Camera Lens Reference Diagram

Kenjusticejr

BIT Beta Team
Joined
May 5, 2014
Messages
182
Reaction score
80
well, for anyone smart enough to do some research and get guidance form a forum such as this, here is a good explanation of lens field of views.

basically, I wish someone would have crammed a pic like this down my throat before I ever purchased my first camera.

In addition.... 640x480 aka 720p can really be disappointing on a cheap camera with a poor lens. Lens Explination.png
 

bp2008

Staff member
Joined
Mar 10, 2014
Messages
12,666
Reaction score
14,005
Location
USA
640x480 is not 720p. 1280x720 is 720p

Nice chart though. Based on that chart, it seems the maximum plate recognition distance linearly correlates with the lens size in an easy-to-remember way. i.e. 6mm is roughly good for 6 meters while 25 mm is roughly good for 25 meters and so on.

Obviously the actual view angle and readable plate distance will vary with different sensor size and resolution, but the numbers above seem like pretty decent estimates.
 

Kenjusticejr

BIT Beta Team
Joined
May 5, 2014
Messages
182
Reaction score
80
Thanks for the correction on the 720p..I think I wrote that because I had it fresh in my mind from seeing a falsely advertised camera on ebay...Anyway, yes, the statement still proves true, 1280x720 can still be disappointing when formatted on a low quality camera with a less than adequate lens and 640x480 is like watching tv on an old 13 inch tube from 1980.... I'm addicted to the HD cameras now....
 

hmjgriffon

Known around here
Joined
Mar 30, 2014
Messages
3,401
Reaction score
980
Location
North Florida
Thanks for the correction on the 720p..I think I wrote that because I had it fresh in my mind from seeing a falsely advertised camera on ebay...Anyway, yes, the statement still proves true, 1280x720 can still be disappointing when formatted on a low quality camera with a less than adequate lens and 640x480 is like watching tv on an old 13 inch tube from 1980.... I'm addicted to the HD cameras now....
Yeah, even 1080p doesn't look so good to me, I'm spoiled by 3mp lol that is like the minimum my brain can handle now. Though I started with a few 640x480, then 720p, then jumped to 3mp.
 

Kenjusticejr

BIT Beta Team
Joined
May 5, 2014
Messages
182
Reaction score
80
got 4 3mp cams on the way from china.. hope to have them by next week :)
 

networkcameracritic

Getting the hang of it
Joined
Mar 10, 2014
Messages
719
Reaction score
203
Not sure the information is valid. Taking plate capture as an example at VGA resolution, I would say that at 30m, at 12mm lens would be worthless and you would need closer to a 40-50mm lens to read a plate. I've shown a 12m lens reading a plate during the day at about 25m but that was 3MP, not VGA. Also, every lens/sensor combo is different, so a 4mm lens on one camera may not be the same as a 4mm on a different camera, even within the same brand .
 

Kenjusticejr

BIT Beta Team
Joined
May 5, 2014
Messages
182
Reaction score
80
think that was based off a 2mp camera at 1080p resolution..but yes, a 640x480 cheapy camera wouldn't provide the needed detail to view a plate.
 

networkcameracritic

Getting the hang of it
Joined
Mar 10, 2014
Messages
719
Reaction score
203
Haha, not so cheapy. I use a camera at VGA resolution to read plates that probably cost more than you are paying for 1080P. With lens, camera and housing, it runs about $1,300 street price. That does not include the $900 IR illuminator.
 

hmjgriffon

Known around here
Joined
Mar 30, 2014
Messages
3,401
Reaction score
980
Location
North Florida
Haha, not so cheapy. I use a camera at VGA resolution to read plates that probably cost more than you are paying for 1080P. With lens, camera and housing, it runs about $1,300 street price. That does not include the $900 IR illuminator.

Yeah I'm pretty sure if you zoom in enough on a plate with VGA you'll be able to make out the numbers. :D Which camera is that?
 

networkcameracritic

Getting the hang of it
Joined
Mar 10, 2014
Messages
719
Reaction score
203
Ah, that is the misconception. What everyone wants is that megapixel view that includes a plate number all that is around it and I've shown that is possible during the day with a cheapy 3MP camera and a 12mm lens. The problem is at night. You have to expose for the plate to see it, when you do that, all else is very dark. People expect that if they expose for a nice picture, the plate will be fine, but then they see the plate is just a white blank rectangle and headlights blow everything out and don't realize they need to make the image much darker, but by doing so, it's worthless for anything other than capturing plates, so why have 1080P or 3MP when there are 720P or VGA cameras that have way better low light sensitivity. To give you an idea, some cameras made for this have a max exposure of 1/500th of a second. I've used general purpose cameras between 1/90th an 1/250th of second max exposure to be able to read plates. Of course you have to reduce gain way down otherwise you just get a noisy worthless image.

