Camera Quality Less Than Projected PPF - Why? What To Do?

hello all,

I just installed several 12mm 4MP hikvision OEM cameras to record the plate numbers. Those are 20 fps but we have it on a property so nobody drives fast there anyway.

I used IPVM calc so I figured those cameras would be good enough to see the plate number clearly, I supposed to get 50-60 ppf. In fact, the plate is not readable even during the daytime.

I have played with camera focal length in a calc to see an estimated view and compare with what I have in reality. It looks like camera has 8mm lense instead of 12mm. Is there a way to determine a focal length? I have several those cameras on a shelf for future use but it doesn't seem a good idea anymore.

Camera specs:

SC-304-XB

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Brian Rhodes

IPVMU Certified

Hello Dennis:

One way to double check the focal length to to measure the width of the target area at the calculated distance.

I don't know your target distance, but for example if it is 100 feet, the width for 12mm focal is 40 feet. For 8mm, the width at that distance is about 60 feet. (Assuming 1/3" imager)

Does that make sense?

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Dennis Ruban

In reply to Brian Rhodes

it does, thank you!

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Undisclosed #2

IPVMU Certified

In reply to Brian Rhodes

...Assuming a 1/3" imager...

It is a 1/3" (nominal) diagonal format, but the problem is that its not a 4:3 aspect ratio sensor as the generic camera calc assumes. its an Omni 16:9, meaning that the view is wider then what the calculator will give.

The camera spec only gives a 4mm example, but you can see how its off already:

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Undisclosed Manufacturer #1

I have heard of some low cost cameras "cheating" and not giving you a true lens, for example advertising a 2.8-12mm and you get a 3.8-8 or similar.

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Dennis Ruban

I finished the measurements and found it's actually 12mm. But the quality is really bad: blurry image instead of a clear picture even when I have 60-80 ppf.

I was pretty sure 40+ ppf should be enough during the daytime but it looks like I need to replace my cameras now

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Undisclosed #2

IPVMU Certified

post snapshot

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Dennis Ruban

slow moving truck is driving in. Suppose to be 70+ ppf according to the ipvm calc but it's hard to read the plate

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Undisclosed #2

IPVMU Certified

Dennis is that snapshot uncropped and at full resolution? 2688x1520?

It looks a bit too square.

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Undisclosed Integrator #3

What is the recording resolution set for? How much bit rate and encoding type?

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Jay Hobdy

IPVMU Certified

I am not sure about the calculator but I would measure the width of the road at that point. I would measure as it is seen on the screen, at that angle

I tried to upload a pic but it wouldn't show the upload option? @brian rhodes

I guesstimate 50'. Your camera is 2688 pixels wide. 2688/50 = 53.76 pixels

I think it may be wider than 50' which will drop your PPF.

From the image I saw, and what I saw on the calculator, I think a new design is in order. I would put a pole out by the street, and use a different camera. I think you are going to have some significant issues at night.

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Michael Miller

Yea that setup barely going to work during the day and never going to work at night. You are going to have all kinds of issues with IR light at night time because of that tree in the FOV. We always shot for 100PPF for LP shots and that always works day and night.

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Undisclosed Integrator #3

In reply to Michael Miller

Good catch on the tree. It changes the whole scene with IR. He could change the FOV to a much tighter shot, disable the camera IR and place a better IR illuminator out of the FOV as an option.

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Dennis Ruban

•Oct 24, 2017

In reply to Michael Miller

what's wrong with a tree? I've checked the night recordings and that tree doesn't reflect anything. There's a road sign that does but still, it's on a side and does not affect the picture quality.

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Undisclosed #2

•Oct 24, 2017

IPVMU Certified

Dennis, can you post uncropped night (and day) shots?

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Dennis Ruban

•Oct 23, 2017

snapshots I posted are cropped, not an original camera resolution.

Recording resolution, fps, quality - everything is configured to provide a best possible picture. Bandwidth is limited to 16384 kbps, it's a top for Hik. I just tried to avoid any picture quality degradation because of compression.

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Undisclosed #2

•Oct 23, 2017

IPVMU Certified