture - I have recently had the opportunity to use
both the Phase One P25 and the Leaf Aptus 22 Digital backs. Shooting in
incandescent light (a 1K hot light), I notice that even when using a grey
card for color correction, there is significant noise in the shadows when
shooting at 400 iso.
This is apparent when printing via RIP or printer driver to the HP 130 or
the Epson 9600, using either "canned" profiles or profiles I have made
myself. As I do not see nearly as much noise in the shadows when shooting
daylight color temp, or when using daylight strobes, I was wondering if
anyone can shed some light (arrgh) on this issue - and suggest corrective
action, either in capture or print phase.
Thank you,
David Saffir
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden