Don wrote:

> The operational word is, "concurrent". I do not believe that John H.

is the only one that can not look at a finger which is only 18 inches
away, and at the same time see infinity. I can not do it. The
deviation is, approximately, more than 3.1mm


Chuck:

The idea is to make the view look the same (or better) than it did while viewing the scene directly. Since one can not focus his attention on a finger at 18" and infinity at the same time viewing direct, it should be at least ok if he couldn't do it while viewing a slide.


Don:

>Incidentally, I do not believe that our eyes have near enough depth of field to be able to perform such a feat.

Chuck:

Having more depth of field in the slide than in your eye, to me, would be a plus. I could move my eyes from subject to subject without having to refocus (Tilt my head up or down with my glasses on) and it would be more enjoyable then direct viewing. With outdoor light (sunny 16) I find that my eyes stop down and give me good focus from arms length to infinity without glasses even though my old eyes focus at or beyond infinity. I have never noticed that having better focus on anything was a problem. Sharpness in a picture does not hurt my eyes.

I really don't believe that you can get good DoF from 18" to infinity with a MF stereo camera, at least not with any I have seen, so such a picture is not likely. My TEST picture of the Pitcher Plant was done to show that DoF plays out before OFD becomes a problem. Using F/22, I focused the Sputnik all the way in (about 1 meter or so, ) and photographed from a low tripod so that I had plants in at 18 inches, the Pitcher Plant at one meter and the background way out (infinity). I had to make my own mount so as to be able to have infinity at zero parallax and not have window violations.

No one has told me that they can not converge on anything in the view but they do complain about things being out of focus even though the Pitcher Plant is sharp while extreme near and far are not. (Maybe they are just being nice.) No doubt someone with an adjustable inter-ocular viewer could adjust the inter-ocular to where a 65mm infinity spacing would create a painful toe-out of the eyes but I use my Saturn.

I find that adjusting my Sputnik to F/32 and focusing at twice the distance to the nearest object, I can get acceptable DoF from 5 feet to infinity resulting in 3mm OFD. With 3mm OFD I can mount in commercial mounts that have 62 mm aperture spacing using an infinity spacing of 65mm and keep everything behind the window with no eye divergence or strain. I can mount more OFD by modifying the mount (or through the window) but then DoF starts becoming a problem.

I would not buy a MF stereo camera that can not do, or can not be easily made to do, F/32 or tighter.

Regards,

Chuck






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> I focused the Sputnik all the way in (about 1 meter or so) and
> photographed from a low tripod so that I had plants in at 18
> inches, the Pitcher Plant at one meter and the background
> way out (infinity). I had to make my own mount so as to be
> able to have infinity at zero parallax and not have window
> violations.

This, apparently, was a stereo image with, "extreme depth", though not
very much could have been in, reasonable, focus. If the Sputnik was
actually focused at about, "1 meter", the DoF, (at f/22), would only
include a reasonably sharp image from about 2 feet, out to about 5 feet.
A long ways from infinity.

The, on film deviation,(OFD), would be more than 10mm.

Near point- 18 inches,(457mm).
Far point- Infinity.
75mm fl lens.
62mm interocular spacing.

Therefore, fl, 75mm x base,62mm, divided by, near point, 457mm = OFD.

Therefore, 4650mm/457mm = an OFD, of 10.2mm.

Some consider an OFD of from 1.5mm to 3.0mm as being OK.


Best regards,

DON

Chuck Holzner wrote:

> Don wrote:
>
>
>>The operational word is, "concurrent". I do not believe that John H.
>
> is the only one that can not look at a finger which is only 18 inches
> away, and at the same time see infinity. I can not do it. The
> deviation is, approximately, more than 3.1mm
>
>
> Chuck:
>
> The idea is to make the view look the same (or better) than it did while viewing the scene directly. Since one can not focus his attention on a finger at 18" and infinity at the same time viewing direct, it should be at least ok if he couldn't do it while viewing a slide.
>
>
> Don:
>
>
>>Incidentally, I do not believe that our eyes have near enough depth of field to be able to perform such a feat.
>
>
>
>
> Chuck:
>
> Having more depth of field in the slide than in your eye, to me, would be a plus. I could move my eyes from subject to subject without having to refocus (Tilt my head up or down with my glasses on) and it would be more enjoyable then direct viewing. With outdoor light (sunny 16) I find that my eyes stop down and give me good focus from arms length to infinity without glasses even though my old eyes focus at or beyond infinity. I have never noticed that having better focus on anything was a problem. Sharpness in a picture does not hurt my eyes.
>
> I really don't believe that you can get good DoF from 18" to infinity with a MF stereo camera, at least not with any I have seen, so such a picture is not likely. My TEST picture of the Pitcher Plant was done to show that DoF plays out before OFD becomes a problem. Using F/22, I focused the Sputnik all the way in (about 1 meter or so, ) and photographed from a low tripod so that I had plants in at 18 inches, the Pitcher Plant at one meter and the background way out (infinity). I had to make my own mount so as to be able to have infinity at zero parallax and not have window violations.
>
> No one has told me that they can not converge on anything in the view but they do complain about things being out of focus even though the Pitcher Plant is sharp while extreme near and far are not. (Maybe they are just being nice.) No doubt someone with an adjustable inter-ocular viewer could adjust the inter-ocular to where a 65mm infinity spacing would create a painful toe-out of the eyes but I use my Saturn.
>
> I find that adjusting my Sputnik to F/32 and focusing at twice the distance to the nearest object, I can get acceptable DoF from 5 feet to infinity resulting in 3mm OFD. With 3mm OFD I can mount in commercial mounts that have 62 mm aperture spacing using an infinity spacing of 65mm and keep everything behind the window with no eye divergence or strain. I can mount more OFD by modifying the mount (or through the window) but then DoF starts becoming a problem.
>
> I would not buy a MF stereo camera that can not do, or can not be easily made to do, F/32 or tighter.

Don Lopp wrote:

>This, apparently, was a stereo image with, "extreme depth", though not
>very much could have been in, reasonable, focus. If the Sputnik was
>actually focused at about, "1 meter", the DoF, (at f/22), would only
>include a reasonably sharp image from about 2 feet, out to about 5 feet.
> A long ways from infinity.
>
>The, on film deviation,(OFD), would be more than 10mm.

Exactly right Don. Even though at F/22 The depth of field was overstressed a good bit, THE PARALLAX RESULTING FROM OVER 1 CM OF OFD WAS NO PROBLEM CONVERGING.

The Sputnik I used for that test would not close tighter than F/22 and since I have extended the range of the ones I still have to f/32, I just may repeat the test, but I think the result will still show that DOF will be played out even though OFD (parallax) is still not a problem.



DoF is the limiting factor to depth with MF stereo cameras, not OFD. If you think otherwise, send me a stereo pair, shot with a normal base, that is sharp throughout and has too much OFD. I want to see it.

Show me,

Chuck




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