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Realistic camera requirements for close-up outdoor viewing
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| tazo |
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Posts: 13
Joined: 19 Jul 2008
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Posted: Sat Jul 19, 2008 11:11 pm
Post subject: Realistic camera requirements for close-up outdoor viewing
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I am trying to figure the requirements for a fixed IP camera that would record people approaching a front door at about 8 ft distance. The camera will be outdoors, so varying light conditions, but there will be a constant 60W light source. I need to be able to identify faces.
Obviously I don't need a really high resolution, extremely low Lux level and IR, but I'm not sure what would be reasonable camera requirements to start with in this location.
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| ak357 |
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Posts: 239
Joined: 16 Nov 2005
Location: Canada
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Posted: Sat Jul 19, 2008 11:48 pm
Post subject: Re: Realistic camera requirements for close-up outdoor viewi
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| tazo wrote: |
I am trying to figure the requirements for a fixed IP camera that would record people approaching a front door at about 8 ft distance. The camera will be outdoors, so varying light conditions, but there will be a constant 60W light source. I need to be able to identify faces.
Obviously I don't need a really high resolution, extremely low Lux level and IR, but I'm not sure what would be reasonable camera requirements to start with in this location. |
I would suggest that u allocate at least 50-70 pix of horisontal res
if u know what i mean
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| CameraGimp |
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Posts: 93
Joined: 10 Oct 2007
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Posted: Sun Jul 20, 2008 8:49 am
Post subject: Re: Realistic camera requirements for close-up outdoor viewi
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| ak357 wrote: |
I would suggest that u allocate at least 50-70 pix of horisontal res
if u know what i mean |
I doubt very much he knows what you mean, or why would he be asking in the first place.
I'd guess you mean you need about 50-70 pixels of horizontal resolution on a face to make it out for identification purposes?
If so he is saying you need to think about the field of view (lens focal length) as well as the camera camera resolution. A low resolution camera with a tight field of view can be better than a high resolution one with a wide field of view.
You won't need a mega pixel camera, but get a high resolution conventional camera (480 - 520 TVL resolution) and select your lens so a face takes up 50 - 70 TVL of the 480TVL, or about a 1/10 of the screen.
Can't help with low light performance. Hopefully someone else will offer a suggestion.
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| tazo |
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Posts: 13
Joined: 19 Jul 2008
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Posted: Sun Jul 20, 2008 8:05 pm
Post subject:
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ak357, Thanks, that is what I was looking for. I will plan on 50-70 pixels of horizontal resolution or better.
CameraGimp, good point about the field of view. The camera would have a tight field of view and would need to cover only 5 ft of width at that 8 ft distance. I took a photo of the view (cannot post it yet since I'm a newbie) and with the camera's 5.8 mm lens I would only need 1/2 to 2/3 of the image width.
I did a quick check and with 480 horizontal lines of resolution, I will have about twice the minimum mentioned for face recognition. Thanks.
I still am not sure about the low light requirements.
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| Thomas |
Moderator
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Posts: 1948
Joined: 17 May 2004
Location: Houston, TX
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Posted: Sun Jul 20, 2008 9:05 pm
Post subject:
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| tazo wrote: |
ak357, Thanks, that is what I was looking for. I will plan on 50-70 pixels of horizontal resolution or better.
CameraGimp, good point about the field of view. The camera would have a tight field of view and would need to cover only 5 ft of width at that 8 ft distance. I took a photo of the view (cannot post it yet since I'm a newbie) and with the camera's 5.8 mm lens I would only need 1/2 to 2/3 of the image width.
I did a quick check and with 480 horizontal lines of resolution, I will have about twice the minimum mentioned for face recognition. Thanks.
I still am not sure about the low light requirements. |
Keep something in mind. Photo camera lens size and CCTV lens will give differing fields of view for the same size lens. Consult a lens calculator.
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Thomas
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| tazo |
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Posts: 13
Joined: 19 Jul 2008
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Posted: Tue Jul 22, 2008 12:44 am
Post subject:
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| Thomas wrote: |
Keep something in mind. Photo camera lens size and CCTV lens will give differing fields of view for the same size lens. Consult a lens calculator. |
Good point, I did not know that. There are tons of lens calculator sites out there. Do you have a favorite?
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| Thomas |
Moderator
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Posts: 1948
Joined: 17 May 2004
Location: Houston, TX
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Posted: Tue Jul 22, 2008 5:52 am
Post subject:
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| tazo wrote: |
| Thomas wrote: |
Keep something in mind. Photo camera lens size and CCTV lens will give differing fields of view for the same size lens. Consult a lens calculator. |
Good point, I did not know that. There are tons of lens calculator sites out there. Do you have a favorite? |
Not really, the math is pretty straight forward.
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Thomas
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| BennyBoy |
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Posts: 30
Joined: 04 Jun 2008
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Posted: Tue Jul 22, 2008 4:43 pm
Post subject: Re: Realistic camera requirements for close-up outdoor viewi
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| tazo wrote: |
I am trying to figure the requirements for a fixed IP camera that would record people approaching a front door at about 8 ft distance. The camera will be outdoors, so varying light conditions, but there will be a constant 60W light source. I need to be able to identify faces.
Obviously I don't need a really high resolution, extremely low Lux level and IR, but I'm not sure what would be reasonable camera requirements to start with in this location. |
12mm lens should do it.
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