Author Topic: Focus pulling at dark  (Read 964 times)

Offline Alex_Myopic

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Focus pulling at dark
« on: February 23, 2016, 01:24:21 AM »
At very dark conditions we loose about 1D of visual acuity (night myopia) due to expansion of the iris. Jake also recommends focus pulling at closer distance because of depth of field by wearing sunglasses sometimes. In this case we have high contrast.

https://www.youtube.com/watch?v=RCA2I2VUn4w

Now I made a very interesting observation. At night with open lights sometimes I can hardly read small subtitles. Then I close all the lights (no sunglasses) and the problem remains but after about 10-15 minutes of trying to dissolve the blur (focus pulling) and sometimes blink hard, the subtitles become very sharp even with no light at all and this lasts. So even with the pupil expanded I can achieve sharper vision than before. Maybe it is because with no lights there is high contrast in the tv, since then the tv is the only source of light. This way the eye can focus better (something like active focus) just in the central vision, the point it wants to dissolve blur.

Offline Blue Eyes

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Re: Focus pulling at dark
« Reply #1 on: February 23, 2016, 11:33:28 AM »
Hi Alex

I would add that I find it much easier to release tension around my eyes when it dark.  I have found that you do need some light for something to focus on though. So not pitch blackness.

I have been out many times in the dark streets just to work on my eyes which I feel is the best way of improving night vision. I get the impression its not really done much by people.  However every time I do it my eyes love it and know I should do it more often then I do.

Mike

Offline Alex_Myopic

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Re: Focus pulling at dark
« Reply #2 on: February 24, 2016, 02:05:35 AM »
Hi Blue Eyes,

I agree the light coming from the tv helps focusing much, it's not like focusing on a printed page at dark or very low lighting.