Re: Pinhole camera

[roger haar <haar@soliton.physics.arizona.edu>]

Leigh,

	I appreciated you coming out early and having someone make an
attempt at pinning down ideas that we all use while assuming an intrinsic 
definition.  (The difficulty with definitions is clearly illustrated by 
biologist attempt to define a species as a group of lifeforms the can 
(and do) interbreed.  One hole in this definiton is that if there are 
a thousand males and no females left, the species does not  exist.)  I 
look forward to your article.

	Just a few comments on your definitions.

	First, I assume they are intended for an advanced audience, and 
think it might be very hard to use at a non-science major introductory 
level.

	It seems to me that light coming directly from a physical object 
may be classified as an image by your definitions.  Do you want to include 
in the set of things that are images the observed patterns on the wall 
produces by waving a flashlight or laser about?  Is there no diference 
between a red line on the wall, a stipe on red on the wall from a moving
laser, a projected red line on the wall and the image of a red line of wall
produced by a lens?

	In regards to the pinhole camera, from your definition, the 
pinhole-film (or viewing screen) combination produces an image, but not 
just the pinhole itself.

	Adding an observer seems to add the optics of the human eye to 
the situation.

	Using human's consciousness as part of a definition of a physical
phenomena is a potential minefield (or mindfield).  What if a flash of 
light triggers a flashback in someone's consciousness?  Here I am clearly 
playing the devils advocate, but my intentions are honorable.

Thanks
roger haar

 *************************************************************
On Fri, 27 Jun 1997, Leigh Palmer wrote:

> Roger Haar has coaxed me out of the penalty box four days early. I have
> in preparation, together with Lorne Whitehead of UBC, a submission to
> AJP on this very topic, the formation of images in the broad sense. I
> will be very interested to learn what you all think. For purposes of
> this discussion I would appreciate your comments on my own definition
> of image (and image formation) which is central to the development in
> our paper. The pinhole camera image is one of my examples, and it is
> certainly an image under my definition. I have two versions in mind,
> and I will give both for emphasis and perhaps conceptual clarification:
>
>   An optical image is that aspect intrinsic to a set of light waves
>   which either produces the perception of a semblance of form in the
>   eye of an observer, or has the hypothetical potential to do so.
>
>   An optical image may be said to exist if a set of light waves
>   incident upon the eye of an observer induces a percept (an
>   impression of the presence of an object) in that observer's
>   consciousness. An image also exists if a hypothetical observer
>   could perceive it.
>
> Note that the involvement of an observer (or a hypothetical one) is
> central to the idea of image in this treatment.
>
> Leigh