3 ms·

Is there an obvious way to tell that these are exactly the same? Or is this a pixel level comparison that is not mentioned?

jldugger 2y ago
Look at the "scratch" on the right end of the leftmost dash. That "noise" shouldn't be replicated, right?
Lammy 2y ago
Try looking at the artifacts, not the actual bands. There's a little black hairline on the top right corner of the leftmost band, and a similar line toward the left of the middle band.
tom_ 2y ago
Ironically there was a whole post about basically exactly this the other day: https://news.ycombinator.com/item?id=42655870 https://news.ycombinator.com/item?id=42655870
striking 2y ago
There's a video that's quite convincing: https://youtu.be/K0Xio5yo_x8 https://youtu.be/K0Xio5yo_x8 It inverts the second image and passes the first and third images under it, and when there is a complete overlap the combined images make a nearly perfectly gray rectangle, showing that they cancel out.
barbazoo 2y ago
The page has another comment with an animation where they're overlaying the images to show how similar (same?) they are.
colechristensen 2y ago
Any image manipulation program like photoshop with layers, you put the suspect images on top of one another and use filters to subtract one layer from the other (I'm not sure which filter operation works best, it might be multiply or divide) and then work to align the two layers. Differences and similarities become extremely obvious. You can also get the raw pixel information by converting to a bitmap and comparing values, but it's easier visually because it's pretty trivial for a simple image modification to change all of the pixel values but still have the same image.
munificent 2y ago
The linked video makes it pretty clear by subtracting one image from the other and showing the difference: https://www.youtube.com/watch?v=K0Xio5yo_x8 https://www.youtube.com/watch?v=K0Xio5yo_x8

jldugger 2y ago

Look at the "scratch" on the right end of the leftmost dash. That "noise" shouldn't be replicated, right?

Lammy 2y ago

Try looking at the artifacts, not the actual bands. There's a little black hairline on the top right corner of the leftmost band, and a similar line toward the left of the middle band.

tom_ 2y ago

Ironically there was a whole post about basically exactly this the other day: https://news.ycombinator.com/item?id=42655870 https://news.ycombinator.com/item?id=42655870

striking 2y ago

There's a video that's quite convincing: https://youtu.be/K0Xio5yo_x8 https://youtu.be/K0Xio5yo_x8 It inverts the second image and passes the first and third images under it, and when there is a complete overlap the combined images make a nearly perfectly gray rectangle, showing that they cancel out.

barbazoo 2y ago

The page has another comment with an animation where they're overlaying the images to show how similar (same?) they are.

colechristensen 2y ago

Any image manipulation program like photoshop with layers, you put the suspect images on top of one another and use filters to subtract one layer from the other (I'm not sure which filter operation works best, it might be multiply or divide) and then work to align the two layers. Differences and similarities become extremely obvious. You can also get the raw pixel information by converting to a bitmap and comparing values, but it's easier visually because it's pretty trivial for a simple image modification to change all of the pixel values but still have the same image.

munificent 2y ago

The linked video makes it pretty clear by subtracting one image from the other and showing the difference: https://www.youtube.com/watch?v=K0Xio5yo_x8 https://www.youtube.com/watch?v=K0Xio5yo_x8