it's an additional % decrease on to the camo value your tank has. So if your tank has 400 camo, it'll be 440. Also, how much your tank is covered by shrubbery, the other guy's vision range/commander % and everything is a factor in how close he needs to be to spot a tank fully covered. If you leave a big chunk of your tank exposed, he'll see you from way further out than if you're completely covered.
I don't know how much camo the PIV has but remember ever shot you take decreases your camo value, with some guns completely wiping out any camo values you have (like the 152mms on the xSU-152 series). Also agree with camo net on the PIV, as its more useful than binocs. (PIV has a pretty bad view range anyway)
Also I'd transfer the crew to the new tank, and get 75% crews for your money-maker tank. Your new stock tank needs all the help it can get to not suck.
The KV/KV-3 change is probably coming later next year. French tanks will come first, so not anytime soon, so get the tanks if you want to play them, not because you want new slots. I personally hated the KV-3, it's like driving a bucket...
Not sure if you pulled the "400" out of thin air or not--pretty sure you did though But I'm having a lot of difficulty finding any concrete info on how camo (and thus camo net) actually work.
The most "scientific" discussion I've found is here:
http://wiki.worldoftanks.com/Battle_Mechanics (under camouflage)
They link to a thread that translates a German thread; at point, there were tables with apparently tons of info & probalby explains everything I want to know. BUT the picture links don't work anymore. And the thread itself was locked--apparently WOT devs got upset about ppl trying to reverse engineer the camouflage system and banned all discussion?
After more searching, this thread:
http://forum.worldoftanks.eu/index.php?/topic/49238-how-does-cammo-net-work-exactly/
leads me to this page:
http://www.wotdb.info/
Right click on a tank of interest, choose "more info" to see "invisibility factor". Not all tanks have a more info tab.
From the wiki page's notes on "Detection Mechanics", they say an SU-14 in a bush would be detectable at 200 meters regardless of camo net/crew skill. This is consistent with that .info page b/c its invisibility values for the SU-14 are miniscule. So 25% increase of 0.01 is still useless.
They claim a hetzer would only be visible at about 50m. Its stationary invisibility is 0.6. With the 25% boost from camo net + crew skill, that probably boosts to like 0.8-0.9 range or more.
Pz IV has stationary invisibility of 0.3. So after camo net, that's about 0.38. My *guess* is that this means behind a bush, you're detectable at maybe 150m without camo net & 120m with camo net.
So that difference doesn't seem huge. There are of course a lot of assumptions I'm making here (due to an epic lack of real info! ugh)... like assuming that 'invisibility factor' is precisely what camo net modifies, and assuming detection range scales linearly with invisibility factor.
From what I've gleaned, leaving "any" chunk of your tank fully exposed is the same as not being hidden at all. ("Any" in quotes b/c if you have a chunk exposed that is not hit by a 'vision ray' cast from enemy tanks, then it doesn't matter. But from that wiki page, it seems virtually impossible to use this to your advantage b/c a good number of rays are cast.) And I always try to hide a good distance behind bushes so that firing my gun doesn't hurt my hidden-ness.
Also, I don't understand the comment about the bad view range. With the goofy turret, the view range is 420m on pz iv. Binocs (+25%) cap at 500, so with binocs, I'd have max possible view range. Whether that's really useful or not is a diff story (esp since you have to wait 6sec). So given that, coated optics might be superior...b/c that'd boost me to 460m (out of a max 500) always instead of only when stationary.
But yeah, still super unclear on how camouflage works & the benefits of camo net/crew camo skills. It's clear that on vehicles with low camo (heavies, high tier mediums & spg, and high tier TD to a lesser extent), these camo bonsues are worthless. And it's clear that they're super worthwhile on a low-mid tier TD or SPG. But the middle region of like medium tanks is less clear. I guess I could just buy it (100k is cheap) & try, but I'm guessing that unless the difference is night & day, it'll be very hard to discern the benefits and things like placebo-effect come into play.
edit: holy crap, when was the last module sale? I totally want to stock up on those suckers too
edit2: And if you look in the "credit factor" item in the "more info" tab, you can see why a lot of tier 5 tanks are considered good money-makers.