What the heck is an f-stop?

Started 5 months ago | Discussions thread
Paul Anderegg
Forum MemberPosts: 68
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Re: What the heck is an f-stop?
In reply to bobn2, 5 months ago

Remember that the SNR is ultimately determined by the amount of light that the sensor collects. Remebering that the linear ration between 1/3" and 2/3" is 1.8, which gives an area ratio of 3.24 or 1.7 stops. So in the example above, you gain 0.7 stop going from f/1.4 to f/1.8 and lose 1.7 stops due to the smaller sensor. So in the end the smaller sensor is losing you a stop in terms of total light. If the question is, what is the lowest light for a given quality (discerning detail in the darker areas) the you are better off with the 2/3" f/1.8 combination gained up 0.7 stop above the 1/3" f/1.4 combination.

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Bob

Just to make sure there is no misunderstanding here.........the lenses in question, be they the f1.4, or f1.8, are specific to the sensor size mount, and not interchangeable.  I will give you three links of the "same" lens (would appear) in different mounts, so you can give your take on if they are the same "glass".  This identical lens series thing has been around as long as CCD video cameras have been.

Fujinon 18x7.6BERM 2/3"

Fujinon 18x5.5BERM 1/2"

Fujinon 18x4.2BERM 1/3"

The constant aperture of the 1/3" model still baffles me.

Paul

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