The way stacking penalties work in EVE ( and Dust, you can check the stacking penalties against Cardiac and Kinetics and they will follow this pattern. ) is like this:

For positive modifiers:
Base * Skill Modifier * Skill Modifier * (1+Module_Modifier) * (1+Module_Modifier*Stacking Penalty) * (1+Module_Modifier*Stacking Penalty)GǪ

For negative ( reductions ) modifiers:
Base * Skill Modifier * Skill Modifier * (1-Module_Modifier) * (1-Module_Modifier*Stacking Penalty) * (1-Module_Modifier*Stacking Penalty)GǪ

The stacking penalty increasing for each additional module.

The stacking penalty can be approximated by = 0.5^(((n-1)/2.22292081)^2) where n is the number of the module. This makes the modules work with the following efficacy.
1st module = 100%
2nd Gëê 86.91%
3rd Gëê 57.06%
4th Gëê 28.30%
5th Gëê 10.60%

If we apply this to a medium suit, which has a base scan profile of 50 dB, we get the following:

Base = 50 dB
Skill Modifier = 2% reduction in scan profile per level of 'Profile Dampening' (10% reduction at level 5)
Complex Profile Dampener = 25% reduction in scan profile
Enhanced Profile Dampener = 20% reduction in scan profile
Standard Profile Dampener = 15% reduction in scan profile

So a medium suit with level 5 in profile dampening and 2 complex profile dampeners will have:
50 * 0.9 * (1-0.25) * (1-0.25*0.8691) Gëê 26.42 dB scan profile

This is clearly lower than the 28 dB scan precision of a prototype active scanner and the suit will not be detected.

However if you have a medium suit with level 5 in profile dampening and 1 complex profile dampener and 1 enhanced profile dampener you will get the following:
50 * 0.9 * (1-0.25) * (1-0.20*0.8691) Gëê 27.88 dB scan profile

This is also clearly lower than the 28 dB scan precision of a prototype active scanner and the suit should not have been detected, how ever it is detected. ( we tried a few different prototype scanners and all of them detect this suit. )

Now we assume the reason for it being detected is because of the "armour bug".

In game:
Complex armour plate has a movement penalty of 5%.
Complex ferroscale plate has NO movement penalty how ever we assume it actually has one that is set to 0%. ( The calculation will show why we think this. )
Medium suit: 5.00 m/s
1st module, complex armour plate: 4.75 m/s
2nd module, complex armour plate: 4.54 m/s

Now the weird bit, we put on a ferroscale plate.

3rd module, complex ferroscale plate: 4.64 m/s

A few quick calculations to show stacking penalties:
5.00 * (1-0.05) = 4.75
5.00 * (1-0.05) * (1-0.05*0.8691) Gëê 4.54

Now for the weird bit:
5.00 * (1-0) * (1-0.05*0.8691) * (1-0.05*0.5706) Gëê 4.64

As you can see here both the assumption that the ferroscale actually has a movement penalty of 0% and that it is calculated 'first in line' in the stack is confirmed.

Now supposedly EVE ( and Dust ) are to apply the largest modifiers first and then the smaller ones. This leads us back to the example of a medium suit with 1 complex- & 1 enhanced profile dampener being detected by a prototype active scanner. You see if you apply the stacking penalty in the "wrong" order you will get:
50 * 0.9 * (1-0.20) * (1-0.25*0.8691) Gëê 28.18 dB scan profile

Which would explain why the suit is, currently, being detected by a prototype active scanner.

Very nice guys. Thanks for this.

On related note, I have noticed a few things that apply to longer (sniping) ranges. Obviously these ranges are not applicable to active scanners.

1. The chevron gets brighter as you move your sight closer to the target.
2. When you look right at a target, you can see it at pretty much any range. Out to >500m, even though your damage drop off makes it way less likely you will do serious damage. I have seen a few scout suits where all you get is a red dot and no chevron but I remember these from previous versions and can't remember (or don't notice!) if I have seen this recently.
3. The "wedge" where you can see something is progressively smaller than 60 degrees at longer distances. From your data at close (<80m) range, the "wedge" is 60 degrees. At 200m it is much smaller (I have not tested the width, but it is much smaller). At 400m it is even smaller (I have not tested the width, but it is quite a bit smaller). It would be interesting to see if this "width" changes depending on the precision modifiers and dB profile of the target suit.

If you catch me, I'd be happy to test the longer range observations with you in-game.

Again, thanks for this.


Munch

Oh, just noticed that DFT has Scan Profile as a non-stacking attribute (i guess it didn't mention stacking in the description). Your results suggest that it is stacking. Is this pretty much the consensus of the community? Also what about Scan Radius (it is also currently marked as non-stacking in DFT)

Me and a corpmate did a bunch of testing with active and passive scanning and yes 'Precision Enhancers', 'Profile Dampeners' and 'Range Amplifiers' all suffer from stacking penalties.

Edit 1: I do not know if anyone got a confirmation that this is a bug from a dev, to be fair I do not remember anyone saying that they heard back from any dev regarding this. I am certain, how ever, that it was reported back when ferroscales were introduced.

Edit 2: It was confirmed as a defect by 'CCP Cmdr Wang' back in july. Link to weekly bug reports: https://forums.dust514.com/default.aspx?g=posts&m=1057188#post1057188 - '[BUG] Ferroscale speed bonus?'

'xxwhitedevilxx M' reported the bug on the forums in the begining of july: https://forums.dust514.com/default.aspx?g=posts&m=1009079#post1009079

Thank you Haerr

I've released DFT 3.4.2 which enables stacking penalty on those modules, thanks to your evidence.

It also replicates the "armor bug" by giving it a minuscule negative penalty. I should have caught that one sooner
If you find more such issues, please post them in the DFT thread so i can take care of it.

Cheers

Great posts people, props to bojo and Haerr for providing nice in depth math, I have saved these calculations for future reference.

I am most interested in characteristics of passive scanning as I am a heavy and dodging profile scans would eat up to valuable of real estate.

I assume those are implicating the stacking penalty?

But hot dang that's a hot scout buff
(Unrelated: Looks like heavies are getting a buff as well, I think that bringing the heavy and light closer to par is a step in right direction)

It works but modules are vastly underpowered compared to active scanners and nobody but CCP knows how passive scanning actually works.

Base range on all Light and Scout suits change from 10 -> 16

Gallente Scout
Base: 16 m
+Suit L5: 24 m
+Range L5: 36 m
+1Complex: 52.2 m
+2Complex: 72.62 m
+3Complex: 91.26 m
+4Complex: 102.88 m
Google Docs - documents is updated as well.

I am a blip.

Alright, I've brought this up two or three times but I have re-done my testing videos to provide a more clear demonstration of what I'm getting at. I'd like to bring this up for discussion and see what the rest of you think about this, whether it should be changed or not.

http://www.youtube.com/watch?v=TNmx53VMazo

- Targets at 0m will appear on minimap, regardless of profile/precision.
- Targets on screen will appear on minimap, regardless of profile/precision, up to 75m
- Aiming down the sights of your weapon increases the brightness of their chevron/icon on the minimap, even if they are not on screen.
- Bringing the crosshair over a target will reveal their icon/chevron regardless of profile/precision (a tactic used by snipers to reveal location even if they cannot visibly see them).

Think there needs to be changes to this?

Edit: Grit_Breather on IRC explains it pretty well: "ADS increases forward scan cone range but doesn't reduce angle accordingly"