# How lossy is C-RAW?



## AlanF (Oct 17, 2019)

I have been playing with C-RAW with the 90D because it gives half the file size and twice the burst. I haven’t noticed any loss in IQ but haven’t tried serious tests yet. On opening with Adobe RAW and saving as a DNG file, the file size is the same as .CR3 RAW file conversion. I’d appreciate the expert opinion on how much is lost by the C-RAW compression.


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## Labdoc (Oct 17, 2019)

Quick look: Canon's new compressed Raw format


Inside Canon's new EOS M50 lies a new Raw format dubbed CR3, and with it, an option to record compact C-Raw files that are 30-40% smaller than their losslessly compressed CR2 equivalents. But what – if any – impact does that have on image quality for everyday shooting? Let's find out.




www.dpreview.com


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## koenkooi (Oct 17, 2019)

AlanF said:


> I have been playing with C-RAW with the 90D because it gives half the file size and twice the burst. I haven’t noticed any loss in IQ but haven’t tried serious tests yet. On opening with Adobe RAW and saving as a DNG file, the file size is the same as .CR3 RAW file conversion. I’d appreciate the expert opinion on how much is lost by the C-RAW compression.



Have you tried the lossy DNG option for those? The reports I've seen on the interwebs say it's "good enough" and "better than jpeg" and it does give me files that are a lot smaller in size.
I only use it for exporting processed pictures that I want to be better than jpeg, not as source for processing though.


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## Antono Refa (Oct 18, 2019)

Why not put the camera in a controlled situation (studio lighting, tripod, attach camera to PC for remote control), shoot a photo once raw & once c-raw, export to 16 bit TIFF, and subtract the one photo from the other?

If the compression is lossless, the difference would be uniform noise. If the compression losses details, the difference would have some pattern, e.g. show up around edges.


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## AlanF (Oct 18, 2019)

koenkooi said:


> Have you tried the lossy DNG option for those? The reports I've seen on the interwebs say it's "good enough" and "better than jpeg" and it does give me files that are a lot smaller in size.
> I only use it for exporting processed pictures that I want to be better than jpeg, not as source for processing though.


I’m just using C-RAW for smaller files in camera. For long term storage I will save them and not the dngs.


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## AlanF (Oct 18, 2019)

Antono Refa said:


> Why not put the camera in a controlled situation (studio lighting, tripod, attach camera to PC for remote control), shoot a photo once raw & once c-raw, export to 16 bit TIFF, and subtract the one photo from the other?
> 
> If the compression is lossless, the difference would be uniform noise. If the compression losses details, the difference would have some pattern, e.g. show up around edges.


Not an easy job for me as I don’t have a studio set up or lighting.


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## Antono Refa (Oct 18, 2019)

AlanF said:


> Not an easy job for me as I don’t have a studio set up or lighting.



I hope someone with the appropriate equipment would do it. Sounds like material for an interesting page for one of the popular photography sites.


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## stevelee (Oct 18, 2019)

I have a 128GB card in my G5X II and a mostly empty 6TB drive hooked to my Mac. Somehow saving file size seems to be the least of my concerns.


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## Maximilian (Oct 18, 2019)

stevelee said:


> I have a 128GB card in my G5X II and a mostly empty 6TB drive hooked to my Mac. Somehow saving file size seems to be the least of my concerns.


Hope, you'll also have a good backup if one of these ever fails. 
I already had one HDD crash


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## AlanF (Oct 18, 2019)

stevelee said:


> I have a 128GB card in my G5X II and a mostly empty 6TB drive hooked to my Mac. Somehow saving file size seems to be the least of my concerns.


Saving file size might not mean much for a G5X II but with a 90D C-RAW allows a 44 frame or so burst rather than half that and faster writing to disk.


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## Quirkz (Oct 18, 2019)

I’ve only got my own observations and no expert knowledge on this. As far as I understand, it IS a lossy compression, but a very light one (ie, x2 vs jpg for example at x10 or x20)

I’ve looked closely at images I took and could not see any loss of fine detail, so it seems to be very good to my eyes, and I use it all the time with no regrets or concerns. 

Your requirements are likely higher than mine though and most people. If there are issues that I don’t see, you might with all that tight cropping you’re more likely to do for birding.

I’m also pretty curious about what trade offs they made for the compression.


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## privatebydesign (Oct 18, 2019)

The thing that sits in the back of my mind about lossy RAW compression is the future, that is, I am staggered at how much better modern software can process my old RAW files compared to how I could process them back then. I can well understand trading that future unknown possibility for the much better buffering when using compression, but for me personally, however I'll keep shooting the full fat versions.


