Advice welcome on lens for 5MP box camera

[mechBgon 0]

I'm considering a new lens for my front window camera. It's a Grandstream 5MP box camera with a 1/2" sensor and CS-mount stock lens (varifocal manual-iris, unknown manufacturer). The camera/lens is relatively inexpensive, so I'm wondering what to expect from an aftermarket lens. In the attached sample pic, the camera is near the wide end of its zoom, so I don't expect miracles, but it would be nice to be able to read the license plate on that car in good lighting conditions. Also, grade-school kids walk this way to/from school, so if anything went down, I would like to have good info for law enforcement. Any opinions on whether it's worth trying a new lens?

 

 

 

The other thing I'm up against, is that the scene varies from bright sunlight to dimly-lighted nighttime. People passing the window are at close range, so it takes a fairly fast shutter speed to get clear face identification. The best compromise seems to be 1/125th-second. But that swamps the camera in daylight. So the other selling point for a new lens is that I can pick up an auto-iris model and hopefully stick to one shutter speed.

 

 

 

 

welcome to the surface of the sun

 

I scrounged for a 1/2" auto-iris varifocal 5MP lens and there aren't many options. I found this one: http://www.bhphotovideo.com/c/product/869727-REG/Tokina_tvr4518hddc_ir_TVR4518HDDCIR_1_2_5_MP.html Any other nominees are welcome. Any advice on the real-world value of a 5MP-rated lens over 3MP?

[ssmith10pn 0]

If you have a CS to C adapter this lens does a nice job.

 

http://www.fujifilmusa.com/products/optical_devices/security/vari-focal/1-2-auto/dv34x38sa-sa1/

[mechBgon 0]

If you have a CS to C adapter this lens does a nice job.

 

http://www.fujifilmusa.com/products/optical_devices/security/vari-focal/1-2-auto/dv34x38sa-sa1/

 

I'm game, I'll get one of those with a CS-to-C adapter and try it out. Thanks ssmith

[MaxIcon 0]

Another decent 1/2" zoom lens for a reasonable price is the Arecont MPL4-10, though it's a manual iris lens. They typically run just over $100. Your current lens shows a fair bit of chromatic aberration (all those purple fringes, pretty common on inexpensive lenses), but looks fairly sharp, for looking through a window. Getting sharp focus on a 5MP cam with a CS mount lens can be tricky, as very small adjustments can change focus a good bit.

 

You should be able to set your camera for a maximum exposure time with variable exposure below that. That is, it would auto-adjust exposure, but never go longer than your maximum exposure time of 1/125 or whatever. That would give good daytime control but avoid the motion blur at night. I'm not sure how the Grandstream supports that type of setting, though.

 

The license on that image is only about 25 pixels wide, which isn't enough for ID, in general, and wouldn't be helped by a sharper lens. You'd need to zoom in more, or hope for a capture with the car closer to the camera. For a straight on view, you'd need 40 pixels per foot minimum (a license plate is about a foot wide), and more when it's at an angle like this or if the lighting isn't great.

[buellwinkle 0]

We researched some lenses for an upcoming project and found Fujinon to have good quality and they make a large variety of auto-iris lenses. We were looking at one for a 1MP camera, 5-50mm, autoiris and it was about $100. It could be a 1/2' 3MP lens would work just as well. As a photographer, Fujinon has a much better reputation for quality than Tokina. You may need a C to CS adapter like we did.

[tomcctv 190]

Hi. I don't think you need to do anything with your lens ..... 5mp camera should pick up plates no problem.

 

Your problem is mounting camera behind class ........ In every one of your pictures you are also getting image of counter. Overlay on your image. Plus you can't get 100% focus though a window. Befor you spend

Any more money try mounting your camera outside.

[ssmith10pn 0]

Does that guy have a gun in his hand?

[mechBgon 0]

Thanks everyone for the input. Yeah, looking at an angle through two layers of window glass, plus interior reflections, sure doesn't help. It would be worse if I didn't put a matte-black glare shield behind the camera to intercept the actual store interior.

 

Grandstream currently doesn't have an exposure "cap" feature, or I'd definitely use that. In lieu of that option, or the necessary skeels to script an exposure change tied to sunrise/sunset times, I'll see how the auto-iris option works out, and post a fresh picture late next week for anyone who's curious.

 

The license on that image is only about 25 pixels wide, which isn't enough for ID, in general, and wouldn't be helped by a sharper lens. You'd need to zoom in more, or hope for a capture with the car closer to the camera. For a straight on view, you'd need 40 pixels per foot minimum (a license plate is about a foot wide), and more when it's at an angle like this or if the lighting isn't great.

 

Good point. I'll keep my expectations realistic.

 

Does that guy have a gun in his hand?

 

Yes, and he was aiming it all over the place too, including at occupied residences and through our front window. I think he was testing the laser sight. This area's a bit sketchy at night.

[mechBgon 0]

I ordered the recommended Fujinon lens from an outfit that never shipped it, and ignores my efforts to contact them Time to have PayPal lower the boom on 'em.

 

Meanwhile, I ended up with a similar Fujinon auto-iris 3MP-rated lens, the DV3.8x4SR4A-SA1, from a different online store. This one is supposed to be day/night. Below are comparisons of my stock manual-iris lens and the auto-iris Fujinon, for anyone who was curious.

 

 

 

 

 

Optically, I think I'm getting about the same effective performance*. And there's only so much you can expect when the camera's looking through a double-pane window at a 45-degree angle. But now I can leave exposure locked at 1/125th-second and be done with it.

 

*I should qualify that... I noticed at dusk that the camera removed its IR-cut filter and the focus went fuzzy. Apparently not IR-corrected. In my case it doesn't matter much, because after dark the only light sources are visible light anyway, so I can leave the camera in "daytime" visible-light-only mode and the focus doesn't shift. Sample below. All these pics were reduced to 60% JPEG quality to fit under the 500kb limit, by the way.

 

[ssmith10pn 0]

IR correction has nothing to do with it.

You have no IR.

 

You need to tweak the focus at dusk when the iris is wide open.

Back in the analog days we would focus through a piece of welding glass to get the iris wide open.

[mechBgon 0]

IR correction has nothing to do with it.

You have no IR.

 

You need to tweak the focus at dusk when the iris is wide open.

Back in the analog days we would focus through a piece of welding glass to get the iris wide open.

 

I'll definitely revisit the focus at dusk when the iris is wide-open. Although the camera itself has no IR, I was under the impression it was picking up the ambient IR from the sun, hence why the cameras have an IR-cut filter for daytime operation. Since I was watching the camera at the time, I toggled the IR-cut filter on/off to see if that was the cause of the fuzzy focus, which seemed to be the case. But regardless, I'm betting I can improve the open-iris focus like you said.

 

I found a couple more of that lens on Large Auction Site for $50 a pop and grabbed one for my entryway camera too, since it faces the same varying light conditions to a lesser degree.

[ssmith10pn 0]

I think we both misunderstood each other.

 

Yes the cut filter is to take out ambient IR in the day time which is really not an issue with megapixel cameras.

The IR correction is to help with focus shift when using a IR source for light at night.

[mechBgon 0]

Oh, gotcha. I did revisit the focus with the iris wide open at twilight tonight, just to get the most out of the camera under the circumstances.

 

I wish I had more illumination out there in that parking lot, it's like a black hole. I'm just the bicycle mechanic, so I'm at the opposite end of the food chain from the people who ought to be adding more lights (the property owners, or the property managers, or the business owners). If I could, I'd slap up a couple IR illuminators, but the front of the building is, like, 2ft thick concrete