What the heck is an f-stop?

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Paul Anderegg
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What the heck is an f-stop?
5 months ago

I am may be in the market for a broadcast video camera soon, and am having some issues understanding the relationship between sensor size and f-stops.

For those not familiar with broadcast video cameras, the sensitivity is rated as f-stop at 2000 lux necessary to produce a certain video signal level (brightness).. The first generation of CCD video cameras, 1990, were rated at f5.6 @ 2000. The next generation, around 1993, was rated at f8, then f11 hit around 1996. The best ever standard definition cameras were the Panasonics, which reached f13 @ 2000 around 2004.  These ratings are for the 0db (no gain up) settings of a video camera.

So fast forward to today, and you've got mostly f10 @ 2000 HD gear, with a few more expensive f11 and maybe 2 or 3 at f12. Which brings me to my inquiry. I am trying to figure out which of the following two cameras would be best suited for night and low light use. A JVC GY-HM890 (f11@2000 1/3" chips) with a constant f1.4 lens, or a Panasonic HPX600 (f12@2000 2/3" chip) with an f1.8/wide-f2.3/tele lens.

With the same 18x series lens, the JVC would be f1.4 at full telephoto, where the Panasonic would be at f2.3. My confusion with this results from not understanding how f-stops relate to sensor size. Is an f11@2000 rating for a 1/3" the same as an f11@2000 rating for a 2/3", or is that aperture just some random number once you start playing around with sensor size? Short of putting two cameras side by side in the same light, there seems to be no technical info about this on the internet that I can locate with google.

Although this is a video inquiry, it would seem that the PHOTOGRAPHY world would be better equipped to technically answer this question. Also, in the video world, Canon and Fujinon sell the same series lenses in 2/3", 1/2", and 1/3" versions, so I am assuming they are the same glass. Not sure why the 1/3" versions all have constant apertures, perhaps the small sensor just takes advantage of the larger glass elements designed for the larger sensors? Thanks in advance.

Paul Anderegg

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