On 14 Apr 2005 at 21:10, Mark Cassino wrote: > I can't get the original page to load, so thanks to Fred for posting the > extracted page. > > I'm rather surprised by how poorly the FA 1.7 does at wider apertures. > Similarly surprised that the Ricoh 50mm f2.0 did so poorly. > > I'm trying to put these numbers into perspective with the *ist-D.... > > Let's see - 23.5mm x a5.7 mm sensor with 3008 x 2008 pixels works out to > about 128 pixels per mm. With LPM being a factor of on half pixels per mm > (it takes one pixel for the line, one for the background) then the > theoretical maximum resolution of the *ist-D / DS is only 64 lpm.... ???? > > Is my math wrong on that, or are most of these lenses equal on the *ist-D / > DS? > And for that matter, more or less equal with most films except the highest > performing slide films (I seem to recall that Velvia could resolve something > like 160 lpm? Or maybe that was DPI... My memory is about as good as my > math.)
Testing the resolution *ist D using USAF chart I found that the camera/best lens combos can manage no more than about 46lppm absolute resolution. >From the archives: Subject: RE: *ist D resolution (was:Soon to be new istD owners) Date: Tue, 13 Jan 2004 09:24:46 +1000 On 12 Jan 2004 at 22:28, Jens Bladt wrote: > Hi Rob > Hmmm. Not so sure about how to test lens resolution on film. > I'm sure 100 linepairs pr. mm has been occationally achieved on film. Hi Jens, Plenty of resources here: http://members.ozemail.com.au/~distudio/lenstesting/ > Simple math tels me that 3000 pixel covering 24mm gives 125 pixel/mm. But you > need three to make a PAIR of lines. Gives you appr. 43 line pairs/mm, right. > So, using a 6MP body is like using the poorest lens ever made by Pentax - > resoluton wise, of cource. Sure, the Kell factor in this case appears to be about 0.7 therefore the resolution in lpmm can effectively be calculated as 3008pixels/23.5mm/2pixels*0.7kell factor=44.8lpmm. I used a conventional test chart in conjunction with a very high resolution lens in order to reduce it's effect on the measurement and I calculated an optical resolution of 44.6lpmm and this was before I made any theoretical calculations. > Like 100 lp/mm seemed to be "the sound wall" of analog photography, it seems > appr. 5000 dpi is "the sound wall" of current digital photography. But I'm > sure they'll break throug this sometime soon. SONY is now marketing a 8MP > consumer camera - with a 2.0 Carl Zeiss lens - for appr. 1000$ (Sony DSC > F-828). Maybe we'll get there earlier than we relly want. I don't think so, I doubt there will be that much to gain by making smaller pixels, look at the noise generated by the Pentax *istD at higher ISO already. Smaller pixels will reduce the effective exposure latitude, colour accuracy and increase the noise floor. Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
