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Does APS-C glass vignette on GH2 + Speedbooster?
  • SangyeSangye

    I just sold my Voigtlander and ordered a Nikon-MFT Speedbooster, and am planning on buying a Sigma 18-35mm f/1.8 to use with it. However, I just ran the math and am a little confused.

    If the crop factor on the GH2 is 1.86, and the MBSB effectively reduces the crop factor by 0.71, then the new virtual crop factor should be 1.86*0.71 = 1.32. 1.32 is more like APS-H size, not APS-C. Doesn't that mean APS-C glass will vignette?

    Another way to look at it would be to begin with the Nikon APS-C crop size, 1.5, and divide it by the MBSB coefficient, 0.71. This returns 2.11. If my math and my understanding is correct, that's the maximum sensor size, expressed as a crop factor of full frame, that a APS-C Lens with a Speedbooster should cover. So it should cover the BMCC, but not the GH2.

    Am I thinking about this right, and will I encounter significant vignetting if I tack an 18-35 with a MBSB onto my GH2?

  • 17 Replies sorted by
  • inqb8trinqb8tr

    Your maths is right, but I think that it is lens dependent. Most of the lenses made for aps-c format have bigger image circle, for example tokina 11-16 covers full frame at 16mm, and at 11mm it vignetess (on ff), but still I doubt that it would vignette on the Speedbooster. It will all end up on user experience and reports, same as for c-mounts, this one does and that one doesn't vignette. Something like that.

  • adamquesadaadamquesada

    Regarding that I've read that the Tokina 11-16 + speedbooster vignettes @11mm on the GH2 but not GH3.

  • grisnjamgrisnjam

    Page 7 of the "18-35mm F1.8 Sigma DC zoom lens, $799" thread:

    http://www.personal-view.com/talks/discussion/6733/18-35mm-f1.8-sigma-dc-zoom-lens-799/p7

    Shows the extent of vignetting with the booster and Sigma on the GH2 (post by SeekingHeartwood, it's gone by 21mm).

  • adamquesadaadamquesada

    Does not vignette on the GH3 in video at all ;) sweet

  • tetakpataktetakpatak

    @Sangye Chris Brandin and few more guys (incl. myself) have had a discussion in one thread some months ago and we've spent a bit of time measuring the real crop factor of the GH2.

    It seems to be quite exactly 2x
    I did myself some tests on improvised test charts and never got factor beyond 1.92
    Saying that, the lowest value may have been my counting error.

  • itimjimitimjim

    Tokina 11-16/2.8 with SpeedBooster and GH2 vignettes at 11mm. However, it's gone at about 11.5-12mm. Not really a problem. The edges are quite mushy though, which is a problem.

  • DenzoDenzo

    Been following this topic but still don't get what lenses cause vignetting / no vignetting.

    Is there anybody who could't explain the math or the rules behind this / How do I know if a lens in general causes vignetting or not besides testing it on my camera (GH1)?

    Thanks a lot!

  • kurthkurth

    Everybody wants to know about the sigma. I'd like to know if the tamron 17-50 works ?

  • grisnjamgrisnjam

    @Denzo

    The Speedbooster is designed to work with FF lenses so a FF lens will always work. If a APS-C lens or other target sensor size lens works depends on the image circle they cast which varies from lens to lens. As such if the lens is designed for something smaller then FF the only real way to know is to test it.

  • DenzoDenzo

    @grisnjam

    sounds interesting but what do you actually mean with FF ? Could you please explain things a little more general for noobs like me :) thx

  • grisnjamgrisnjam

    Full Frame or the classic 35mm film standard. See here for more info on sensor crops:

    http://digital-photography-school.com/full-frame-sensor-vs-crop-sensor-which-is-right-for-you

    If the lens is designed for a full frame camera it will work. Lenses optimized for smaller sensors (APS-C, ect) will vary.

  • DenzoDenzo

    Thanks a lot grisnjam..... It took me a while, but now I see the relation of sensor size, the lenses focal lenght, lens diagonal size and size between sensor and lens...... :D

  • vpeterovpetero

    @Kurth I have the tamron 17-50, the vignette is tiny similar to Page 7 of the "18-35mm F1.8 Sigma DC zoom lens, $799" thread:

    http://www.personal-view.com/talks/discussion/6733/18-35mm-f1.8-sigma-dc-zoom-lens-799/p7

    I think its usable especially if you plan on widescreen aspect ratio such as 2.33 : 1 or 2.35 : 1

  • kurthkurth

    @vpetero

    thanks. Looks like the non-multi-aspect ratio sensor of the gh3 ( as well as the g6 ) is ok for shooting 1080 video. Am I correct in that assumption. That would mean that the tamron with speedbooster would be about the best choice for a 24-70 f2 lens available. Sure wish metabones would release the eos w/contacts version. That would open up a lot of possibilities. I assume you have the nikon version. How is it to change aperture on the tamron ?

  • vpeterovpetero

    @kurth

    Yes I have the nikon G version. its got an aperture ring on the adapter it-self and for what its worth I think it works fine. Your right on the GH3 I assume there shouldn't be any vignette.

  • T2iRebelvsGH2LOUIST2iRebelvsGH2LOUIS

    18-35mm F1.8 Sigma DC zoom lens is this lens available for the Panasonic GH2 now to date 7.5.2014 ???

  • SangyeSangye

    The great thing about the Nikon G version is that it gives any lens a stopless aperture. This is huge, and makes it a pretty obvious choice in my book.

    After using the 18-35mm on a Speedbooster as my primary lens for most of what I've shot on my GH2 in the last 4 months, I can say that it really works perfectly. Vignetting is only bad when using the included lens hood while between 18 and 24mm or so. There is very slight vignetting at 18-20mm without the lens hood, but it's hardly noticeable and has never been an issue for me. There are many popular "stock" lenses with worse vignetting than this setup.

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