vari-focal or not?

[acableconnection 0]

Should i install vari-focal or not. What are the plus/minus? I dont need to zoom..

What about lux? what numbers to be able to see at night with a little bit of light

[CollinR 0]

If you have little experience go varifocal, if you already know you need a standard lens just buy that.

 

Few situations require you to change it after it's installed.

[survtech 0]

A major upside to varifocal is that they can be adjusted to exactly the field of view desired. A major disadvantage is that they are harder to zoom and focus. They are great for their flexibilty.

[CollinR 0]

Totally agree and why I suggest them to inexperienced installers, they can make it very easy.

 

Varifocals also cost more and don't provide the quality some fixed lenses do. Thats of course fujinon to fujinon not fujinun to fujinon.

 

It's a bigger deal in megapixel then SD analog systems so don't expect a glaring difference.

[acableconnection 0]

thanks guys. that was the answer i was looking for. ive installed a ton of vari-focal, but the only area that i thought needed them was, over registers, to get the exact view you needed.

now help me pick out a dvr. motorcycle shop 100'*200 14 cams 5 outdoors. all motion

[rory 0]

Also depends if you can find an Auto Iris Fixed lens.

[phred 0]

Minimum Lux level is a camera CCD sensitivity rating.

 

The lower the Lux figure the better for low light.

 

Rough guide:

 

Street lights 1 – 10 Lux

 

full moonlight 0.1 Lux

 

dark cloudy night 0.0001 Lux

 

So in theory anything lower than 0.1 Lux should do if there is some lighting nearby.

 

Unfortunately, manufacturers specs are not exactly reliable.

 

Many use tricks like frame integration where the camera 'holds' several

frames and adds them together to enhance apparent low light

performance. This effectively reduces the shutter speed and motion will appear blurred.

 

The big brand names tend to have more honest specs, so a Panasonic

rated at .1 Lux may outperform a no-name that uses frame integration to

obtain a rating of .001 Lux

[rikky 0]

just go varifocal. After all, for most suppliers price differences between standard auto iris fixed lenses and standard varif. lenses are minor.

[SBTVideoman 0]

Not all varifocals are created equal.

Not all use fully multicoated glass optics

Some even use plastic lens elements as it is cheaper.

 

Some varifocals (especially those that go quite wide, eg 2.5 or 2.8mm at the wide end) noticeably distort vertical lines away from the centre of the image.

 

Finally - all varifocals suffer from lens "ramping" - this is where the maximum lens aperture deteriorates as you zoom the lens in.

 

Those of you who do either 35mm or digital SLR photography will be familiar with the "standard zoom" commonly sold, being a 28-80mm F3.5 - F5.6 type lens.

The key here is that the maximum aperture is F3.5 @ the wide end, but falls away to F5.6 at the telephoto end.

 

CCTV varifocals suffer the same way...but virtually all lens manufacturers only publish the "best" F stop...being at the wide end.

 

For example, a 5-50mm F1.3 varifocal is NOT F1.3 at the 50mm end.

 

This is NOT intended as a recommendation to NOT USE varifocals....but just be aware there are some inherent compromises in their design. They are great for many applications...but not all are equal.