First post here, so be gentle!
I'm looking at my new pdf for SR4, and I'm under the complete impression that the Availability ratings of the various enhancements add to the rating of the device.
On page 324 it shows two separate tables, one entitled 'Vision Enhancement' (containing the aforementioned contacts, plus goggles, binocs, etc) and the other entitled enhancements (which of course list all the, well, enhancements you can get).
The vision devices have separate ratings than the enhancements, yes, but down the column for the enhancement avail ratings it distinctly shows a + beside each.
That's probably a good indicator that it adds to the base A.R. of the shades/contacts/goggles/whatever.
Therefore in chargen, you can fit a lot less in a pair of contacts (A.R.=6) than goggles (no availability rating, hence available anywhere unenhanced).
This helps limit things to reasonable limits (imho) in chargen. However, it does seem to imply that you
could buy a pair of 'contacts of doom' containing all the possible vision aids if you managed to succeed against an insanely high A.R. as was previously mentioned. Of course, with such a high A.R. they would definitely be considered super-tech beyond the normal realm of Shadowrun SOTA.
In fact, they would have almost
twice as high an availibility rating as a Panther Assault Cannon!!
The only bits of weirdness that bug me?
The most you can fit in a pair of cybereyes is 16 capacity worth of enhancements. That is actually 4 units shy of fitting every enhancement (with maxed ratings) into the cybereyes.
Meanwhile, if you can manage the sky high availability, you can get contacts that have ALL the enhancements.
I don't know about you, but I'd think you can fit more into a pair of cybereyes than in a pair of thin contacts.
On the flip side? I would think I could fit more enhancements into a pair of binoculars or goggles than a pair of cybereyes. Since you wouldn't have to miniaturize the components as much, it would also be alot easier to do, and hence have a lower availibility.
Unfortunately, even a pair of full-sized goggles with all the bells and whistles would have an availibility rating of 30!!!
Couple cool things I'd like to point out though....
The Image Link enhancement doesn't add to the avail rating of the different devices, so no worries about it taking up the affordable A.R. instead of that flare compensation you wanted to squeeze in.
Even better, both Image Link and an Eye Recording Unit (camera for photos and videos) are INCLUDED standard in EVERY set of cybereyes. Don't forget you no longer have to worry about buying extra headware memory for the recorder.
These are all things that cost a lot of extra space,nuyen, and/or essence in SR3.
OH! I almost forgot something almost as cool...
Every smartlink modified gun now comes with a small camera on the gun that you can use to look through and target the gun around cover or a corner without exposing the rest of your body. Also, if you want, you could purchase enhancements for the 'guncam'.
Anyway, I hope that helps!
-Ravennus