IR, wide diffused or narrow focused?

Discussion in 'Dahua' started by cuz, Feb 10, 2019.

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  1. cuz

    cuz Getting the hang of it

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    Hello, I’m trying to select some cameras to use indoors in a business. I am looking for a camera with night IR that has a wider, shorter beam rather than a narrow, distance focus. I am already using the Dahua 2MP starlight turret Camera and that seems to have a narrow IR beam designed for distance. Is there a Dahua turret that’s better for use indoors that can cast a wider “short throw” IR that will allow me to see a wider angle without the need to see much past 15-20 ft?

    Thanks.
     
  2. J Sigmo

    J Sigmo Known around here

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    I haven't found any cameras whose built-in IR is wide enough. It seems that they all produce a narrow spot in the center of the field of view which burns out that area while leaving the majority of the image too dark.

    I think the best results are obtained by switching the internal IR off and using one or more external IR light sources. What I've ended up doing is just using normal white lighting from standard fixtures at night. That also lets you keep the cameras in their color mode.
     
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  3. Dodutils

    Dodutils Pulling my weight

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    there are lens in front of each IR LED, may be they do have a standard size and you could replace them with another model, or you could turn off internal IR lights and buy some external "wide" IR light projector as @J Sigmo proposed, I already used this solution for the same reason.
     
  4. NoloC

    NoloC Getting comfortable

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    Agree completely. I was wondering is there any reason not to use visible light? I guess when the fixtures were incandescent the energy used was greater but now that led lights have become so efficient, why would we use IR?

    Unless stealth is important it seems supplementing with visible led light has a number of advantages.

    Curious what you guys think?
     
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  5. lifeatredline

    lifeatredline Getting the hang of it

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    A vid I made a few years ago using a standalone infrared illuminator and a low lux runcam owl sensitive to infrared. It shows pretty well how distance, width, and washout effect the view.

    Sent from my SM-S327VL using Tapatalk
     
  6. J Sigmo

    J Sigmo Known around here

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    What I've seen used in a lot of cameras are off-the-shelf IR LEDs for their IR illuminators. Typically, the LEDs have their lenses built into them. The single-element LEDs are usually in T3 or T1 packages where the lens is part of the molded package itself. The LED manufacturer can position the actual die closer or further from the front of the package to adjust the "zoom" if you will (set the beamwidth), or use a package with no rounded lens shape to the front of the package.

    But unfortunately, it seems that most camera makers choose LEds with narrow beams, resulting in the burned-out center and underexposed majority pattern. Being cynical about it, I figure they want to be able to advertise the longest possible IR range, but they dont mention that this results in the extremely uneven illumination that we usually see.

    Ideally, they'd match the pattern of their LEDs to the field of view (for fixed lens cameras) or make it wide enough to cover the medium setting (at least) for varifocal and zoom cameras.

    The fancier flash units for photo cameras actually employ a zoom feature that zooms the flash to match the angle of view reported by the lens/body to get the best efficiency while still providing even coverage of the scene. You actually hear and feel the flash mechanically adjusting as you zoom a zoom lens on the camera.

    Of course providing auto zoom of the IR LED illuminators in zoomable security cameras would add considerably to their price. But the burned out center we see with most fixed-lens cams is inexcusable IMO.
     
  7. Dodutils

    Dodutils Pulling my weight

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    @J Sigmo if you search for "led lens" on google you'll find a lot of sizes, shapes and light angle, none of my cams have "fixed" lens I mean they are all per lens parts that can be changed if you find the right format.
     
  8. cuz

    cuz Getting the hang of it

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    Well at least I’m not the only one with this concern. I was wondering if the cameras with multiple IR’s around the actual camera lens might work better than the cameras with only one or two IRs?
     
  9. J Sigmo

    J Sigmo Known around here

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    Not in my experience. I have a few built that way, and because the manufacturer chose LEDs with fairly narrow beam widths, those cameras produce a fairly profound bright spot in the middle of the image.

    If they designed the PC boards just right, and then carefully bent the legs of some of the LEDs to create more spread to the light pattern, they could accomplish what we want, but in no case, did they do that in any of the cameras I have that use that style of built-in illuminator.
     
  10. TechBill

    TechBill Getting comfortable

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    The camera indoor will do far better in the dark than the camera outdoor since the IR will bounce off walls illuminating the room. Keep in mind that the starlight turret have a pretty powerful IR which if it anywhere too close to an object or wall then it will create a hotspot.
     
  11. cuz

    cuz Getting the hang of it

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    That’s kind of why I was asking the question. I want a camera with a less powerful “softer” IR to minimize the hotspot. I don’t need a strong IR to reach far, I want diffused IR to cover a wider area.
     
  12. nbstl68

    nbstl68 Getting comfortable

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    I read in another thread here somewhere the IR and spread vary between the fixed and the varifocal cameras too with I believe they said the varifocals have a more narrow beam pattern because of the expectation of using the zoom somewhat so the IR would cover the further distance with the downside being a larger hot spot when not zoomed...the fixed would have a somewhat wider spread IR pattern because the focal length is always known and thus they use the wider IR. I think to prove this or not we would need someone who has two similar model cameras fixed and varifocal versions set up in the same location and do an image or video comparison of the IR coverage from both. It would be interesting to see if this was true that the fixed camera would provide a broader IR spread with less hot spot.
     
  13. J Sigmo

    J Sigmo Known around here

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    While I don't have a fixed-focal length Dahua to compliment tests with one of their Varifocals, I can say that the two varifocals I have do, indeed, suffer from a pronounced central hot spot when zoomed wide. I would buy a fixed focal length version, at the wide focal length, if I knew that it would have a wider spread with its IR illumination. I would then replace the varifocal unit I presently have installed in this location with the fixed focal length model. As it is, the porch light in this area, which is on all night, provides decent light for that camera and it never switches to IR/B&W mode unless there's a power failure or someone switches the porch light off.