ebay CCTV camera has "magic" auto iris and backlight switch

[rowan194]

Just had a colour CCTV camera delivered, I opened it up to see if it
was just a standard module board that I could squeeze into a smaller
case... to my surprise, I found the auto-iris connector only has V+
and ground wired (no video or drive - is the lens supposed to guess
how bright it is?) and the backlight compensation switch is mounted
but it has NO wiring at all!

The manual is a real hoot too, it's even worse than the usual chinese
english (probably auto-translated)

Video quality seems decent enough.

I guess you get what you pay for.

 

[John Tserkezis]

rowan194 wrote:

... and the backlight compensation switch is mounted
but it has NO wiring at all!

That's what I was going to ask, do the v+ and ground wires actually go
anywhere? I guessed not...

The manual is a real hoot too, it's even worse than the usual chinese
english (probably auto-translated)

Some time back, our secretary at work said the solar thingy on her
big-buttoned calculator wasn't working.
After a few more probing looks, it appeared the calculator is just plain
dead. I said the solar thingys aren't even connected, they're just slabs of
plastic purely for looks.
A subsequent disassembly and reconnect of the built-in battery fixed it.

Video quality seems decent enough.

For what you paid? I've worked with cameras they actually _do_ use in CCTV
applications, and there's a reason they cost what they do. Aside from an
actual working iris, they give a better image too.

I guess you get what you pay for.

You've got that right.
--
Linux Registered User # 302622
<http://counter.li.org>

 

[rowan194]

It gets better: when I pulled the supplied switching plugpack out of
the socket the front broke off, exposing its internals and breaking
off one of the mains wires. That's not quite so funny.......

 

[John Tserkezis]

rowan194 wrote:

No, an attached auto-iris lens *will* be powered, but it won't do much
else without a signal output.

Then why would the Chinese spend money on iris functionality, a motor, and
associated control circuitry, if it's not being used? Seems to me, they'd be
by far more likely to have some "wire" connecting the two to make it *look*
"right" rather than function.
Like my solar calculator example, it's deception. You have only the price
to go by.

Couldn't pin 3 (video) have just been wired in parallel to the
composite output, or does it need buffering?

No, you just need the raw video output, pre-processed by the auto "software"
level. Feed that to the iris (along with power of course), and the negative
feedback (within the iris) takes care of the rest.
Three wires. Gnd, +v, and video. Never seen any other implementation,
though I haven't worked with a HUGE amount of cameras, just lots.

Video quality seems decent enough.

For what you paid? I've worked with cameras they actually _do_ use in CCTV
applications, and there's a reason they cost what they do. Aside from an
actual working iris, they give a better image too.

I'm using it for some basic home security so it doesn't need to be a
super good image.

I'm going to guess that's a CMOS camera rather than CCD, and I'll also
hazzard a guess that the plugpack is NOT C-Ticked?

Size is also important which is why I was pleased to
see there was a small module inside.

There are other options where you can get just the CMOS video image element,
(your choice of lenses too!) with a small board on the back (much like yours,
but smaller). You have to supply power yourself, but comes with (short) cables.
You can retro fit these into the "dome" covers, or even buy domes with
cameras in them (at a higher cost). Would end up smaller and neater than that
chunky box.

I made up a simple page with a couple of pics of this...
http://www.gadgetguts.com/cheap-cctv-camera/

For what you're getting, I really don't think it's the best value for money
out there.

(after looking at the AC adaptor) Yeah, that did it, now I'm scared.
--
Linux Registered User # 302622
<http://counter.li.org>

 

[rowan194]

On Nov 27, 9:35 am, John Tserkezis
<j...@techniciansyndrome.org.invalid> wrote:

rowan194 wrote:
... and the backlight compensation switch is mounted
but it has NO wiring at all!

That's what I was going to ask, do the v+ and ground wires actually go
anywhere? I guessed not...

No, an attached auto-iris lens *will* be powered, but it won't do much
else without a signal output.

Couldn't pin 3 (video) have just been wired in parallel to the
composite output, or does it need buffering?

Video quality seems decent enough.

For what you paid? I've worked with cameras they actually _do_ use in CCTV
applications, and there's a reason they cost what they do. Aside from an
actual working iris, they give a better image too.

I'm using it for some basic home security so it doesn't need to be a
super good image. Size is also important which is why I was pleased to
see there was a small module inside.

I made up a simple page with a couple of pics of this...

http://www.gadgetguts.com/cheap-cctv-camera/

 

[rowan194]

On Nov 27, 11:17 am, John Tserkezis
<j...@techniciansyndrome.org.invalid> wrote:

rowan194 wrote:
Couldn't pin 3 (video) have just been wired in parallel to the
composite output, or does it need buffering?

No, you just need the raw video output, pre-processed by the auto "software"
level. Feed that to the iris (along with power of course), and the negative
feedback (within the iris) takes care of the rest.
Three wires. Gnd, +v, and video. Never seen any other implementation,
though I haven't worked with a HUGE amount of cameras, just lots.

Right, so the module needs to support it. That probably explains why
the backlight compensation switch isn't wired. I'd guess the auto-iris
lens is still fed power to keep it in a consistent (either wide open
or stopped down as far as possible) state.

Here's the ebay listing, I don't know whether the seller is aware of
this little "issue."

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=150184644969

 

[John Tserkezis]

rowan194 wrote:

Right, so the module needs to support it. That probably explains why
the backlight compensation switch isn't wired.

No, I can't see why. The backlight compensation does exactly what you think
it does, it manually forces the iris (either the external auto-iris, or the
internal gain) brighter to cater for the dim (relevant) parts of the image.
Problem is, this is rarely something that can be handled by an on/off
switch, you really don't know how far the brightness needs to be shifted to
get a decent image in the non-bright area between one installation and the next.
Regardless of this, real-life installers position the cameras in FRONT of
light sources, so you don't get this problem in the first place.
In other words, this backlight compensation function is mostly pointless
even if it did work.

And largely irrelevant to whether or not the external lens has a functional
iris or not anyway.

I'd guess the auto-iris
lens is still fed power to keep it in a consistent (either wide open
or stopped down as far as possible) state.

No, default (no power) is wide open.

Here's the ebay listing, I don't know whether the seller is aware of
this little "issue."
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=150184644969

Aware? Who knows. Care? Definitely not.
--
Linux Registered User # 302622
<http://counter.li.org>

 

I guess the seller saw this thread because he offered a replacement
plugpack, or a $US2 (!) refund.