I used a simple test chart with lines - nothing serious - and I am not claiming the 40 lp/mm being more accurate than +/- 5. But still better than the 25 lp/mm that could be expected according to your table. I don't know better off hand, but your theory does not feel right to me.
Sven Zitat von "J. C. O'Connell" <[EMAIL PROTECTED]>: > Because sensor resolution and lens resolution interact and > the result is NOT the minimum of the two, the result is > (sensor-res*lens-res)/(sensor-res+lens-res) from what I have > read on the subject. i.e. if sensor and lens are both 60 lpmm > then system total result is only 30 lpmm. In order to get a system total > resolution very close to the sensor resolution, the lens resolution > has to be very high like 10 to 100 times higher, not just a little higher. > > How are you measuring to get your results? Curious. > JCO > > ---------------------------------------------------------------------------- > J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com > ---------------------------------------------------------------------------- > > -----Original Message----- > From: keller.schaefer [mailto:[EMAIL PROTECTED] > Sent: Monday, January 26, 2004 4:10 AM > To: [EMAIL PROTECTED] > Subject: RE: D: SMC 1.4/50mm FA / APS vs FF > > > JCO, > > I am puzzled. In my own humble attempts at testing *ist D performance I > achieved > a maximum resolution of around 40 lp/mm, which according to your figures > would > only be possible with a 110 lp/mm lens - a lens which I do not have (I > think). > > It is clear that lenses need more resolution as the image capturing area > gets > smaller. But I always assumed that as long as the lens resolution exceeded > the > (real life) sensor resolution, I would be in the green. This also > corresponds > to test shots taken with say a 1.4/50 where you can see the image improving, > as > you gradually stop down from f=1.4 to f=4. > Between f=4 and f=11 I am unable to see any difference in image quality (16 > and > 22 then get worse again). To me this says that between 4 and 11 the lens > resolution exceeds the sensor resolution. > > Why are you assuming that the effective resolution depends on the lens > resolution, even if it is way above the sensor resolution? > > Sven > > > > Zitat von "J. C. O'Connell" <[EMAIL PROTECTED]>: > > > Let me TRY to clarify. The "TOTAL RESOLUTION" or detail of an image is not > > determined > > by lpmm, it is determined by (lp/mm*Hdimension)*(lp/mm*Vdimension) > > This is essentially (TOTAL horizontal lines * TOTAL vertical lines) > > recorded. > > > > Now assuming you have two Better than Perfect lenses of say infinite lp/mm > > attached. > > The TOTAL RESOLUTION of a full frame or APS 6Mpixel sensor would be the > same > > assuming the correct focal lengh factor is used (1.5?) for the different > > sensor > > sizes. > > > > BUT, we dont have perfect lenses. I used Excel to calculate the > difference > > in TOTAL RESOLUTION which I call Megalines squared below. Since infinite > > resolution would crash the program, I used an imaginary lens with 10,000 > > lp/mm > > as a reference. As you can see by the data below, with a perfect lens, > > there > > would be nearly zero difference in TOTAL RESOLUTION using Full Frame vs. > APS > > sized 6Mpixel sensors. BUT with real lenses in the 30 to 100 lp/mm range, > > a FullFrame 6Mp sensor would yield an image with 40% to 25% more detail. > vs > > an > > APS 6Mp sensor. This is signifigant and not only that, each pixel would > > be 125% larger in area yielding less noise and/or more sensitivity. > > Bottom line is a full frame sensor will perform better than an APS sensor > > using real lenses if they both have the same Mpixels. Even using the best > > 100 lp/mm lenses, FF is going to be 25% sharper, and FF will be even more > > sharp as the lens resolution falls lower to more typical levels. Seems > > paradoxical > > but thats the geometry. Comments welcome, spreadsheet available. BTW > > is *istD effective sensor 16X24mm as I assumed in these calculations which > > I based on the 1.5 crop factor and same aspect ratio??? > > JCO > > > > FULL FRAME, 6 Mpixel sensor, 2000X3000 pixels, 24mmX36mm > > --------------------------------------------------------- > > lens sensortotal total resolution Mlines^2 > > lp/mm lp/mm lp/mm (lp/mm)*24mm*4*(lp/mm)*36mm*4 > > 10000 41.6 41.4 5.931 > > 200 41.6 34.4 4.099 > > 190 41.6 34.1 4.025 > > 180 41.6 33.8 3.946 > > 170 41.6 33.4 3.860 > > 160 41.6 33.0 3.767 > > 150 41.6 32.6 3.666 > > 140 41.6 32.1 3.555 > > 130 41.6 31.5 3.433 > > 120 41.6 30.9 3.298 > > 110 41.6 30.2 3.149 > > 100 41.6 29.4 2.983 > > 90 41.6 28.4 2.797 > > 80 41.6 27.4 2.589 > > 70 41.6 26.1 2.353 > > 60 41.6 24.6 2.086 > > 50 41.6 22.7 1.782 > > 40 41.6 20.4 1.437 > > 30 41.6 17.4 1.050 > > 20 41.6 13.5 0.630 > > 10 41.6 8.1 0.225 > > > > > > APS, 6 Mpixel sensor, 2000X3000 pixels, 16mmX24mm > > ---------------------------------------------------------------------- > > lens sensortotal total resolution Mlines^2 TOTAL Resolution Loss > > vs. > > lp/mm lp/mm lp/mm (lp/mm)*16mm*4*(lp/mm)*24mm*4 Full Frame (in %) > > 10000 62.5 62.1 5.926 -0.1 > > 200 62.5 47.6 3.483 -15.0 > > 190 62.5 47.0 3.397 -15.6 > > 180 62.5 46.4 3.306 -16.2 > > 170 62.5 45.7 3.208 -16.9 > > 160 62.5 44.9 3.103 -17.6 > > 150 62.5 44.1 2.990 -18.4 > > 140 62.5 43.2 2.868 -19.3 > > 130 62.5 42.2 2.736 -20.3 > > 120 62.5 41.1 2.594 -21.3 > > 110 62.5 39.9 2.440 -22.5 > > 100 62.5 38.5 2.272 -23.8 > > 90 62.5 36.9 2.090 -25.3 > > 80 62.5 35.1 1.891 -26.9 > > 70 62.5 33.0 1.675 -28.8 > > 60 62.5 30.6 1.439 -31.0 > > 50 62.5 27.8 1.185 -33.5 > > 40 62.5 24.4 0.914 -36.4 > > 30 62.5 20.3 0.631 -39.9 > > 20 62.5 15.2 0.353 -44.1 > > 10 62.5 8.6 0.114 -49.2 > > -------------------------------------------------------------------------- > -- > > J.C. O'Connell mailto:[EMAIL PROTECTED] http://jcoconnell.com > > -------------------------------------------------------------------------- > -- > > > >
