I have never used a Mac computer, yes really never. But I can tell you that on a Windows machine it is necessary to download something called a codec (coder/decoder) and install it in order to see DNG files outside of Adobe products. If there is something similar to that for the Mac, it might help you. Since I don't know anything about Mac computers, I apologize if this is poor information.
I have the same problem, but in lightroom CC. I was using lightroom 5 (non cc) before and all of my DNG files seem to show up just fine as thumbnails in Mavericks (10.9.3). When I now use lightroom cc to convert my NEF files to DNG, Mavericks does not seem to be able to display a thumbnail or a preview. But the old DNG files still work. It seems to be a problem with a small change Adobe made and hasn't told Apple yet. Given the fact that Apple is doing away with Aperture and encouraging people to transition to lightroom, this may not be a problem for long, but a fix right now would be nice.
Just to follow up for anyone reading, I think I've recreated the problem.
1) import into lightroom and copy as DNG.
2) right click on photo from within lightroom and say 'edit in' Photoshop
3) Go through Camera RAW and start editing the photo directly in Photoshop (not in Camera RAW)
4) Save the file (you'll be forced to because Photoshop does not appear to want to save in DNG format)
5) the file then appears in your lightroom
6) say you now want the tiff/psd/etc. edited file as a DNG.
7) I then right-click on the file to export as a DNG and this is when the DNG no longer appears in finder with a preview, but as a generic icon.
Regarding your point #4. Photoshop cannot write to proprietary raw files, nor can it write to DNG files. They contain raw image data, and Photoshop cannot do that. By the time that image is opened in Photoshop it is no longer raw image data, and you would be accomplishing nothing by trying to save it as a DNG or convert it somehow. That's not possible and shouldn't be considered. Once you have edited a photo in Photoshop you need to just work on the PSD or TIF file, returning to the DNG or raw if you want to start over and create another version in Photoshop. Since what you're trying to do In step #6 is not a normal workflow, I'm wondering if maybe Photoshop is just deleting the DNG file. I am only guessing, because I have never tried to save a TIF or PSD file as DNG.
Hello I thanks for respond.
I think you are taking this a little bit out of topic. Let me explain myself better: When you save a file as DNG format file it works ok and the thumbnail shows in finder, but if you try to resize the DNG file when you are saving it (either on lightroom, camera Raw or Adobe DNG converter), the new file (resized) will not show the thumbnails in finder.
What for? my nikon d7100 create huge files and sometimes you have pictures of uncles' bob party and you want to keep an 8 megapixel DNG file instead of a 24 MP file just for storage, and I want to see the thumbnails for easy sorting. In the end is like have an Medium or Small RAW file.
I didn't think I was taking it off topic. I don't recall reading anything about resizing until your last response. You just indicated that you were converting TIF and PSD files to DNG. You can't do that any more than you can uncook something. You cannot create a DNG file containing raw image data from a file that has been edited in Photoshop. Photoshop does not have the capability of saving raw image data. That is why it needs Camera Raw. My suggestion to you would be to resize the TIF or PSD file and work with it. I might be wrong, but I don't believe there is a way for you to make a raw file, DNG included, smaller.
I was the one how create the original post, and never said anything about TIFF or PSD. Omit roberneimyer1983 comment because it has nothing to do with the original question.
You are right. Your thread has been hijacked, I didn't notice. I'm afraid I don't have a solution to your question since I'm not a Mac user.
Thanks for your insight JimHess. Someone else on another post pointed out how Photoshop changes the color profile and other things and then trying to make this file into a DNG again confuses Mavericks (and, presumably, other flavors of OS X). Admittedly, the process I described is unorthodox and not what may want to do. Thank you.
A.J.: First, I am offended by your suggestion to omit my comment. I was simply trying to provide help in finding a cause of a general problem people are having across the internet. That problem, as you pointed out, is that modifying a DNG in some way in photoshop results in the thumbnail no longer being visible. Your modification is the size. Mine was not. But it was a general modification in photoshop and an attempt to reconstitute the file as a DNG that seems to be common theme, whether this workflow makes sense or not. Additionally, I'm very new to digital photography and tried to be helpful. I would advise you (as an educator who knows the consequences of negative first-time experiences) to be more mindful that not everyone on here is as experienced as you and everyone can benefit from being clearer in their questions and their comments.
Second, as JimHess pointed out, in manipulating a DNG file in any of the programs in a way that alters the actual file (not changing some setting that is ultimately stored in a side-car file or does not actually alter the photo) is probably the root of the problem. Changing the file size by altering pixel count may first require one of your adobe products to physically alter the file information in a way that stops Mavericks from being able to recognize the contents as RAW information. Does this make sense?
Really sorry if I did offend you. Didn't mean it. It was more trying to take the thread back to the point.
I appreciate you took the time to try to help.