selecting lens

[shabonaa 0]

how can i select the lens?

 

what is the realtion between focal lens, fov, and Zoom( no. of X optical zoom)

[vin2install 0]

Get a Varifocal lens and make life easy.

[scorpion 0]

http://en.wikipedia.org/wiki/Lens_makers_equation

http://en.wikipedia.org/wiki/Optical_coating

http://en.wikipedia.org/wiki/Back_focal_plane#Focal_points_and_planes

http://en.wikipedia.org/wiki/F-number

http://en.wikipedia.org/wiki/Lux

http://en.wikipedia.org/wiki/Fabrication_and_testing_of_optical_components

http://www.mrpinhole.com/calcpinh.php

 

FISHEYE

http://en.wikipedia.org/wiki/Fisheye_lens

ZOOM

http://en.wikipedia.org/wiki/Zoom_lens

VARI FOCAL

http://en.wikipedia.org/wiki/Varifocal_len

TELEPHOTO

http://en.wikipedia.org/wiki/Telephoto_lens

What is inside of a zoom lens

http://www.adaptall-2.com/articles/InsideZoomLens/InsideZoomLens.html

 

 

The lower the mm number the wider the viewing angle.

 

The higher the mm number the more zoom factor you have.

 

6mm is your starting point.

 

The 4mm is a wide angle lens. 4mm and 3.8 are easy to make, and are most common on off the shelf cameras such as bullet cameras, and "DVR kits in a box".

 

2.8 is a Fisheye lens.

 

 

Camera Variables that effect picture quality regardless of lens:

chipsets used for the camera "eye"

WDR

Matching the camera to the DVR (native camera size verses native DVR size)

 

Lens selection that effect picture quality:

Plastic verses glass lens.

Quality of glass grinding to achieve lens shape

Lens Coating to achieve extra quality such as reduced glare ect.

 

 

http://scorpiontheater.com/camlab.aspx

[ipman 0]

The post above shows it is not easy to select lens.

 

I recommend software utility ver. 5.3 from http://www.jvsg.com

- you see what you get because of 3D-preview.

- you have exact calulations of focal length, field of view, angles and other staff.

 

It does make sense to have a look.

Edited February 23, 2010 by Guest

[andyscan 0]

My portable test monitor has a built in camera with selectable lenses,, kinda makes life easy but usually use varifocal anyway.

[vsg 0]

Hi, ipman

 

Thanks for your recommendation. This lens software is what I was looking for!

[robert 0]

Hi, ipman

 

Thanks for your recommendation. This lens software is what I was looking for!

 

There is one easier

http://www.dallmeier-electronic.com/en/products-electronic/cameras/view-designer.html

[ipman 0]

Hi, ipman

 

There is one easier

http://www.dallmeier-electronic.com/en/products-electronic/cameras/view-designer.html

Well, Robert I am not agree.

I would say the View Designer is too basic.

It even calculates horizontal projection wrongly.

Lets make a small test:

 

Camera Installation Height = 6.5 m

Sensor Size = 1/3"

Lens focal length = 4 mm

Distance = 10 m

Object size = 1.8 m, like here

 

Let's see horizontal projection in "IP Video System Design Tool 5.3", "Video Cad6" and "View Designer 1.0".

 

Additionally imagine you put a 1.8m tall man at 4m distance from camera and 3.3m on the right (orange man - in JVSG at mouse cursor position).

 

 

 

As you can see man at (4m; 3.3m) is visible but View Designer shows the max right position at 4.5m/2 = 2.25 m. But it is not correct.

 

Please download JVSG tool and compare results yourself.

Edited November 26, 2008 by Guest

[robert 0]

Looks nice software, downloaded, tried, looking good for lenses, but not so good for storage calculation and network bandwidth as its shows completely different numbers compared to Arecont Vision calculations.

 

But yes, difference is quite a bit

[ipman 0]

Looks nice software, downloaded, tried, looking good for lenses, but not so good for storage calculation and network bandwidth as its shows completely different numbers compared to Arecont Vision calculations.

 

It would be an offtopic here, but I have made a test of BW calculation with Arecont and Axis calc:

 

Bandwidth, MBit/s (2MegaPixel, 6 FPS, Parking Lot):

Compression                             | Arecont | JVSG 5.3  | AXIS
---------------------------------------------------------------------
Low Compression  (MJPG-10 HighQuality)  | 13      | 13.6      | 12
Medium Compression (MJPG-50 LowQuality) | 7       | 7.4       | 6.3
Hi Compression (MJPG-70 Poor Quality)   | 5       | 5.85      | 5.3

HDD storage space (30 days, 100% recording):

Compression                             | JVSG 5.3 | Arecont  | AXIS
---------------------------------------------------------------------
Low Compression  (MJPG-10 HighQuality)  | 4.3      | 4        | 3.6
Medium Compression (MJPG-50 LowQuality) | 2.4      | 2.4      | 1.9 
Hi Compression (MJPG-70 Poor Quality)   | 1.79     | 1.75     | 1.6

 

I would say BW&HDD space estimations are surprisingly accurate

[robert 0]

Well, I got something different. Any ideas why?

 

 

[ipman 0]

Robert, it looks like the trick is in arecont "% Motion Detection Activity" parameter. On your arecont screenshot you have option "50% motion activity" selected. But in the IP Video Tool you have 100% recording.

 

You can just specify "50%" recording activity and get almost the same result - BW: 33.9 MBit (32) HDD:2.5TB (2.4)

[ipman 0]

Robert, looks like your pictures disappeared

[Soundy 1]

Here is 6 steps to help you find the best lens:

1.Determine the focal length you'll need

2.Decide if you want a prime or zoom lens

3.Select a maximum aperture

4.Choose between first or third party lenses

5.Evaluate any extra features

6.Read reviews and narrow your options

 

I am using Sony Alpha DSLR-A200, It is awsome. You can have a look.

 

Good advice in general, but we're specifically talking about CCTV lenses... There's not often a lot of choice in maximum aperture (most CCTV lenses are in the f/1.4 to f/1.8 range), first-party selection tends to be fairly limited (with not a huge range in quality between first and third party), there's not generally much in the way of "extra features" to be had (auto or manual iris is about the gamut), and even fewer reviews to be had.

 

CCTV lenses simply aren't studied and debated to death the way SLR lenses are...