New HDR time-lapse challenges at f11

So with the first few HDR skies shot, merged and test rendered into animations, I was quietly confident that this might not be quite as hard as I thought.

Not Quite!

My assumption that people would prefer slightly reduced dynamic range (shooting at f3.5 iso 100) vs the full dynamic range (iso 50 @ f11) for a reduction in lens flares was not correct. Good thing I have testers!

Shooting at f11 creates a number of new problems that I’m about to begin tackling. This will probably set me back another couple of weeks or so, especially with this weather forecast in Adelaide being rain all week long.

Flicker

Shooting anything but wide open causes flickering due to tiny changes in the shutter diaphragm aperture. You’d think that every time you shoot at 1/1000th at f11, that’s exactly what you’d get, but unfortunately that’s not the case. The aperture will actually open a slightly different amount every time, I suppose its not easy to make this precise, or camera manufacturers don’t see it as a problem for most cases (and they’re right).

Deflickering isn’t actually that difficult if you use software like LRTimelapse, but then using the resulting deflickered brackets might still cause problems at the merging stage, that’s something I’m about to try out.

Dust

A stopped down aperture also shows up dust. I thought that by now someone would have made an in-camera dust removal solution that works, but they haven’t! So I’m going to have to go back to my old dust removal kit I used with my 20D (or get a new one, I think there could be issues with using some cleaning solutions on a sensor that has an in-camera dust removal system). This is something I’ll have to fix at all costs, as we can’t have dust specks in the sky. Hopefully a combination of dust removal on the sensor and in Lightroom will solve this without too much problem.

You can see the dust spots on the above image as visualised by Lightroom – each circle is where I’ve removed either dust or a lens reflection blob.

Lens Flares

The actual streaking around the sun isn’t quite as bad as I thought it’d be, but the reflections are. I’m going to have to see if LRTimelapse can tween the positions of spot removal between key frames to remove these. I’m a huge fan if it can!

Promote Limitations

While I love this particular piece of hardware, I may have to try a tethered laptop instead to capture the entire range of the sun as well as the bright blue sky. Although I have pretty low hopes for that solution for various other reasons.

Now that I’m shooting f/11 with the ND filter, a bright blue sky is still under exposed with a 2 second long exposure. When you then do that 2 EV jump again, you’re looking at 8 seconds, which means huge cloud blur and ghosting, as well as greatly increased shooting time over all.

Another option might be to shoot 1.7 EV steps, which results in a 4 second end exposure. That’s still unfortunately quite slow, and means we shoot 10 brackets per sky.

Everything is not *quite* there is it? If I could only magic an ISO change out of the Promote on that 2 second exposure on the end, it’d be perfection! Or shoot at f3.5 and magic an aperture change at 1/8000th down to f11. I think the most optimal solution probably would be to keep the aperture at f3.5 all the way from 2 seconds to 1/8000th, and then change aperture – that way we have a steady 2 EV step without any flickering and reduced lens flares/dust.

Sigh! I’m still actively bugging the poor Promote guys in the hopes something can be done, but at the end of the day we might have to live with a sky that is either slightly banded from pushing the brightness, or slightly low on dynamic range, or that has somewhat blurry clouds overhead.