Vingetting Speebooster + 18-35 + BMPCC4K?

I was noticing some fairly apparent vignetting when shooting against a solid whiteish colored wall with the BMPCC4K + Sigma 18-35 + Speedbooster Ultra 0.71x. I also noticed some fairly "weird" bokeh when full wide open on this combo...

I'm wondering if this is more due to this lens or the Speedbooster or...?

It's still usable of course, and not very noticeable when not shooting against a solid color wall or something like that, but I'm still curious what is likely the culprit here.

I attached some cell phone shots of my monitor to show what I mean. Overcast mid-day, white wall, no matte box, ND, etc. Shooting in UHD 4:1, 35mm, etc. The camera might be a little underexposed to show the effect more.


Anyone else notice this?

IMG_4715.jpeg (128.76 KiB) Viewed 929 times

IMG_4716.jpeg (190.2 KiB) Viewed 929 times

Yes, you are pushing to to the edge of the lens’ projected 8amge circle at 18-20mm withnthe Speed Booster and full gate on the Pocket 4K, so you are going to have some soft vignetting.
Cheers

Yes, you are pushing to to the edge of the lens’ projected 8amge circle at 18-20mm withnthe Speed Booster and full gate on the Pocket 4K, so you are going to have some soft vignetting.
Cheers

Thanks Denny, thats what I figured and would somewhat expect it at the 18-20mm end, but I'm still surprised its that noticeable at 35mm...I hadn't ever seen it on GH5S, etc but I guess the slightly larger sensor of the BMPCC4K is going to push it to the limit anyways. Would this still happen using a lens with more coverage, or is this more due to the Speedbooster?

I believe that’s a function of the lens when combined with the SpeedBooster. If you were using a lens designed for a ‘full frame’ sensor, I don’t think you’d see a vignette.


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Yes, you are pushing to to the edge of the lens’ projected 8amge circle at 18-20mm withnthe Speed Booster and full gate on the Pocket 4K, so you are going to have some soft vignetting.
Cheers

Thanks Denny, thats what I figured and would somewhat expect it at the 18-20mm end, but I'm still surprised its that noticeable at 35mm...I hadn't ever seen it on GH5S, etc but I guess the slightly larger sensor of the BMPCC4K is going to push it to the limit anyways. Would this still happen using a lens with more coverage, or is this more due to the Speedbooster?

different speed booster/lens mount adapters will give you different results. I had a cheap ef to mft adapter that had vignette, then i got a cheaper one with built-in NDs that had no vignette

Yes Chris, I agree, different units have a different focal conversion. My experience was with the Metabones SB, which is the one I was referring to.
Cheers