The computar lens should work fine since it has a fixed 1.8f aperture. This will allow maximum light to enter the lens even when zoomed in. However, this is a very expensive lens. We do offer a 2 Megapixel IP Bullet with a 6-60mm lens. Not sure if that would serve you better. We also offer a 5 Megapixel Box camera which would allow you to use the digital zoom and get high quality snap shots from long distances and you could use a smaller and less expensive lens. 

As for the lens compatibility, the lens will mount and function properly, but if you try to use the lens at a wide aperture instead of zoomed in you may be able to see the lens housing in the image on IP cameras that use a 1/2″ sensor instead of the 1/3″ sensor. However it seems unlikely that you will use the lens that way. 

As for RS-485 control, our 3 megapixel and 5 megapixel IP box cameras have built in RS-485 and Pelco D is an accepted protocol. 

Glad you are happy with our service. We do our best. Their are many contributors that are not employees as well. As for the zoom capability, you have to have something to compare it to. So for example, if you were comparing it to an analog camera and DVR that was recording at D1 resolution the comparison would work like this:

D1 resolution = 704 x 480 pixels = 337920 pixels total

5 Megapixel resolution = 2592 x 1944 pixels = 5038484 pixels total

5038484 / 337920 = 14.91 so a 5 megapixel native image is 14.91 time larger (and 14.91 times more detail) than a D1 resolution image. So you can get the same effective magnification with 1/15th of the zoom. So if you needed 187mm zoom with a D1 resolution recording then you should be able to get the same image detail with a 5 megapixel camera and a 12mm lens. 

This is all theory, but should be correct.