It\'s a bit concerning that Sony themselves are using this \"compressed\" vs \"uncompressed\" terminology when speaking of an issue which is about lossy compression versus lossless compression. The important bit - lossy vs lossless- seems to be missing. I don\'t think anyone really wants a fully non compressed raw (as long as we get lossless compressed raw).
Is there any downside to compressing lossless? Why wouldn\'t Sony use it?
It\'s less engineering effort to provide uncompressed RAW than to support two different versions of compression.
Frankly, given the almost-nonexistent problem with the current RAW compression I think an option of uncompressed + the current RAW compression is fair enough.
People can use uncompressed when shooting star trails, and the existing ARW the rest of the time...
...but Sony already have in-house a version of compressed, lossless raw which they offered simultaneously with craw (lossy raw) many years ago. I think offering a fully uncompressed raw is a bit crazy in this day and age (2:1 lossless compression should be no big deal).
The 700 & 900 had uncompressed raw and craw which was the 11/7 lossy compression. They didn\'t have compressed lossless raw. My A900 files are 35-40 mega bytes in size with full raw. By the way speed difference between the two raws is negligible.
You are wrong about that as they certainly did with the A900 and I used it!
A typical lossless compressed raw file from the A900 is around 36MB\'s and opens to about twice that size. It\'s roughly 2:1 compression. Ironically, this size - 36MB\'s - is very close to the lossy compressed raw from my 36MP A7r.
You can confirm the raw is compressed (2:1) by simply doing the math (26 x 36 will give you your 1GB in the spec as well)...
Hmmm A900 was 24MP and had 12bits per sample i.e. 1.5 bytes per sample and 24 * 1.5 = 36. So if A900 raw files were 36MP then it indicates there was no compression. It does indicate that the data was packed i.e. it didn\'t waste 16-bits to store 12-bits but no real compression
The opened a900 raw is always around 2x (69.8MB\'s to be exact) when opened at 8bit and saved out as 8bit tiff. Maybe there is a different way to talk about compression but this is how I\'ve always understood it. Long ago (early digital days) I believe raws (which were typically based on a tiff format, maybe they still are?) were around the same size as the opened file (thus they were not compressed).
The raw files have no color data so they have only one sample per pixel. When you open it you don\'t see the raw data, you see the demosaiced image in which the missing RGB samples have been filled in through interpolation. So that should increase the overall data by 3 times. However then you also go from 12-bit to 8 bit which reduces the size by 1.5x and you get to an overall 2x increase over RAW data.
Now I\'m curious to here from the expert about this (theSuede or...).
While I am certainly not an expert like theSuede, I think does fall within the realm of my limited knowledge
Well, if you are correct, it\'s interesting as this is not the typical way compression is talked about generally (not by engineers but such as in Photo schools). The use of the term compression in this setting refers to saved file size by camera vs opened file size, which is where the 2:1 compression comes in for the raw format that Sony once used.
If by \"uncomprssed\" Sony is talking about offering a raw that is half the size of the opened 8bit file, then I would have no issue with that as it would be the same as they once offered (such as in the A900).
Well if you want to call it compression then in this case \'compression\' is being performed by the bayer sensor by throwing away 2/3rd of the data at every pixel The RAW file itself is recording all the 36MByte of data from the sensor without any compression. When people talk of lossless compression in RAW files they are talking about techniques like ones used in ZIP files, using which you can store the 36MByte of RAW sensor data in less space but don\'t throw away any information while doing so.
It\'s a bit concerning that Sony themselves are using this \"compressed\" vs \"uncompressed\" terminology when speaking of an issue which is about lossy compression versus lossless compression. The important bit - lossy vs lossless- seems to be missing. I don\'t think anyone really wants a fully non compressed raw (as long as we get lossless compressed raw).
Is there any downside to compressing lossless? Why wouldn\'t Sony use it?
It\'s less engineering effort to provide uncompressed RAW than to support two different versions of compression.
Frankly, given the almost-nonexistent problem with the current RAW compression I think an option of uncompressed + the current RAW compression is fair enough.
People can use uncompressed when shooting star trails, and the existing ARW the rest of the time...
...but Sony already have in-house a version of compressed, lossless raw which they offered simultaneously with craw (lossy raw) many years ago. I think offering a fully uncompressed raw is a bit crazy in this day and age (2:1 lossless compression should be no big deal).
The 700 & 900 had uncompressed raw and craw which was the 11/7 lossy compression. They didn\'t have compressed lossless raw. My A900 files are 35-40 mega bytes in size with full raw. By the way speed difference between the two raws is negligible.
You are wrong about that as they certainly did with the A900 and I used it!
A typical lossless compressed raw file from the A900 is around 36MB\'s and opens to about twice that size. It\'s roughly 2:1 compression. Ironically, this size - 36MB\'s - is very close to the lossy compressed raw from my 36MP A7r.
You can confirm the raw is compressed (2:1) by simply doing the math (26 x 36 will give you your 1GB in the spec as well)...
Hmmm A900 was 24MP and had 12bits per sample i.e. 1.5 bytes per sample and 24 * 1.5 = 36. So if A900 raw files were 36MP then it indicates there was no compression. It does indicate that the data was packed i.e. it didn\'t waste 16-bits to store 12-bits but no real compression
The opened a900 raw is always around 2x (69.8MB\'s to be exact) when opened at 8bit and saved out as 8bit tiff. Maybe there is a different way to talk about compression but this is how I\'ve always understood it. Long ago (early digital days) I believe raws (which were typically based on a tiff format, maybe they still are?) were around the same size as the opened file (thus they were not compressed).
The raw files have no color data so they have only one sample per pixel. When you open it you don\'t see the raw data, you see the demosaiced image in which the missing RGB samples have been filled in through interpolation. So that should increase the overall data by 3 times. However then you also go from 12-bit to 8 bit which reduces the size by 1.5x and you get to an overall 2x increase over RAW data.
Now I\'m curious to here from the expert about this (theSuede or...).
While I am certainly not an expert like theSuede, I think does fall within the realm of my limited knowledge
Well, if you are correct, it\'s interesting as this is not the typical way compression is talked about generally (not by engineers but such as in Photo schools). The use of the term compression in this setting refers to saved file size by camera vs opened file size, which is where the 2:1 compression comes in for the raw format that Sony once used.
If by \"uncomprssed\" Sony is talking about offering a raw that is half the size of the opened 8bit file, then I would have no issue with that as it would be the same as they once offered (such as in the A900).
Well if you want to call it compression then in this case \'compression\' is being performed by the bayer sensor by throwing away 2/3rd of the data at every pixel The RAW file itself is recording all the 36MByte of data from the sensor without any compression. When people talk of lossless compression in RAW files they are talking about techniques like ones used in ZIP files, using which you can store the 36MByte of RAW sensor data in less space but don\'t throw away any information while doing so.
Jun 16, 2015 at 10:01 PM
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