Archived posting to the Leica Users Group, 2010/10/31
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Jeff, you're the one that got it right first
time. It's indeed a problem with the blue channel.
To get good colour balance, with colour film we
needed the correct film type and lots of
different filters. Ordinary household 60w bulbs
were just a nightmare because they emit almost no
blue light. So we had to use filters like an 80A
plus additional blue filter like an 80C or 80B to
get close to neutral, with a 4 stop light loss,
and still have mostly reddish light.
Now in digital you're trying to get neutral
colours at 2250?K, so when you use the white
balance slider you're introduceing 5 or more
stops of blue gain, which makes it look blotchy.
If you actually had 5600?K light to start with,
you'd be fine and have little noise.
If you want to see what your M8 or 9 can do in
low light when the colour balance is 'normal',
take a low light shot illuminated by a maybe
distant daylight LED source, or a 'photoflood'
and put an 80B filter over your lens or gel in
front of the light, or take the picture with the
use of a 100w bulb and put an 80A and an 80B over
the lens. If you do the latter, your exposure
times will go way up, but the imbalance between
the red and blue channels won't be as extreme.
>2010-10-30-22:32:57 Howard Ritter:
>> In answer to your question about the low noise level in bright-light
>> exposures at ISO 2500, here's my suspicion: The amount of noise in a
>> given exposure depends on a number of variables, one of which is the
>> duration of the exposure.
>
>Well, maybe. But I also note that when there's bright light, it's
>usually sunlight, while dim light is often something with a warmer
>color balance like incandescent lights (or candles). When I
>particularly notice noise, it's often when I start with something with
>very little blue energy in it naturally, and try to balance the color
>temperature out to look not-entirely-orange. That requires cranking
>up the underexposed blue pixels, which respond by peppering the frame
>with blue noise.
>
>Or is it some entirely diffrent phenomenon you're talking about?
>
> -Jeff
>
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* Henning J. Wulff
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