4/24/2023 0 Comments Rawtherapee highlight recoveryHDRMerge also allows you to treat HDR images as any other raw image, introducing them in your normal raw development workflow. This is inspired by what Guillermo Luijk implemented with Zero Noise. This ensures the lowest possible level of noise and highest detail in the output image. The resulting image then consists of the most-exposed pixels from the input images that are not saturated. In fact, it can safely assume a linear response function of the camera. The advantages are that it is very fast, requires little to no input from the user, and can be very optimistic on which pixels are the best ones. HDRMerge merges raw images directly, without development. Then, part of the noise of the least-exposed input image is transferred to the output, and ghost artifacts are difficult to deal with. Usually, the output pixels are calculated as a weighted sum of their corresponding input pixels. It must calculate a non-linear response function of the camera and take conservative decisions on whether a pixel is useful or not. As a result, the merging process is complicated. So, why should I use HDRMerge?Ĭommon HDR programs develop (demosaic) the input raw images prior to merging, performing several non-linear transformations: white balancing, highlight recovery, demosaicing and gamma correction, sharpening and denoising, among others. Likewise, HDRMerge generates an HDR image that can be later tone-mapped with another program, but this image is still raw, so the program needs to support high dynamic range raw images in the DNG format. Then, you can open this HDR image in an application which supports HDR images and apply a tone-mapping operator to squash the dynamic range while retaning detail. For instance, Luminance HDR allows you to save the (non-raw - typically TIFF, OpenEXR or Radiance RGBE) HDR image which results from exposure merging. Something that many people do not realize is that these two tasks are entirely independent of each other. Tone mapping, on the other hand, involves taking this HDR image and compressing its dynamic range so that is can be presented on a medium with a lower dynamic range, such as a computer screen or paper. Not exactly… Common HDR programs, like Luminance HDR or Photomatix, actually perform two tasks:Įxposure merging involves taking the most-exposed pixels of a set of images with different exposures and combining them so as to obtain a single HDR output image with a higher dynamic range than any of the inputs. This tool also offers a GUI to remove ‘ghosts’ from the resulting image. The output raw is built from the less noisy pixels of the input, so that shadows maintain as much detail as possible. It can import any raw format supported by LibRaw, and outputs a DNG 1.4 image with floating point data. It does so using either multiple exposure-bracketed raw files (any camera), or a single raw file which contains multiple exposure-bracketed frames (Fuji EXR and some Pentax cameras). HDRMerge creates raw images with an extended dynamic range.
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