Lens Question

[Palomino 0]

Hello all,

 

How do I figure out how much space at a certain distance a specific lens will cover in a certain camera. Is there a math formula I can use for this?

 

Im looking for an Outdoor dome camera that can cover a specific choke point for reading licience plates at about 125' away.

 

thanks

[Soundy 1]

http://lmgtfy.com/?q=cctv+lens+calculator

[AZRob 0]

Just as a note, reading a license plate at 125' away will be a challenge. You'll probably need at least a 50mm lens at a minimum (with a 1/3 in. CCD) and even then it won't do it in all lighting conditions. Very difficult to read license plates reliably, especially at night.

 

 

 

Hope this helps!

[AZRob 0]

One more thing, try to minimize the angle between the direction of travel of the car and the angle of the camera. In other words, try to mount the camera in a place that is as close to being directly behind the car if trying to capture the rear license plate. If the angle is too great, the image will be blurred as the car travels across the view of the camera.

[Palomino 0]

ThankYou,

 

Next question, Do you guys think a Panasonic WV-CW484S/15 with the 15-50mm lens would be able to read a plate number from 125 away?

 

Thanks for any opinions

[AZRob 0]

You may also encounter glare and blooming effects from the car lights when trying to capture license plates at night time. Please note, that I'm not trying to discourage you from trying to capture plates, just know that it's not as easy as it sounds. It's possible but at night time it really becomes a challenge. Daytime is a bit easier.

 

Best,

Rob

[AZRob 0]

Hi Palomino,

 

That Panasonic is a very respectable camera, very high quality. However, in my opinion 50 mm at 125' is still going to be a bit of a stretch. I won't say it's impossible but it might be beyond the capability of the camera.

 

At 125' with a 1/3 in. CCD and 50 mm lens, the field of view is about 12 feet wide which is almost double the width of a car. Ideally, you would want something like an 8 foot wide view or less to really zoom in on that plate. This would require a 75 mm lens.

 

So the short answer is, you MIGHT just barely get a plate at that distance with the 50 mm but I wouldn't count on it.

 

I wish I could be more optimistic, but I have to be realistic too. It's a tough thing to get a plate, especially at 125 feet!

[Palomino 0]

Thanks for the post AZRob,

 

I install cameras all the time but am not usually involved in choosing which one to put in so Im trying to educate myself. Ive probably installed over 200 Panasonic WV-CW484's but never for plate reading and I dont think ever with the 15-50mm lens. I wish they made a 75mm or so lens for these cameras but from my searching 50mm is the best I see. I also like the panasonics because they seem to hold up so well over time. We go out to fix pelco ptz's and speco's and other brands all the time but very rarely a panasonic even the ones mounted outdoors here in wisconsin without the heater dont seem to breakdown.

 

Is there a camera you would recommend for me that would be under $600 or so?

[Soundy 1]

It probably maxes out at 50mm because that's the biggest lens that will fit inside the dome housing.

 

Instead, look into a WV-CP484, the "box camera" version of that dome. That will let you use pretty much any available C/CS-mount lens that suits your needs, with all the same features (SDIII, auto-backfocus, etc.). Right now I'm looking at an f/1.8 5.5-82.5mm lens that would suit this use nicely. Mount it and the camera in a good environmental housing (Pelco EH3512, for example) and you're good to go.

 

One consideration: with capturing moving objects like this, you want the highest shutter speed possible to avoid motion blur. Especially at night and in low-light situations, most cameras will need to drop the shutter speed to allow more light in. It's important to find the "fastest" lens (ie. with a larger maximum aperture) that you can - the more light the lens allows through, the faster the shutter you can use.

 

In this case, f/1.8 may not be enough; you may need to try for f/1.4-f/1.2 or better, if they exist. That may also require avoiding varifocals and going for a fixed-focal length lens (as varifocal construction makes for larger, more complex and more expensive designs).

 

Tamron has a handy lens calculator on their site - I plugged in the viewing distance as 125ft. and the field width as 8ft. and got the following:

Tamron CCTV & FA lens calculator

 

Your object distance is 125 ft/38.1 m.

 

To cover a horizontal area of 8 ft/2.44 m and a vertical area of 6 ft/1.83 m, you will need

 

* For 1/3" cameras: a focal length of 75 mm.

* For 1/2" cameras: a focal length of 100 mm.

* For 2/3" cameras: a focal length of 137.5 mm.

* For 1/1.8" cameras: a focal length of 84.38 mm.

 

The following Tamron lenses fit your needs:

 

Vari-Focal: 1/3"

13VM20100AS 20-100mm F/1.6 Aspherical, Manual Iris - NEW

13VG20100AS-SQ 20-100mm F/1.6 Aspherical w/connector, DC Iris - NEW

 

Motorized Zooms: 1/2"

12PZG10x8C 8-80mm F/1.8 Compact Zoom, DC Iris

 

Motorized Zooms: 1/3"

13PZA20x56 5.6-112mm F/1.6, Video Iris

13PZP20x56 5.6-112mm F/1.6 w/Presets, Video Iris

 

Motorized Zooms: 1/2"

12PZA10x8C 8-80mm F/1.8 Compact Zoom, Video Iris

12PZM10x8 8-80mm F/1.8, Motorized Iris

[AZRob 0]

Hi Palomino,

 

To get a camera under $600 that will reliably capture a plate at 125' reliably and under all lighting conditions is going to be very tough. Soundy, also brings up a great point about shutter speed. This is very important when capturing plates on moving cars. Bear in mind, that as you go to a faster shutter speed, the amount of light reaching the imaging sensor is decreased, so you have to have alot of light, either visible or IR to make sure the object is illuminated sufficiently.

 

I tried a sub-$600 camera that claimed to be able to capture plates and it was a disaster. Didn't work at all. Terrible.

 

As I said before, license plate capture is a tricky thing to do reliably, in all lighting conditions with a moving vehicle. Bosch has a new line called the REG-Sentry and it comes in two versions. One with a 15 ft. range, and the other with a 78 ft. range. However, these are likely to be a bit expensive (most likely alot more than $600) but they are geared towards very high reliability.

 

If you do find a reliable plate camera for less than $600 please let me know, as I haven't found one yet.

 

Your best bet might be to take the advice given by Soundy and try the Panasonic lens 75 mm with the box camera. That's the only one that I would think would have a chance.

 

Let me know how it works for you!

 

Best,

Rob

[Soundy 1]

And on that note, another consideration: any lens like that is going to be rather pricey on its own - probably figure another $150-$200 *on top of* the cost of the camera itself.

 

Realistically, the only near-100% reliable way to capture plates is with a strobe. That's how border patrol does it, that's how law enforcement does it (photo-radar and red light cameras), and they're pretty much impossible to beat - Mythbusters tried at length to beat the speed cameras, and failed every time. When you're hitting the plate with a 1/30,000th-of-a-second burst of ultra-bright, tightly-focused light, shutter speed and vehicle movement becomes pretty much irrelevant - even a $100 camera should work in that instance.

[shoreviewsecurity 0]

Hey Soundy,

 

Mythbusters did beat the camera but had to exceed some off the chart speed. I forget what but I think better than 100mph.

 

That was a good episode. They even did a re-visit on the myth and as you mentioned

 

" Myth Busted "

 

I agree, very tough to capture plates at distance. I just turned down a job because of the same scenario. He wanted to capture plates at 100'+ using a box cam and 50mm lens. I told him I would NOT guarantee 100% capture. He proceeded to mention that the other bidder would. I again thanked him for the opportunity and wished him well. Just not worth the aggravation.

 

 

Mike

[Palomino 0]

Thanks guys,

 

This is for my own personal driveway at a vacation property not for any customers. I think I will get the Panasonic CW484 with the 50mm lens and see if it works from on the garage to the choke point 125' away. If not I will do a little trenching and mount it on a post next to the choke point.

 

On a side note we had installed a camera for a high end customer on their very large house that reads plates from about 150' away at a specific choke poiint. It was a speco dome camera, but I do not know exactly which one. I heard we have had to replace it twice under warranty. If the camera was durable at all I would probably buy that one but speco's just don't seem to hold up from my experience installing them.

 

Thanks

[zmxtech 0]

sorry to state the obvious.

 

A license plate camera will have NO trouble reading from 100 feet away..

 

but if you want to do it DIY an IR bandpass filter and matching IR illumination at the filters freq can work well. but it can get expensive.

 

 

 

z

[Soundy 1]

sorry to state the obvious.

 

A license plate camera will have NO trouble reading from 100 feet away..

 

Well then, what specifically IS a "license plate camera"? Make and model? Special features?

[zmxtech 0]

Talking purely IR based ANPR:

have a look at the extreme/bosch ones.

I have used the regx its great but for short distances.

 

In this case you would need a 75mm lens or so and IR to get 100 feet.

[it would be a box camera/filter/separate IR makeup.]

[Lloyd 0]

Instead, look into a WV-CP484, the "box camera" version of that dome. That will let you use pretty much any available C/CS-mount lens that suits your needs, with all the same features (SDIII, auto-backfocus, etc.).

