reducing blockiness of satellite imagery?

[Damien BRUNET 0]

Hi,I've read all your messages and they give me help !However, I've got some questions to ask you :- With ImageTools, Luis said that the "Lanczos3" filter was the best filter. I made some tests and I find that the "Bicubic" filter gives the best results with my satellite pictures. Am I wrong ?- Holger, where are the "sharpening filters" in Photoshop ? Which option do you use and how did you do to have such wonderful pictures ?As for me, I also have blockiness in some photosatellite pictures.Regards,;-)Damien BRUNET.e-mail : damien.brunet@udb.fr.st

[Holger 0]

Hi Damien:I briefly looked at Elrond's utility and compared "bicubic" in Photoshop with his "Lanczos3" filter. For my source resolution (15 meters) the results are nearly identical. The Lanczos3 has slightly less jagged edges, which is probably more noticable at higher source resolutions. You have the right idea: do tests with your specific image and pick the one that provides better results for you.Photoshop sharpening tools are (surprise, surprise) in the menu Filter > Sharpen. The 'Unsharpen Mask' is the one to use as it provides a number of options. Search the help file for 'unsharpen' and it tells you what the parameters do. I found Amount:150%, Radius: 1.5 pixels, and Threshold: 5 levels best for my source image. I run the unsharpen mask on the original image *before* increasing the resolution (via 'Image Size') and also follow the tip on the Photoshop help page to convert the RGB image into Image > Mode > Lab Color and run unsharp mask on the Lightness band only (selected via Windows > Show Channels, then click on the Lightness channel). However, the optimum procedure for your type of image will probably differ and there's no way around experimenting and reading the documentation.Cheers, Holger