From Peter's article at The PureView Club:
Looking more into RAW
In digital photography the RAW file plays the role that photographic film plays in analog photography. RAW contains the full resolution data as read out from the sensor. That sensor is overlaid with a filter, consisting of a mosaic of a matrix of a red, green, blue and another green filter. To obtain an image from a RAW file, this mosaic of data must be converted into standard RGB form. This is often called “RAW development” and the resulting picture can be saved as JPEG or TIFF.The pros and cons
RAW has many benefits. In a RAW file only the shutter speed, the aperture and the ISO are fixed data. All other image parameters are in your own hands when you develop a RAW file. So you can directly influence the white balance, contrast, sharpness, colour tones and colour space. You can bypass the camera settings that were used during the capture for sharpness and noise reduction.You can imagine what that will do for the still ongoing discussion about the settings Nokia has chosen for the 5 MP pictures of the Lumia 1020. This does not mean necessarily that you’ll just get a better result, but at least you can make your own choices and personalize your pictures completely.
RAW files have a bigger dynamic range compared to JPEG, and, benefiting from that, you can set the highlights and shadows much better. Also, in RAW there is more “headroom” in the exposure, which means that within a certain range, you can underexpose and overexpose. Exposure compensation, sort of, after capturing. A last big advantage I want to mention is that RAW developing is completely non-destructive. The original RAW file stays unaltered.
The drawback of RAW is the bigger file size, on average about 4 times. For the Lumia 1020 people will immediately cry, “We need that SD card!” But in practice I think this will not be a big problem, because you choose selectively which shots you want to have as RAW. For the RAW converting you will transfer your RAW file to your computer so you free your camera’s memory again.
The option to shoot in RAW (i.e. save a .DNG file) will certainly be welcome, as Peter says, for 'selective' shots. Specific sunsets and landscapes etc. I can see how this might be useful to some people in some situations, plus there's the bragging rights (for Nokia) behind being able to claim that their smartphone camera 'can shoot in RAW'.
But I would like to put this into perspective:
- Just as I found when I started analysing the real world differences between different JPG compression schemes on the Nokia 808 ('fine' vs 'superfine'), you have to being incredibly picky to notice any difference whatsoever, and the same will apply to the average 5 megapixel oversampled photo from the Nokia 808 or Lumia 1020 (with their 41MP sensors) and that taken on the upcoming Lumia 1520 (with 20MP sensor).
Simply put, the quality is already so high (relative to their potential and to the limits of the physics of such small devices) for 99% of photos that choosing to shoot that shot in '5MP + 34MP RAW' will simply result in a (much) larger high resolution photo to deal with - impractical to upload and share around.
- By opting for the 5MP/RAW combination, you'll be denying all on-phone editing access to the higher resolution shot, i.e. you won't be able to 'reframe' or 'zoom later'. Rather foiling the point of the Lumia 1020's (and the new 1520's) main selling point.
The main attraction of handling RAW shots, of course, is that you get to the image data before those nasty noise reduction and sharpening algorithms get to work, plus you also sneak in before any equally destructive JPG compression routines. But just be aware that the potential gains may not be quite as high as you might imagine.
At the risk of sparking yet another Symbian/Windows Phone 808/1020 flame war, it should be noted that the ethos behind the Nokia N8 (12MP sensor) from 2010 was always to have zero processing, i.e. the images it created were as natural as possible. The Nokia 808 (2012) took this one step further, with not only minimal image processing by default, but the benefits of oversampling producing the 'purest' images I've ever seen - which in turn meant less noise and artificial detail needed to be encoded in JPG form. Peter even refers to this in his article, pointing out that photos taken on the Nokia 808 in 'Creative' mode with manually lowered exposure can be treated as RAW and astonishing results created, a real tribute to the 808's camera.
The Lumia 1020, over in the Windows Phone world, currently shoots with quite a lot of image processing, gaining benefit from oversampling but also tuning its images to popular 'saturated'/'sharpened' taste. The good news is that with Nokia Black, devices like the 1020 will gain oversampling that's closer to the way the Nokia 808 handled its camera images - think more natural and with less need for destructive processing.
At which point, I acknowledge the aforementioned bragging rights for RAW capture but have to predict that almost no users will ever need it because the standard output from their camera phones will already be easily good enough.