Rob, Thanks for taking the time to provide this. I shall download and study it a bit.
-- Best regards, Bruce Monday, January 3, 2005, 5:55:49 AM, you wrote: RS> On 2 Jan 2005 at 22:44, Bruce Dayton wrote: >> Hello Rob, >> >> Nice shot! It certainly is nice to see something warm when it is cold >> (actually not that cold, but rain for quite some time now). RS> Hi Bruce, RS> Thanks, glad you got a bit of virtual warmth out of it :-) >> You mentioned that you corrected for CA and other distortions. I >> would love to see the comparison to the original to see what the 15mm >> does without corrections. RS> No problems, I did however make an error in that the bottom LH crop I made was RS> from the distortion corrected file, in any case either would have had the CA RS> dealt with as I do this in the Pentax RAW convertor. I've now replaced the crop RS> with a crop from the uncorrected file plus I also made similar crop(3) of a RAW RS> conversion without CA correction. RS> http://home.swiftdsl.com.au/~distudio/temp/IMGP8081crop2.jpg RS> http://home.swiftdsl.com.au/~distudio/temp/IMGP8081crop3.jpg RS> As you can see the uncorrected CA isn't too bad at all though it is slightly RS> non-linear due to the lenses strange distortion profile so it can't be RS> corrected fully with simple linear tools. RS> Like most WA lenses it exhibits some barrel distortion however it also has a RS> slight secondary distortion towards the edges which renders straight lines RS> along the edges as undulated. Not that it's worse than other similar lenses but RS> it can be noticeable when shooting architectural subjects or the like. RS> I've posted another two images to show the whole scene pre and post geometric RS> distortion correction: RS> http://home.swiftdsl.com.au/~distudio/temp/IMGP8081.jpg RS> http://home.swiftdsl.com.au/~distudio/temp/IMGP8081cor.jpg RS> Differences are best observed by toggling between images when they are over- RS> laid such as pasting one image over the other in PS as a layer then toggling RS> the top layer on and off. RS> The final image was attained by rotating very slightly, adjusting for RS> perspective distortion and cropping to a 2:3 ratio. RS> Cheers, RS> Rob Studdert RS> HURSTVILLE AUSTRALIA RS> Tel +61-2-9554-4110 RS> UTC(GMT) +10 Hours RS> [EMAIL PROTECTED] RS> http://members.ozemail.com.au/~distudio/publications/ RS> Pentax user since 1986, PDMLer since 1998
