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M-Raw and S-Raw - a really bad idea.

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eraserhead

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The despair amongst the pixel peepers at Canons achievement in making an astounding 18MP sensor for the 7D seems to be accompanied by a lot of people who know no better saying things like 'I'll be shooting in s-raw or m-raw'. I don't think they realise what a lame idea of canon's these formats are.

The purpose of shooting raw is to keep as much of the information from the sensor as possible, so you can use it to optimise the image you want. These two formats jettison a whole load of information for a small saving in file size.

This page ( http://lclevy.free.frcr2/#sraw ) gives some information on how these so-called raw files are constructed. It's as follows:
  1. The raw data is demosaiced (so straight away you've lost control over the demosaicing method)
  2. the file is downsampled to the output size (so you've lost control over the downsampling method and lost half or 3/4 of the pixel data)
  3. it's converted into YCbCr format.
  4. The astute amongst you will realise that now a 9MP mRAW file is actually bigger than an 18MP CR2, since it now has three values at each pixel position. So, to save space we throw away half or 3/4 of the Cb and Cr values (losing even more information).
The sraw (or mraw) file is going to compress a bit better than the real raw, since so much of the information has been thrown away. Nonetheless, the outcome is a file not much smaller, but missing a huge amount of the original raw information.
What's the point?
 
There are always people who shoot raw but think 18MP is too many. I don't know who those people are and what are their reasons but sRaw/mRaw gave them an option to get less MP. For others you can just ignore the feature. I have used 50D for a year and never have even tried them once. I just want to keep my full 15MP raw files in my computer.
eraserhead said:
The despair amongst the pixel peepers at Canons achievement in making an astounding 18MP sensor for the 7D seems to be accompanied by a lot of people who know no better saying things like 'I'll be shooting in s-raw or m-raw'. I don't think they realise what a lame idea of canon's these formats are.

The purpose of shooting raw is to keep as much of the information from the sensor as possible, so you can use it to optimise the image you want. These two formats jettison a whole load of information for a small saving in file size.

This page ( http://lclevy.free.frcr2/#sraw ) gives some information on how these so-called raw files are constructed. It's as follows:
  1. The raw data is demosaiced (so straight away you've lost control over the demosaicing method)
  2. the file is downsampled to the output size (so you've lost control over the downsampling method and lost half or 3/4 of the pixel data)
  3. it's converted into YCbCr format.
  4. The astute amongst you will realise that now a 9MP mRAW file is actually bigger than an 18MP CR2, since it now has three values at each pixel position. So, to save space we throw away half or 3/4 of the Cb and Cr values (losing even more information).
The sraw (or mraw) file is going to compress a bit better than the real raw, since so much of the information has been thrown away. Nonetheless, the outcome is a file not much smaller, but missing a huge amount of the original raw information.
What's the point?
Click to expand...
 
carlk said:
There are always people who shoot raw but think 18MP is too many. I don't know who those people are and what are their reasons but sRaw/mRaw gave them an option to get less MP. For others you can just ignore the feature. I have used 50D for a year and never have even tried them once. I just want to keep my full 15MP raw files in my computer.
Click to expand...
But what are they saving? and do they know that these 'raw' formats are about as raw as a McDonald's hamburger. If they want smaller files, full res JPEG probably retains more of the original file information than these so-called 'raw' files.
 
Luckily Canon isn't so stupid as to introduce a pointless file format.
They did introduce a direct print button though...

I don't quite agree with his remark about why YCC after quoting me, but I do agree that the ratio of samples in sraw files is:
2Y : 1Cb : 1Cr

I think the YCC color space is simply for the sake of using lossless JPEG, and the underlying data is actually:
2G: 1B : 1R
eraserhead said:
The despair amongst the pixel peepers at Canons achievement in making an astounding 18MP sensor for the 7D seems to be accompanied by a lot of people who know no better saying things like 'I'll be shooting in s-raw or m-raw'. I don't think they realise what a lame idea of canon's these formats are.

The purpose of shooting raw is to keep as much of the information from the sensor as possible, so you can use it to optimise the image you want. These two formats jettison a whole load of information for a small saving in file size.

This page ( http://lclevy.free.frcr2/#sraw ) gives some information on how these so-called raw files are constructed. It's as follows:
  1. The raw data is demosaiced (so straight away you've lost control over the demosaicing method)
  2. the file is downsampled to the output size (so you've lost control over the downsampling method and lost half or 3/4 of the pixel data)
  3. it's converted into YCbCr format.
  4. The astute amongst you will realise that now a 9MP mRAW file is actually bigger than an 18MP CR2, since it now has three values at each pixel position. So, to save space we throw away half or 3/4 of the Cb and Cr values (losing even more information).
The sraw (or mraw) file is going to compress a bit better than the real raw, since so much of the information has been thrown away. Nonetheless, the outcome is a file not much smaller, but missing a huge amount of the original raw information.
What's the point?
Click to expand...
--

. 。o O o 。 . 。o O o 。 . 。o O o 。 .
 
