Hi Gunther,

I've got a sequence that I shot the other day that has progressive (and obvious) jumps in vignetting due to aperture ramping.

I was shooting a sunset into twilight using a Samyang 24mm f/1.4 lens, and the D750 was being ramped with DSLRDashboard (of course, shutter and ISO were being ramped too).

I started the sequence in the daytime at f/16, and finished at f/1.4. With each change of aperture from around f/4.5 to f/1.4, I can see a sudden extra vignette being added (it's not too heavy, but it is obvious), and it happens right at the 2*/3* frames (the ones with the aperture changes). This is after I smoothed out the overall exposures as usual using the HG wizard in LRT.

Here's the video, the vignettes can be seen starting just after 14 seconds:

https://vimeo.com/216328559

Any tips to avoid the problem? I had it happen on an important day to Milky Way sequence, and I "fixed" the vignette jumps with progressive radial filters that I added and edited manually in LR, but it took hours and still isn't perfect.

Cheers!

Chas

To prevent this I set the max aperture to f/4 and only ramp to that then continue with ISO and only ramp the aperture again when it's completely dark. It's hard to correct in post - you could try Lightrooms lens corrections, but I guess it won't make it seemlessly.

With qDslrDashboard it's easy to follow my strategy: just set max aperture to f/4 at the beginning and when it's completely dark change it to f/1.4. The rest wil go automatically.

Thanks for the info, Gunther. I'll do it the way you suggest in the future.

I've never changed the max aperture in DSLRDashboard during a sequence, nice to know that the app will notice a change like that and ramp aperture again.

One clarification: if it's full dark when I change max aperture in the app to 1.4, won't the app have already ramped shutter speed and ISO to max values? If the app sees that it can then ramp aperture to a new max value, will it do anything if the light levels are no longer changing?

And no, lens corrections in LR don't help, I tried (just in case someone else stumbles up on this thread).

Thanks again for the very useful reply,

Chas

Of course the other values will then be ramped earlier. So just wait until it's dark (but before the ramping fully ended) then change the aperture max value. The idea is that you won't see the vignetting change then so much.