# After images while reading

**URL:** <https://boards.straightdope.com/t/after-images-while-reading/687148>\
**Category:** Factual Questions\
**Created:** [April 28, 2014, 2:18am UTC](https://boards.straightdope.com/t/after-images-while-reading/687148 "2014-04-28T02:18:46Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\
**Post date:** [April 28, 2014, 2:18am UTC](https://boards.straightdope.com/t/after-images-while-reading/687148/1 "2014-04-28T02:18:46Z")

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When I read in a dark room in my iPad Kindle app, I tend to get afterimages of the page, even though I have the brightness turned down. This doesn’t happen if I read a paper book or my e-ink Kindle with a book light. It doesn’t seem that the iPad is any brighter, even though it is a light source.

Why do I get the afterimages with the iPad?

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**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\
**Post date:** [April 28, 2014, 2:50am UTC](https://boards.straightdope.com/t/after-images-while-reading/687148/2 "2014-04-28T02:50:28Z")

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As I think you know, the answer is that you are staring at a light source. It probably _is_ brighter than your book under a book light, or, at least, contrasts more with the dark surroundings, and in such a way that the edge between light and darkness is much sharper. An afterimage with a relatively sharp edge is going to be more noticeable than a more diffuse one.

Are these negative afterimages, or positive ones?

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<div class="post-metadata">

**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\
**Post date:** [April 28, 2014, 12:31pm UTC](https://boards.straightdope.com/t/after-images-while-reading/687148/3 "2014-04-28T12:31:43Z")

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Negative. The black text creates an afterimage of white text on a dark background that kind of floats around. It’s not so disruptive that I can’t read, but is occasionally distracting.