Monday, 8 October 2012

More shadow ghosts - flying and lurking!

Bird shadowTake a look at the photo, right. Though it looks dark, it was only slightly underexposed. The photo is untouched (apart from cropping to highlight the area of interest), straight from the camera. The photo shows some vegetation with water in front and behind (even though it may not be obvious). But note the shape in the water at the bottom. I t looks like the reflection, or shadow, of a bird in flight. But where is the bird itself? Could this be a shadow on it's own, without the object that casts it, like a shadow ghost?

The second photo, below, has been lightened and the contrast increased. As a result you can now see the bird that cast the shadow clearly, flying low over the water. The reason the bird is difficult to make out in the original photo is because both it and vegetation behind are dark, blending into each other. This kind of thing occurs quite frequently in anomalous photos. Digital photos have a low dynamic range compared to film. The dynamic range is the number of shades of grey between white and black. With a low dynamic range, it can be difficult to distinguish overlapping objects in dull or bright lighting conditions.

I mentioned recently that I have a poor memory. This means that, after a gap of a few weeks, I can see the same misperception twice, having forgotten about it! So it was that I saw the 'door ghost' (originally reported as a doppelganger - see here) once again. Briefly, I am seeing bits of my own body reflected in the frosted window in a door. Part of the reason that this misperception works is that, due to the lighting conditions, the 'ghost' appears very dark. It is a case of very high contrast lighting conditions, just like the bird photos here. Even though human vision has a much better dynamic range than photos, there are still conditions where it can be fooled, like this is one!

Bird shadowOn this occasion, not only did I see a 'dark figure' behind me once again but, this time, it looked quite specifically like someone's legs and feet standing on the path right behind me. It was particularly effective because that is exactly what you'd expect to see, given the angles involved, if someone really was standing in that position behind me. Examining the 'legs' carefully, I worked out that it was my hand! I happened to have two fingers crooked while the others were held straight. The effect, when reflected and viewed like a shadow in the frosted glass, was like a shadow pair of feet with legs above them. It was the most convincing version of the 'door ghost' yet! Indeed, for a second or two I really thought there WAS someone standing there, until I remembered the misperception! Needless to say, there was no one there - yes, I checked!

Incidentally, looking at the 'enhanced' photo, right, notice how, although we can now make out the bird well, details from the ripples in the water have vanished! Whenever, you alter an image to bring up a particular feature, you inevitably lose something else. Any alteration to a photo inevitably destroys some of the original data in the photo. This is why you should never 'enhance' a photo too much as it will become less and less like the original. Indeed, go on 'enhancing' enough and you will introduce artefacts - objects that are purely a result of using the photo editing software. These artefacts are 'objects' that were never in the original image at all!

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