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Re: Determing true resolution of an image? [message #29589 is a reply to message #29572]

Tue, 05 March 2002 15:06

Martin Downing
Messages: 136
Registered: September 1998

Senior Member

"David Fanning" <david@dfanning.com> wrote in message
news:MPG.16eecdf16f798ad3989831@news.frii.com...
> William Connolley (wmc@bas.ac.uk) writes:
>
>> I'd like a procedure to take a digital image (a photo) and, by in some
>> way reducing the image and comparing the "inforamtion" left, to
determine
>> the "true" resolution. What I have in mind is to scan in an analogue
photo
>> at very high res, and to try to determine what res needs to be retained.
>
> What does "information" mean in this context?
>

I was looking into something like this a while back, where I would interpret
"information" as representation of the theoretical object input image
signal. If you measure the FT of the output, you can look for the maximum
frequency at which there is still significant power above the noise level.
The resolution of the image could then be set to twice this frequency.

Alternatively, if you just want a "nice" looking image, you can look at
lossy methods of reduction such as JPEG compression as well as reducing the
resulution, and then use volunteers to decide what level is almost as good
as the original.

Martin

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[Message index]

		Re: Determing true resolution of an image? By: wmconnolley on Thu, 07 March 2002 05:51
		Re: Determing true resolution of an image? By: Martin Downing on Tue, 05 March 2002 15:06
		Re: Determing true resolution of an image? By: David Fanning on Tue, 05 March 2002 11:44
		Re: Determing true resolution of an image? By: chrisduckworth on Thu, 07 March 2002 22:28

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