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Re: [OM] Mega Pixel equivalent of medium format negatives

Subject: Re: [OM] Mega Pixel equivalent of medium format negatives
From: Moose <olymoose@xxxxxxxxx>
Date: Tue, 04 Nov 2014 15:59:17 -0800
On 11/4/2014 5:08 AM, Chuck Norcutt wrote:
Not so easily determined. Resolution is ultimately limited by diffraction. But diffraction varies by wavelength with blue being least affected followed by green and then red.

If you shoot a 4/3 image at f/8 the diffraction limits leave the blue at a max of 16 MP but cut the green to 8 MP and the red to 5 MP.

Remember analog TV? The color was at a much lower resolution than the luminance.

To get the theoretical maximum out of a 16 MP 4/3 sensor you'd have to limit aperture to f/6.3 or maybe even f/5.6. Only at these or larger apertures would you then be able to consider the effects of reds and blues having fewer sensels.

Well, phooey. I was trying to avoid this ... As with contrast, in my last post, the kind of loss of resolution you describe may also be changed in post. Deconvolution increases effective resolution, partially recreating the 'signal' before it went through the convolution of lens defects, including aperture size.

In theory ( that tricky thing, again), I understand that with full information on what the lens does to light passing through, the original may be completely reconstructed. General purpose, non lens specific deconvolutions can't do anything near that, but it can recover some resolution.

A lot of things that were true for film and optical prints are not the same anymore. Unless adjustments are made, they are often inaccurate for digital. It's my sense that deconvolution and contrast adjustments, local and global, add about a stop, so f8 is not, in effect, diffraction limited on 4/3. Even f11 gives away very little I can see, with the right tools and ability to use them. I've been using f9 as my default lately. Maybe because I like odd things? Or bumped it and didn't change it back? ;-)

You make me think it might be interesting to run deconvolution at different intensities on the color channels. Likely too crude for much use. Oh dear, am I channeling Mike G? :-)

That reminds me. I still haven't re-compared DxO's lens/sensor specific deconvolution to FM's generic version. OH well, another day.

Convoluted Moose

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