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## bhf3737 (Oct 18, 2019)

C-RAW is lossy for sure, but how much and how it will affect the picture taken? Obviously any image compression will affect smooth gradients first, therefore a practical test would be taking picture of a scene with smooth transition from very dark to very bright in RAW and C-RAW (in B/W and R/G/B) and visually comparing the results. I'll try to check this in the weekend ahead. But from what I have seen so far, there shouldn't be visible difference under normal conditions, that is, no weird pushing/pulling of shadows/highlights.


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## stevelee (Oct 18, 2019)

Maximilian said:


> Hope, you'll also have a good backup if one of these ever fails.
> I already had one HDD crash


Photos that I might want to do something with later get placed on Blu-Ray discs. The most recent ones also stay on the computer’s internal SSD for a good while, and that is backed up in Time Machine. And of course the JPEGs I have on line are on remote servers. I did have a hard drive fail one time. Nothing of importance was lost. Perhaps any prints I have made are good for a hundred years, but at least should outlive me. None of that is foolproof, but is likely to suit my purposes just fine.


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## Maximilian (Oct 18, 2019)

stevelee said:


> ... to suit my purposes just fine.


Thanks for the reply. I wasn't expecting any. 
But I see, you are prepared and I (honestly) hope, that you will never have any data loss.


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## stevelee (Oct 18, 2019)

AlanF said:


> Saving file size might not mean much for a G5X II but with a 90D C-RAW allows a 44 frame or so burst rather than half that and faster writing to disk.


I take more shots with the G5X II than with my 6D2. The former is for travel. I’m over 1200 shots in my second week of a trip. With the 6D2, I’m doing more “serious” shooting, and therefore at a much slower rate.

I have never had occasion to take more than a 6- or so shot burst With either. Mostly bursts for me are for auto bracketing in 3 or 5 shots. As long as I don’t have a space problem and no need for huge bursts, I’d like my Raw files as unaltered as possible. I don’t own a camera that shoots C-Raw, and have no plans to buy anything else for a few years, so it is moot for me. But I do find it interesting that file size is a regular problem for some users even in our day of plenteous storage.


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## AlanF (Oct 18, 2019)

stevelee said:


> I take more shots with the G5X II than with my 6D2. The former is for travel. I’m over 1200 shots in my second week of a trip. With the 6D2, I’m doing more “serious” shooting, and therefore at a much slower rate.
> 
> I have never had occasion to take more than a 6- or so shot burst With either. Mostly bursts for me are for auto bracketing in 3 or 5 shots. As long as I don’t have a space problem and no need for huge bursts, I’d like my Raw files as unaltered as possible. I don’t own a camera that shoots C-Raw, and have no plans to buy anything else for a few years, so it is moot for me. But I do find it interesting that file size is a regular problem for some users even in our day of plenteous storage.


If you do not shoot long bursts, then don't worry. Similarly, if you have a big hard drive, then fine. RAW files from my 5DSR average 65-70 Mb each, and 15,000 will fill my 1Tb of cloud storage - and I like to back up on the cloud. During our last birding trip, we took some 10,000 shots between us.


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## Kit. (Oct 18, 2019)

privatebydesign said:


> The thing that sits in the back of my mind about lossy RAW compression is the future, that is, I am staggered at how much better modern software can process my old RAW files compared to how I could process them back then. I can well understand trading that future unknown possibility for the much better buffering when using compression, but for me personally, however I'll keep shooting the full fat versions.


On the other hand, think how much more information about the subject could be extracted by the future software after processing those much longer bursts.


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## privatebydesign (Oct 18, 2019)

Well in general in a burst you get one or two peak action images, wings in perfect position, the peak of a swing/hit/action, having multiple images before and after don't really hold much value at this point or the foreseeable future. Maybe in generations they can make a 3D holograph or something from a 40 image sequence but that is so far away I won't be around to see it and neither will my insignificant images. Meanwhile the differences anybody can see in 15 year old software and current software gives visible improvements.



Kit. said:


> On the other hand, think how much more information about the subject could be extracted by the future software after processing those much longer bursts.


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## Kit. (Oct 18, 2019)

privatebydesign said:


> Well in general in a burst you get one or two peak action images, wings in perfect position, the peak of a swing/hit/action, having multiple images before and after don't really hold much value at this point or the foreseeable future.


I'm pretty sure in about 5 years the software will be able to learn kinematics and textures from the series of images and to use that to enhance (sharpen, denoise, remove motion blur etc.) individual frames.


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## Mt Spokane Photography (Oct 19, 2019)

At 100%, the difference is visible. I've seen different examples online and downloaded them to compare. I'm not constrained by memory and don't shoot fast bursts, so I use raw for photos I want saved, and jpg for temporary ones.


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