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Thread: Converting RAW to JPEG

  1. #1
    Digital's Avatar
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    Converting RAW to JPEG

    It seems that the more I learn about RAW files the more questions I have.
    In order to print a RAW file you need to convert the file to JPEG (or TIFF). Once you convert it to a JPEG your file is compressed. Is it a question that with a RAW file you started out with more information (data) so you can stand to lose some of that data. For example with RAW I can choose either 12 bits or 14 bits on the RGB channels. So once I convert to a JPEG file I now have 8 bits on the RGB channels. Did I lose all of that color in the conversion?
    Forgive my ignorance; however like I said the more I learn about RAW files the more questions I have.
    Any feedback will be greatly appreciated.

    Bruce

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    Re: Converting RAW to JPEG

    Hello Bruce,

    Perhaps it would be better if you think about the number of bits as the number of shades available in each R,G and B channel, rather than just calling it "data". For a 12-bit RAW file, that gives you (theoretically) 4096 shades for each channel, where 0=no brightness and 4095=maximum brightness. (In reality you often end up with less, which we won't go into now). When the RAW content is turned into the working file (which is only used while editing) the working space is more, typically 16-bit, to give you some editing headroom and to work in binary values (words) more convenient to the computer CPU. When the moment of truth arrives (time to save) you can choose from all the file format options that your Editor provides, depending what you are going to do with your image. There are many more options than just JPEG and TIFF in most editors, as you probably know.

    Anyway, you did not "lose all of that color" in the conversion. However, in converting to an 8-bit (0-255 per channel) format, each 16-bit value in the working file is converted to the nearest available value in the 8-bit world, so what you lose is color resolution - each pixel now has "only" 16 million colors available instead of your 12-bit original 68.7 British billions (1000-million). No sad loss, our eyes can't even distinguish one 8-bit color shade from it's neighbor, so don't worry too much about color resolution, for now.

    The quality of JPEG compression is what you set it to. Minimum gets you a horrible image with much color and shade data lost forever. Maximum compression loses you surprisingly little. I use 9 (out of 12) in Photoshop Elements for "important" images and 3 for web shots. You might want also to read about the PNG format.

    I think that's all I can manage on the subject. Others will be along shortly to tell you more, I'm sure.
    Last edited by xpatUSA; 10th February 2013 at 11:27 AM. Reason: mas clarificación

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    Re: Converting RAW to JPEG

    Quote Originally Posted by Digital View Post
    In order to print a RAW file you need to convert the file to JPEG (or TIFF).
    My software will print directly from a RAW file. I imagine that it is using the full-resolution JPEG embedded in the RAW file, but I don't know for sure. My reason for mentioning this is that perhaps you don't need to create a separate JPEG or TIFF to print a RAW file on your system. If you are outsourcing your printing, I'm sure you are correct that you will need to provide the company with either a JPEG or a TIFF.

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    Administrator Manfred M's Avatar
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    Re: Converting RAW to JPEG

    A few other points that need a bit of clarification. Even if you have all that data, in the real world is is less than useful because you are limited by your eyes, by your computer's display and by the printing process.

    1. Monitor - unless you have a pricey, high gamut computer screen, you are limited to 8-bit per channel colour. This is what themost computer screens claim to be. Even this claim is somewhat dubious as these monitors are natively 6-bit per channel and they made up the difference using technical tricks called dithering (cycling bits off and on quickly). I have yet to see any hard technical data as to how well the actually work, and as these techniques are likely to vary from manufacturer to manufacturer, it's hard to make a definitive statement.

    High gamut monitors use a more expensive technology and natively display 8-bit per channel colour and through dithering techniques take that up to 10-bit colour. This is still below what your camera that captures; 12-bit or 14-bit colour. Some medium format camera output 16-bit colour data

    The other issue with monitors is that they can display around 8 or 9 stops of colour range. A modern DSLR can easily capture 12 or 13 stops.

    2. Printing - even the best colour printers only reproduce a few hundred thousand individual colours. Even high end printers run around 8 different colour cartridges at a time, and by varying dot size and dot spacing, they emulate the full colour gamut. The colour print has even less dynamic range that your monitor - it is in the range of 5 or 6 stops.

