Originally posted by yusuf You are ignoring the math - refer my previous post. It is technically NOT possible to have k-5 file with less info to have less artifacts than A7/a7r files having more info but I'll be happy to learn if you can prove it technically.
Again, the following is a simple calculation
K5 - 16MP*14 = 224 lossless Mbits
A7 - 24MP*11 + 24MP*3 = 264 lossless Mbits + 72Mbits lossy bits
A7r - 36MP*11 + 36MP*3 = 396 lossless Mbits + 108Mbits lossy bits
It is a fact that A7/a7r lossy compression having artifacts in some cases but it's worse only when compared against comparable cameras (FF, 24MP and above) but not against k-5.
I'm not ignoring the math, and I appreciate you providing me with a simple calculation I can understand, though I'll admit I'm a little confused as to why total
quantity of data - which is in Sony's favour due to the resolution of sensors - should be considered better than
quality of data, which is lossless in the K-5. The Sonys are recording less lossless bits per pixel, or area, than the K-5 - no?
Let's put the K-5 aside for a moment and replace it with the K-3, which has a 24MP sensor. Using your simple calculation, the K-3 would record 24MP*14 = 336 lossless Mbits. The A7 would, as you've shown, record 264 lossless Mbits and 72 lossy Mbits. So for the 24MP both cameras are working with, the A7 is providing less data due to lossy compression - the same lossy compression that can result in artefacts, posterisation, and some loss of information in shadows.
But this is just simple math. Let's bring the K-5 back into the picture and compare the image quality to that of the K-3 (I own both). The K-3 wins on resolution and the fact that it has no AA filter. But otherwise - and this is borne out by many owners in these forums - the K-5's image quality holds up remarkably well by comparison. In fact, some owners here prefer the K-5 series to the K-3, especially where dynamic range is concerned.
I can't address your request to prove anything technically - that's not where my limited skills lie, sadly. You can choose to accept - or not, if you prefer - my claim that I have images where artefacts and posterisation have appeared, and shown unexpectedly poor results in shadow recovery, due to Sony's lossy compressed raw files... issues that would not have occurred with lossless compression on the K-5 (or, indeed, uncompressed raw on my A7 MkII). I'm not saying that makes the K-5 better, I'm not saying it makes the A7 worse - I'm just stating what I've observed in my own files.
It's worth noting that I wasn't even aware of the lossy compression - I'd never researched it; never even heard of it - until I noticed such artefacts in a limited number of my HV's photos, and started looking for reasons online. So it's not like I read about the issue then started imagining the effect. I saw it in my own photos
first - just a few, but a few is more than none. And those artefacts would not be there without the lossy compression.
I will go back to the DPR example I posted, since that's all I have readily available. With or without the math, how would you explain the artefacts on the right edge of the moon? And would you expect to see those on any raw image from a camera that does not use lossy compression? I propose that you would not. Does that make the overall image worse than you could expect from the K-5? Not necessarily... it just means those artefacts wouldn't be present with the K-5 (or the K-3, or the A7
MkII set to uncompressed raw).
I'm going to leave the discussion there, as we can't move forward unless I (a) trawl through my photos for examples, then (b) set up a side by side shoot with my HV and K-5. With the greatest of respect, I don't have time to do that in order to prove a discussion point. I'm happy to accept that you're unconvinced.