Date: Fri Apr 13 11:20:29 2007

Author: Richard Berg

Subject: Re: [Phys-l] pinhole camera

Post:

I believe the logic is that there is no focusing so there is no image. A
pinhole produces a "negative shadow" in which the bright area is the
"shadow."

You can certainly expose a film with it because the light is actually
there. You can also use it as an object for a lens. But if you select an
adjacent plane you can also expose a film with that or use it as an
object. If you produce a true "image" with a lens, it becomes defocused
if you view it on planes different from the image plane. Not so with a
pinhole image. All of the light from a point on the object is "focused"
onto the corresponding point on the "image" as these terms are usually
defined.

I think "pinhole image" does not have the characteristics of an image as
it is normally defined.

Dick

On Fri, 13 Apr 2007, Steve Wonnell wrote:

>
> Dick,
>
> Why not? The "image" can be projected on a screen. Photographs can be
> made with the pinhole. I understand that the pinhole is not a lens
> nor a mirror...but the "image" sure seems like an image.
>
> Steve W.
>
>
> On Fri, 13 Apr 2007, Richard Berg wrote:
>
>> Date: Fri, 13 Apr 2007 10:33:30 -0400 (EDT)
>> From: Richard Berg
>> Reply-To: tap-l@lists.ncsu.edu
>> To: tap-l@lists.ncsu.edu
>> Subject: Re: [tap-l] [Phys-l] pinhole camera
>>
>>
>> I presume that everyone knows that a "pinhole image" is NOT an image.
>>
>> Dick
>>
>> ******************************
>>
>> I am thinking it would be a good way to show students that light travels
>> in straight lines, and to introduce them to real images (rather than begin
>> with virtual images in a plane mirror).
>>
>> ***********************************************************************
>> Dr. Richard E. Berg, Professor of the Practice
>> Director, Physics Lecture-Demonstration Facility
>> U.S. mail address:
>> Department of Physics
>> University of Maryland
>> College Park, MD 20742-4111
>> Phone: (301) 405-5994
>> FAX: (301) 314-9525
>> e-mail reberg@umd.edu
>> www.physics.umd.edu/lecdem
>> ***********************************************************************
>

***********************************************************************
Dr. Richard E. Berg, Professor of the Practice
Director, Physics Lecture-Demonstration Facility
U.S. mail address:
Department of Physics
University of Maryland
College Park, MD 20742-4111
Phone: (301) 405-5994
FAX: (301) 314-9525
e-mail reberg@umd.edu
www.physics.umd.edu/lecdem
***********************************************************************


Back