One of the curses of shooting with Sony cameras is their RAW file format. Currently they only offer two methods for saving RAW files:
- a RAW file with lossy compression,
- an uncompressed RAW file.
Did you notice what’s missing? Sony doesn’t offer a lossless compressed RAW file unlike every other camera manufacturer. This makes me incredibly mad!
The lossy compression scheme works very well for saving space. My 42 MP files from my A7RII camera take up on average about 43 MB per image or about 1MB per megapixel. This is about par for the course for RAW formats provided by any of the major camera manufacturers.
The drawback of the compressed format is that you are losing data from the file which can sometimes result in visible image artifacts. Some photographers say that they’ve never seen these and it’s a theorectical issue only. That may be true if you shoot in controlled lighting like a studio but as a landscape photographer I definitely run into this problem — see my examples below.
Due to the outcry from the user base, Sony decided to release an uncompressed RAW option in late 2015. This is great because you could take advantage of all the data coming off the wonderful sensors. No more worrying about whether an artifact was going to show up. The drawback is that uncompressed files are huge. My 42 MP RAW images are about 85 MB each, or about 2 MB per megapixel. This is horrible and managing this extra data (especially as it works it’s way into all my various backups) is painful.
Recently Sony announced the A7R IV camera body with a 61 MP sensor. I’m really excited about this body because of the combination of high resolution and great dynamic range. But I’m dreading working with the files because they still have no option for lossless compression on their RAW files.
Lossless data compression algorithms have been around for decades (since the 1970s). There’s no excuse for not offering this as an option. I really don’t understand why Sony can fail so badly on this point – this is something that’s obvious to anybody with a technical background.
As promised, here are some examples of Sony compression artifacts that I’ve encountered in actual shooting. Generally the artifacts occur around a high contrast edge and are usually become more noticeable when bringing up the shadows. The first case is a cityscape taken just after sunset when the building lights have started to come on.
Here is another example where I am shooting the interior of an abandoned train car. The artifacts occur around the edges of the windows.
This third example involves fireworks, probably the worst case and the compression leaves horrible artifacts. Normally I would turn on uncompressed RAW but this time I forgot to adjust my camera settings.
Because of space reasons, I don’t normally use the uncompressed RAW format and only turn it on when I know I’m in a situation where compression artifacts are likely to occur. But it’s easy to misjudge or simply forget especially when you are thinking about other aspects of the image and are under time pressure. Come on Sony, fix this and provide a workable losslessly compressed RAW file.
Reader Alex Kunz suggested converting the Sony RAW files into the DNG format to save space as DNG files use lossless compression. I downloaded Adobe’s converter and ran a few tests with my uncompressed files (mostly night sky images). This indeed saves significant space. The losslessly compressed DNG files are ony about 40 MB which is actually slightly smaller than the lossy compressed RAWs and less than half the size of the uncompressed files.
However I’m not willing to convert and throw away my original RAW files. At least not yet. While DNGs maintain the image data you can find reports of less than complete support of the metadata especially concerning profiles and lens corrections. So for now, DNG is something that I’m going to put on my evaluate and consider list but I won’t fully adopt it.