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 version based on the results from the Focal Lens Calculator. The FOV ended up being way different than anticipated. There have since been other posts made stating there really is no direct correlation between the calculated varifocal focal length and the fixed focal length.
Cut to my most recent install:
I installed two varifocals over my backyard and determined it was likely a better application for a fixed, but I did not know what the comparable fixed camera would be. Knowing I could not rely on the calculator I set the varifocal to various, calculated focal lengths in an attempt to see if a 3.6mm or 6mm fixed would be appropriate. The results are below.
Varifocal: IPC-T5442T-ZE
Fixed: IPC-T5442TM-AS
VF @ 3.6mm
VF @ 4mm
VF @ 5mm
VF @ 6mm
Based on the above and a very calibrated test involving me hanging off of a ladder and holding a fixed 3.6mm in the same location to compare the field of views, I determined the closest varifocal setting would be around 4.5mm.
After mounting, the results are below (overlooking the subtle alignment differences). It's safe to say that 4.5mm is damned close to a fixed 3.6mm; use this information how you will.
VF @ 4.5mm and the Fixed 3.6mm
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 version based on the results from the Focal Lens Calculator. The FOV ended up being way different than anticipated. There have since been other posts made stating there really is no direct correlation between the calculated varifocal focal length and the fixed focal length.
Cut to my most recent install:
I installed two varifocals over my backyard and determined it was likely a better application for a fixed, but I did not know what the comparable fixed camera would be. Knowing I could not rely on the calculator I set the varifocal to various, calculated focal lengths in an attempt to see if a 3.6mm or 6mm fixed would be appropriate. The results are below.
Varifocal: IPC-T5442T-ZE
Fixed: IPC-T5442TM-AS
VF @ 3.6mm
VF @ 4mm
VF @ 5mm
VF @ 6mm
Based on the above and a very calibrated test involving me hanging off of a ladder and holding a fixed 3.6mm in the same location to compare the field of views, I determined the closest varifocal setting would be around 4.5mm.
After mounting, the results are below (overlooking the subtle alignment differences). It's safe to say that 4.5mm is damned close to a fixed 3.6mm; use this information how you will.
VF @ 4.5mm and the Fixed 3.6mm