Gao Gao said:
Luckily Canon isn't so stupid as to introduce a pointless file format.
They did introduce a direct print button though...

I don't quite agree with his remark about why YCC after quoting me, but I do agree that the ratio of samples in sraw files is:
2Y : 1Cb : 1Cr

I think the YCC color space is simply for the sake of using lossless JPEG, and the underlying data is actually:
2G: 1B : 1R
Click to expand...
How does that invalidate anything I interpreted form the article? The point about using YCC is that they can decimate the chrominance components to save space. If you read further, you'll see there are two level of decimation going on, depending on the sraw mode. sraw1 is 4Y:1Cb:1Cr. We don't know what mraw is, but the principle is likely the same.
 
Condor99 said:
I don't get the point of your post. If you don't want to use mRAW or sRAW then don't use it. Why are you putting people down because they want to use it??? So what if the file size is bigger or smaller or compressed or whatever? What does that have to do with you?
Click to expand...
I'm more putting Canon down for misleading people about what this feature is and what it does, and the people who have misled others into believing that there is anything to be gained by decimating pixel counts apart from file space. The point is, sraw and mraw are very bad solutions to the file space issue, they don't save much space and lose a load of information. Much better something that keeps the resolution and throws away unnecessary coding of unused DR.
Calling them raw is simply fraudulent.
 
eraserhead said:
Condor99 said:
I don't get the point of your post. If you don't want to use mRAW or sRAW then don't use it. Why are you putting people down because they want to use it??? So what if the file size is bigger or smaller or compressed or whatever? What does that have to do with you?
Click to expand...
I'm more putting Canon down for misleading people about what this feature is and what it does, and the people who have misled others into believing that there is anything to be gained by decimating pixel counts apart from file space.
Click to expand...
The FIENDS!!!!!
 
eraserhead said:
I don't think they realise what a lame idea of canon's these formats are
Click to expand...
I don't think you realize, that there are photographers, who can make good use of this feature. I have never made any sRaw image with my 40D, but that does not mesn, that it is a "lame idea". It gains time and storage space and it delivers a very high quality image.
eraserhead said:
  1. The raw data is demosaiced (so straight away you've lost control over the demosaicing method)
Click to expand...
This is an issue only if the shot is noisy and you want to control the noise reduction. Otherwise there is no loss.
eraserhead said:
  1. the file is downsampled to the output size (so you've lost control over the downsampling method and lost half or 3/4 of the pixel data)
Click to expand...
1. What if one doesn't need the high resolution image, to start with?

2. No, you don't lose 3/4 of the pixel data. That 3/4 was single-color, which is now integrated into the result.
eraserhead said:
  1. it's converted into YCbCr format
Click to expand...
This is totally irrelevant .
eraserhead said:
  1. The astute amongst you will realise that now a 9MP mRAW file is actually bigger than an 18MP CR2, since it now has three values at each pixel position
Click to expand...
The really astute among us has already realized, that both "small raw" files are much smaller than the full raw, even though not proportionally to the resolution.
eraserhead said:
So, to save space we throw away half or 3/4 of the Cb and Cr values (losing even more information)
Click to expand...
No, we don't thow that away, because that did not even exist. You are keeping forgetting, that the image started out with mosaic data , there was no 3 * pixel count image data.
eraserhead said:
The sraw (or mraw) file is going to compress a bit better than the real raw, since so much of the information has been thrown away
Click to expand...
It does not compress better. There is less data in it, thus the compressed size is smaller as well.

--
Gabor

http://www.panopeeper.com/panorama/pano.htm
 
Do you own a Canon DLSR? At least one that shoots sRAW or mRAW? You joined DPR about 1 week ago and it looks like 90% of your posts are in the Olympus forum is why I ask. If you've never shot in these modes then what is it that makes you an expert on Canon's decision to provide an option that some people consider to be very useful? Reading one article on the Internet?

Canon knows that not every shot taken requires the full 18MP and provides us with an option to shoot at smaller resolutions and file sizes. Most of us realize the downside to using the mRAW or sRAW options. I use sRAW on my 40D a lot and for the types of shots I take it suits me just fine. I've even been known to shoot in JPEG (the horror!). If I'm taking shots where the absolute best IQ is required I switch over to full RAW. I happen to think having the option is kind of cool.

Here's an sRAW image straight from my 40D to show the types of shots it delivers, converted via DPP:

http://farm3.static.flickr.com/2571/3824805786_c35b36bbe3_o.jpg

This printed beautifully at 12x18 and hangs in my office. I'm sure the pixel peepers would argue that I should have shot at full resolution and if the two were compared side by side the difference might be visible upon close inspection.

I don't understand why people get so wrapped around the axle about a feature like sRAW. No one is holding a gun to your head (or mine) and forcing you to use the option. If the option holds no value for you then just move on. Now if Canon crippled the camera and forced this option on us that would be a completely different matter. I've ordered the 7D but know the video won't be something I use very much. But you don't see me shouting from the rafters that adding the video was a bad idea. And I plan on using the mRAW option a lot too!

