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JPEG vs RAW




My camera can take save images as both JPEG and RAW at the same time. In this example, the JPEG is on the left and the RAW on the right.

JPEGs save much faster, take up much less space, are usable just as they are, can be opened by just about anything and Windows can automatically display a thumbnail of the image. The biggest drawback of JPEG is that it is a lossy format, and working with a JPEG just makes things worse.

RAW files, on the other hand, contain the unprocessed data directly off the image sensor. They are higher quality, offer finer control, are generally 12 or 14 bit (vs JPEG's 8 bits) and are lossless. The drawbacks are its enormous file size (7 times larger than JPEG on my camera) and a proprietary format that might be difficult to open in the future.

In this particular image, notice the sky is a truer blue, there is more contrast in the clouds, the ground haze is more visible, the tractor wheels and clouds are whiter and the grass a bit greener on the RAW side.

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Comments

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twigmouse
May. 9th, 2009 03:59 am (UTC)
RAW should look exactly the same as the JPEG in most cameras, until you make changes to the RAW file in the software on your computer.

The advantage of RAW is that you can make changes to the raw data from the CCD before saving it as a JPEG. If the RAW file when saved to a JPEG looks better than the JPEG out of the camera, it just means that the software on your computer is doing a better job of tweaking the settings than your camera does.

I do all my shooting in RAW+JPEG. The camera saves two files for each photo I take. When I first open the RAW in the Nikon software, it is identical to the JPEG from the camera. I then go and tweak the black and white points, contrast, white balance (this one comes in VERY handy when using flashes or shooting in mixed light) dynamic range, etc.
tiggerfox
May. 9th, 2009 05:13 am (UTC)
How can we tell the image you linked is a jpeg =P

I shoot in DNG myself for archiving and save to jpg or png later depending on what I am doing with the file, such as posting to the web. Storage space is a non issue imo.
rustitobuck
May. 9th, 2009 06:30 am (UTC)
The difference in the color saturation is more likely due to a difference in the presumed color profile of the two images, or the profile stored in the image. Either that, or the camera did some processing before making the JPEG. It could be that the response curves of the sensor are not linear, and so the camera is correcting to probably sRGB before compressing.
captpackrat
May. 10th, 2009 12:46 am (UTC)
The camera has a handful of AWB profiles it can select from, either automatically or manually, that it uses to create the JPEG. If it chooses incorrectly, you can fix it later in software, but you're still working with an already lossy-compressed JPEG. It also has noise correction and other routines it runs through when creating the JPEG. The RAW file does none of this, leaving it to the user to select the best options during "development".
marko_the_rat
May. 9th, 2009 10:27 am (UTC)
It turns out the grass really is greener on the other side! (Sorry.)
crim_ferret
May. 9th, 2009 07:28 pm (UTC)
I'd much rather grab the RAW file, save in a lossless standard format like TIFF or PNG and work with that. Even if you do capture in JPEG, save in one of those until you're done to minimize the crap that multiple times through JPEG will introduce to the image. This is from the point of view of somebody who wants to squeeze the most out of an image.

If it's just for casual snapshots, it likely doesn't matter all that much.
bluedeer
May. 12th, 2009 09:40 am (UTC)
Yeah, part of it is because of the compression and averaging of colors to make it happen. I bet the Tractor on the JPEG is an average of more of the same shade of red than the one in the RAW. RAW is analagous to BMP, though even BMP has headers that tell a proram how big it is, how many colors it is, and what its dimensions are, while each RAW is always so different yet just same enough that whatever generates it and its proprietary software that opens it knows these details to begin with and don't need them encoded in the file. So if you know the RAW data header you can open it in pretty much any image program that can read a RAW format...provided you can provide the data header. Which can be a pain in the butt.
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