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Re: [OM] You might find this interesting --

Subject: Re: [OM] You might find this interesting --
From: frieder.faig@xxxxxxxxxxxxxxxxxxxxxxxxx
Date: Wed, 9 May 2001 17:22:38 +0200
 On Wed, May 09, 2001 at 11:53:37AM -0000, Alan wrote:
> 
> It relates to some of Gary's recent comments about film limitations:
> 
> --------------- From rec.photo.xxx--------------------------------------
> Resolution of camera lenses where are the limits - and why?
 According to
> this law no camera lens used in photography, still or motion, can produce
> resolutions higher than given in the following table (Approximate, rounded
> off values for white light spectrum of even energy distribution. In unevenly
> distributed spectra of gas discharge light sources somewhat higher
> resolutions may be achieved.)
> 
> 
> f-no......................resolution
> .............................(line pairs per millimeter)
> .45.............................35
> .32.............................50
> .22.............................70
> .16...........................100
> .11...........................140
> ...8...........................200
> 5.6...........................280
> ...4...........................400
> 2.8...........................560


IMHO, are this values very optimistic. I guess they are valid only in the 
center at large distances. Over the angel of field and for shorter distances,
This values has to be reduced even more. (See tables for best apperture for 
macro!)
 
> 
> In practical photography other limitations of resolution occur, too. The
> existing depth-of-field concepts, for example, lead to a limit at 30 line
> pairs per millimeter, simply because they assume that the image of a sharp
> point may be considered sharp as long as the unsharp disc it actually is
> (called the "circle of confusion") grows no larger than 1/1000th of the
> focal length of the respective standard lens. In 35 mm photography only
> 1/1500th is allowed. 1/1500 th of the 50 mm standard focal length equals
> 1/30th mm. 

The value for D.O.F calculations depend on your demand of quality. I´ve found 
a old book, which used 1/1000th of the standard focal length. Today  1/30th mm
is most comon, but I´ve read in a book for high quality use 1/2000th. 
- How things change....


> 
> The most obvious limitation of resolution in everyday photography, however,
> is unwanted motion with handheld cameras. Even a seasoned photographer with
> a very "calm" camera will hardly find resolutions higher than 40 line pairs
> per milli-meter in his photographs unless he uses an adequate tripod. CLN
> will detail on this topic in a later issue.

I think this is the most importend limit. But as experience show`s is this 
quality enough
in most cases. To record a quality like this a digital camera need`s at least 
5.5 Mpixels.

When the KB-photograhy started in the 20th, they used the rule that a picture 
with
 one million points is good enough for usual eye. 

Frieder Faig



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