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Subject: To the window
Date: 2018-07-30 12:53:18
From: John Thurston

In _very_ simple terms, it is a question of which end of the
"Z" space you confine.

When mounting 'to the window', I set the near point in my
image at the aperture spacing of my mount. (For our 80x132
cardboard mounts, that is 62mm.) Everything in the image now
falls behind those apertures. If I have composed my image
correctly, the objects at infinity will not be so far apart
that my eyes must diverge to fuse them.

When mounting 'to infinity', I set the infinity points of my
image at a predetermined spacing (larger than aperture
spacing) and let the near points fall where it may. If I
have composed my image correctly, the near objects will not
be so close they extend through the window.

This question will quickly diverge into a discussions of
orthoscopic stereo, viewer-lens spacing, taking/viewing
focal lengths, human eye spacing, etc. Check the archives
for lengthy discussions and religious arguments.

--
John Thurston
Juneau, Alaska

Subject: Re: To the window
Date: 2018-07-30 13:09:45
From: Bob Aldridge

In practice there is just one really good reason to mount to infinity.
And that is that, if you are projecting a stream of images onto a screen
(e.g. in an AV show) having everything accurately mounted that way will
ensure that observers' eyes will not be tugged unnaturally with each
change of image...

However, of course, very few people project MF slides at all, let alone
in AV shows. So, under those circumstances, the advantages of mounting
to the window make that the way to go.

Bob Aldridge

On 30/07/2018 19:53, John Thurston juneau3d@thurstons.us [MF3D-group] wrote:
> This question will quickly diverge into a discussions of
> orthoscopic stereo, viewer-lens spacing, taking/viewing
> focal lengths, human eye spacing, etc. Check the archives
> for lengthy discussions and religious arguments.
>
> --
> John Thurston
> Juneau, Alaska

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Subject: Re: To the window
Date: 2018-07-30 14:31:17
From: John Thurston

On 7/30/2018 11:09 AM, Bob Aldridge Bob@Stereoscopy.net
[MF3D-group] wrote:

> In practice there is just one really good reason to mount to infinity.

I'm now awaiting Chuck Holzner's voice from beyond the grave
to give us three other good reasons.

I miss Chuck :(

--
John Thurston
Juneau, Alaska

Subject: Re: To the window
Date: 2018-07-30 23:13:51
From: borisstarosta

I'll answer for Chuck, because I knew him well, and he taught me everything I know about mounting to infinity.

1. In response to Bob Aldridge... you can (and should) mount to infinity in any medium that you use for presentation, not just MF slides or projected MF slides. I've tired out many an unsuspecting eyeball with my 3d slides and stereocards, so I know from experience. For example, in stereocards, typical infinity separation is about 3.5 inches. To be safe, you could use 3 3/8" The important point is not to use a specific infinity separation, but instead to stick to an infinity separation that works for your medium, and then stick to it religiously across all your images.

2. Mounting to infinity is valuable to your audience even if the viewing situation is a hand viewer or stereoscope. Any time more than one or two images will be presented, mounting to infinity will make it easier on your audience. It takes physical and mental work to fuse stereoscopic images. To the extent that you make this work easier, that you reduce the amount of work needed, this makes your 3d images more pleasant to view, and will enhance the general public's assessment of all things stereoscopic.

3. Keep in mind that the general public - or any novice 3d audience - has not had the physical training that you've probably had in viewing stereo images. Once you've trained, you become mostly oblivious to the physical challenge of viewing stereo images. Your audience being not trained, these challenges remain significant to them.

4. If you have a set of images mounted to the window, where the far or infinity points vary in separation/disparity, not only does your audience have to re-converge their eyes with every new image, but the convergence/accommodation mismatch is also renewed differently each time, further straining your mind's eye.

All that being said, there will be images in your catalog that you simply cannot mount to infinity, by ordinary means. For example, you might have images that do not have visual points at infinity (e.g. many of my studio nudes, where all visual points may lie in the range of three to five feet from the camera.) But even in this situation, you can mount to infinity if you've shot with a prepared camera. Chuck had filed carefully spaced notches into the film gate edges of his Sputnik, so that even absent infinity points in the scene, infinity points were produced on film by the notches.