T3D Re: T3D custom lenses for viewers

[bercov@xxxxxxxxxxx (John Bercovitz)]

> Custom designing lenses for a viewer is a great idea, 
> but I see too many difficulties to be optimistic.

I agree but the guy designs oculars as a specialty for
a living and has a company of twenty people and he's
optimistic but hey, he's got to be part salesman too.
So what if the cost of the design is zero?  He's still
selling.  8-)

> As far as I know, you need to view on-axis in any normal 
> eyepiece.

The Star D has no IPD adjustment and it works fine with 
a simple lens albeit non-ortho at 50 mm.  The V-M is also
fixed at 65 mm.

> My eyes are 57mm apart, and many people are in the 70s, 
> so a compromise covering the 60s wouldn't work for many.

To lay numbers on it, the 5th percentile is 58.5 mm and the
95th percentile is 68.5 mm so the standard stereo IPD of 65
should cover quite a few people with +/- 5 mm.  It would be 
better if the 65 were changed to 63 but that's not the stereo
standard.

> A designer can tell you with certainty that 'this lens will 
> work to these specifications', without making one for you.  
> But until you look through a lens of those specs, it's tough 
> to say that the lens will make you happy, especially regarding 
> the significant costs.

That's an importatnt point - how is the prototype pair to be 
funded?

> If the highest quality loupes for viewing negatives are the 
> proper focal length, I doubt that a custom designed lens would 
> greatly improve the performance over them.

If we're only talking focal length, sure.  But I don't believe
the other requirements of a loupe are 100% compatible with the
other requirements of a stereo ocular.  Needs such as entrance
pupil size/location or field coverage would be different in 
degree if nothing else.

> The price for these lenses almost certainly wouldn't include a cell

Then I've been misled.

> Fabricating a viewer is a very difficult project, if you're 
> going to include IPD and focus adjustments.

I agree and would suggest these need to be mated to existing chassis.

> I really doubt that we could sell 250, or even 100.

I wonder too which is why I asked the list's opinion.

> I think we'd want 35mm, 7 perf, but I don't think there's 
> enough consistency in cameras we use to make 'ortho' anything 
> but an arbitrary compromise.

Oh, I think it's close enough to ortho; a lot closer than what we
have now.

> I hope we get lots of reports from the conference, I'm sure there's 
> no end of interesting talks & displays.

I'm sure too.  Now I just have to get more time at them.  You
of all people should be here!  8-)  (COme on down and I'll introduce
you to this guy and you can tell me what you think.)

John B


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