widefield flats

[jambouk]

How best to take flats when just using a DSLR and a camera lens? The white t-shirt trick just results in a nearly in focus t-shirt as it's a very wide angled lens.

Thanks for any ideas.

James

[Psychobilly]

I struggled with skyflats with wide angle lenses.

I use a white screen displayed on the laptop/desktop and move the camera around randomly between shots...

I have also got a USB powered A3 LED lit  tracing panel I run it of some Kodak  Li-ion batteries - the ones you can use to charge your mobile devices...

http://www.ebay.co.uk/sch/i.html?_sacat=0&_nkw=tracing+led&_frs=1

http://www.ebay.co.uk/itm/Kodak-2000mAh-Power-Bank-Pack-Portable-USB-Battery-Charger-For-Mobile-Phone-/201370562571?hash=item2ee29ef00b

Info and discussion in this thread http://stargazerslounge.com/topic/236672-decent-quality-flats-for-dslr/?p=2567108

Peter...

[jambouk]

Peter,

Thanks for that. I've tried with the laptop screen on white, but the histogram is very broad, maybe covering 0 to 33% along the x axis. Reducing exposure time then doesn't leave a gap at 0% saturation.

I'll have a go at stacking with and without these flats and see what happens.

Thanks.

James

[Psychobilly]

What lens are you using and at what aperture...?

Some ultra-wideangle lenses can  have a stop or more of vignetting when used wide open a stop is 50% reduction and would explain the broad histogram....

Peter...

[jambouk]

Samyang 24mm. f/2.

The laptop flats did a pretty good job at helping with the vignetting.

Thanks.

James