3 ms·
"Supposed to" in what context, by whom?
by gjm11 5y ago
"Supposed to" in what context, by whom?
- enriquto 5y agoIn any context, by everybody. This is what happens when you move far away from an object, which is what "zoom-out" or "downscale" is all about. The total amount of light that you receive from an object decreases with the square of the distance.
- planede 5y agoYes, but if you scale to half size (in linear size), then the overall luminance could go down by 1/2*1/2=1/4, not more, not less.
- formerly_proven 5y agoAccording to this logic scaling an image down would make it darker.
- enriquto 5y agoIt does. Imagine a one pixel wide vertical white line on black background. As you downscale it, by whatever reasonable means, the line becomes a darker and darker grey. EDIT: This is in the context of the image shown in the article, which is a gradient image consisting in light lines over black background. Of course, if you have thin black lines on white background, they will become ligter upon downscaling. In practice, on a real image, some parts will become darker and others lighter, depending on their particular textures.
- gjm11 5y agoIf you have an image consisting of a thin white line on a black background, then indeed as you scale it down the pixels covering that white line will become darker because each pixel corresponds to a small amount of white in a mostly-black square. (I am making some assumptions about what scaling is meant to mean here, but the conclusion doesn't change much if you think about it differently -- e.g., with pixels as point samples of a bandwidth-limited function.) But those pixels are also larger and the ratio (amount of light in image) : (number of pixels in image) should not change. The author of the OP is complaining that when you take an image and rescale it, its overall average brightness changes.