Adobe expands DNG format with inclusion of smaller, Lossy DNG option
Alongside its ACR and Lightroom updates, Adobe has extended the specifications of the DNG format, including the creation of a more compact, Lossy DNG option. The format has also been extended to respect in-camera cropping and allow for the inclusion of full HDR data and the non-image areas around merged panoramas. We spoke to Lightroom Product Manager, Tom Hogarty, about the changes made in v1.4 and the reasons behind them.
Probably the biggest change is the inclusion of a lossy DNG format, which Hogarty pitches as being a middle ground between JPEG and full Raw. 'If you look at the output of a [Canon EOS] 5D Mark II, its Raw files are about 25MB, while its JPEGs are about 6MB. The difference in quality and capability between the two is significant enough that many photographers are happy to put up with the additional demands of the larger files.'
'Lossy DNG allows something in-between the two in terms of size but retains the flexibility in terms of adjusting White Balance and preserving detail,' he explains: 'For example, the out-takes from a wedding shoot, that the photographer is unlikely to ever be able to sell or make any money from. This gives them a way of reducing the amount of storage space they need, but they still have the file if they do ever need it.'
'It's based on standard JPEG compression. What's lost is some of the range of the adjustments you can make - if a file is four or five stops underexposed, you'll find it's not quite as flexible as the full file. You can still do a lot, though and it's only in extreme case that you might notice.' he says.
'Lossy DNG allows something in-between Raw and JPEG in terms of size but retains the flexibility in terms of adjusting White Balance and preserving detail'
The amount of compression in the Lossy DNG is fixed, yielding files that are typically around a third of the size of Standard DNGs. There's also an option to reduce the pixel size of the file when you create a Lossy DNG, giving what Adobe is calling DNG Proxies. These make it possible to create more readily portable and shareable files with Raw-like processing flexibility.
Beyond this, the v1.4 specifications also add the ability to record details of a crop that should be applied to the Raw data (such as a camera shooting its non-native aspect ratio, but capturing the whole sensor's data). This crop can later be over-ridden (and option available using the 'DNG recover edges' plugin for Lightroom), but means the starting point for processing is the one you selected at the time of shooting.
In addition, DNG v1.4 files can include 32-bit floating-point data, allowing them to retain all the information from multiple Raw files combined as part of an HDR process. 32-bit floating-point data allows the retention of hundreds of stops-worth of dynamic range information. Another change that allows the data from multiple files to be combined in a single DNG is the ability to include undefined (or transparent) pixels, such as the non-image areas around a merger panorama.
Both changes come from Adobe looking forward, Hogarty says: 'It's where the industry is going. No cameras or software yet offer this, but we can imagine them wanting to.' And this coincides with Adobe's continued efforts to see DNG accepted as an industry standard - 'we talk to a lot of manufacturers and other software makers to find out what they want - we take a lot of feedback and look to maintain an open dialogue on the directions DNG should develop in.'