[LRflex] Re: Interesting info for digitographers
- From: "Aram Langhans" <leica_r8@xxxxxxxxxxx>
- To: leicareflex@xxxxxxxxxxxxx
- Date: Wed, 09 Nov 2005 10:42:30 -0800
Hey, but doesn't the same physics of Airy discs apply for film cameras to?
I don't think film people can jump for joy. Maybe the more random nature of
film sensors (grains) fares better than a regular pattern, but the lens is
still diffrraction limited at some point.
Aram
>From: Douglas Sharp <douglas.sharp@xxxxxx>
>Reply-To: leicareflex@xxxxxxxxxxxxx
>To: leicareflex@xxxxxxxxxxxxx
>Subject: [LRflex] Re: Interesting info for digitographers
>Date: Tue, 08 Nov 2005 23:36:24 +0100
>
>Andy,
>If someone can tell me what size the sensor is, it's diagonal, and what
>the distance is from centres of adjacent pixels, I'll take a crack at
>working it out with the method they used in the magazine.
>
>The interesting part about the info is -it has absolutely nothing to do
>with the angle of the light hitting the sensor, it's the circle around a
>point of light (Airy Disk, which I believe also has something to do with
>resolution for astronomy - seems to be lurking somewhere in the back of
>my mind). the smaller the aperture the larger the diffuse circle of
>light (with respect to the size of the aperture) around the point(ray)
>of light it's letting through. At a certain aperture this exceeds the
>distance between two adjacent pixel centres and can't be resolved as a
>point any more. Then the article gets into wave and particle theory as
>explanations, which is probably unnecessary 'cos it all ends up as a
>reasonably simple mathematical formula. At the end of the day it's not
>the number of pixels that define the resolution for very small apertures
>but the size of a pixel. looks as if the next development should be an
>automatic algorithm for cross coupling groups of 4 adjacent pixels as
>soon as the aperture exceeds f11 (or the limit defined by the sensor
>geometry). I suspect that the 3 "layer" Foveon chip in the Sigma does
>something along these lines.
>At least I hope that's right, I'm a Geophysicist not a Physicist.
>If I have time tomorrow I'll translate and post the article, and the
>formula for working it out.
>Douglas
>
>Andy Wagner wrote:
>
> >Interesting comment!
> >Do we know how the DMR stacks up in this comparison?
> >I remember reading somewhere that the problem Leica was having with
>introducing a digital back was because the angle of light hitting the
>perimeter pixals was causing havoc with sharpness. Also pixels sensitivity
>to light and the way they interprate colors varys with the same angle.
> >
> >LONG LIVE THE SL's :-))
> >Douglas Sharp <douglas.sharp@xxxxxx> wrote:
> >In the latest issue of ColorFoto (Germany) there's an interesting
> >article about the limitations of digital cameras at certain lens
>apertures.
> >It's all to do with refraction and pixel sizes, Airy disk size or
> >Fraunhofer circles of diffraction - the main article is pretty much
> >physics/optical theory but the list of cameras and limiting apertures is
> >interesting.
> >
> >What it boils down to is - it's not worth stopping down to get a sharper
> >image any further than the apertures shown below, it just won't increase
> >sharpness, in fact it will get unsharp.
> >(NOT DOF, that, of course, will increase)
> >
> >Camera/aperture
> >Canon EOS 1Ds Mk II 11.8
> >Canon EOS 1D Mk II 13.4
> >Nikon D70 12.9
> >Fujifilm S3 Pro 12.5
> >Canon EOS 20 D 10.6
> >Sigma SD10 15.0
> >4/3 cameras 9.0
> >
> >And it gets worse for compacts.
> >
> >It finally explains why my macro shots with f16 were not as pin-sharp as
> >those with f8.
> >Douglas
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> >------ >--
> >Regards
> >YXAndy
> >
> >
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