P3D Re: Twinned Pentax ZX-M and lens pairing

[Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

I'm posting this for Wlad (no charge!).

Gabriel



Greg E. 
>   Have you taken flash photos with your setup?

Yes, I use one Pentax flash connected inserted to the flash shoe
on one camera. I have described my experience in one of my previous
posts:

> There is a small problem though. If you want to use one flash for both
> cameras, the shutter speed should be 1/30. Even with 1/60 I was getting
> occasionally partly exposed picture on the camera without the flash 
> (on 36 exp. roll of film I got 3 of those). With 1/30 I took 3 full 
> rolls (3x36)x2 and all of them were correct. I was surprised to find 
> out that this low speed doesn't introduce any motion blur - flash light
> does "fast timing" well enough (my last shots were taken during 
> Tropicana show with lots of fast dancing and they are great).


When I started using that Pentax pair I suspected that I may get some
problems with flash synchronization, so I was taking shots with 1/60
shutter speed set on both cameras. Those 3 wasted slide from the camera
without the flash had a black strip at the bottom, about 1/5 of the
picture surface. Since I have started using 1/30 speed, I don't have
any problems.


========== ### ========== 

Now I would like to ask something. Not long ago there was a post
about Twinning Olympus Stylus. The information provided woke 
up my curiosity again. I'm trying to gain some knowledge about 
judging lens quality. The following was written:

> This is a four element (in four groups) 35 mm f/2.8 lens. The limit 
> for a simple 35 mm lens, even with high index glass, is f/3.5 and 
> you will get some illumination falloff at that (such as the Tessar 
> on the T4).

How do you judge the lens? How problems manifest themselves on the 
image (what do they look like)? What is Illumination falloff? 
What's the difference between "sharp" and "contrasty"? 
I guess I already asked too much. I'll appreciate any info. 
Can somebody suggest any literature I should go through?

I didn't know that Yashica T4 had some flaws in it's quite 
"famous" lens. All reviews I've read were very positive about 
the optics.

I was also wondering what are the best ways to pair the lenses for 3D.
Some earlier posts were suggesting just to compare the size of the
image projected on the wall through the lenses. There was the thread
on P3D about it last year. Is it enough to test just that? What was 
done to find good pairs, for example for Realist camera, when it was
manufactured? 


Regards
Wlad