Re: Digital lens question

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Read Kingslake.  Learn something.

S.
----- Original Message -----
From: "karl shah-jenner" <shahjen@xxxxxxxxxxxx>
To: "List for Photo/Imaging Educators - Professionals - Students"
<photoforum@xxxxxxxxxxxxxxxxxxxxxx>
Sent: Sunday, August 22, 2004 2:57 AM
Subject: Re: Digital lens question


>
> ----- Original Message -----
> From: "steves" <sgshiya@xxxxxxxxxxxx>
> To: "List for Photo/Imaging Educators - Professionals - Students"
> <photoforum@xxxxxxxxxxxxxxxxxxxxxx>
> Sent: Sunday, August 22, 2004 12:52 PM
> Subject: Re: Digital lens question
>
>
> > Okay Karl, you can explain that to the Department of Defense that
installs
> > lenses on their satilites for digital imaging.  I got my information
from
> > the lens designer while working in a photo gallery in Carmel.
> >
> > Go well.
>
>
>
> I'm quite sure Steve that the gentleman you refer to is well aware of the
> diference between virtual and real images..  Lenses used for image
formation
> must converge the light to a focal point, lenses used for viewing through
> (like a telescope) allow our eye to be the part of the optical path that
> does the convergance.
>
> Either way for an image to form the light must converge.
>
> Auxilliary lenses however need not converge the light, neither need a
*part*
> of a lens system whether called a lens in it's own right or not - but the
> optical system, all the lenses that make the whole must finally converge
the
> light to a point of focus.
>
> let me put it this way.  The light reflecting from any given point will
> radiate outwards, this light diverges and makes no image.  Light
travelling
> from a bright source at a huge distance produces diverging rays that as
far
> as we are concerned approaches being parallel - it too makes no image.
>
> If it did we'd have images of stars all over our walls at night!  as soon
as
> we use our eyes to look at these things we focus - a process that changes
> the focal length of our lens and we converge the light to make an image on
> our retina.  Same thing with a camera, except we change the position of
the
> lens in relation to the film and thus bring the light to focus on the
film.
>
> point a camera (digital or not) at the source of parallel rays (say a
star)
> with no lens mounted and snap a pic.. all you'd get would be fog.  no
image.
> that parallel light is no good, the light needs focussing
>
> karl
>
> k
>
>
>


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