Michael, I've asked Samsung to comment here. Let's see what they have to say.
I agree with you about the output of other lens calculators vs the 5080's specification. I do not have a guess about why it's different.
In addition to the sensor size variation possibility, remember that actual back-focus distance will affect FOV, and assembly tolerances may even mean a slightly different FOV from one camera to the next within a model line. I wouldn't be surprised if a manufacturer may measure the FOV on a number of finished cameras and then pick the numbers that are most favorable for the marketing.
Slightly related example: back when I was working in car audio, it was common practice (probably still is) for amplifier manufacturers to measure amp output at maximum supply voltage, and use that as their power ratings. Since an automotive electrical system regularly varies between 12V and 15V (with dips and spikes well outside that range), you'd get substantially more measured output power when providing the rails with 25% higher voltage, which looks much better on the ad copy... but also means you get significantly lower output when running on battery (engine off) or at *normal* operating voltages of 13.5-14V.
At that time especially (early 90s) the "wattage race" was similar to the "megapixel race" with everyone trying to come up with some new trick or edge to have better numbers than the other guy, which as often as not with cheaper models included conveniently omitting (or small-printing) specs like THD (total harmonic distortion), which is a product of signal clipping caused by pushing the output past the rail voltage - gives you a lot more measured RMS output, but sounds like crap; this might be considered analogous to low-light or low-noise specs on high-MP cameras.
Since there was (and AFAIK still is) no industry-standard way to specify output, let alone any regulatory controls, there was no way to really know how accurate or meaningful those numbers were. The high-quality, "professional grade" amps used regulated power supplies, meaning they would give the same output across the entire output voltage range, so if you were buying a 200W amp, you knew it would give you 200W all the time (these were usually very up-front about THD and other related numbers as well).
But I digress...
I used the Samsung as a benchmark (since they do publish their FOV) to compare to the calculators. My experience is that the numbers they publish are realtively accurate. Thus, it seems to me that the calculators are pretty useless. I see a pretty wide varilation in the published FOV for similiar chip size and lens. Is there any real way to estimate the FOV for manufacturer that don't deem it important to publish their FOV or soes this need to measure in a lab by the manufacturer?
Is there any real way to estimate the FOV for manufacturer that don't deem it important to publish their FOV or soes this need to measure in a lab by the manufacturer?
Well ultimately its just trig, the problem is that you need to know the exact size of the horizontal and vertical dimensions of the imager. If you know that and as long as the manufacturer is showing you all the pixels its hard to see how it could be much off. Though may have to the calculation yourself, since your limited to predefined imager formats.
Of course if the lens itself doesn't really have a 2.8mm focal length then, like Matt said, you might get a degree or two out of the back focus adjustment but I think it wouldn't be the sharpest theoretical picture.
The good news is that for the larger sizes of sensors there is no legacy fractional inch format, so the size stated is the real size. For instance with the old H3 Avigilon cameras notice how they describe the sensor in fractional inches at the top with the imaging area at the bottom. Do the math and you will see that the horizontal and vertical dimensions do come close to making a diagonal of 1/3.2".
Whereas on the new larger sensor for the H4 everything works out, because its not stated in fractional inches, but in decimal inches.
...combine a 1/3" sensor that's actually 1/2.85" ...
Actually the typical size of a 1/3" sensor is less than 1/4", Brian equated it to nominal lumber sizes. Though your point still stands that even then there can be variances. I'm going to measure my television now, Samsung of course.
Chesapeake & Midlantic
Sorry to resurrect this conversation, but my question is this: whom do I believe when the calculator and the spec sheet is off?
For example, the DS-2CD2132F-I has a 1/3" sensor and a 4mm lens. Running those numbers through the IPVM calculator yields a HFoV of 61.93°, but the spec sheet says 79°.
We had an issue with some FLIR cameras recently. It was our mistake basing our product selection on focal length alone. We assumed, incorrectly, that similar domes using 1/3" sensors would give similar AOV with the same focal length. However, what we found was that the varifocal lens used on the 1/3" sensor camera was made for a 1/2.7" sensor, which made the AOV at the 2.8mm setting about the same as the 3.6mm fixed version that had a matching 1/3" lens.
Moral of the story, use the AOV as your basis, but test, test, test.