HDR generator settings controls how the HDR/SDR image is generated. For images that are slightly off-aligned, turn on the alignment control. The app supports three image alignment methods.

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There are two types of image merge method supported in this app: Exposure weighted merge and Exposure fusion. The outcome of the 'exposure weighted merger' is a true high dynamic range image. This high dynamic range image can be exported as a radiance hdr file. Because high dynamic range images can not be displayed on the ordinary screen, a process known as 'tone mapping' is required to compress the dynamic range back to a more acceptable standard dynamic range image.

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On the other hand, the "exposure fusion merger" spits out a standard dynamic range image (or low dynamic range image) directly without the help of tone mapping. This merger can also be used to process non-HDR images.

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Image alignment parameters: 

 

 - Median Threshold Bitmaps: This method jitters images in the stack to align them. The amount of jittering is defined by the 'Image Max Shift Bits' slider. 

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 - Visual feature matching (ORB): This method attempts to map common visual features across multiple images, then use these information to align the images. The 'Feature matching size' slider controls the grid size that is used for hunting visual features.

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 - Enhanced correlation coefficient: This method jitters images in the stack to align them. Unlike the MTB method, this alignment method allows you to specify how the images are jittered. 

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• Translation: shift images along X and Y directions

• Euclidean: Translation + Rotation

• Affine: Translation + Rotation + Scale + Shear

• Homography: Affine + Perspective

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Image merge method:

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 - Exposure weighted merger: uses exposure time and image pixel value to reconstruct a high dynamic range image.

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• "Response smoothness" slider controls the smooth function of the calculated camera response function. If merged artifacts such as color banding appears, try use a larger smoothness value.

• "Mid-tone weight" slider controls how importance is for a well exposed pixels in the merged image. Within the source photos, the pixel on the same coordinate(x,y) will have different value on different photos because these photos are taken using different exposure settings. The merger uses this setting to calculate the final pixel value. The more weight you assigned to the mid-tone value, the more obvious will be for mid-tone pixels appears in the final image.

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 - Exposure fusion: allows user specify how multiple photos are merged. This merger can also be used to merge non-HDR bracketed photos. When merging pixels across photos in the stack, it allows the user to specify what aspect of an photo is more important (ie, carries more weight) in the final image. 

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• Merge Ct. weight: the importance of contrasts/focus in the final image. When set to 1, area that is well focused in one photo will appear more obvious in the final image. This is often use in 'focus stacking' (ie take multiple photos of the same subject, with different focal points, then merge them together to get a super deep DOF)

• Merge St. weight: the importance of saturation in the final image. When set to 1, area that is higher color saturation will appear more obvious in the final image. 

• Merge Ex. weight: the importance of well exposed pixel in the final image. When set to 1, pixels that are considered well exposed from one photo will be used to render the final image.

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Tone mapping method sliders:

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Tone mapping methods are organized by the algorithm's first author name. Depends on the scene, one algorithm may work better than others. Reinhard seems to be a good all arounder. Please use the support email to contact me if you need more information on various tone mapping controls.

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• Gamma: applies gamma curve to the image, when set to 1.0 no additional gamma correction is applied

• Saturation: color saturation of the final image

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