When are RAW files modified?

Question

I know that Lightroom is based on the idea of non-destructive editing.
However, even tho I'm still a LR newbie, it does look to me like there
are a few cases in which LR does modify a RAW file as it came from the
camera (e.g., the NEF bug). Where would I find an accurate list of the
operations that do cause a modification of RAW files. (For example, is
inserting metadata on import one of these?)
(This is my first post here. Does anybody else find it odd that the
posting software considers "Lightroom" and "metadata" to be misspelled?)
Many thanks.
--Milt--

Answer 1

Milt,
>(This is my first post here. Does anybody else find it odd that the posting software considers "Lightroom" and "metadata" to be misspelled?)
Yes :)
>I know that Lightroom is based on the idea of non-destructive editing. However, even tho I'm still a LR newbie, it does look to me like there are a few cases in which LR does modify a RAW file as it came from the camera (e.g., the NEF bug).
Is the term 'nondestructive editing' being used correctly here? The way I typically see the term used in Adobe's literature and doc is not applicable to RAW files.
Before CS3 Photoshop did/does destructive editing with its filters. With Photoshop filters if you apply certain effects and filters they degrade the image in memory so if you try to apply an opposite filter or undo the effect, tough luck. Nondestructive editing in CS3 (and in Lightroom) allows application of effects and filters in a 'virtual' manner that can be backed out, applied multiple times or changed without image degradation.
None of this applied to RAW files because Photoshop and Lightroom do not touch the *image* bits of any camera manufacturer's RAW file (metadata changes aside). You cannot open a RAW file like a .NEF in Photoshop and save it as a .NEF RAW file -- it has to be saved as PSD, TIFF, DNG or whateverand you can do destructive editing in those formats with filters, rotations, etc. The original RAW file itself, however, always remains intact. So no PS or LR editing can be destructive in that sense.
Lightroom virtualizes all of its edits so you can back out any LR edit without degrading image quality. That is nondestructive editing -- again, of the image itself. That said, changing camera metadata in a RAW file is not something I can see immediate use for, I admit. But even that doesn't touch the actual RAW image bits.
>>For myself, I will not start using LR on anything except experimental copies of my photo library until I am fairly confident I have this list in hand so I can avoid doing the things on the list.
Your call, of course. But the only way to avoid something bad happening to your file is to have a copy of the file somewhere else. A lot of things can damage your file that have nothing to do with LR. I have copies of all my photos on a separate computer. My next step wrt that will be to burn Blu-Ray disks to keep offsite.
I also have 5500 photos that Lightroom is doing quite an amazing job with for me overall. Printing (certainly with titles) is the weakest link in LR (I've made some feature enhancement requests/recommendations for the Print module in that area) but the rest of the program has removed most of the hassle, drudgery and unnecessary expense/waste from photography and made it a truly new, fresh joy again, just like it was for me 30 years ago when I bought my first SLR.
Cheers,
Robert