Re: [Leica] OT pinhole lenses

[D Khong <dkhong@pacific.net.sg>]

>D Khong stirred the pot with:
>
>>If I am not mistaken, pin-hole lenses are used in architectural
>>photography. Straight lines must be strait, everything is in focus, the
>>image is distortion free.
>
>Dan,
>I wonder if you are referring to glass lenses with a very very small 
>aperture rather than a plain pinhole (hence the term 'pinhole lens')? 
>Despite what someone or other claims, a plain pinhole does not focus light 
>rays (LUGgers please contact me off-list if you disagree with that 
>statement) so the image they produce always looks rather blurred. The 
>addition of a simple refractive (eg glass) element to a pinhole that is not 
>diffraction limited improves the image significantly because it brings the 
>light rays to a focus. The aberrations created by the refractive element 
>will be small because of the very small aperture. This is a really easy 
>experiment to carry out if you have a close-up lens.

Malcolm

This subject was brought up in a recent conversation and it was more
theoretical discussion than enything else. I am sure that, for the purpose
of real life application, the glass element would be crucial in the process
of obtaining the required image.

Dan K.