I am unsure if this would be of any help to anyone but I can write it up in a little more detail including my thinking while doing this including the bits where I think I should have got better or went wrong as I still have the work file. A mini tutorial that is, assuming I am not seen as being pretentious, well overtly so :wink:.
Tony, thanks for your generosity and patience. This is so valuable it's been made a sticky and the thread name changed to better explain what the thread deals with. Well done!.
First a big thanks to all for such nice comments. I am pleased that you have found the information helpful. I actually had not realised the amount of prep. necessary to write this type of tutorial, but I was pleased to do it particularly after such responses.
Pa, I will be following up with a further part about building the mask with I hope more detail to fill in the missing bits (seems appropriate bearing in mind the subject :smile. I hope to complete this over the weekend.
In the meantime I can see that my statement may have been confusing. When you have produced the mask and are satisfied you obviously need to apply it to the image prior to using the Median filter. Normally you would expect the mask to be showing right next to the image in the layers palette, the white parts of the mask allowing the filter to do its work on those areas while the black parts of the mask protect the image from the effects of the filter.
Sometimes it is easier and maybe better practice to produce the mask on a duplicate image then bring the mask back into the original as an Alpha channel that will reside in the Channels palette. Once you need to use the mask you can click on it in Channels and activate it by pressing the Load as a Selection button (the small circle). The effect this has it to highlight the mask areas which can then be used to apply the filter of choice to those highlighted areas only on the current selected layer.