viewfinder magnification

OK lens experts, I beseech thee. I understand how to magnify the image
that is displayed on the ground glass of the viewfinder, such as on a
Nikon F3. But how do the magnifiers work that attach to where you
normally place your eye. You can't put a pocket scope back there and
zoom in. Yet is is possible to magnify this image since Canon, Olypus
etc sell low power magnifiers to attach to the back of a viewfinder.
Try to keep it simple if you can.

In article .com,
wrote:
OK lens experts, I beseech thee. I understand how to magnify the image
that is displayed on the ground glass of the viewfinder, such as on a
Nikon F3. But how do the magnifiers work that attach to where you
normally place your eye. You can't put a pocket scope back there and
zoom in. Yet is is possible to magnify this image since Canon, Olypus
etc sell low power magnifiers to attach to the back of a viewfinder.
Try to keep it simple if you can.

Well, yes you can place a pocket scope back there, if by pocket scope,
you mean a small telescope (focusing at infinity) rather than a micro-
scope (focusing closely). Nominally, the light leaving the viewfinder
is parallel (as if coming from infinity); that is, the viewfinder is
focused on the ground glass. Placing a small telescope (which is what
the viewfinder magnifiers are) behind the viewfinder, magnifies the
image just as it does for light coming from infinty. The cornea then
focuses the parallel light from the magnifier on the retina.

Rob Johnson
take out the trash before replying

On 15 Mar 2005 01:58:10 -0800, wrote:

OK lens experts, I beseech thee. I understand how to magnify the image
that is displayed on the ground glass of the viewfinder, such as on a
Nikon F3. But how do the magnifiers work that attach to where you
normally place your eye. You can't put a pocket scope back there and
zoom in. Yet is is possible to magnify this image since Canon, Olypus
etc sell low power magnifiers to attach to the back of a viewfinder.
Try to keep it simple if you can.

You can use a pocket scope to magnify the viewfinder image- I have a
tiny toy telescope that works great for that purpose. The magnifiers
sold by Canon et.al. are just little telescopes.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

wrote:
OK lens experts, I beseech thee. I understand how to magnify the image
that is displayed on the ground glass of the viewfinder, such as on a
Nikon F3. But how do the magnifiers work that attach to where you
normally place your eye. You can't put a pocket scope back there and
zoom in. Yet is is possible to magnify this image since Canon, Olypus
etc sell low power magnifiers to attach to the back of a viewfinder.
Try to keep it simple if you can.


magnification = Objective Focal Length / Eyepice (occular) Focal Length

That makes it simple enough. Thanks.

I'm assuming the smallest apperture finder I could find would be the
way to go here.

Geez, one more post. Rifle scope perhaps?

Chris L Peterson wrote:
You can use a pocket scope to magnify the viewfinder image- I have a
tiny toy telescope that works great for that purpose. The magnifiers
sold by Canon et.al. are just little telescopes.

I'd like to give this a try. Any specific suggestions on what to buy,
like ? -

http://www.scientificsonline.com/cat...cd2=1111114547

- Canopus56

On 17 Mar 2005 18:53:59 -0800, "canopus56" wrote:

Chris L Peterson wrote:
You can use a pocket scope to magnify the viewfinder image- I have a
tiny toy telescope that works great for that purpose. The magnifiers
sold by Canon et.al. are just little telescopes.

I'd like to give this a try. Any specific suggestions on what to buy,
like ? -

http://www.scientificsonline.com/cat...cd2=1111114547

Those are microscopes. You need a telescope, something like
http://www.scientificsonline.com/pro...Q_pn_E_3104400 maybe.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com