If you open an image and zoom to 100% (which should map 1 pixel to one pixel on the screen?) the bar at the bottom shows "interpolating …" - why ? 1:1 should not make any interpolation necessary?
Pascal de Bruijn
You may want to read up on what RAW files actually are… since they are not simple bitmaps.
These are of particular interest:
I think what the op really wants to know is why is it the case that there is a message about interpolation when you select 100% zoom, but no message when you select 50%, 25%, etc.
I was kinda curious about that, too. Perhaps UFRaw does a very quick lower-quality interpolation for smaller zoom values, and then produces a higher quality interpolation for any zoom value 100% and greater?
Well, in theory at 25% size or less you could just average clusters of 4 pixels, it would be quite fast. I'm not sure if UFRaw does that.
AIUI, this is pretty much what ufraw does. For a long time, you couldn't select a zoom level higher than 50% because simply averaging doesn't work in higher zoom levels.