Go out and take some pictures or something!
eraserhead said:
The despair amongst the pixel peepers at Canons achievement in making an astounding 18MP sensor for the 7D seems to be accompanied by a lot of people who know no better saying things like 'I'll be shooting in s-raw or m-raw'. I don't think they realise what a lame idea of canon's these formats are.

The purpose of shooting raw is to keep as much of the information from the sensor as possible, so you can use it to optimise the image you want. These two formats jettison a whole load of information for a small saving in file size.

This page ( http://lclevy.free.frcr2/#sraw ) gives some information on how these so-called raw files are constructed. It's as follows:
  1. The raw data is demosaiced (so straight away you've lost control over the demosaicing method)
  2. the file is downsampled to the output size (so you've lost control over the downsampling method and lost half or 3/4 of the pixel data)
  3. it's converted into YCbCr format.
  4. The astute amongst you will realise that now a 9MP mRAW file is actually bigger than an 18MP CR2, since it now has three values at each pixel position. So, to save space we throw away half or 3/4 of the Cb and Cr values (losing even more information).
The sraw (or mraw) file is going to compress a bit better than the real raw, since so much of the information has been thrown away. Nonetheless, the outcome is a file not much smaller, but missing a huge amount of the original raw information.
What's the point?
Click to expand...
 
GaborSch said:
No, we don't thow that away, because that did not even exist. You are keeping forgetting, that the image started out with mosaic data , there was no 3 * pixel count image data.
Click to expand...
Thanks for debunking Eraserhead's bogus claims so thoroughly!

I'm amazed at the quality of sRAW files on my 40D and how the abiltiy to adjust color balance and exposure is retained much as if it were a full RAW file. The only thing that appears to be lost is resolution (as would be expected with the fewer pixels).

Based upon his erroneous claims, it sounds like eraserhead has never worked with sRAW or mRAW files.

--
Mike Mullen
 
I've seen people knocking on the smaller sRAW files since they first came out. Well they are not bad for just doing some fun captures or snaps. If people don't like them don't use them. Saves a heck of a lot of space from the CF card to the HDD and using the 5DmkII, that means alot sometimes.
P.S. They produce very good images also.
 
eraserhead said:
Condor99 said:
I don't get the point of your post. If you don't want to use mRAW or sRAW then don't use it. Why are you putting people down because they want to use it??? So what if the file size is bigger or smaller or compressed or whatever? What does that have to do with you?
Click to expand...
I'm more putting Canon down for misleading people about what this feature is and what it does, and the people who have misled others into believing that there is anything to be gained by decimating pixel counts apart from file space. The point is, sraw and mraw are very bad solutions to the file space issue, they don't save much space and lose a load of information. Much better something that keeps the resolution and throws away unnecessary coding of unused DR.
Calling them raw is simply fraudulent.
Click to expand...
You don't own a Canon and you have never shot an sRAW or an mRAW photo in your life and you come on this forum acting like some kind of expert in the subject because of some information you misinterpreted from another website. Go back to troll school, you have flunked out.
--
Tom
My portfolio:
http://picasaweb.google.com/SeilerBird/MyTop51Photos#
 
--I've compared mRAW on my 5D MKII to full-sized RAW and it does not even come close to the IQ I get if I just downsize a full-sized RAW file. If I remember my testing correctly, my 20D produces sharper results at the 5D MKII mRAW resolution than the actual 5D MKII mRAW file does.

There is definetly some loss of IQ in the smaller RAW file sizes. I don't claim to know what is going on, but I don't need to know. I can trust my eyes.

I understand the need to sacrifice resolution for more space on a memory card, but I can't see myself ever taking this feature seriously. You'd see me chucking useless and redundant images off of my card, to gain the extra space. That's been my habit...

Regards,

Russ



Greater is He that is within me, than he who is in this world...
 
I don't need to shoot a 25mb file to print a 8 x 10 in fact I could use a 20D for that... but when I need or want it I also have full raw.....

If you had a 50D or 5D2 you would quickly realise that every pic no longer needs to be shot at full raw to be an amazing shot.. The sensors are getting so good the sraw modes are fine for most shots... I would say the 5D2 shooting sraw1 will still produce a better pic than a 50D or any lesser camera at full raw and I only have to deal with a 15mb file....

So I think it's a great idea at least we have a choice on file size. Check these photos and see if you can tell which ones are full raw or sraw...

http://stevehillphotography.smugmug.com/Photography/New-Photos/7517671_D2hiW#585933014_6nDGZ
 
eraserhead said:
carlk said:
There are always people who shoot raw but think 18MP is too many. I don't know who those people are and what are their reasons but sRaw/mRaw gave them an option to get less MP. For others you can just ignore the feature. I have used 50D for a year and never have even tried them once. I just want to keep my full 15MP raw files in my computer.
Click to expand...
But what are they saving? and do they know that these 'raw' formats are about as raw as a McDonald's hamburger. If they want smaller files, full res JPEG probably retains more of the original file information than these so-called 'raw' files.
Click to expand...
really?
ever try to alter white balance, save highlights, etc. from a JPEG?
 
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