Problem shooting day to night timelapses with 10 stop ND filter.. Thoughts please

[Brendan Isaac]

Hey guys - trying to shoot some slow shutter timelapses with my 7D. I am using my 8-15mm canon fisheye zoom with some kodak wratten 2 ND 3.00 (10 stop) optical gel behind the lens. Shutter priority 15 second exposures - the aperture starts at around f20 during the day with hope that as the light drops it will open up to f4 gradually. ISO is set to auto so it stays at iso100 until it needs to rise once the aperture as reached f4. My problem is that metering seems to be failing and not opening the aperture as the light falls. Any thoughts?

 

[paulherrin]

probably a good question for the 7d forum...

install magic lantern. watch some tutorials.

 

[Liam Hall]

Too much ND. Also, I'd advise shutter priority, so light trails get longer as the light falls rather than the depth of field getting shallower. At f/20 on a 7D you're going to suffer from diffraction, so much better to open up a few stops. Try one in aperture priority, using spot or centre weighted metering. You'll need to remove the flicker in post.

 

[Brendan Isaac]

Thanks for the useful response Liam I will give it a go