[Leica] CS2 and noise reduction.

[douglas.sharp at gmx.de (Douglas Sharp)]

Hello Ted,
Most of the noise problems are, IMO, something that won't bother anyone 
who's just wanting to look at a good print, a grainy BW shot is good too.
The problem people have with digital noise is when it's "coherent" i.e. 
ordered or produces patterns, non-coherent or random noise shouldn't 
really bother
anyone much, it's a fact of life , just like film grain.Then again there 
are those people who swear by film who insist on finding something wrong 
in a digital image, on the other hand, there are a lot of pieces of 
digital equipment that produce utter rubbish when pushed beyond their 
limits.

Noise reduction just flattens the bumps and fills in the gaps and 
smooths out, like plastering a pebbledash wall. Just use enough plaster 
to hide the single pebbles and  retain the structure, - use too much and 
the details disappear and look flat. If you're up close it's structured, 
at 10 metres it's flat.
The right kind of processing which can recreate the ordered/patterned 
noise (recognise your enemy) should be able to simulate and reverse the 
process which made the noise in the first place (technically: 
frequency/wavenumber filters or FK-filters) The noise "problem", if it 
is one, comes with the randomised stuff that doesn't fit in any pattern 
and overlays the actual image content (data or signal - which is those 
little bits of picture we call pixels, just like grains on a film, only 
on a fixed grid or net) separating the content from the interference 
(noise) becomes more difficult and takes a lot more clever 
processing/programming effort.
At the end of the day the removal of "noise" or better, interference 
(Random Noise Attenuation or RNA for techies) never works perfectly, 
just like trying to get rid of the hiss on a distant radio broadcast.As 
far as it goes  it's like trying to remove the fog from an autumn picture.

The most dangerous tweak in processing digital (and scanned stuff) is 
still sharpening, the second is noise reduction both are often overdone- 
So,if it ain't broken, leave it alone. But, unfortunately, as with other 
technical stuff people tend to think that because it's "state of the 
art" or "cutting edge" it must be good, and if it's not perfect straight 
off it must be corrected. Just like people who put salt on their dinner 
before having tasted it.
Or just ask someone with a digital watch - 95% of 'em are conviced it's 
showing the right time, even without checking against the "pips" on the 
radio.
cheers
Douglas

Ted Grant wrote:

> It would be great if in simple language some one will explain this 
> question. Considering this is a question from the dimwit level.
>
> Please explain how some of you people have a noise problem and I've 
> only seen it in a few picture situations where I suppose I pushed my 
> luck in almost available darkness situations and near blew the shot?
>
> I'll tell you what really really ticks me off no end is, to have some 
> techie guy look at one of my 13X19 colour photographs shot by 
> available window light, soft gentle beautiful light, a portrait type 
> photograph of a young lad like many of us shoot. And jaw on about 
> "noise" here, there and a few other places in the print. And for the 
> life of me I can't see what the hell he's talking about.
>
> Now he's looking at the print from maybe 6-8 inches away, for the life 
> of me I try my hardest to see and understand this stuff because I 
> really did want to learn from this fellow. But all he did was royally 
> piss me off no end with his "noise poppy cock numbers and meaningless 
> words nonsense!"
>
> I took the print from him, held it at a normal viewing distance for 
> it's size and asked a simple question. "How does it look as a 
> photograph?" His immediate response, "Oh my gosh it's a beautiful 
> photograph!"
>
> My response... "So what's all the bull shit about noise viewed at 6 
> inches
>
>> from the print if you're so impressed with the photograph viewed at a 
>> proper 
>
> distance for size?"
>
> His response?.......... no answer! He either didn't know or appeared 
> more than embarrassed! I opted for just another numbers guy!
>
> So OK already, what's with the noise stuff? I know it's supposed to be 
> found in dark areas, but if you shoot it correctly in the first place, 
> why would there be any screwing around trying to get rid of something 
> you can't see unless yer 6" inches or less away from the print?
>
> Be nice now, I'm not trying to be a smart ass, I really want to know 
> about this noise thing because quite frankly I've yet to see what the 
> heck you are talking about. Well Ok I suppose in a couple of badly 
> printed photographs where I over tweaked it without knowing what I was 
> doing. Like under what conditions do you see this quite obviously?
>
> Remember, keep it simple as though you're speaking with someone who 
> only understands this is a computer screen, not a TV set. ;-)
> ted
>
>
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