RAW file size - details - coverage

Discussion in 'Image Processing' started by ronyzmbow, Apr 15, 2012.

  1. ronyzmbow

    ronyzmbow Mu-43 Rookie

    Dec 12, 2011
    I have started to use my new Olympus E-PL1 camera with RAW files.

    I was not so pleased with the results in PSE ACR and Lightroom so I have decided to try THE SAME RAW file in Capture One Express and Raw Therapy.
    I was shocked to discover that the area covered with Capture One Express and Raw Therapy is larger than ACR and Lightroom - to my astonishment it is like having a wider lens - in all four corners of the image there more details and objects that cannot be seen in ACR! - notice a red car on the right side and a blue boat on the left side - it looks like either from a wider lens or like another file!
    I have checked both in Photoshop ACR and Lightroom and the Lens Correction option is turned OFF.
    Still kind of a small mystery to me...

    I do not see this phenomena with images from Sony DSC R1 and Pentax K-10.

    See the attached images

    Later on I came upon this information -
    In order to elaborate on the issue following some information I have collected from Luminous Landsacpe web site and Thomas Knoll, who is one of the original authors of Photoshop and the creator of Adobe Camera Raw.
    " You may not realize it, but your digital camera does not give you every pixel that it records.
    In most cases this is because the manufacturer masks off pixels at the very edges of the frame. This is done for a couple of technical reasons.
    1. Many of the image processing algorithms (de-mosaicing, noise reduction, sharpening) that camera firmware (or raw conversion software) apply to raw sensor data are not "point operations", but instead "neighborhood operations". When computing the output value of that pixel, the algorithm needs to know not only the input value of that pixel, but also the input values of the pixels in the local neighborhood. The pixels at the very edge of the recorded image do not have a complete local neighborhood, so the algorithms need make some guess as to their value, which means that output results for these edge pixels will be not quite as accurate as the pixels a few pixels away from the edges. By trimming away these pixels, the camera manufacturers guarantee that all the output pixels are of maximum quality.
    2. Sometimes image sensors do not have aspect ratios that exactly match the standard aspect ratios (3:2, 4:3, 16:9, etc.). In these cases, there are often different numbers of horizontal and vertical pixels hidden, to cause the final output image to have an exact ratio, When some users print digital camera images, they often do not bother to crop them, so having the camera output images with standard aspect ratios that exactly match standard paper dimensions is an advantage.
    Solving this problem that few people knew even existed, Thomas Knoll, who is one of the original authors of Photoshop and the creator of Adobe Camera Raw, has written a free utility program which recovers all the pixels that any supported digital camera records, whether it's hidden edges or intentionally cropped formats. Called DNG Recover Edges, the utility application is unsupported, and it is not an Adobe product."
    Another interesting comment came from a reader of my thread in DP Review web site forum:
    " RAW images usually contain capture area of the entire sensor, while the intended viewing area is smaller. While capturing the image, both sets of dimensions are recorded with it. From what I have seen so far it is just a few pixels on each side, but your examples show quite substantial difference. The purpose of that is to simplify the conversion from RAW to Jpeg as the edges require different algorithms, as well as to discard the areas with the most quality issues (i.e. vignetting, CA, poor sharpness).
    I've seen an utility that was making the full captured image available - simply by copying the tag describing the physical sensor dimensions into the image dimensions field, but I'm not sure if it would cover your camera's format. If I remember correctly it was working with .dng files only."


    Attached Files:

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  2. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Real Name:
    As was mentioned on the other forum you posted this to...

    All sensors include extra pixels around the edges. These are used for various types of calibration, and for improved Bayer interpolation at the edges. Certain raw converters also use them when producing the image. Adobe has chosen to follow the manufacturer specifications, and use those pixels for their intended use.

    The extra pixels give a max of about a 1.7% increase in linear resolution. If this matters to you, don't use Adobe, Olympus or Panasonic's RAW converters.

    This makes no difference. The m4/3 specification requires that lens correction be enabled for correct rendering. Thus Adobe, Olympus, Panasonic, and other compliant raw converters do not allow you to disable lens correction.

  3. Ig7

    Ig7 Mu-43 Veteran

    Aug 24, 2011
    I have a very "dumb question" and apologize for it in advance, but when you import the RAW files into Lightroom or open it with Photoshop, does either program automatically apply changes to the image as far as the sharpening, color, etc.? How about when it is converted to DNG?
  4. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Real Name:
    The preview that it displays uses default settings when imported or converted to DNG. You can however change the defaults for each camera model, if you prefer.