I am currently figuring out which lens I should get. I found the Sigma 18-35mm, f/1.8 DC HSM ART which looks quite interesting as I want to have a nice bokeh and shallow DOF. But it is for APS-C only.

I will use the Metabones Speedbooster 0.71x on my BMPCC4k, so the crop factor is 1.349, so slightly bigger than 1.5 of APS-C. Is the image circle of the Sigma big enough to support 1.349 crop without much vignette?

Image Circle

I found this image on https://www.the-digital-picture.com/Comparisons/Sigma-18-35mm-f-1.8-DC-HSM-Lens.aspx and if I have done it right, the red circle is my "MFT" and the golden one is APS-C. Could anyone check if it's done right?

Also, does anybody know if it has a direct focus or a servo focus?


1 Answer 1


Your calculations are right.

But if you take a look here: https://www.fredmiranda.com/forum/topic/1279757/0 The vignette is much stronger. With the images provided by Aloicious I get a vignette.

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