exposure + contrast = contrast + exposure ?
July 6, 2015 6:03 PM   Subscribe

Are the operations applied by digital photo effects (e.g. sharpening, contrast) commutative? That is, will the outcome differ based on the order the effects are applied?

Or does it vary in some complicated way? Let's say specifically in something like the iPhone's built-in camera app, but I assume most of the common operations are similar in any image editing program.
posted by Nomiconic to Technology (2 answers total) 1 user marked this as a favorite
It depends on the operations. I would expect that sharpening and contrast wouldn't generally affect one another (though in extreme cases it might), but sharpening and resize would produce different results if the order was changed.
posted by Chocolate Pickle at 6:19 PM on July 6, 2015

Best answer: Insofar as the image effects can be represented as convolutions, i.e., you get an output image by convolving the input with the kernel corresponding to the effect, they are commutative, which is a property of convolutions. So effects like blurring, sharpening, edge detection are all commutative. However, effects that operate on images as linear (affine) transforms, such as brightness or contrast adjustment, aren't commutative, and wouldn't commute with other effects that act as linear transforms when applied or with effects that act as convolutions.
posted by un petit cadeau at 6:27 PM on July 6, 2015 [5 favorites]

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