Well, it's a combination of quite a lot of factors. The namber of bits of uncompressed RAW data are:
K-x: 12MP x 12 bits/pixel = 18MB, K-5: 16MP x 14 bits/pixel = 30MB. So on the K-x you're seeing about a 20% saving, while on the K-5 you're effectively getting close to no compression at all. (This ignores the couple of MB of overhead in the DNG file, but it's a close enough approximation for a preliminary estimation). If I look at the shots I took with that same body on the previous time I used the camera I'm only seeing DNG sizes of around 20MB. I was intrigued, so I looked a little closer. I think the single biggest factor is that you're using higher ISO (1250 in the couple of shots I looked at), while most of the time I'm shooting at 320 or lower. This suggests to me that by the time you crank the ISO up to 1250 you're approaching the point where the low bit of that 14-bit pixel is effectively noise, so lossless compression isn't helping you much. Note that the 20MB I typically see on the K-5 is actually a better compression ratio than the K-x is achieving. On Thu, Feb 07, 2013 at 05:46:38PM +0100, Dario Bonazza wrote: > 14 bits instead of 12 bits could be responsible for that. > > Dario > > -----Messaggio originale----- From: Aahz Maruch > Sent: Thursday, February 07, 2013 5:38 PM > To: Pentax-Discuss Mail List > Subject: What's in there? (DNG: K-x vs K-5) > > So I'm starting to work on the shots I took Saturday with John's K-5 and > the shots I've been taking with the K-x Larry's letting me borrow (thanks > Larry!), and I notice that the 12MP K-x has roughly 15MB DNG files, while > the 16MP K-5 has roughly 30MB DNGs. Does the K-5 really store that much > more information per pixel? > -- > Hugs and backrubs -- I break Rule 6 http://rule6.info/ > <*> <*> <*> > "I won't accept a model of the universe in which free will, omniscient > gods, and atheism are simultaneously true." --M > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above > and follow the directions. > > > ----- > Nessun virus nel messaggio. > Controllato da AVG - www.avg.com > Versione: 2013.0.2897 / Database dei virus: 2639/6085 - Data di > rilascio: 06/02/2013 > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
