How to calculate zoom from Lens range?

[aforum]

Hi can someone please tell or direct me: how can I confirm the zoom range based on lens range?

E.g. if it says lens = "4.5- 148mm"
I thought the calculation is 148 / 4.5 = 32.8X Optical zoom,

But I thought these cameras only come in 30x then 36x formats. Thus when someone says their camera is "36x" optical zoom, but their lens specs only says "4.5- 148mm" (which could calculate as 32.8 optical) - then that may be an indication that their Lens stats are a lie.

Or am I wrong that the zoom calc isnt XX / X? (Can a 36x zoom lens start at 4.5 to 148mm - and still have 36 stages of zoom?)

And if camera 2 advertised 30x zoom, but "lens range" = "3.3-97mm" (29.3), then which camera would have the final closest image display (irregardless of zoom stage amounts)?
(Im thinking the 148mm has the highest final zoom, but not sure if that is dependent on it's starting lens size.)
Thanks.

 

[samplenhold]

(Im thinking the 148mm has the highest final zoom,

All things being equal, that would be correct. Certainly a 148mm will get you closer than a 97mm. But it also depends on the sensor size and the type of lens mounting.

So here are two different comparisons, each comparing a fixed lens camera with a varifocal camera set to the same focal length. Both cams are mounted side by side in each example and are Dahua turrets.

This one is two different models. A T5442TM-AS which has a 4MP sensor that is 1/1.8" in size and a fixed 6mm lens, compared to a HDW5231R-ZE which has a 2MP sensor that is 1/2.8" in size and a varifocal lens set at 6MM. Notice that FOV is a little different.


Next we have the same T5442TM-AS 6MM fixed lens cam comparing to the same series cam but a different model which has a varifocal lens. They both have the same size sensor which is a 4MP in the 1/1.8" size. The varifocal cam is set to 6MM. As you can see, the FOV is different.



Here is a thread that some of the other folks in this forum discussed the differences.

Comparison of a Fixed Lens and a Varifocal Lens Camera's FOV

I was testing out a new Dahua T5442T-ZE 2.7-12mm Varifocal camera (from @EMPIRETECANDY ) and was going to compare it's performance to the Dahua HDW5231R-ZE and the HDW5431R-ZE cameras, which are 2.7-13.5mm varifocals, along with the T5442TM-AS fixed lens at 6mm camera. The HDW5431R-ZE has been...

ipcamtalk.com

 

[aforum]

Thanks so much for the pictures! I appreciate that.

A related question. I see a lot of the high end PTZ cameras have only 4MP. (My NVR is 6MP max, but I aim for 5MP since it is faster to display.)
So do the high end cameras (sold by IPcamtalk) have better lens that their 4MP has as much detail as a regular 5MP? Or does the 4MP have less detail?

 

[samplenhold]

Sensor size is more important that MP size. More pixels does not automatically translate to better picture quality.

See this thread:

The Importance of Focal Length over MP in camera selection

At the urging of several folks here, I created a thread to show the importance of focal length and how focal length can be more important than megapixels (MP). I mentioned some of this in the post regarding The Hookup’s latest video demonstrating different cameras, including one sold from a...

ipcamtalk.com