Here are the three source images:
The differences among them are obviously in the amount of noise that was added to the image. No noise was added to the first image – any noise there was in the original capture. 10% level “Uniform” noise was added to the second image in Photoshop. 20% “Uniform” noise was added to the third image in the same way.
The soft photograph was chosen to avoid masking the noise with a lot of other sharp detail – this image provides very smooth gradients from black to white, where noise is typically easier to detect. I also chose this image because it is nearly – but not quite – monochromatic. This meant that I could increase the effect of the noise by using color noise rather than limiting to monochromatic noise – and that the color noise would tend to be more visible against the nearly monochromatic background.
The original set of 6 jpgs includes two from each of the three versions shown here. For last-minute fun you could still visit the comment page and try to a) determine whether or not the differences are visible and b) which pairs of images are the least noisy, more noisy, and most noisy.
More information to come later this evening.
Ernie:
Interesting point about the “rules.” I could run these three examples the same way, but I don’t think I will. They don’t have the same role in the experiment – in this case there is no challenge to identify whether or not their is a difference, the nature of the difference, or arrange the images in any particular way. Here, I’m pretty certain that the differences is pretty obvious, as it was intended to be.
That said, anyone who wants to test whether or not a difference would be visible can use the images to set up their own personal sequence. In fact, you can easily do it by opening three copies of the page containing the images in three different browser tabs. Use the vertical “thumb” to scroll them so that a different images appears on your screen in each tab and then simply switch among the tabs to compare.
Dan
Ok, I can clearly and easily see the differences here…but when I went back to the presented six images I could not, even though I had two particular spots to look at.
But I think the above images are not following the rules stipulated and that is mainly why you can see the differences. To wit, you said, “please limit your consideration of the images to viewing them in your browser on the linked page.”.
So let’s have the same three pictures above, but at the same relative size and resolution of the six photos. I think the differences will disappear for me at least.