Re: [Phys-l] pinhole camera

[Bernard Cleyet <bernardcleyet@redshift.com>]

Michael Porter wrote:

> On Apr 12, 2007, at 6:25 PM, Bernard Cleyet wrote:
>  
>
> > There was an additional criterion posed by Michael P. viz.  that  
> > the eye
> > substituted for the screen does not see the object:
> >    
>
> Careful, there, you don't want to put your eye where the screen was,  
> unless you are extremely near-sighted! This would be like trying to  
> read a book by pressing your eye up against the paper. You need to  
> back up a bit to put the image a comfortable distance from your eye.
>  
That probably is what I had done using a projected image from a slide 
projector in response to a post claiming one couldn't see such a real image.

> > ...  However, I had always used the "pin hole" -- usually a
> > forefinger, rolled up in the thumb and finger angle, close to my  
> > eye, so
> > I didn't "know" whether magnification results when the aperture is
> > distant from the eye.  I just tried it, curtains closed, using our  
> > front
> > door's faux stained glass window.  Wow!
> >    
>
> I'm not sure what you are trying to say here. Yes, you see the object  
> through the pinhole. If you are nearsighted as I am, the object  
> appears in better focus, but I don't see any magnification effects.
>  

You are correct, thank you.  I saw an optical illusion wherein the glass 
circle appeared larger, because I saw less of it (vignetting?).  It was 
quite striking; now that I know better it's much less, like many optical 
illusions when disabused.

> ---
> Michael Porter
> Colonel By Secondary School
> Ottawa, Ontario, Canada
>
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