![]() By being non-destructive, LightZone preserves the original "digital negative," which contains the maximum information captured by the camera and allows additional images with different transformations to be produced from the original image. When LightZone edits an original digital image, a new resulting post-edit image file is created, and the original image is left unaltered. LightZone is a non-destructive RAW editor. Once created, a style is easily applied to multiple images, allowing those standard camera compensations to be applied to every image before the photographer views or edits it. Using styles, photographers make and save their preferred compensations for each RAW image based upon camera-specific characteristics. LightZone can create and apply pre-determined image transformations, called "styles," to an entire batch of pictures in a single operation. Regardless of whether you apply a “constant b” or “varying b” or “b=0” operation, if the operation is not done in a linear gamma RGB color space, the operation produces gamma artifacts.LightZone is a free, open-source digital photo editor software application capable of editing JPEG and RAW files similar to Adobe Photoshop Lightroom. An example of a “constant b” operation is to put a solid color layer over the image layer using Addition or Subtract blend mode.Īny such offset applied to a scene-referred image does mean the image is no longer scene-referred. “Black point” types of offsets don’t use a constant “b”. Moving the offset does take you away from the “linear response curve” portion of the sensor’s ability to record light. Moving the black point (“noise floor”) for interpolating the raw file also is an offset, and changing this offset is equivalent to saying “I think the default noise floor is wrong for this image” or perhaps “there’s information in the deep shadows below the noise floor that’s worth recovering”. If you look at operations that are analogous to y=ax+b, where “b” isn’t 0:Ĭonsider using Levels to move the black point of the interpolated image file. ![]() If b isn’t equal to zero, then you are applying an offset that does destroy the proportional relationship y=ax. In all three cases, the “b” in the analogous linear algebra equation “ax+b” equals 0. These two operations can be combined as one operation, by multiplying the original image by a=(1.5 times 0.5, 1.75 times 0.5, 2.0 times 0.5). To make the image darker, you might multiply the image by a=(0.5f, 0.5f, 0.5f), which is equivalent to applying -1 stop of exposure compensation. It will also clip a lot of channel values unless you are using floating point processing. ![]() For example, you might multiply the image by a=(1.5,1.75,2.0), which means multiplying all the red channel values by 1.5, all the green channel values by 1.75, and all the blue channel values by 2.0, which will give the image a decided cyan-blue color cast. So for example let’s say you have an image file that’s been output to disk as a properly white-balanced and scene-referred image:Ĭhanging the image’s white balance will preserve the scene-referred nature of the resulting image. So even when editing a camera-saved jpeg, there are advantages to bumping the precision up to 16-bit integer or 32-bit floating point, and converting to a linear gamma RGB working space.Ī “scene-referred” relationship to the scene that was originally photographed would be captured by the equation “y=ax” written individually for each channel (“b” is set equal to 0). ![]() It does guarantee that algorithms like Gaussian blur, Multiply, Normal blend and such will mix the existing image colors without introducing “gamma artifacts”. “Linear gamma image editing” just means that the RGB working space has a linear gamma TRC, where “channel_value_in = channel_value_out” or “y=x” for the image’s ICC profile’s Tone Response Curve:Ĭonverting an image to a linear gamma RGB working space of course doesn’t guarantee that the RGB channel values have anything like a scene-referred relationship to the scene that was originally photographed. I’ve done some maths in the past, so I know linear means a “y=ax+b” relationship ![]() Hi that’s the 2nd time in 2 days I’ve seen “linear” used to refer to photo adjustments, the other being tutorial in the “Leaves in May” thread. ![]()
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