How to determine zoom level?

[subterminal]

I bought the variable focus IPC-T5442T-ZE for the purpose of planning and figuring out what/how many cameras I will need, then buying the fixed-focus version of them. I've seen several folks say that the fixed-focus has better low-light performance, which is why I'm doing this.

My question is: is there a way to gauge what zoom level is roughly equivalent to 2.8mm, 3.6mm, etc? I'm logged into the camera's web GUI and see the slider bar, but there's no indication of what level of zoom I'm at or how that would maybe translate to a fixed 2.8, 3.6, etc.

I want to set the camera as close to what the fixed 2.8mm and 3.6mm cameras would be so I can do my planning a bit better, especially since that one planning tool I used some years ago costs money now.

 

[wittaj]

You will find there is no real comparison between the focal lengths of these cameras and "real" cameras.

Heck even taking the 5442 6mm fixed lens and setting up the 5442-ZE to the equivalent 6mm and you will find the field of view is different for both. The 5442-ZE had to be set to a 9mm equivalent to get the same field of view as the 5442 6mm fixed lens.

You can see a member here demonstrated this:

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

 

[subterminal]

You will find there is no real comparison between the focal lengths of these cameras and "real" cameras.

Heck even taking the 5442 6mm fixed lens and setting up the 5442-ZE to the equivalent 6mm and you will find the field of view is different for both. The 5442-ZE had to be set to a 9mm equivalent to get the same field of view as the 5442 6mm fixed lens.

You can see a member here demonstrated this:

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

Hm, interesting. So different lenses don't make them directly comparable.

However, I should still be able to use the variable-focus to roughly gauge which camera I need, right? If the fixed 2.8mm has a FOV of 114*, then I should be able to set my variable-focus to roughly 114* FOV, right? If so, is there any way to gauge what the FOV currently is given a random zoom value?

 

[subterminal]

Nevermind. Found this thread which concludes that the FOV numbers are all made-up bullshit anyways.

The cameras seem like great quality for the money, and I can't wait to have them setup, but there are janky, questionable things that do leave a bad taste with me.

 

[wittaj]

Yeah, you either accept the better quality video with some wonky stuff or go with consumer grade just scan a QR code but then video is crap

 

[Ri22o]

I had a similar issue and just tried various settings to see which was the closest to an existing 3.6mm that I had. I found that setting zoom to 440 (4.5mm on the calculator) gave me the closest to 3.6mm.

You can see various calculated focal lengths and their FOV here, for reference.

Varifocal vs Fixed focal length comparison.

I know there are a couple other threads on this, but I wanted to make my contribution. It is always highly suggested for new installs to first get a varifocal and then use it to determine the focal length you need for a given field of view. I had replaced one of my varifocals with a fixed...

ipcamtalk.com

 

[Revo2Maxx]

Something I thought I would add, I know this is almost a year old. However I thought it might help others that happen to find this thread and wonder why something isn't adding up from 1 camera to another..

Remember this, There is a formula for getting the true lens size. It has something to do with the cameras Lens that is installed and the cameras Sensor size. What do I mean, Well to determine the true millimeter MM of the view in a CCTV or camera system you need to consider the lens focal length and sensor size. The focal length determines how much of the scene the lens can capture. Longer focal length narrows the view and magnifies distance objects, Shorter provides wider view. While the sensor size affect the FOV Field of View, Larger sensors capture wider and smaller have narrow angles. So to get the true MM of a camera this is the formula, Sensor Width X Focal Length divided Sensor Diagonal. In other words. A 8mp camera with a 2.8mm lens that has a sensor size of 1/1.8 wouldn't be the same as a 4mp camera with a 2.8mm lens on a 1/2.7 sensor. While in this case of what I just posted it is really close to the same with 1 being 2.51mm and the other being a 2.67mm. However if that 8mp camera had a 1/2.7 sensor with 2.8mm lens would be almost 2.47mm so they are all close. However when you add a camera with a VF lenes being manual or motorized this makes this even more complicated.

What I wish I could find is a IP camera with Presets on a Zoom camera like I have on my older 2016 and 2017 5mmx50mm TVI analog camera. Seeing I use this camera at 2 different areas of view in my scene it would be good to find a IP camera that has same preset features even if only offering 4 different levels. Where my TVI has 255 lol I would never need more then 2 or 4 presets for just a zoom camera.. Main reason is this cameras scene is Road, At night closer to only capture plates and day time out some to capture plates and people.. Once I find replacement camera with Presets for IP camera I can use only IP cameras. Until then I am stuck using my 8mp AI DVR with analog cameras..