    3. Your eyes - while even the lowest quality colour space that is commonly used is capable of displaying 8-bit colour (8-bits of Red data, 8-bits of Green data and 8-bits of Blue data), sRGB is capable of displaying around 16 million distinct colours, your eyes are only capable of distinguishing around 10 million distinct colours (really around 7-bits per channel).

    So all this worry about losing colour data when you compress to 8-bit jpegs is somewhat of a moot point, in most instances you'll never miss it. Another point to remember is that working and resaving a jpeg image is not going to result in an ongoing deterioration of colour data. Once the data has been compressed, subsequent saves of the same image are going to invoke the same algorithms and the output is pretty well identical to the input image.

    So why shoot RAW at all? If you are planning to do fairly heavy duty image manipulation, your PP software will more data to work with and you are less likely to see banding or other jpeg artifacts in your output. You also get a clean image and don't have to use whatever was built into your camera; writing to jpeg by your camera involves some sharpening and contrast enhancement.

    I personally shoot jpeg + RAW and end up using the jpeg image around 95% of the time, when posting my images to the internet. Jpeg versus RAW has generated a lot of discussion (here on CiC and elsewhere) and I do understand both points of view. I do what works best for my own workflow.
    Last edited by Manfred M; 10th February 2013 at 11:56 AM.

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    Re: Converting RAW to JPEG

    Quote Originally Posted by Mike Buckley View Post
    My software will print directly from a RAW file. I imagine that it is using the full-resolution JPEG embedded in the RAW file, but I don't know for sure.
    We're up early today, Mike?

    Assuming Nikon, is that the embedded JPEG you get when you select RAW+JPEG in-camera image quality? Reason I ask is that. on my D50, the embedded JPEG is only what they call Basic JPEG quality (16 to 1 compression ratio).

    On X3F files from my Sigma, you get two embedded JPEGs, like it or not, one medium size, the other thumbnail size. If you want them, you have to extract them yourself with a utility.

    Here's a medium size one:

    Converting RAW to JPEG

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    Re: Converting RAW to JPEG

    Quote Originally Posted by xpatUSA View Post
    We're up early today, Mike?

    Assuming Nikon, is that the embedded JPEG you get when you select RAW+JPEG in-camera image quality? Reason I ask is that. on my D50, the embedded JPEG is only what they call Basic JPEG quality (16 to 1 compression ratio).
    No, to both counts. I got up at 7:00AM. You got up early, so go back to bed.

    As for the other issue, it has to do with Nikon's software, not the camera. Once you edit and save a RAW file in Capture NX2, the software will automatically embed a full-size JPEG in the file. That's true regardless of the size of the embedded JPEG produced by your camera. I think Nikon View NX2, which is free, will do the same but I haven't used it in a long time and never used it to post-process files.

    I think the D50 is the last model Nikon made that doesn't embed a full-size JPEG in the RAW file. I'm reasonably confident that my D80 does, though it has been a long time since I looked that up.

    By the way, when you configure the camera to "RAW + JPEG," that doesn't have anything to do with the size of the embedded JPEG in the RAW file. Instead, that configuration produces two files from every shutter release -- a RAW file and a JPEG file.
    Last edited by Mike Buckley; 10th February 2013 at 12:34 PM.

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    Re: Converting RAW to JPEG

    Quote Originally Posted by Mike Buckley View Post
    My software will print directly from a RAW file. I imagine that it is using the full-resolution JPEG embedded in the RAW file, but I don't know for sure. My reason for mentioning this is that perhaps you don't need to create a separate JPEG or TIFF to print a RAW file on your system. If you are outsourcing your printing, I'm sure you are correct that you will need to provide the company with either a JPEG or a TIFF.
    Yes, with Lightroom 4 (also with LR 3), you can print directly without having to create a JPEG or TIFF first. I also don't know if LR uses the JPEG embedded in the RAW file. I just know it works

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    Re: Converting RAW to JPEG

    I print from LR, and AFAIK, LR does not use an embedded jpeg to print. I only create jpegs to post on the web or, when I don't print myself, to send to a lab. With Jeffry Friedl's plugins, you can upload to the web while converting to jpeg on the fly, without leaving a jpeg file on your computer.

    With all the discussion of bit depth, something else was not mentioned: jpeg is a lossy compression method. How lossy is determined by the quality level you choose in exporting or saving. This is not just a matter of bit depth.

