<p>Your calculations are right.</p>

<p>But if you take a look here: <a href="https://www.fredmiranda.com/forum/topic/1279757/0" rel="nofollow noreferrer">https://www.fredmiranda.com/forum/topic/1279757/0</a>
The vignette is much stronger. With the images provided by Aloicious I get a vignette.</p>

CC BY-SA 4.0
2019-01-22T20:19:54.647Z
2019-01-22T20:19:54.647Z
Tim
<p>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.</p>

<p>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?</p>

<p><a href="https://i.sstatic.net/nj0sj.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/nj0sj.png" alt="Image Circle"></a></p>

<p>I found this image on <a href="https://www.the-digital-picture.com/Comparisons/Sigma-18-35mm-f-1.8-DC-HSM-Lens.aspx" rel="nofollow noreferrer">https://www.the-digital-picture.com/Comparisons/Sigma-18-35mm-f-1.8-DC-HSM-Lens.aspx</a> 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?</p>

<p>Also, does anybody know if it has a direct focus or a servo focus?</p>

<p>Thanks!</p>

<lenses>
Sigma 18-35mm, f/1.8 DC HSM ART Image Circle / BMPCC4k with 0.71x
Timothy Lukas H.
# Sigma 18-35mm, f/1.8 DC HSM ART Image Circle / BMPCC4k with 0.71x

(Asked by: username_0 on 2019-01-20)

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](https://i.sstatic.net/nj0sj.png)](https://i.sstatic.net/nj0sj.png)

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?

Thanks!

**Tags:** lenses


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## 1 answers

### Answer by username_1 on 2019-01-22. Score: 2 | Accepted answer

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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