Determining lens focal lengths

[gadgetguy 0]

Hi,

 

I'm new to the forum.

 

I'm having a hard time trying to determine the lens focal lengths I might need for group of 6 outdoor Pano 484s in heated fixtures. Each camera would cover a different size area. I would like to max out the camera's low light potential and image quality with fast (F1.2 or better) fixed lenses. I have seen the focal length demo on spycam's website, but still am unsure.

 

I thought about getting a 5-50mm zoom and using it with a spot monitor to get an estimate for each of the six focal lengths I might need, but the zooms don't seem to label their range. They just say wide-tele.

 

Any advice appreciated.

[Jasper 0]

Maybe this thread might help you out.

 

http://www.cctvforum.com/viewtopic.php?t=3315&highlight=lens+calculator

 

Welcome to the forum.

[gadgetguy 0]

Thanks Jasper. That program looks very helpful. Rory mentions a viewfinder. Do you or anyone else have any info on this viewfinder?

 

If I am trying to optimize the quality of the video, am I better off with the fast, fixed lenses or should I just go the easy route and get a quality zoom for all the cameras?

[Gesualdo 0]

try one of these

http://www.stamhost.com/spo/calculators.html#

 

http://www.securityideas.com/securitycam/freebcal.html

 

http://www.discount-security-cameras.net/lens-calculator.html

[JMANOFNVS 0]

Doesn't anybody use a lens wheel anymore???

[rory 0]

Link to all Computar Lens Accessories:

http://www.cbcamerica.com/cctvprod/computar/access/index.html

 

Computar ViewFinder PDF:

http://www.cbcamerica.com/cctvprod/computar/access/access_pdf/vm300data.pdf

 

If you want decent low light without IR, a f:0.95 lens, you can get them from Fujinon or GE in 2.9-8mm VF AI lens.

 

They also have 2.7-13.5mm Day Night lenses, though these would primarily be for IR apps.

[gadgetguy 0]

Guys,

 

Thanks so much for all the excellent help. I am hoping to get away without using IR by using low voltage halogen uplighting in the landscape. As you all know, this type of lighting is not very bright. I'm hoping that a top notch Day/Night cam coupled with fast lenses will provide useable images at night when these "nightlights" are on. If anyone has tried this, please chime in.

 

As an aside, Panasonic made some fixed f 0.75 in the 2.5, 4, and 9 mm focal lengths. They are now discontinued according to the pano website. Does anyone know if F 0.75 actually provides an advantage over the currently available f1.2 in low light situations? Some dealers seem to still have the f.75's in stock.

 

Regarding zooms, we know from photography that the F stop increases as you increase the focal length and light sensitivity falls off significantly. Also, to some degree, image quality is reduced when a zoom is compared to a high quality fixed focal length lens. Given the relatively low res of these video cameras, perhaps this is all a mute point?

[Jasper 0]

Yes a f0.75 will work better in lower light than an f1.2. The lower the f number the better it is in low light.

[jisaac 0]

if you are talking about power zoom lenses earlier in the topic. Then this is about that. The only thing you have to watch out for power zoom cameras is the auto focus. Rain and glare are two things that will make you sick when you watch it. Otherwise they are extremely nice to have.

[rory 0]

Ofcourse a low lux camera will handle it better also, such as one with an Exview CCD. I cant speak on the Pano, but I dont quote it for low light day night apps.

[gadgetguy 0]

Rory that viewfinder looks like it's exactly what I was looking for. Thanks. I assume you just hold it up to your eye and that you do not have to attach it to a camera?

 

The Pano 484 is .5lux color and .06 lux b/w. The GE/Kalatel and others with the sony super exview chips appear to be similar in lux ratings. Am I missing something?

 

If f.75 is significantly better for low light than f1.2, why did Pano D/C these lenses?

[rory 0]

the GE Exview is 0.2 lux color, 0.01lux BW ..or less, give or take, thats the highest points. If you were looking at an OEM specs, then it would be the face plate lux specs, 0.02 color, 0.001 BW.

 

Normally the specs are based on f:1.2 lenses, so if you use lower f: stop on some cameras such as the GE, or other Exviews, it makes a huge difference.

[securitymonster 0]

I use the VM300 viewfinder from CBC/Ganz and its great! Comes in handy when I just want a quick visual. And yes, you just put it up to your eyeball! Its handy to pass off to customers while your bidding a job and they are right there with you!

[Cooperman 0]

gadgetguy,

 

As they are hot filament light sources, LV Halogens spew out lots of Infra Red light, so although they may not look particularly bright to an observer, a half decent B&W or Day/ Night camera should be able to exploit the near IR component to help produce a resonably bright image. As with any lighting, the quantity and location will be key , as to whether you get a nice well illuminated image.

 

As regards lenses, exactly the same principles apply for CCTV lenses, as they do for photographic optics. That said, photo. lenses are generally much better corrected, and the level of distortions and definition issues, are actually far less than you would normlly experience with some average jobbing CCTV offerings.

 

Where a "zoom" type lens adjustment is indicated as either Far or Near, it is almost certainly a Varifocal lens, and not a zoom. In practical terms, you will almost always get better performance from fixed focal length lenses than you will from "zoom" types.

 

If you have experience of using photographic cameras, it is relatively easy to relate CCTV lens coverages, to (for example) 35mm optics; although in practice, using larger format lenses on smaller format imagers, will always offer the best return in terms of overall image quality.

 

Simple example, a 50mm lens on a 35mm SLR, would have an equivalent coverage to an 8mm on 1/3", or 12mm on 1/2".

 

In each example, an 8 or 8.5mm (2/3" lens) on 1/3", and 12.5mm (1 inch lens) on 1/2", would cost slightly more for the optic, but the lens (and picture) quality would be significantly better.