Lens twisting to eliminate flickering on the D800 + Sigma 8mm

My time lapse HDR sky project has hit a bit of a snag, and that snag is flickering. When using an aperture setting of f11, I’m getting flickering due to the aperture opening slightly differently each time, a common problem with time lapse and stop motion when using auto lenses and anything but a wide open aperture. I need f11 in order to exposure the sun properly during the day, or for full, day-length time lapses.

Lens twisting, the solution to flickering?

I thought I had just found the solution to eliminating flickering with my D800 + Sigma 8mm. Namely, you can stop the camera (well, Canons!…) from opening/closing the aperture with every photo by disconnecting the lens from the camera. I’ve tried this on my setup, however every time I twist the lens, the aperture visibly closes right down to f22, and f22 on this lens is pretty terrible *perfectly fine, my mistake – read below on “f22”. There’s also the issue with f22 requiring huge long exposures to capture the sky properly, around 8 seconds, which causes blurred clouds.

I just wrote to Sigma:

I’m using your fisheye lens to create timelapse footage, however I’m getting flickering, caused by the electronic aperture not being 100% precise (as happens with all lenses like this).

My question is, is there any simple modification could I make to your lens to force it to use say, f11 and not be controlled by my nikon d800?

I’ve tried setting f11 on my d800, holding in the DOF preview button and twisting/disconnecting the lens, however the lens then stops down to f22.

If you have any idea how I could solve this and keep the aperture opened to f11 at all times that would be great.

Thanks very much.

I got this reply, great to know that Sigma listens and spends time to reply:

Hello Jay,

The Diaphragm on our Nikon mount lenses is mechanical and it is held at the desired f/stop by the camera body. The inconsistency is coming from the diaphragm actuating assembly in the camera. I do not know how to correct this.

So I made an incorrect assumption about the Nikon lenses having an electronic aperture system.

Nikon Fix

I’ve been talking to Gunther from LRTimelapse and he’s been a great help – he’s shown me a fix for Nikon lenses that involves placing an object into the lens aperture assembly to stop the aperture from closing down. If you shoot time-lapses, he has an ebook that covers a lot of tricks for getting good time lapses.

f22 lens issues

*edit: previously I’d shown this as an example of how the Sigma 8mm fisheye looks stopped down to f22, however it was in fact due to an inferior sensor cleaning solution I’d used days beforehand which left residue on the sensor. I’m recommending any digital photographer use Visible Dust‘s solution to avoid this:

Purple colouring and horizontal glare was caused by residue on the sensor

Go here for a comparison and to see the same frame as above after cleaning with Visible Dust’s solution (coming soon).

Last hope for day length and noon time lapses

I’m about to try out the Nikon time lapse fix now and I’ll keep you up to date. I’d all but given up hope, so thanks again to Gunther. Really at this point I have a large number of people to thank, I wouldn’t be so far along with this without a lot of help from a lot of testers, developers and artists.

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