P3D Re: 7-perf Red Buttons

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

>> If you open up the slide carrier windows, you can see 7 perf, 
>> but anywhere near the edge they are not at all sharp. They are 
>> sharp enough in the middle of the field and become blurry near 
>> the edge.....not right at the edge, but maybe 2/3 of the way 
>> to the edge.  

I am sorry but my experience does not allow me to agree with these
statements.  I just sent half an hour looking at a bunch of 7p
slides in my red button viewer... They look sufficiently sharp 
even right at the edges.  I cannot see much difference (or enough 
difference to bother me-note, to a large degree this is subjective).  
They might be not as sharp as the center but I would not call them
"not at all sharp" or "blurry".

I can only think of two explanations for the difference in our
experiences: 1) My eyes are not as good/sharp as yours.  2) Your
red button's optics are not as sharp as mine.  None of two sounds
convincing.  So, what is the problem?  I really don't know... But 
I do know that a number of people in this list use Realist 7-p 
viewers (I have personally modified a few dozen of them) so I 
invite them to offer their opinion too.

The mofidied red button viewer is still the best 7p viewer for me.
Others so-called 7p viewers do not even cover the full 7p viewing
area.  Considering that the majority of users still use single-
element viewer like Reel 3-D's $3+ one, a Brumberger, Star-D, Life-
Like, KI, etc., the achromatic lenses are a BIG improvement.

>> This is nowhere near as good as could be, a flat field magnifier 
>> (such as a high quality loupe used to magnify negatives) would 
>> give vastly better performance.

The "vastly better" performance again is in they eyes of the 
beholder.  Out of curiocity, how much does *a pair* of high quality 
flat field magnifiers would cost and what is their focal length 
*to cover the full frame width*?

>Archomatic doublets are only sharp and flat for about 65% of the 
>center field; the edges go soft and distort (pincushin?). 

"Only as sharp" needs some qualifications... How much "as sharp"?
Is there an explanation for the 65% or are we just making up 
numbers?  I am sure the size and focal length are factors too.

>They are not close to equaling the performance of the
>camera optics...

Which camera optics?  Does that include the run-of-the-mill 3-
element lenses like in a Realist 3.5 camera?  How well does
this camera cover 7p *at full aperture* (I emphasize this because
viewing is done at full aperture)???

As we have discussed before, camera optics and viewer optics have
totally different requirements.  You would not be very happy 
trying to use your favorite Belplasca camera lenses to view the 
slides it took.
    
-- George Themelis


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