We use an Axis Q1604 + 5-50mm Fujinon lens and an Axis housing. It is 720p, but sort of waste to use 720P because to get the best capture, I have to limit the view to about the width of the car and VGA is plenty for that field of view. In it of itself, it does not do too bad with lighting just from the license plate lights. But with a Raytec RM100 illuminator, we can actually see the car and not just the plate. I set it to 4fps and we get about 2-4 plates captures as the car drives by, That would be good up to 30-40mph, faster would require a higher frame rate.
 

hmjgriffon

Known around here
Joined
Mar 30, 2014
Messages
3,401
Reaction score
980
Location
North Florida
Ah, that is the misconception. What everyone wants is that megapixel view that includes a plate number all that is around it and I've shown that is possible during the day with a cheapy 3MP camera and a 12mm lens. The problem is at night. You have to expose for the plate to see it, when you do that, all else is very dark. People expect that if they expose for a nice picture, the plate will be fine, but then they see the plate is just a white blank rectangle and headlights blow everything out and don't realize they need to make the image much darker, but by doing so, it's worthless for anything other than capturing plates, so why have 1080P or 3MP when there are 720P or VGA cameras that have way better low light sensitivity. To give you an idea, some cameras made for this have a max exposure of 1/500th of a second. I've used general purpose cameras between 1/90th an 1/250th of second max exposure to be able to read plates. Of course you have to reduce gain way down otherwise you just get a noisy worthless image.

We use an Axis Q1604 + 5-50mm Fujinon lens and an Axis housing. It is 720p, but sort of waste to use 720P because to get the best capture, I have to limit the view to about the width of the car and VGA is plenty for that field of view. In it of itself, it does not do too bad with lighting just from the license plate lights. But with a Raytec RM100 illuminator, we can actually see the car and not just the plate. I set it to 4fps and we get about 2-4 plates captures as the car drives by, That would be good up to 30-40mph, faster would require a higher frame rate.

That is pretty freaking awesome, are you capturing these for fun or is this for some purpose?
 

networkcameracritic

Getting the hang of it
Joined
Mar 10, 2014
Messages
719
Reaction score
203
Everything in life I do is for fun. But this is used to open the gates to our community based on a plate match.
 

icerabbit

Getting the hang of it
Joined
Apr 14, 2014
Messages
583
Reaction score
74
Location
FL <~> ME
Everything in life I do is for fun. But this is used to open the gates to our community based on a plate match.
Fancy!

Does that by chance scale down to do pet recognition and open/close a cat flap ;)

I've had a raccoon and a stray cat wander in the house. Not fun & safe for the creatures who's home it is. It causes big fights, sends fur flying, stuff gets broken, ...
 

icerabbit

Getting the hang of it
Joined
Apr 14, 2014
Messages
583
Reaction score
74
Location
FL <~> ME
Not a bad draft for a chart. It could be improved some (like field of view width at distance shown), but then in the end there are too many factors to keep it simple.

I plotted some angles and fields of view last week, in an attempt to dial in better what I need to order, and trying to circumvent visual obstacles I can't move.
 

icerabbit

Getting the hang of it
Joined
Apr 14, 2014
Messages
583
Reaction score
74
Location
FL <~> ME
You can get automatic pet doors it seems, with much better reliability than a camera with image recognition :)

http://www.petdoors.com/electronic-RFID-magnetic-collar-keys.html
I've looked at those or similar product in the past. Almost bought it. The issue is cats need a break a way collar and if they lose the collar they can't get back in, plus then replacement tags were either $$$ or non-existent (just buy a new kit). I've had a cat lose a collar before and one cat get stuck with a collar; plus one incident where the cats were chased by a pit bull and ran like a cheetah for cover into the house. Not a time to have a collar issue or door issue. But, I guess the same RFID issue would go for face recognition. Way back when I read about a guy who did it via a webcam where the cat entered a tunnel and was checked whether it was carrying in wildlife, and would not open the door if it did.

Anyway. It was just a brainstorm thought regarding recognizing stuff on camera and activating/operating something.
 

digger11

Getting comfortable
Joined
Mar 26, 2014
Messages
355
Reaction score
373
I've looked at those or similar product in the past. Almost bought it. The issue is cats need a break a way collar and if they lose the collar they can't get back in, plus then replacement tags were either $$$ or non-existent (just buy a new kit). I've had a cat lose a collar before and one cat get stuck with a collar; plus one incident where the cats were chased by a pit bull and ran like a cheetah for cover into the house. Not a time to have a collar issue or door issue. But, I guess the same RFID issue would go for face recognition. .
If our cats weren't indoor only cats I'd get one of these: http://www.amazon.com/SureFlap-DualScan-Microchip-Cat-Door/dp/B00GAZZIMY
It would read the chip the cats already have implanted.
 
As an Amazon Associate IPCamTalk earns from qualifying purchases.
Top