[meteorite-list] Meteorite Photography (Must read!)

[Chris Peterson]

Just to put a quantitative spin on this, the physical size of the Airy disc 
(the diffraction spot produced by a point source) is directly related to 
focal ratio. Any lens at f/22 will produce a diffraction spot 27 um in 
diameter. Any lens at f/8 will produce a diffraction spot 11 um in diameter. 
Any lens at f/5 will produce a diffraction spot 7 um in diameters.

Most digital cameras these days have pixel sizes in the range of 5-6 um. 
What that means is that if you use the lens any slower than f/4 you are 
losing resolution to diffraction effects. The lens needs to be operated 
faster than f/4 in order for the diffraction and the pixels to be well 
matched. Of course, you have to offset that against the fact that as the 
focal ratio gets smaller, aberrations- especially off-axis aberrations- get 
more severe. That's the idea behind the rule-of-thumb that optimum sharpness 
is usually seen a stop or two below wide open.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "Dark Matter" <freequarks at gmail.com>
To: "Meteorites USA" <eric at meteoritesusa.com>
Cc: "Meteorite-list" <meteorite-list at meteoritecentral.com>
Sent: Wednesday, January 27, 2010 12:49 PM
Subject: Re: [meteorite-list] Meteorite Photography (Must read!)


> Sorry, but it won't. The measures are small, but the optical physics are 
> real.
>
> http://www.kenrockwell.com/nikon/50-comparison/f-stops.htm