On 02 Mar 2003 00:16:41 GMT, mitchgross@aol.com (MitchGross) wrote:

RG Baker wrote:

>>And the result is 720x480 ... never better, ever.

>>

>>As has been said, there are better images than others where both have the

>>same resolution -- but you can't exceed the resolution of the format.

>>Period.

>>

>>Maybe you aren't saying different -- but if you are saying that a device

>>that records 720 samples per scan line can exceed a resolution of 720

>>samples per scan line, I have to disagree.

>>

>>GB

>I'm not saying different. I'm saying that this is how one gets the most out of

>those 720 samples. That's why it is referred to as "apparent resolution."

>

>Mitch

I think "RGB" short answer should suffice (but when did that ever

stop me from further comments?! ;-), but, here are more comments...:

-- I agree with you that within any given medium, even one with

severe limitations, there are visible variations in image quality

(heck, that's the very point of:

www.David-Ruether-Photography.com/vid_pict_characts.htm

www.David-Ruether-Photography.com/camcorder-comparison.htm

www.David-Ruether-Photography.com/sony_dcr-vx2000.htm

www.David-Ruether-Photography.com/camcorder--comparison.htm

www.David-Ruether-Photography.com/perspective-correction.htm

[and for stills, www.David-Ruether-Photography.com/slemn.html]).

Even with broadcast SDTV, viewed on a good TV, it is

obvious that even this 340-line-limited medium can look very

good, and even better than good 540-line-limited Mini-DV

original material viewed directly - and even the lowly 240-line

VHS format can look very good in this format with carefully

prepared commercial copies of VERY high quality original

material...).

-- I think by now it is recognized that within a format, the maximum

attainable resolution is a fixed quantity (at least for DV...). But

"resolution" is not the same as "sharpness" - the first is measurable

(though with difficulty, given what TV resolution looks like near

the limit of the system...); the second is subjective, and it can vary

for a given resolution considerably, even under otherwise identical

conditions. Factors like lens characteristics, image-processing,

subject lighting, subject colors, etc. can modify the perception of

image sharpness considerably.

-- If all else is equal, with multiple lenses tried, the lenses with the

higher resolution will produce higher resolution images if all the

lenses are at the same stop, and all the lenses are not at a stop that

is diffraction limiting for all the lenses - but the resolution on tape

cannot exceed the format's resolution limit. If all the lenses are at

the same stop, and all the lenses are at a stop that is diffraction

limiting for all the lenses, all will produce the same resolution

(barring manufacturing defects in the lenses), though the sharpness

can vary a bit depending on lens characteristics (like brilliance,

contrast, and the way the lenses handle diffraction [the form the

diffraction effect takes]) - and it cannot exceed the format's

resolution limit.

-- Resolution is interactive; the resultant resolution of a system

cannot exceed "the weakest link", but how closely it approaches it

depends on how much higher than the limit its best components are.

With film, the "Resultant Resolution" of a 2-element system,

like given lens and film resolutions with "Higher Resolution"

and "Lower Resolution" elements is approximated by the formula,

1/RR = 1/HR + 1/LR. I assume this effect holds for TV as well,

though the proportions may vary. Assuming that they do not, a

resolution of 540 TV-lines and a lens capable of 540 TV-lines

(or 720 pixel-resolution) would result in a paltry 240 TV lines

on tape. If we substute a much better lens (assuming with this

that the lenses are not within diffraction-limiting), with 5400

TV-lines of resolution, the resultant resolution is 490 TV-lines.

What saves us here is the difference between lens resolution

"in air" and "in the medium" (and with the way "TV-lines" are

rated) - a lens "aerial" resolution is normally far higher than it

is on the much lower resolution imaging format, so the

resultant resolution is usually closer to the limit of the lower

part than the formula might suggest. But this also indicates how

hard it is to closely approach the format resolution limit - it

takes a very much higher resolution lens to improve results

somewhat. (RGB and others are free to jump in and point

out my logical and factual lapses here...;-)