For Sigma use, the full size JPEGs have to be uploaded to the sigmadslr users gallery so that they can be adjudged for quality, hence need for full size, meaning the optimum size (middle one) from SPP at Level 12 JPEG.
The Challenges on dpreview for the different camera models is to add some extra interest - so not actually necessary to send any images to them if you do not wish to. These can be a smaller size and lower level JPEG (I have made mine 8" longest side, 100ppi and Level 8 JPEG).
To upload to the sigmadslr gallery (relative to the camera model) you need the username and password - easily obtained from Rick Decker or Laurence Matson. If you are unfamiliar with using a pbase account, ask for guidance but one tip, rename the files you are sending to have, say, your name first for identification in case you find adding (editing) your name as the Author baffling.
As, when and if one or more of your images is/are selected - on the pbase sigmadslr gallery sites - you would be given directions on how to submit the X3F RAW file.
Hope that clarifies. It really is quite straightforward. The Challenges is virtually unconnected to the selection for use by Sigma but encouraged to provide extra interest for all the Sigma Forum members. (Well, that's how I read it)
Although I have submitted (smaller) images into the Challenges for the SD9 and SD14 sections, I personally dislike competitions as such and would normally avoid them like the plague.
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Zone8
The photograph isolates and perpetuates a moment of time: an important and revealing moment, or an unimportant and meaningless one, depending upon the photographer's understanding of his subject and mastery of his process. -Edward Weston
http://www.photosnowdonia.co.uk/ZPS
