Talk:Kowa SW

Found one: http://www.flickr.com/photos/98922823@N00/4920305283/ Edward Vielmetti 17:48, 28 February 2011 (PST)

Weird camera! If you have success finding an image in our pool, you can go ahead and add it, don't need to Talk: unless there's some issue. --Vox 19:47, 28 February 2011 (PST)

For photos in our pool, use the long Flickr URL form in/pool-camerawiki . It makes the origins of the permission to use human-readable; also I suspect it keeps the link from breaking if non-pro user adds 200 subsequent photos (I haven't tested this conclusively). --Vox 19:50, 28 February 2011 (PST)

What is a "Keplerian viewfinder"? --Johnbear (talk) 09:58, 10 December 2015 (CST)

There is a Keplerian type of telescope, and I assume the VF is a reversed one of those (as a Galilean VF is a reversed Galilean telescope). I would need to look up exactly what Kepler's telescope is, though! Should probably have done that before: I think I'm responsible for the phrase being there (it's in one of the linked pages).--Dustin McAmera (talk) 11:22, 10 December 2015 (CST)

In fact, yes; that's it, at least roughly, though I've confused myself trying to find out all about it (I suspect I may have been through this before; maybe I saw the curious VF on the camera, felt it needed to be commented on, and tried to find out what it was, but failed because I'm too stupid to understand it!)

Kepler designed his telescope only shortly after Galileo did his. As a telescope, it's supposed to be easier on the eye, because it puts a positive lens nearest the eye. I'm not sure whether it's reversed for use as a VF or not.

I found some patents for Kepler-type finders, starting in the 1980s. They're all a bit too advanced to use in an explanation, and trying to use them to teach myself is what's confused me. However, I learned something. One of the features of the Kepler telescope, and finder, is that it would give an inverted image, but this is avoided by including silvered prisms or mirrors in the light path, so the whole thing can be folded and shortened. I suspect that Keplerian finders are more common than we know, and may be included as part of quite a lot of reflex finders, but not referred to as such. Some of the patents included the observation that the Kepler design makes it possible to put a scale (say a light-meter readout) in the VF and for both the scene and the scale to be in focus for the user: that seems a familiar situation with reasonably-modern reflex finders.

I will try to find a more straightforward source of a good explanation (one that I can understand myself!); if I can, I'll probably add a paragraph to Viewfinder, and look for places in the wiki that should link to it. For now, I need coffee and paracetamol! --Dustin McAmera (talk) 12:29, 10 December 2015 (CST)

From the bits of information I can find (which I also understand) it seems to be something to do with adding another lens to a Galilean telescope that increases the field of view (and I don't actually understand how that might work?). I agree it may be the case that this isn't uncommon, but what intrigued me about this camera was it's tiny little viewfinder lens.

--Johnbear (talk) 13:50, 10 December 2015 (CST)

Yes: tiny. Hard to believe it isn't a very dark view. I found a Google-books preview of a more modern edition of the Ilford Manual than I have (mine is from 1978 or something like that). I now understand that the Kepler VF is liked (a) because it is easy to include a zoom facility in it, (b) it combines well with prisms and mirrors (as above) to give a compact unit, and (c) because it's easy to provide dioptric correction or a magnifier, which are kind of the same thing. Kepler VFs are indeed quite common in complex little electronic zoom cameras. Not so common in the (apparently) uncomplicated form used on this camera. --Dustin McAmera (talk) 16:57, 10 December 2015 (CST)

I've looked into this, while trying to avoid the physics, and seek a simple explanation. Finding and looking at images of the back of the camera goes a long way to explaining it. The viewfinder eyepiece is not in line with the viewfinder objective lens, indicating the light path is altered by mirrors/prisms (most likely the latter). I think that's the key to it: it's like most viewfinders are reverse telescopes, and this keplerian thing is like a reverse binocular. That'll do me! It probably also explains why the objective lens is so tiny, because binocular objective lenses are tiny compared to telescope's. It's right and proper that the wiki page should mark the finder's difference, but I don't know how the foregoing could be translated into a wiki-suitable explanation. The only remaining problem is ... now I want a Kowa SW !!!!

--Johnbear (talk) 15:10, 11 December 2015 (CST)