HDRShop has no image editing tools. However, it is possible to edit HDR images using traditional LDR image editors.
First, we need to choose the image editor we wish to use. In the current version of HDRShop, the only way to change the editor that is launched automatically is to change the file extension association for .BMP files from within Windows Explorer. To do this, go to an explorer window, and choose 'Folder Options' from the Tools menu.'
A dialog similar to the one below should open. Click on the 'File Types' tab, and find the 'BMP' extension.
Click the 'Change...' button to change the associated program. Choose the program you wish to use to edit images in. In this case, we are going to use Adobe Photoshop.
Click 'OK' and the program you chose should now be associated with BMP files.
Now on to the editing:
First, load up the HDR image you wish to edit. In this example, I am using the memorial.hdr image.
Then, adjust the exposure by hitting '+' and '-' until the region you wish to edit is visible (that is, not too dark and not too bright). The image below was darkened six stops so that the ceiling windows are visible, and can be edited.
Next, choose 'Edit in Image Editor' from the File menu.
This will write a temporary .BMP image file to the current directory, and attempt to open it with the default .BMP editor (as defined by windows explorer). HDRShop will display the message 'Hit OK when edit complete' (as shown below); do not hit OK until your edit is complete and has been saved back to the same .BMP file.
Switch to the image editor that should have opened up (Adobe Photoshop in this case).
Apply your edits.
Save the edited LDR image in the same .BMP format (24 bit windows, uncompressed)
At this point we are done with the editor. Return to HDRShop and hit 'OK' on the dialog box. HDRShop will then load in the edited file and apply the changes to the HDR image.
HDRShop will only change the pixels that were changed by the LDR editor. This means that high-dynamic range values will not be modified (unless of course you painted over them in your edits). In our example, re-exposing the image back to the original levels, you can see that the detail has been preserved.
Finally, a hint when painting on HDR images in this fashion: it's good to keep your RGB colors away from zero. I wouldn't even use anything below 15 (on a 0-255 scale) in any of the color channels. If you need to paint something darker, go back to HDRShop and re-expose it so it is bright, and then paint it. Not only does this help eliminate the banding, but it also helps with the 'realism' of the image by avoiding extremely saturated colors.