 

The following Tamron lenses fit your needs:

 

Vari-Focal: 1/3"

13VM20100AS 20-100mm F/1.6 Aspherical, Manual Iris - NEW

13VG20100AS-SQ 20-100mm F/1.6 Aspherical w/connector, DC Iris - NEW

Motorized Zooms: 1/2"

12PZG10x8C 8-80mm F/1.8 Compact Zoom, DC Iris

 

Motorized Zooms: 1/3"

13PZA20x56 5.6-112mm F/1.6, Video Iris

13PZP20x56 5.6-112mm F/1.6 w/Presets, Video Iris

 

Motorized Zooms: 1/2"

12PZA10x8C 8-80mm F/1.8 Compact Zoom, Video Iris

12PZM10x8 8-80mm F/1.8, Motorized Iris

 

I have been running WV-CP484 with a Tamron 13VG20100AS-SQ 20-100mm F/1.6 Aspherical for over two years.

It monitors the last half of my 1100' driveway.

I can't read licese plates at the far end, but I can sure see what is going on.

 

Palomino, what part of Wisc do you live in?

I live in South central Wisc.

[Palomino 0]

Thanks guys,

 

I live in Milwaukee but this is for my rec property in Marinette County. I definitly want a dome camera as I do not want the look of a box camera hanging off an arm. It just wouldn't look right in the northwoods of wisconsin.

 

The speco camera I had mentioned before I found out today was a CVC7WMTDV. I am still trying to find out which lens we put inside it though. I guess this speco has a lot more room in the dome for the lens then the panasonic according to what Im told.

 

I may actually reluctantly try the speco due to it being half the price almost and also the fact that I have a soffit to put it under on my garage. The customer we were having a problem with had the camera on a south facing outside wall with no cover so it got beat by the weather all the time. The other we had installed was on a light poll unprotected. I was told today that failure was most likely lightning related damage. Neither of these issues should be a problem for me.

[Kiwi 0]

I'm able to read licence plates at the entrance to my driveway which is 90' away with a lens focal length that just encompasses the approaching vehicle. Aside from the lens (about 70mm) the biggest issue is night time illumination.

 

Even with the camera elevated to about 30' the headlights overwhelm the camera's dynamic range. A potential solution is to place a reflective surface at a strategic place to bounce some light back to the licence plate. In my case the iron gate provides enough reflection back when closed, but a white sign may work just as well.

 

I used a JVC box camera and a Computar 8-80 electric zoom inside a home made weatherproof enclosure.

[AZRob 0]

Kiwi,

 

Thanks for posting great images. I take it that the camera has a 1/3 in. CCD?

 

As other folks have said, night time is the tricky part but your idea of having the gate reflect light back to sufficiently illuminate the plate (and possibly diminish some of the headlight intensity) seems to be quite effective!

 

Best,

Rob

[Kiwi 0]

Yes, the JVC TK-C925U has a 1/3" sensor and is a true day/night camera.

[AZRob 0]

Palomino,

 

This camera is probably a bit expensive, but it appears to have impressive license plate capture, even with headlights glaring into the camera:

 

http://www.stardot.com/video/stardot-lpc3.html

 

The future of license plate capture looks very promising! Hopefully, the price will come down!

[AZRob 0]

Here's a couple useful links to selecting a lens focal length:

 

Lens Calculator:

http://www.howtosurveillance.com/HowToVideo/CCTV-lens-calculator.html

 

Sample views (video):

http://www.howtosurveillance.com/HowToVideo/security-camera-lens-selection-part2.html

[CCTV_Suppliers 0]

To cover this distance and still be able to capture license plates will require at least 100mm lens... Due to the distance and the clarity of the picture to allow viewing license plates, 1/3" camera may not do... It will give you decent picture, but will not be as clear as you may want it. For this type of application, 1/2" CCD based solution what works.

 

I do not know of any minidome that comes with higher than 50mm lens..

 

The Panasonic minidome mentioned above is a great piece of hardware and with its lens capability, can do some wanders.. but not for this distance.

 

I understand that this is a price sensitive application... and sometimes the budget does not qualify the mean.

 

Here are some suggestion:

Pickup good 1/2" day/night camera (approximately $500.00), 1/2" varifocal lens lets say going from 5mm to 120mm (approximately $150.00), put it in a decent outdoor housing (approximately $150.00) and the results will be excellent... This package will cost more than the Panasonic Minidome pricing, but will give you exceptional results.

 

How about MegaPixel camera with 100mm lens? Dependent on the software that you may use, it can give you yet another very decent results.. Pricing again will be higher than Panasonic solution, but it will deliver your requirement.

[Palomino 0]

Hi guys,

 

Thanks for all the responses. I was able to go up to my place in Northern Wisconsin this weekend where I want to have the plate reading camera and I misjudged the distance. I thought the choke point was about 125' away from the garage where the camera would be mounted, but I took a measuring wheel and the choke point is only 85'-90' away. It looks like this may be within the range of a minidome with a 50mm lens, correct?

 

What do you guys think now?

 

Thx!