Has any one tested the Theia Lens Calculator. Is it accurate? It seems very simple, but if reasonably accurate its seems cool.
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Theia Lens Calculator
U
Undisclosed #1
Apr 16, 2017Yes. I have tested it and it works well.
That is part of the beauty of video surveillance -- at it's core, it is nothing more than simple math. The actual, practical application of those numbers is much more complex, but when looking at something like ppf or HFOV, it's really just mathematics with inputs and outputs.
For what it's worth, you may find some slight variations from one lens calculator to the other, but overall they are all very close.
JH
John Honovich
Apr 16, 2017Having models with actual HFoV / AoVs, like our Camera Calculator does, but Theia does not, is important.
Many, maybe a majority of, camera's actual FoV, differ from what (any) theoretical lens calculation delivers (i.e., inputting the focal length and sensor size). This often has to do with what portions of the imager a camera manufacturer uses or any cropping they do or distortion correction, etc.
That is one of the main benefits of having a database of camera model HFoV / AoV to look up, like we have with 6,000+ cameras in our Camera Calculator database. Theia has their own lenses listed but not that only covers a fraction of a percent of lenses / cameras.
U
Undisclosed #2
Apr 16, 2017Many, maybe a majority of, camera's actual FoV, differ from what (any) theoretical lens calculation delivers....
Especially as the focal length gets to 3mm and shorter; the way lenses map the fov to the sensor at extremely wide angles is never linear, and varies greatly.
AI
Andrea Iniguez
Nov 09, 2017As John points out, the camera manufacturer might use less than the total available pixels of the sensor which will affect field of view.
Our calculator assumes the maximum number of pixels as the default for a given sensor, but allows the user to change that in the settings. In looking at the camera specification you can find out the actual number of pixels being used and input those to make the calculation accurate.
Our calculator allows the user to select the "standard lens" or "standard telephoto" lens options in our calculator which cover the focal lengths from 2mm to 60mm, but may also select one of our lenses.
Another factor affecting FOV is the distortion level of a lens. Each lens has a unique amount of distortion resulting from its design. In our calculator, when our specific lenses are selected, we have assumed the actual distortion profile of the lens so that the FOVs will be more accurate. For the "standard lens" or "standard telephoto", since there is no "standard" distortion level, we have made an assumption about the distortion levels, so the FOVs may not be accurate for the user's actual lens.
In addition to the camera database, IPVM's calculator has some nice features that ours doesn't. For example, it uses Google Earth views. And it allows you to export the overview map with camera layout directly to PowerPoint. It also includes 360 degree fisheye lenses.
If anyone would like more info or support using our calculator, email info@theiatech.com or call 503 570 3296.
Andrea Iniguez, Theia Technologies
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