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).
Hi Bruce, 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. No problems, I did however make an error in that the bottom LH crop I made was from the distortion corrected file, in any case either would have had the CA dealt with as I do this in the Pentax RAW convertor. I've now replaced the crop with a crop from the uncorrected file plus I also made similar crop(3) of a RAW conversion without CA correction. http://home.swiftdsl.com.au/~distudio/temp/IMGP8081crop2.jpg http://home.swiftdsl.com.au/~distudio/temp/IMGP8081crop3.jpg As you can see the uncorrected CA isn't too bad at all though it is slightly non-linear due to the lenses strange distortion profile so it can't be corrected fully with simple linear tools. Like most WA lenses it exhibits some barrel distortion however it also has a slight secondary distortion towards the edges which renders straight lines along the edges as undulated. Not that it's worse than other similar lenses but it can be noticeable when shooting architectural subjects or the like. I've posted another two images to show the whole scene pre and post geometric distortion correction: http://home.swiftdsl.com.au/~distudio/temp/IMGP8081.jpg http://home.swiftdsl.com.au/~distudio/temp/IMGP8081cor.jpg Differences are best observed by toggling between images when they are over- laid such as pasting one image over the other in PS as a layer then toggling the top layer on and off. The final image was attained by rotating very slightly, adjusting for perspective distortion and cropping to a 2:3 ratio. Cheers, 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
