Stab Posted September 3, 2015 Share Posted September 3, 2015 I'm using the GH3 since the day it came out and I'm still very happy with the footage. I am skipping the GH4 and might upgrade to the GH5 once it (ever) arrives. Anyway, I'm also using a Speed Booster (0.71x) and the Sigma 18-35mm. Even at 18mm, there is no vignetting with this setup.I am considering selling my Speed Booster and upgrading to the XL version. I know the difference is only 10%, but I always wanted the Sigma 18-35mm to be a tad wider. And here is the solution The question is, does anyone know if the this lens vignettes at 18mm with the Speed Booster XL while in 1080p mode of the GH3 / GH4? I know that it doesn't do it in the 4K cinema mode, but that has a crop factor of 2.35. I guess the GH3 in 1080p has a 2.0x crop factor so it might get tricky there.Anyone with this setup can tell me if it vignettes? Thanks! Quote Link to comment Share on other sites More sharing options...
MattH Posted September 3, 2015 Share Posted September 3, 2015 The short answer it will just fit without vignetting. The GH3 with the 0.64 speed booster will give you an effective crop of 1.3317. If you google sigma 18-35 full frame you will get examples that show you the full image circle.like here for example: https://witonosfreestyle.wordpress.com/2013/09/09/hands-on-review-on-sigma-18-35mm-1-8-dc-hsm/By measuring that image on your screen you can work out where a 16:9 1.3317 crop image would go. By my measurements it just fits without vignettingOf course, you will be getting a lot of light fall off wide open. (note the difference between fall-off and vignetting).I cant guarantee it will work, of course, but I would bet £50 on it. sanveer 1 Quote Link to comment Share on other sites More sharing options...
sanveer Posted September 3, 2015 Share Posted September 3, 2015 The short answer it will just fit without vignetting. The GH3 with the 0.64 speed booster will give you an effective crop of 1.3317. If you google sigma 18-35 full frame you will get examples that show you the full image circle.like here for example: https://witonosfreestyle.wordpress.com/2013/09/09/hands-on-review-on-sigma-18-35mm-1-8-dc-hsm/By measuring that image on your screen you can work out where a 16:9 1.3317 crop image would go. By my measurements it just fits without vignettingOf course, you will be getting a lot of light fall off wide open. (note the difference between fall-off and vignetting).I cant guarantee it will work, of course, but I would bet £50 on it.Wow. Matt, that's a first for eoshd. That's the Official First Wager here ... ;-) Quote Link to comment Share on other sites More sharing options...
Stab Posted September 4, 2015 Author Share Posted September 4, 2015 So with the Speed Booster XL, the GH3 turns into a APS-H camera. Maybe someone tried the Sigma 18-35 on a 1Dc or something? Quote Link to comment Share on other sites More sharing options...
Liam Posted September 4, 2015 Share Posted September 4, 2015 Yeah, I'd heard and seen some results that on aps-h it has some rolloff but no vignette. But I thought the crop became slightly bigger than aps-h with an xl. Are you sure it's 1.3317x? I heard 1.28x. Might still work, and I might be wrong http://www.fredmiranda.com/forum/topic/1225718 Quote Link to comment Share on other sites More sharing options...
MattH Posted September 4, 2015 Share Posted September 4, 2015 Yeah, I'd heard and seen some results that on aps-h it has some rolloff but no vignette. But I thought the crop became slightly bigger than aps-h with an xl. Are you sure it's 1.3317x? I heard 1.28x. Might still work, and I might be wrong.1.3317 is correct if you are comparing video modes.I suppose in this case (even though it will give the same result) it makes sense to compare the 16/9 diagonal of the gh3 with full frame 3/2 diagonal. Which (with the 0.64 speedbooster) actually gives 1.395 crop. This in theory makes it easier to test on the dog picture here: https://witonosfreestyle.wordpress.com/2013/09/09/hands-on-review-on-sigma-18-35mm-1-8-dc-hsm/You measure the diagonal on your screen, divide it by 1.395. You can then see if that fits within the circle of confusion.Strangely, in the dog picture, the 'circle' seems to have a greater diameter on the diagonal than it does horizontally. So either the lens hood is on or the lens has an ellipse of confusion. If you are talking about 4:3 stills coverage then yes the relevant crop is 1.28 and so you will get vignetting with stills. Obviously requiring either a slight zoom-in or a crop. Quote Link to comment Share on other sites More sharing options...
TheRenaissanceMan Posted September 4, 2015 Share Posted September 4, 2015 The GH3's crop factor in 16x9 is 2.08. Multiply by .64 and you have a crop factor of 1.33. So you're almost at APS-H and a little bigger than S35. Quote Link to comment Share on other sites More sharing options...
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