Flat problem

[Ags]

I thought I would shoot flats for my 55mm lens using my laptop screen - but the results are rather stripy... what went wrong and how do I avoid this in the future?

I've stretched the image to make the problem more visible.

[steppenwolf]

This could be a sync issue. I suspect that the screen has a refresh rate that is interfering with the image exposure length - think wagon wheels on old cowboy movies ...

[Psychobilly]

The shutter speed is a bit to fast so you either need to dim the screen - try adjusting the brightness but this can make matters worse or use sheets of paper as diffusers...

Peter...

[Ags]

Thanks all. I am starting to think I'll never shoot a correct flat!

[Ags]

I tried my monitor on min, mid and max brightness and the stripes disappear at max brightness, although that might just be luck as the exposure at that setting was 1/2000.

Maybe I need one of those flat panels. However, I have never had stripes when using the iPad as flat field (although I was taking flats for a 400mm lens at the time). Using the iPad would involve the risky undertaking of wresting the iPad from its addict/owner.