Friday, April 20, 2012

lazy friday dark adapt

Spent afternoon of Friday, 4-20-12, with a ~3 log unit (~.2%) ND filter over my right eye. Made the following observations:
(Took the filter off after about 4 hours. It wasn’t bothering me much anymore, but I think the plastic and rubber stuff in the goggles was irritating my eyes, which were starting to feel kind of dry and red. Light adaptation is really fast, it’s just been a minute and the (formerly dark adapted) right eye’s image only seems slightly brighter than the left’s.)
  1. Noise: the dark adapted eye’s view is noisy, and the noise intrudes into the dominant view. It’s irritating. The dark adapted view isn’t being suppressed, though, it’s there like a ghost. Double images, from depth, are strikingly noticeable, not sure why.
  2. Pulfrich effect: first time I’ve really seen this work. I put my index fingers tip-to-tip and move one from side to side, fixating on the still one, and the moving finger looks like it’s rotating. My hand even feels like it’s rotating.
  3. Pulfrich effect 2: Fusion isn’t always working, but I seem to be ortho a lot of the time. I just noticed, though, that if I make quick motions, e.g. a flick of a finger, there’s a delay in the motion between the two eyes; the dark adapted image is delayed by several hundred milliseconds! Especially obvious if I focus at distance so I have a double image of the finger. Explains the strong Pulfrich effect.
  4. Noise 2: Just looked at some high frequency gratings. With the dark-adapted eye, the noise was very interesting, looked like waves moving along the grating orientation, i.e. along the bright and dark bars there’s a sort of undulating, grainy fluctuation.
  5. I still have foveal vision and color vision, but both are very weak. Dim foveal details are invisible. High contrast details (text, the high frequency gratings) are low contrast, smudgy..
  6. Motion is kind of irritating, I think because it brings about lots of uncomfortable Pulfrich-type effects. Even eye movements over a page of text can be bothersome, because there is always an accompanying, delayed motion. I’m guessing that the saccade cancellation is being dominated by the light-adapted eye, and so I’m seeing the dark-adapted saccades. I don’t notice a depth effect, but walking around in the hallways I do feel kind of unsteady, maybe because of motion interfering with stereopsis. If objects are still, stereopsis seems to be okay.
  7. If I take vertical and horizontal gratings (64c/512px), add them together, then look at them at 25% contrast from about 30cm (here at my desk), I don’t see a compound grating – I see patches of vertical and patches of horizontal. I’ve never noticed this before; I wonder what differences there are with scotopic vision and cross-orientation suppression..
  8. I tried to watch my light-adapted eye move in a mirror, but the dark-adapted eye just couldn't see well enough. I think a weaker filter would make it possible.

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