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Subject: Mounting to infinity when there is none
Date: 2012-09-24 18:49:26
From: John Thurston

I have always mounted "to the window", but I know there are
those here who "mount to infinity and let the nears land
where they may".

I was working on an image this afternoon and got to
thinking.... This image had the nears at about 2m and the
fars at less than 10m. How would y'all mount this? Do you
take the far-point and treat it as if it were infinity?

________________________________________
John Thurston
Juneau, Alaska
http://stereo.thurstons.us

Subject: Re: Mounting to infinity when there is none
Date: 2012-09-24 19:38:48
From: JR

Stereoscopic imaging is extremely subjective, differing considerably from one image to another. As such, there are times when a particular image may work best when mounted to the window, mounted to the far point (which may or may not be infinity), mounted to the near point, or, more likely, somewhere else.

There are many factors which affect the optimum choice of mounting position, including the stereo window (and any potential edge occlusions), contrast (crosstalk or "ghost" reduction), the subject of interest, geometric patterns, especially with contrasting vertical lines, partial occlusions of objects by other objects in the image, artistic considerations, etc.

Mounting is every bit as much a skill as any other factor in stereoscopic imaging, a skill acquired more through experience than through any specific rules or numerical considerations.   Learning the rules can be helpful, as long as they are used as guidelines, and not absolutes.   As with most aspects of stereoscopy, and even photography itself, compromise is most often the case, weighing one consideration against another to come up with the best compromise for the specific image.

The best way to gain this experience is through practice.   I have often been called upon to teach this skill to newbies.   I suggest that they replicate different stereo pairs several times. MF film and processing tends to be expensive, but the techniques are very similar, regardless of film size. So, until they really become good at it, it is good to practice with a smaller gauge, such as 35mm.

Or, even digital.   Try different mounting positions with copies of the same image.   If digital, you can use a monitor viewer (or freeview) a side-by-side pair (either parallel or cross-view, your preference). Cutting paper masks (or even strips of paper) to represent slide mounts, you can move them around, and find what looks most pleasing, and what you don't like. When you find something that you don't like, analyze it to determine why.   This can be a very low-cost learning tool.

JR
stereoscope3d@gmail.com

On Mon, Sep 24, 2012 at 5:52 PM, John Thurston <juneau3d@thurstons.us> wrote:

I have always mounted "to the window", but I know there are
those here who "mount to infinity and let the nears land
where they may".

I was working on an image this afternoon and got to
thinking.... This image had the nears at about 2m and the
fars at less than 10m. How would y'all mount this? Do you
take the far-point and treat it as if it were infinity?

________________________________________
John Thurston
Juneau, Alaska
http://stereo.thurstons.us

--

Subject: Re: Mounting to infinity when there is none
Date: 2012-09-25 01:34:40
From: Chuck Holzner

From: "John Thurston" <juneau3d@thurstons.us>
Wrote:

> I have always mounted "to the window", but I know there are
> those here who "mount to infinity and let the nears land
> where they may".
>

The idea of "mounting to a constant infinity" is useful to get the same toe in of your eyes for the
same distances to the points in your views. Assuming that you match the viewer FL to the camera FL,
If you always mount to a constant infinity and view with parallel to infinity, (infinity spaced at
the interocular spacing of the viewer.) then the parallax will be the same for the same distance
from view to view. Points will fall "where they should be." Your eyes will view the scene in the
viewer using the same parallex as it viewed the scene direct.

> I was working on an image this afternoon and got to
> thinking.... This image had the nears at about 2m and the
> fars at less than 10m. How would y'all mount this? Do you
> take the far-point and treat it as if it were infinity?

No. With a mounting gauge that has a spacing on it's grid that equals the spacing for a known
object in the view you could use that. The parallax calculation is not difficult to do. Likely
that would be close enough since you don't really know the close or far distance. You would likely
have to make your own mounting gauge. One with several lines on it so you could use it for other
slides.

Another way is to take a reference slide, with infinity in it, taken with the same camera as the
slide you are to mount. The reference slide properly mounted to infinity. With the mount open,
measure the distance from the right side of the left image to the left side of the right image.
That distance will be the same for all slides mounted to infinity from that camera. Mount your (no
infinity in the picture) slide with the same spacing.

Of course if you always "mount to the window", keeping the two meter object behind the window should
work good enough for you as long as the far point is spaced no more than 65mm. (MY favorite infinity
spacing is 65mm.) Having trained your eyes to "fall where it may" parallax, and having a good amount
of parallax in the view (All between 62mm and 65mm.) should be fine for you.

Using my Sputnik and Saturn viewer, 65mm infinity spacing with mounts that have 62mm window
spacing, I have 3mm of OFD to use and the window at 1.6 Meters. I like putting depth in my views
and hate toeing out my eyes.

Chuck Holzner

Subject: Re: Mounting to infinity when there is none
Date: 2012-09-25 07:29:39
From: studio3_d

--- In MF3D-group@yahoogroups.com, JR wrote:

>
> Or, even digital. Try different mounting positions with copies of the
> same image. If digital, you can use a monitor viewer (or freeview) a
> side-by-side pair (either parallel or cross-view, your preference).

Why go through all that trouble? It's incredibly easy with Stereo Photo Maker and a pair of anaglyph glasses. After auto-align, you can use the horiz arrow keys to shift the (scene) window and see in real time (in anaglyph view, of course... also works with pola, if you have passive monitor)

(BTW- personally I pretty much always mount to window, even cheating stray bits through the window to converge subject if needed. The less positive deviation the better)

ron labbe
studio 3D

Subject: Re: Mounting to infinity when there is none
Date: 2012-09-25 09:15:53
From: Chuck Holzner

studio3_d" <ron@studio3d.com> Wrote:

Subject: [MF3D-group] Re: Mounting to infinity when there is none

--- In MF3D-group@yahoogroups.com, JR wrote:
>
> Or, even digital. Try different mounting positions with copies of the
> same image. If digital, you can use a monitor viewer (or freeview) a
> side-by-side pair (either parallel or cross-view, your preference).

>Why go through all that trouble? It's incredibly easy with Stereo Photo Maker and a pair of
anaglyph glasses.
>After auto-align, you can use the horiz arrow keys to shift the (scene) window and see in real time
(in anaglyph
> view, of course... also works with pola, if you have passive monitor)

How do you mount MF stereo slides with Stereo Photo Maker???

Chuck Holzner