P3D Re: slide bar

[koganlee@xxxxxxxxxxxxx]

George Themelis states "Are you looking into taking hyperstereos with a slide
>bar?  This is not the best way to do it.  Moderate hyperstereos (in the
>order of a few times the normal 65 mm) in my opinion are pretty much
>useless."

I strongly disagree with this statement. If you use a normal base of about 2.5 inches with a scene that is about 7 feet to infinity then you 
will get good depth in the image. If your scene goes from 14 feet to infinity the image will have half as much depth than if the base had been 
increased to about 5 inches. If the photographer only had a stereo camera, then it would be some trouble to increase the base, but if they had 
a slide bar that was 2 feet long (as mine is) instead of one that was only a little over 3 inches (as I believe the person who started this 
subject had) it would be no trouble at all, since they were obviously carrying a tripod anyway. To go a little further, let's say that the 
near point of the scene is 20 feet away. Increasing the base from 2.5 to 8 inches would obviously be much better than "useless", and this 
situation would certainly be considered a moderate hyperstereo. Of course, one doesn't have to take my word for it. Few things could be easier 
than making a comparison of stereo bases with the same scene, and then seeing which ones you like best. In fact, I did this many times when I 
was starting out in stereo photography, and there is no comparison as far as I am concerned. It makes sense that one might not want to go to 
the trouble of using a wider base, or have a bias towards orthostereo, but "useless" is a word which makes no sense to me at all.

Personally, I hardly ever use a base less than 4". Landscape photography (my primary interest) lends itself to wider bases. Instead of looking 
for odd branches to put in the foreground, I try to get rid of the foreground entirely and increase the base. I made an 8 foot tall tripod to 
help me do this. In the 14 PSA stereo card competitions I have entered, I have received 5 "Best of Shows" and 19 "honorable mentions", or 
better, with 11 images. The bases of those 11 images were 2.5" (it was made with a Realist), 4" (4 of them), 6", 8", 12" (2 of them), 24", and 
20 feet. I certainly don't think that the judges liked my images because of the wide bases, but I'm sure they didn't hurt either. The final 
word is to check it out for yourself, and don't take my word, or anyone elses, for something that can be so easily determined.

David Lee




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