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Posted by Joe on 11/07/07 22:36
So, back to my original question- was Spex right when he replied to someone,
"What are you so hung up about capturing at 1920x1080 when the actual
resolution of the camera is way less than that at 800+ tvl?"
Joe
"Dave Martindale" <davem@cs.ubc.ca> wrote in message
news:fgqnbr$9v7$2@swain.cs.ubc.ca...
> "David McCall" <mccallmail@verizon.net> writes:
>
>>Often people confuse this measurment of resolution with
>>the number of pixels in rows and columns of the picture.
>>They are related, but not the same.
>
>>Lines of resolution take into account not only the pixel resolution,
>>but also the optics of the camera. A single line consist of a
>>black line as well as the white space between the black lines.
>
>>A simplistic way of looking at it would be to say that 800 lines
>>of resolution would require 1600 columns of pixels.
>>One pixel for the black line and one for white space.
>>Unfortunately it isn't that cut and dried. But that should get you
>>started.
>
> Unfortunately, you're confusing things further.
>
> When still photographers and optical designers talk about "lines", they
> generally do mean "line pairs", which is one black and one white line.
> These are the same size as "cycles", one cycle of a sine wave, which is
> used in MTF measurements, so measuring resolution in line pairs or
> cycles gives close to the same value.
>
> In the video world, "lines" counts black and white lines separately.
> So you need to multiply by two when converting line pairs to video
> lines. And, in theory at least, resolving 800 TV lines takes at least 800
> pixels, not 1600 pixels. (In practice, with real equipment, using
> decent anti-aliasing filters, the number is closer to three pixels per
> line pair or per two TV lines).
>
> But wait, there's more complexity. TV resolution is generally quoted in
> terms of "lines per picture height", even when it is measuring
> horizontal resolution. If you want to know the total number of lines
> *per picture width* that can be resolved, you need to multiply by the
> aspect ratio. For example, a SDTV camera with "500 line" resolution can
> actually resolve 500*4/3 = 667 tv lines, or 333 line pairs, across the
> width of the screen.
>
> another Dave
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