Zoom equivalent on different sensors?

[Phil.g00]

From my DSLR days, the stated mm of a zoom lens had to be understood regarding its sensor size.
In other words, the 35 - 100mm Zoom on a 4/3rds sensor gave approximately the same FOV as a 70 -200mm on a full-frame sensor.
How does it work with IP cameras?
For example:
The SD6CE245XA-HNR is 3.95 mm–177.7 mm on a 1/2.8 sensor
The SD8C448PA-HNF is 6.25 mm–300 mm on a 1/1.8 sensor
The SD8C845FG-HNF is 8 mm–360 mm on a 1/1.2 sensor

Which one of these has the most extended zoom?
Or are they all about equal?

 

[wittaj]

I think I mentioned to you in your other thread you may have to toss out what you know from your DSLR day when looking at these cameras LOL and this is one area.

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

You will find there is zero consistency in trying to compare focal lengths even among the same size sensor and same series model of a camera!

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. And both of these cameras are on the same size sensor.

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

 

[Perimeter]

Which one of these has the most extended zoom?

I'd say: look at their spec sheets. The one with the smallest angle for horizontal fov is the one that is magnifying the most. So it looks like the second one wins.

 

[Phil.g00]

Those are my thoughts as well.
I think it should outdo the other two with its 1.97° FOV.

But it probably isn't the whole story without OIS for a superzoom (optical image stabilisation).
I think electronic image stabilization (EIS) may cause blurring when auto-tracking.
And there will always be a little camera shake, I think.
There is no point in having a massive zoom if the image is too shaky.
The specs don't indicate it has OIS, though.

This one has OIS at 50x PTZ, but I see it is EOL.
SD8A250WA-HNF with a 1.3° FOV.

 

[wittaj]

EIS won't work with auto tracking.

If you have it on a stable base, the shaking is minimal to non existent. Stick it on a pole and it may be a different story.

My PTZs that are somewhere in the 177mm range don't shake or bounce at all at full zoom

 

[Phil.g00]

Yes, I thought there might be an issue with EIS and tracking.
I would like to use a tree as a mounting point.
A very sturdy tree and it won't be too high up, but it is still a tree.
So I think I may need the gyroscopic OIS.

 

[wittaj]

Yeah in that case it may sway LOL.

We have seen people put cameras low on a large tree and you could see it shake, so I could imagine what a PTZ would do.

 

[tigerwillow1]

I've found the spec sheet FOV to be the best area coverage reference, and also the easiest to use.
I have a few cameras on tree trunks and would not have believed anybody telling me how much they can sway if not for seeing it myself. I've got a still-boxed PTZ that I plan on installing in a tree. Wife doesn't like how it will look on the house.

 

[Perimeter]

Has anyone here taken the T5442T-ZE and made a table of fov angle vs zoom setting number? This would be the easiest way to approximate any particular field of view.

 

[tangent]

From my DSLR days, the stated mm of a zoom lens had to be understood regarding its sensor size.
In other words, the 35 - 100mm Zoom on a 4/3rds sensor gave approximately the same FOV as a 70 -200mm on a full-frame sensor.
How does it work with IP cameras?
For example:
The SD6CE245XA-HNR is 3.95 mm–177.7 mm on a 1/2.8 sensor
The SD8C448PA-HNF is 6.25 mm–300 mm on a 1/1.8 sensor
The SD8C845FG-HNF is 8 mm–360 mm on a 1/1.2 sensor

Which one of these has the most extended zoom?
Or are they all about equal?

1/2.8 = 0.357
1/1.8 = 0.555
1/1.2 = 0.833 (close to micro 4/3)
APS-C ~= 1.184 in
Full frame ~= 1.7 in

You can look up the formulas and do the math or assume a directly proportional relationship.

Doing this may not be of as much value as you think, it doesn't really count if it's all just noise does it?

The simplest spec to look at regarding comparing zoom would be AOV or angle of view.
You might enjoy playing with IPVM Designer / Calculator to get a sense of what different cameras could do just remember this is a simulation.

 

[Phil.g00]

Yes, that is the way I am looking at it
As a rule of thumb, it appears that the mm on the 1/2.8 sensor is roughly half that of the 1/1.2 sensor mm for the equivalent FOV.
So the 177mm (on 1/2.8) zoom would approximate the 360mm zoom ( on 1/1.2).
And the 300mm zoom on the (1/1.8) would actually be the zoom with the furthest reach.
(I didn't recheck the specs, but I think it is also the brightest lens)
But none of the PTZ's in my example have OIS, which could be a dealbreaker on a superzoom.