On Sat, 26 Apr 2003 11:59:00 -0700, "Gene E. Bloch" <gino37@nowhere.none> wrote:

>Maxx Taxx wrote:

>> In Europe there is a new Panasonic model called NV-GS50 that replaces

>> the old model NV-GS5.

>>

>> However NV-GS50 has a CCD size of 1/6 compared to 1/4 for the old

>> model. (The old lense was 3.15-31.5mm, f1.8-2.5 filter diam 30,5 and

>> the new one is 2,3-23mm F1,8 filter diam 27mm)

>>

>> I have heard that generally it's better with a larger CCD but I think

>> the difference in lenses might make up for this because otherwise 1/6

>> would be terrible, wouldn't it ?

>The difference in lens focal length is just to match the image size to the

>smaller CCD.

>

>There are thus two problems. Smaller diameter lenses tend to have less

>angular resolution (diffraction effects), and smaller CCDs will have to have

>smaller pixel cells, leading to less low light sensitivity and higher

>amounts of noise (due to random variations both in the number of photons

>hitting the pixel cells and in the number of electrons generated by the

>photons). All this is just physics - you can't work around it.

>

>To me this is a lose-lose situation.

>Gino

Hmmmm.... I've heard this opinion before about shorter

FL lenses having more restricted maximum possible

resolution due to diffraction, but I don't believe in it in

practice, at least for the apertures likely to be used with the

sensor sizes involved. I observe that lenses for 35mm, for

instance, with FLs over a wide range of from 8mm to 500mm,

all show a common characteristic: general optimization

of resolution around f5.6 to f8 in the center, with

reduction at smaller stops due to diffraction... If one

compares lenses of FLs with the same angle of view with

differing sensor sizes and check for the optimum stop

for each FL for the differing formats, there is some

variation, but this would be expected in the design,

given physical size and DOF considerations (there are

no 300mm f2.8 lenses made for 8x10, for instance, but

there are many of the same speed and equivalent angle of

view made for video cameras - but even with the great

disparity of actual FL, the optimum stops for these are

not very different [it isn't worthwhile to make a

large-format lens diffraction-limited at a wide stop,

since it will likely never be used at that wide stop,

and similarly, smaller-format lenses are rarely

diffraction-limited at their widest stops...]). In

other words, short of spending a fortune for VERY

high quality video lenses that may optimize at very

wide stops, most good lenses perform about the same,

regardless of size (and almost regardless of format,

in the center...).