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Re: [OM] Vivitar 2x-teleconverter for Hasselblad: RESULTS

Subject: Re: [OM] Vivitar 2x-teleconverter for Hasselblad: RESULTS
From: "C.H.Ling" <ch_photo@xxxxxxxxxxxxx>
Date: Mon, 16 Mar 2009 23:40:36 +0800
----- Original Message ----- 
From: "Moose"
>
> C.H.Ling wrote:
>
>> I remember I have seen someone mentioned here that resize does not reduce 
>> noise, I'm not sure if it is true.
>
> I've certainly said here that it doesn't "necessarily" reduce noise. In
> practice, my experience is that sometimes it does reduce apparent noise,
> sometimes not, and occasionally, it seems to make it more objectionable.
> I've no theoretical knowledge, but have noticed the effect of down
> sampling on noise seems to vary with the nature of the noise and the
> amount by which the image is being down sampled.
>

I have similar experience, sample down an image usually will not reduce the 
noise.

> There are so many variables involved, especially with film scanning, tha
> most of us have only a limited sample of the real world variation. You
> and I both scan @ 4000 dpi, but with both different scanners and
> different software. Even with the same piece of film, some
> characteristics of both grain and scanner noise will differ.
>

I believe the light source made some difference, Nikon uses LED which 
enhance the grain more.

>
> One difficulty with NR like this is that our eyes, at least mine, tend
> to interpret the noise reduction as a loss of fine detail. The edges of
> the grain tend to make things look sharper. In this case, even if a tiny
> bit is lost, it doesn't matter, as the whole point is to prepare for
> down sampling.
>

This is normal, long ago in the film age I heard people will found the image 
sharper for high speed film where there are stronger grain. For film images 
NR do reduce the details especially for the low contrast one and the fine 
texture on the clothes.

C.H.Ling


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