Does anyone know the bit rate of RAW picture of A55?
And is there a big difference or significant between 12 and 14 bit?

Thanks

I am sure that all Sony DSLRs use 12 bits only. I believe that Nikon have released DSLRs with Sony sensors employing 14 bits RAW readouts. Apparently the difference is marginal but the write rate to card is much slower for 14 bits. At least so I understand.

That's correct - all current Sony models use a 12-bit RAW data format, including the A700 and A900/850 which also have a cRAW (compressed 12-bit) option, or more accurately, an uncompressed option as later and more entry-levels all use forms of compression for the raw file.

I've compared the Nikon 14 and 12 bit results, and also compared them with Sony. For me, the critical zone is the highlight exposure and I can't say that Nikon does any better - ever - than Sony for capturing overexposed but unclipped bright detail. So far of all the systems I've used, including Canon/Pentax/Olympus/Sony, no raw format actually performs better than Sony's for allround 'developability' of the image.

David

My Canon 60D has 14-bit raw, but I don't really see a difference. I suspect it is more a marketing thing. It makes the raw files bigger too -- my 60D 14-bit 18mp raw files are 20-32mb. I prefer the size of my A700 12-bit 12mp craw files which are 12-13mb.

Thanks for the information.
As I know if the sensor is 12 bit, adding more bits in final RAW image does not really increase the quality. But for marketing issues it will really help.