Why I don’t delete my NEFs

Someone asked on Flickr if they should delete their camera raw files after converting to Adobe DNGs. Certainly you can see a strong pressure from Adobe to do so in order to save some hard drive space.

I don’t. Adobe’s DNG converter has the option of storing the original raw file along with it so I don’t see any theoretical harm in deleting the RAW file if that option is checked. Then again, since it increases the file size as much as two files stored separately, I don’t understand the advantage in that other than in file management for those who don’t have an adequate one (i.e. you are using Adobe Bridge or iPhoto instead of Aperture or CaptureOne).

The problem is that without this option checked can you reconstruct the original raw file from the DNG alone? I know of no tool that does this. I know of no incentive for one to be built by Adobe.¹

So what? Well look at the DNG file, it is double the size of a compressed NEF (Nikon raw). Why? Because Adobe’s de-mosaic recipe has already been added/embedded with the RAW.² What if I don’t like Adobe’s recipe?³ What if I’d prefer my vendor’s RAW conversion because they are aware of their own anti-alias/bayer filter and optical design assumptions in their lenses and bodies? What if I use a a 3rd party tool made by real optics engineers that adjust for lens and camera body defects? What happens as these RAW processing tools improve? What option do I have at that point?

None.

I use DNG as part of my photo workflow because unlike TIFF, they can carry metadata. I store and archive DNGs along with the Nikon NEFs in Aperture. But will I don’t delete my NEFs.

And neither should you.

¹ One day I switched to Outlook Express. It was very easy to move my e-mail from Eudora to it and I liked the nice mac-like UI (pre-Mac OS X) and appreciated the speed and search-ability of a database storage system instead of a file/folder one. The problem came what I wanted to leave. The only way to extract my e-mails and address book information was via a AppleScript that took hours to run and did a half-assed job of it. I learned a lesson there: Outlook Express was a roach motel. Is DNG any different?

² I am not saying that this application from the DNG can not be theoretically reversed to recreate the raw file or that Adobe is doing irreversible changes to the raw file format. Actually the main strength of DNG is that it tries to keep all the metadata and raw sensor data intact (as much as it is mappable). There is a world of difference between the theoretical and the practical however.

³ I don’t like it. Adobe Camera Raw applies denoising, contrast adjustment, and sharpening to hide its inherent inferiority—these are post-processing, not development tools, but this significant detail is missed by people who rave about how great ACR is.