Re: Noise levels as a function of pixel size

[A complimentary Cc of this posting was NOT [per weedlist] sent to
Kennedy McEwen
<rkm@xxxxxxxxxxxxxxxxxxxx>], who wrote in article <J1FYSwBtAxqDFw0W@xxxxxxxxxxxxxxxxxxxx>:
> >> >Nope. The maximal f-number of the lens is irrelevant. What is
> >> >important is the actual f-number used for the shot. So with 16x
> >> >scaling f/45 becomes f/2.8.

> >> The maximal f-number is highly relevant, since that is what determines
> >> both the exposure control and the optical resolution limits.

> >Do not know what you mean by "exposure control".

> Control of exposure, in this case control by aperture, as in a shutter
> priority metered system.

Kennedy, I was discussing the situation when one particular shot made
with a larger sensor produces the same result as one taken with a
smaller sensor. Apparently, you are discussing something else;
actually, I do not know what. I can't continue until I understand
what is the context of your statements...

> >The optical
> >resolution limit has nothing to do with f-number of the fully open
> >lens.

> It certainly has, since the maximum theoretical fully open lens is
> f/0.5, whilst the practical limit is around f/0.7. That doesn't leave
> much engineering room if the maximum diffraction limited aperture is
> around f/1, even if the range does go well into the diffraction limit
> zone to f/2.8.

As I said, maximum NA of a diffraction-limited in-the-air lens I know
is 0.93. So I have no idea what you are speaking about (even if under
f/0.5 you mean NA=1...).

> >I'm not discussing f/45 lenses. I'm discussing *shots*.

> As I am. The difference is that I am recognising that f/45 is
> sub-optimal on 4x5" due to

Somebody counted (one of Davids?), and 50% of published 4x5in images
are made at f/45; this is why I discuss this number. Most probably
f/32 can also be (more or less) matched with a tiny sensor. I think
matching f/22 and f/16 would not be possible. However, already f/45
and f/32 cover significant majority of usages of 4x5in format.

Similar to f/16 at 4x5in, there is no hope to match 8x10in film with a
small formfactor sensor (most probably not even with any non-scanning
digital sensor of foreseeable future).

> The benefit of smaller pixels only becomes worthwhile when you can
> achieve the equivalent of the 4x5" format at the resolution limit of the
> optic *and* film, which occurs somewhere around the f/5.6- f/11 region,

AFAIK, 4x5in-format lenses max the resolution about f/16.

> >> Yes, and that is my point really - if you shrink pixels any smaller than
> >> the smallest currently in common use then the burden on the optical
> >> system becomes inordinately expensive and unsustainable as well as
> >> limiting photographic scope.

> >Exactly the opposite. E.g., on a maximum-resolution settings, a cheap
> >2/3'' formfactor ZOOM produces similar resolution image as an
> >expensive PRIME lens for APS formfactor.

> And you can keep preaching that, but nobody seriously believes it.

I'm not talking about believing. It is a resolution; you can check it
with a resolution chart. Just look at dpreview.

> >??? Who talks about single aperture?

> You effectively are, by requesting a pixel pitch which is so small that
> it can only be resolved by an ideal lens which has an f/# only
> marginally greater than the theoretical limit of f/0.5.

Please do not put words in my mouth. Thanks.

I'm taking about a lens which gives a close-to-diffraction limit
performance at f/2.8. Nowhere did I say anything about single
aperture. [And I have no idea what "resolving a pitch" would mean;
maybe you live a world where the camera is more expensive than its
lenses, so you want to use only the settings which would extract the
maximal resolution from the camera?]

Yours,
Ilya
.

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