Woah! Don’t trash your prefs just yet.

There are a lot of DNG files that Mac OSX cannot read and it depends on the raw file produced by different cameras. For instance, my Nikon NEFs, when I used to convert to DNG as part of my workflow are read OK. On the other hand, my Lumix RW2 files when converted to DNG are unreadable by Mac OSX. You can’t see thumbnails in the Finder, nor in Aperture (or any other software that calls on the Mac OSX Digital Camera Raw Compatibility module).

It’s to do with what the camera OS does to its raw file before it saves it to the card and then the DNG conversion being non-linear (or linear, can’t remember). In Panasonic’s case, the Lumix raws have lens correction data stored in them and this doesn’t play nice in the Mac environment after conversion to DNG. They’re fine in the Adobe environment, of course.

So, first of all check whether DNG files produced from your particular camera’s raw files are compatible with Mac OSX.

EDIT: You’re going to tell me that you’ve had no previous problems and that this is a new  issue now, aren’t you? 

Hi Walter

I’ve never used out of camera DNGs, only converted NEFs & RW2s to DNGs. I no longer convert to DNG but I remember trying different DNG conversion engines and various permutations of linear/non-linear demosaicing, fast-load data etc without success. I seem to recall that for some initially non-readable DNGs, fiddling with the demosaicing settings can work (Fuji? Oly?).

What I didn’t do, and now regret, is parcel up the original RW2 files in the DNG wrapper so I could retrieve them now I don’t use DNG anymore. I’ve resorted to converting non-readable DNGs to 16 bit TIFFs instead.

This question came up elsewhere.  Aperture supports RAW DNG, but doesn’t support Linear DNG.  For a number of camera models, their “native” DNG format is Linear DNG.

Files from my Pentax K5’s converted directly in Aperture. No luck when I acquired a K3. The work-around for me was to download Adobe’s raw converter, convert .DNG’s to .dng’s and import into Aperture from these files. A nuisance but manageable until Apple provides an update RAW conversion for the K3.