Could someone explain to me what TV Lines mean when it comes to a camera? I was looking at various specification and came across how many TV Lines a camera has. A quick google search shows it’s also appears to be referred to as the lines of horizontal resolution. Based on that definition it says it’s essentially the number of columns in a picture.
I was looking at one camera that’s popular over in the US for outside broadcasts now - the Sony HDC-4300L which has 2000 horizontal lines at the center in 4K
. Does that mean there are 2000 lines on either side of the center? Because that is significantly less than the 3840x2160 that’s expected in UHD.
I’ve seen it in other manufacturers for regular HD listing 1000 TV lines.
AIUI tv lines in horizontal terms are defined by the number of vertical black lines you could see on a white background at the limit of your system. To resolve 2000 black lines against white at the limit you'd need ~ 4000 pixels (4000 pixels alternating between white and black would let you resolve 2000 vertical lines)
This is obviously a gross simplification ignoring the fact that TV is based on samples, that you have to consider the MTF of your lens and optical sensor system etc. - but as a rule of thumb your TVL resolution is around half your horizontal sample count in an ideal system (assuming equal resolution 3-chip cameras) I think.
AIUI camera manufacturers quote the equivalent full-width resolution that you'd achieve for the performance of given areas - so if the centre of the camera sensor is quoted as 2000 TVL that's the effective resolution of the system at the sensor (if scaled to the full width), however chances are the performance at the edges of the sensor is reduced, so will have a lower TVL spec. It's effectively a way of saying that the centre is theoretically about as good as possible, but the edges degrade a bit.
Annoyingly this definition is at odds with the vertical line count figure - which is the total number of horizontal scanning lines.
Last edited by noggin on 21 October 2018 4:33pm
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