One of the advantages of mirror less cameras is that there is no need for the space for the flapping mirror and pentaprism. This means a smaller flange distance so retro focus lens are not required (though most modern lens are), so lens can be smaller and less complex but give potentially better image quality. No moving mirror means less likelyhood of camera shake, plus without the hump on top housing the pentaprism the camera can be smaller.

The camera just above, the Nikon DF is about as small as you can make a full frame digital SLR with traditional optical viewfinder because of the need for the mirror and pentaprism housing. So why with the current batch of mirror less cameras are companies like Panasonic, Olympus and Fuji sticking a fake hump on top making the cameras bigger, is it hump envy, do they feel the need to look like ‘real’ cameras or is there a valid design reason?
By the way if you want to see a ‘real’ camera check out my Ebony below:



























The downside of this is few programs can read it, you have to process it and create a packaged 14 bit dng; a program like m8raw2dng and a quick trip to the command line will soon create one. Once created this can be imported into your favourite raw processor. The other downside is that you lose the colour profile and editing is far harder. So while you get an image with better image quality but the time taken to edit the file increases enormously.