Question regarding AF lens in domes vs CS lens on box camera

[camera-newbie 0]

Ok.. My next area of interest.. I was looking at both Basler IP box cameras (e.g. BIP2-1920c-dn) and IQEye equiv models and I see most dome models having auto-focus systems but models like the above mentioned Basler have a DC controlled Iris drive system -- are these effectively manual focus that is computer controlled? If this is the case, how well do these work in reality? Is it a set-n-forget type of setup where you do the initial focusing once the setup is more or less complete and just leave it or are these meant to be zoomed in on specific subject(s) remotely? I'm just trying to figure out if I should steer away from the box cameras with the interchangable lenses.

 

Also, IF I go the box camera route, should I pony up extra $$ for the IR adjusted lenses if available?

 

So far, I'm liking what I see in the Basler stuff -- nice n small, decent specs from what I can tell,...

[Soundy 1]

I see most dome models having auto-focus systems but models like the above mentioned Basler have a DC controlled Iris drive system -- are these effectively manual focus that is computer controlled?

Nope - the two are completely different things.

 

Camera-based autofocus (as opposed to lens-based) is actually auto-backfocus, where the camera physically moves the sensor closer to or farther from the lens. It tends to work quite well in most cameras that have it.

 

The lens's iris is there to control the amount of light the lens passes. With a DC-drive lens, the camera controls the iris based on the light level detected. While this does have an effect (or side-effect) on the depth of focus, it DOES NOT directly control or adjust the focus.

 

Also, IF I go the box camera route, should I pony up extra $$ for the IR adjusted lenses if available?

Only necessary if it's a TDN/ICR camera.

[camera-newbie 0]

Thanks.. So I think if I'm interpreting you correctly, cameras such as the Basler BIP2-1920c-dn are fixed (at least from what I can tell) meaning you set the focus and that's the way it stays.

From what I've found on it, yes, that appears to be the case. The back-focus may be manually adjustable (couldn't find specific mention of it, but it's not uncommon), but it's not automatic.

 

However, for the IQEye Sentinel IQ832NE-V6 for instance, it's to auto-back focus and can do it's own focusing.

To a degree. With ABF cameras, you'll generally get the focus "close" using the lens rings, then trigger the ABF for the camera to fine-tune the focus itself.

 

I think what I'm hearing is to shy away from fixed lens cameras unless I'm looking at an area with a uniform distance to ensure everything stays in focus.. --?

Not at all. ABF cameras don't typically use it to constantly adjust focus in real-time. SOME true-day/night cameras will trigger an ABF adjustment when they switch modes between day and night, but not all.

 

Also, according to http://www.iqeye.com/products/sentinel-series.html, "Remote Back Focus for Sharp focusing (IQ86x Models)" - meaning the 832 might not have ABF. Then again, their site only lists the current 86x models, so the 832 may indeed have it (actually, I haven't been able to find ANY details on this older camera - lots of places it's for sale online but very little in the way of technical info).

 

Note that if it does though, "remote back focus" only means you can trigger it remotely to run the adjustment; again, it won't do it all the time to keep everything in focus.

 

Keep in mind, ABF *does not* adjust the DOF to maintain focus through the entire depth of the scene. Generally there will be a defined area in the center of the frame, and it will try for the sharpest focus within that area. Some cameras may be more intelligent, working off the most prominent object in the frame, or may allow you to define what area it bases its focus on, but either way, basically all it's doing is adjusting for the highest level of contrast within a given area of the frame.

 

It comes down to this: ABF is mainly a setup tool. You'll generally use it when you aim and focus the camera, and then never again, unless you change the aim or focus. It's convenient, but far from necessary. Lack of it is certainly no reason to avoid a camera, if everything else about that camera is a good fit.