Raw -vs- Jpeg
RustingInPeace
Registered Users Posts: 255 Major grins
Ok, just bought my first digital camera. I have been shooting Raw and Jpeg. One thing that I noticed is a difference in the size of the files. I use the Canon digital program to convert the Raw files but they are running 9megs compared to 4.8megs for the jpegs. Why are the converted files so much larger than the other files? Am I missing a step somewhere in the processing step that would drop unnecessary information?
“Look, I'm not an intellectual - I just take pictures.” -Helmut Newton-
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I believe you're thinking about this backwards. RAW files are just that, "raw", they are not converted and therefore larger than the jpg files compressed in-camera.
As for unnecessary information... I don't think there's any such thing. Like light, all the data (pixels) you can obtain in your RAW files will help you by giving you a broader work table, if you will.
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Both in Raw and Jpeg I used max file size.
I think I should rephrase my question. What is the difference in compression between in camera or Canon's Digital Pro software? It just seems the files should be equal. I did an experiment today. I took a picture twice, once in Raw and the other as a jpeg. My Jpeg ended up at 5.2 megs. I processed the Raw file to an identical Jpeg with Canon’s software (I changed nothing). That file ended up at 8.7 megs.
When I first learned about compression, it went something like this.
Lossless is the same thing, just smaller, somehow.
Lossy is:
all of Moby Dick -> "Mad Captain Hunts Whale"
Jpg is lossy. Yes, you get the general gist of the image, but the more information you want to preserve, the larger the JPG to begin with. Some information can't be perceived by your eye on a computer monitor, such that jpg compression level of about 6 or 7 is good enough for computer-only images. Prints, however, will show off all flaws, so you'd want to have jpg quality 10 (or better, if possible) when printing.
When you do in-camera jpg, the camera is making all the choices for you. That can be good, because it will know exactly how the shot was taken, because it was there taking the shot with you. That can be bad, though, because the jpg compression routines aren't going to get updated. Newer updates to software will tend to give better results, as the raw converters get better, and that can only be done offline.
Also, when shooting raw, you can recover highlights and shadows more easily, as raw files have a larger dynamic range than jpgs. Jpg's are constrained to 8 bits, and raw usually is about 10-12. Screens only show about 8 bits (and if there's any deviation, its to showing less bits, not more, unless you have a really fancy display), which is why jpg's only show those bits. Which 8 bits you select from the 10 bits in raw can be done in post processing, effectively giving you a chance to correct for the camera misunderstanding how the scene should look.
Basically, out of camera raw processing gives you a digital negative you can process in many different ways, and that flexibility means that different algorithms are used, resulting in different file sizes. Make sense?
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I just took a look at my copy of DPP and the export to JPEG has a quality setting from 1-10. In general, the quality setting on a JPEG compression controls just how lossy it is with higher numbers creating larger files with fewer artifacts. The "10" setting is the default in DPP and appears to generate a higher quality JPEG than the camera does. If you want smaller JPEGs from DPP, lower that setting in the export dialog.
I haven't tried this myself but it sounds like the software uses less compression than the camera. Cameras can have two settings which will affect file size, dimensions in pixels and level of JPEG compression. E.g. my camera has dimensions ranging from 640x480 - 3072x2304 and compression from S-L. The compression setting usually has a quarter circle icon that is either smooth or jagged.
Malte
Ok first off GO DUCKS
Ok in a nut shell;
Jpeg
1. your CMOS sensor is a 12 bit device, Jpegs are only 8bit so there is some of the "loss."
2. When taking a Jpeg some info is not used/discarded once the camera processes the image, white balance for example.
3. There are math round offs errors during Jpeg conversions: see 1.
RAW
1. Other than converting from analog to digital and demosacing not much else is done to the raw file so it is larger.
Which should you use? It's entirerly up to you, there are huge battles raging across most if not all photo forums about the issues. But it boils down to what makes you, the photographer happy.
BTW I like some of your B&W conversions on your homepage, keep on keeping on. :ivar
www.drawingwithlight.smugmug.com
Go to your library and check out a book called, "Real World Digital Photography (2nd edition)" This book does a great job explaing the differences between the two file types. Here's their companion site that doesn't hold too much info. I in no way am associated w/ this book or authors. It's just a GREAT book that tells you everything you need to know when starting out in this confusing world of digi shooting.
This is a path that you really need to walk down on your own.
I'll be happy to provide my .02. I just hink you need to wrap your brain around what these file types really do (the differences are huge) and go from there.