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    Re: Converting RAW to JPEG

    Quote Originally Posted by DanK View Post
    With all the discussion of bit depth, something else was not mentioned: jpeg is a lossy compression method. How lossy is determined by the quality level you choose in exporting or saving. This is not just a matter of bit depth.
    Thanks Dan, I should have called it by name in my first response to the OP but it wasn't too clear, I guess:

    "Minimum gets you a horrible image with much color and shade data lost forever. Maximum compression loses you surprisingly little".

  10. #10
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    Re: Converting RAW to JPEG

    Hi Bruce,

    I think the others have covered it pretty well but I'd just re-iterate a few points.

    With a raw file, no processing has been done in camera. This means that

    • De-mosaicing is done on a more powerful (external) computer rather than on the camera's computer. Some say this can give better results although I suspect that these days the on-camera computer chips are so good that this may be a moot point.
    • All sharpening is done externally which means the user is in full control. Who knows what sharpening algorithms are used within the camera's computer. (You can choose some settings for these but I don't think that really tells you much).
    • There is no lossy compression done on the image (except for some cameras where there is an option for some compression with raw). Once again, there are settings for jpeg quality on a camera (which includes the degree of compression) but these are usually not very informative compared to the standard jpeg quality settings that can be selected in editing software such as PS.



    Dave

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    Re: Converting RAW to JPEG

    I print with my Canon Pixma Pro 9000 ii from PSD files; using Photoshop CS6 and printing through Canon Easy Print Pro software.

    File > Automate > Canon Easy Print Pro

    Of course, this system requires you to have a high-grade Canon Printer. I was lucky to obtain my Pixma Pro 9000 ii printer at the time that Canon was selling off those printers before they introduced the replacement model. The price of this printer was remarkable!

    I attended a Canon Printing Seminar during which the presenter provided a considerable amount of information on printing through the Canon Easy Print Pro software. I really like the capabilities of the combination of Pixma Pro 9000 ii and Canon Easy Print Pro software...
    Last edited by rpcrowe; 11th February 2013 at 03:05 PM.

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    Re: Converting RAW to JPEG

    Each jpeg that you make from a raw file is just one possible expression. Yes, the jpeg is quite limited compared to the raw file. But, all the data in the raw file remains unchanged no matter how many different jpegs you process from it. Your final product will have a specific white balance and tint, one picture control, a certain balance of tones. Lots of information is excluded from the jpeg. But, that is presumably the way you want it. If you want to change it, you can always go back to the raw file and try again. The possibilities are almost limitless. You have the freedom and power to sculpt that image. Since it is compressed, as you say, the jpeg is a final draft. It has a particular shape and density. You might call that less but it is less just as a painting on the wall has less color than what is in all the tubes beside the easel.

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    Re: Converting RAW to JPEG

    Quote Originally Posted by xpatUSA View Post
    The quality of JPEG compression is what you set it to. Minimum gets you a horrible image with much color and shade data lost forever. Maximum compression loses you surprisingly little. I use 9 (out of 12) in Photoshop Elements for "important" images and 3 for web shots.
    This statement confuses "quality" and "compression". In PSE, the number scale describes the quality level of the saved Jpeg image, from 1 (lowest quality) to 12 (highest quality). The quality of the image increases as compression level decreases, so that high values (e.g. 9) represent the minimum compression levels, losing less of the image data and producing larger, higher quality Jpeg files.

    Philip

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    Re: Converting RAW to JPEG

    You can try Fast Stone Photo Re sizer. It's free and does batch re sizing and converting to jpeg and other formats.

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    Re: Converting RAW to JPEG

    Quote Originally Posted by Michaelclark View Post
    You can try Fast Stone Photo Re sizer. It's free and does batch re sizing and converting to jpeg and other formats.
    Plus the latest version has lossless JPEG transitions.

  16. #16
    xpatUSA's Avatar
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    Re: Converting RAW to JPEG

    Quote Originally Posted by MrB View Post
    This statement confuses "quality" and "compression". In PSE, the number scale describes the quality level of the saved Jpeg image, from 1 (lowest quality) to 12 (highest quality). The quality of the image increases as compression level decreases, so that high values (e.g. 9) represent the minimum compression levels, losing less of the image data and producing larger, higher quality Jpeg files.

    Philip
    Just to be clear on the issue, Phil, wot you said is wot I meant.

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