Image processing hokum

Can someone direct me to a reference where they debunk the possibilty of image enhancement as seen in some movies, CSI, etc. Some of the type of thing I mean whas discussed in this thread (see comments by N9IWP, mhendo, GargoyleWB…).

I’m not a photographer, but I think the possibility of some image enhancement procedures involving digital images debunks itself when you think of the image as being composed of pixels. If you have a section of the picture that consists of a given number of pixels, you can enlarge this as much as you want - you won’t get a resolution better than this number of pixels, simply because that’s all information there is to find in the original data.

I guess photographs taken on classic pictures can indeed be enhanced and enlarged pretty far (I guess the limit there is the size number of crystals of which the light-sensitive coating consists, and those, I assume, are pretty small).

How much of a reference do you need without getting into information theory? The linked thread investigated the issue pretty thoroughly. The bottom line is that while you can do some degree of image enhancement re sharpening & detailing in some circumstances you can’t make or squeeze more information out of a digital pic than the pixels contain. The endless resolution enhancement of low res grainy video camera pics as as stock device in TV police procedurals is a silly notion coming and going.

Yeah, this rang a bell for me…it was this nonsense about the kenndy assassination (the alleged “grassy knol shooter”). The so-called 'experts" have blown this picture up, processed it to death-and all I see are some blobs! No gunman, no gun barrel, no hat. I guess it is like seeing faces in clouds-you basically wind up seeing what you WANT to see!

I am a photographer, and it simply comes down to: you can’t create information where there is none. That said, there is a lot you can do to enhance the image and make it more readable to a human, but you’re not adding pixels, but rather changing the data associated with them. The most common enhancement technique is called “unsharp masking.” Basically, as far as I understand it, it makes pictures appear sharper by increasing contrast between certain pixels based on parameters entered by the user. You aren’t, however, increasing resolution in any meaningful way.

What can be done is in a series of still images (usually video capture frames), you can create a single still that contains more information than any individual still by using the information from multiple photos and combining them into one. But, in that case, you are using more information than what is contained in a single picture, so such manipulation is possible.

You can’t get information where there is none, but a computer can see information that the human eye cannot. There are some pretty cool examples of what can can done IRL.

The Virgin Mary held up a liquor store in 1998? :eek: