To DNG, or not to DNG

People sometimes ask me "Should I convert my Raw files to the DNG format?" I honestly don’t know.

Well, let’s clarify – some people have no choice. If their Adobe software is older than their camera, then the only way they can open their Raw files is to convert them. No ambiguity there. (More info)

But lots of other people have Photoshop or Lightroom as new or newer than their camera, so they can open their NEFs, or CR2s, or ORFs, etc, just fine. For those people, conversion to DNG becomes a matter of choice.

Plenty of people do recommend DNG conversion. It’s the generic raw format, and they say it’s meant to be "future-proof", so that we’ll be able to open and edit our files forever, regardless of software evolutions over the coming years. I'm mildly skeptical about this, to be honest. It seems to assume that the Adobe company will last longer than the Canon and Nikon companies, for example. Who is bold enough to predict that? Not me. Anyway, I honestly don't know whether DNG is the future-proof format or not.

Other people convert to DNG because the files are slightly smaller, and the disk space saving is worth it. That sounds sensible.

But despite all of that, I don’t convert to DNG format. Why? Because I love XMP files!

XMP files are the little separate files that are created when you edit a Raw file. The XMP files (known as a "sidecar file") holds all your edit data. They’re very small, but very important. When you see XMP files in your folders, please don’t delete them – they’re your friends 🙂

DNG files don’t have sidecar files. The XMP data is stored within the DNG file. Just one file instead of two – that probably sounds very sensible to you. But not to me.

In this post I wrote about XMP files and why I like having them around when I’m editing. Here I'll discuss the one big reason why I prefer not to convert to DNG format – speed of backups.

Backups are darn important, of course. Everyone has a different backup strategy – mine is quite simple. One or more times a day I run a backup of my internal hard drive onto my external one. The SyncToy backup software scans my internal drive, and copies all new files (either newly-created, or recently modified) onto the external drive. That way, my external drive is an up-to-date copy of my internal.

"What does this have to do with DNG??" you’re asking yourself.

Well, let’s say that on Tuesday I downloaded one hundred new raw files to my computer. Tuesday’s backup would take a little while, right? Because 100 raw files is a lot of data to transfer. Tuesday’s backup would take some time, regardless of whether the files were DNG or not.

On Wednesday, I edited those raw files. How long would Wednesday’s backup take? If the raw files were DNG, the backup would take the same (long) amount of time that it took on Tuesday. But since I keep regular raw files, and therefore have separate XMP files, the backup is lightning fast, because the only things that need to be copied over are the 100 tiny XMP files. The raw files themselves haven’t changed.

So yeah, speed of backup. That’s why I don’t convert to DNG.

If you have an online backup system, what I’ve described in this article will probably make lots of sense to you. Not having to upload entire raw files again after editing? Priceless.


If you have a question about this article, please feel free to post it in Ask Damien.