Raw files and digital preservation

Paolo mentioned RAW files last week, which - now that high quality digital cameras are now available for a few thousand pounds, and some museums are using them - is becoming a live topic for digital preservation.



Question: you've set up a camera to take some shots of some objects for an online project. The camera says you can save the images as jpegs, tiffs or raw files. Which do you choose?



Well, when you take a picture with a digital camera, you will have a choice of file formats to save it in. The choice varies from model to model (and is I suppose driven by marketing considerations). But RAW, jpeg and sometimes tiff are usually supported.

• a jpeg file will have been processed by the in-camera software to give a 'better' picture - normally by boosting contrast and saturation.


• a tiff file will be similarly processed


• a raw file will be the data, just as it came from the sensor. This is typically less attractive from the consumer's point of view, but will definitely have more information in it.


• professional photographers will therefore often save images as raw files because they can do more with them in an image processing package (typically Photoshop

So ... in your digitisation project, you're obviously going to save your images in raw format for archive purposes, and generate jpegs from those archive copies for your web project, right?

Well maybe not, because:

• the manufacturer's all have their own 'proprietory' raw file formats, so a raw file from an Olympus camera will have an .orf suffix - ('olympus raw format' maybe?) and a Canon or Nikon will have a different one


• so for example, normally you can only open an .orf file with Olympus' own image processing application (though you might find a 'plug-in', or additional functionality, to add to Photoshop so it can handle them)


• what's more, camera manufacturers sometimes don't support a specific image processing application, or a format, so the format is 'orphaned', and if you have a large collection of files in that format, which you are unable to convert, you have a big problem

Any solutions?

• Adobe are promoting a royalty free raw format, DNG (Digital Negative). In theory, a wide range of image processing applications could include the capacity to process these. And, you'd simplify workflow if you only have one raw format to deal with. And, because the specification is publicly documented, you could hope that major technological shifts could be accommodated.


• tiffs are widely recognised as an archival quality format, so you could shoot in raw and convert to tiffs - especially since a) your camera is unlikely to save in dng format, b) not many people use it and c) if the format isn't widely adopted, it in turn may be orphaned.

As often, there are no easy answers. If you want to know how the sector is responding, search the MCN mail list for a recent discussion by practitioners on this subject.

In practice, the answer is often to do what most of your peers are doing, especially if that includes a few big names like Smithsonian and British Library!