Subscriber Discussion

Do I Need A Camera With Optical Zoom Here?

There are fixed cameras with optical zoom, the contractor is advising us to purchase this camera instead of manual varifocal/zoom lens, he is stating that the benefit of this feature it is not affected by vibration and it does not require re alignment of the lens focal length after installation (which will enhance the operational procedure and require less frequent access to the site) as it will be done remotely. Is this correct ? I have asked several manufacturer and they advised me that this is correct however it is not needed for 10 to 15 years in door camera cases and this feature is a must for outdoor cameras mounted on poles…

My case is that the cameras are ceiling mounted on semi-outdoor/indoor area “soffit”.

Accepting this will increase the number of cameras hugely, as I am looking for a camera that shall have a wide angle of view (in the range of 107 degrees), I appreciate your expert opinion and advise.

Also I appreciate if you can assist me in finding an IP camera that is Wide Dynamic range with motorized verifocal lens and wide angle (not less than 107 degrees).

There are 3 categories relevant here:

  • manually adjustment of focus
  • automatic adjustment of focus but no optical zoom
  • automatic adjustment of focus AND optical zoom

If you want the focus to be automatically adjusted, you can get a camera that does so and not pay for optical zoom.

Stepping back, though, the issue with vibration will be primarily about the image shaking (as the whole camera moves) rather than simply it getting out of focus.

Stepping back further, do you have a preferred camera choice right now? What have you been looking at?

I fetched an Axis P-3353 not long back that's a real trooper, I think its got almost everything you want, (the angle only goes as wide as 105, not 107), as for the price though, ouch, it'l take the mustard off the hotdog as we say round here...

107 degrees will be the most difficult specification to meet in a motorized zoom camera (or even just an auto-focus camera). Most camera in this class will have lenses in the 3-12mm range and will give an H FOV of 80 degrees or so. The Axis camera that Jim mentions above with its 2.5mm @ F1.2 would meet your requirements almost perfectly (and maybe price doesn't matter so much when the offering is so unique! :-) )

Hikvision seems to be making good cameras, we started using them a lot last September and have good luck with them, they have this DS-2CD7254FWD-EIZ(H)(S), 2.7 ~ 9 mm @F1.6, angle of view: 101° ~ 30.4° (not quite 107) I have not used this particular model but I have used the bullet version that has very similar specifications DS-2CD8254FWD-EIZ. I dont know how true their claims are to 120 dB WDR but it seems to preform well. Price point is reasonable too.

Both Axis and Hikvision are good options, either way your customer would probably be happy with them.

Long and short of it is, a camera with auto back-focus should suffice, since it will address the "expected" need to tweak focus from time to time, while zoom really isn't something you'll need to alter on an ongoing basis. It's a feature that's built into the camera body, so you then have an option of which lens to use to get the view you want, rather than something that's part of the lens and thus usually means a combined camera/lens unit.

The catch is, you do have to make sure it can be triggered remotely... which SHOULDN'T be an issue with most IP cameras, although with an analog camera it would require a separate RS-485 connection. There may actually be a few older IP cameras floating around that only support control via RS-485 as well, so it's best to be sure in advance, because that's not something you want to learn AFTER everything is purchased ad installed.

It's not clear whether the expected problem with vibration is image shake, or the idea that focus may drift because of it... if the zoom, focus and backfocus are properly locked down on a standard varifocal lens, there should be no change due to vibration. If image stability is the concern, none of these particular options (remote zoom, remote focus, ABF) do anything to address vibration or camera shake. For that you need some form of image stabilization, which is a whole other realm.

camera with auto back-focus...

If a camera just says its got 'auto-focus' that means adjust focal length at the lens, I reckon. And auto back-focus would adjust the distance of the lens to the sensor, right? So is auto back-focus a continual auto-focus or like a one touch thing? Isn't just remote back-focus enough?

With allowances for marketing types' penchant for making things up on the fly...

You are correct, auto-focus typically involves moving the focus ring of the lens itself, while auto-backfocus adjusts the lens/sensor distance by moving the sensor (or less commonly, the lens mount). The former is a function of the lens, the latter a function of the camera.

In almost all cases, an AF lens is controlled by the camera, and in almost all cases with CCTV, that means the lens and camera are an integrated unit, which potentially limits your lens options to those specifically designed for - and sold with - the camera. I've seen a very few lenses that had remote-controllable zoom and focus independent of the camera, but those merely had connections to power the motors and required some sort of driver to interface with RS-485, AF, etc. You could use something like that and just run wires to the lens to send it the power to adjust via switches or something... seems like a lot of screwing around though, and your selection of lenses would be extremely narrow.

Since ABF moves the sensor even without a lens attached, you can typically use any suitable lens on the camera, which gives you the option to use whatever is best for your purpose. For extreme wide angles, Theia makes some really nice (if somewhat spendy) C/CS-mount lenses.

You're also correct, JUST remote backfocus would probably do the trick... however, I haven't seen any cameras that had motor-driven backfocus that didn't have ABF. I've used manual remote focus on some cameras and it's a nightmare to work with - you'll spend more time trying to get it right than you would just putting a ladder up to the camera.

In most cases with CCTV, both AF and ABF are one-shot triggered by something else, be it a change in zoom, switching the IR cut filter, or a manual signal of some kind. I seem to recall a couple cameras that had a continual AF mode, but I'm not sure what the value of that would be in most CCTV installations, as something passing close to the camera (flying creature of some kind, for example) could conceivable trigger the AF to re-adjust, thereby throwing the rest of the scene out of focus for a short period... or even indefinitely if the camera doesn't "think" to re-focus afterward.

Great explanation! One thing I don't get though is what do you mean by 'manual remote focus' being a nightmare? Is it because of latency issues or something? Why would it be harder than going up the ladder?

The ones I've done manual control of the focus on generally give you two or three options of "steps", of how fine the control is - large steps get you close to the setting you want, small steps to fine-tune. Problem is, it usually take a lot of click-click-click back and forth to get that fine tuning done, and there's always a lag between clicking, and seeing the results... not "harder" as such, but it can be very time-consuming and frustrating, especially if you have to do it on more than a couple cameras.

When you have that ability to start with, autofocus should be a given. I've only seen one camera that had remote-controllable focus that DIDN'T also have autofocus, though...

From your experience, is it true that over time of first installing the camera, the camera focal length will change and will need re adjustment for indoor and semi indoor environment ? If yes,

1- is the optical remote zoom is the correct choice to minimize the site activity of the operation and Maintinance team ?

2- can this be solved with auto focus, like a box equipped with dc iris lens or dome cameras ?

3- after how many years this will happen, once a year or once in 10 years ?

I know you are askin' for Matt's opine, but if you don't mind me taking a whack at it too, just so I can compare with, and see if Matt done learn me a lick...

1. No, optical remote zoom is not neccesary to minimize on-site support. Remote back-focus preferably with auto back focus is enuff to make up for any drift.

2. Yes, if you mean autofocus thru the lens, that should also work just fine, though I don't believe that just because a lens has dc auto iris it has autofocus also. However it is more flexible to choose ABF because you are not tied to specific lens options.

3. A long time... I'm least sure about this one, but I can say I've seen cameras stay in-focus for 5 plus years. I was gonna say that rubber o-rings might deform slightly over time as they dry, and depending on the daily temp changes you might get some warping of the metal c ring threads, and that glass technically being a liquid and all and gravity being what it is, that the thick middle of the lens might creep down a bit, but I don't really know, so I won't. ;)