Opinions using a Sigma 18-35mm 1.8 Nikon with Speedbooster on GH4?

[Edward Calabig]

I'm contemplating a GH4 with a sigma 18-35mm or a Voigtlander 17mm. I'd really like the versatility of the range but not sure how the sigma would hold up when it comes to cropping. I'm looking at getting a GH4 strictly for architecture and cropping during interviews and speakers during events. This leads me to another question. About how much can you crop the image in 4k before you start to see image degradation?

Thanks!

[Alastair Traill]

Hi Edward,
The Metabones Speed Booster reduces the focal length of the lens whereas you seem to be wanting to effectively increase focal length by cropping. In this case you may be better off with an adapter that is optics free (and cheaper) so that you get the full 18-35 mm of the Sigma 18-35. The GH4 has an EX Tele Conv. Func(tion) that more than doubles the image size without loss of quality which may be of interest. However it does not work in 4k.

[Edward Calabig]

Ah great I did not know that! Thanks.

[Kent Jakusz]

Edward;
4k is 4x the resolution of 1080 so if your output is 1080 I believe you can crop 100% and maintain the same resolution as 1080.

Don't take this to the bank however.

Kent

[William Hohauser]

4K is a little over twice the size of 1080 HD which is slightly less than 2K. So you can conceivably take a 4K file and zoom in 200% in an HD timeline without losing detail.

[Rob Hargreaves]

What would the focal length and aperture (full frame equivalent) be for the Sigma 18-35mm 1.8 Nikon with Speedbooster on GH4?
Any actually using this combo, and I want to compare versus SLR magic 25mm f/0.95

[Kevin McRoberts]

I use the Sigma 18-35 boosted and unboosted on GH2 and AF100... it's a very very very good bit of glass.

Caveats... it's large, so unbalances the GH cameras a bit - not unusably so. Also, make sure you get a good quality adapter. I have two glassless adapters from Fotodiox, one "pro" and one not so pro. The non-pro version renders the lens varifocal. With the Fotodiox Pro adapter and the Speedbooster, the lens is parfocal (Metabones also makes a non-boosted Nikon G adapter with a far better iris ring design than competing models). While the focus ring doesn't have hard stops (it does have 'soft stops'), it's fully manual and repeatable, and works well with a follow focus when desired.

Boosted, the lens becomes: [18-35 f1.8]*0.71 = ~13-25 f1.3
On standard 2x crop, FF equivalent would be 26-50mm. On 2.3x 4k crop, FF equiv would be 30-58mm

Other similar lenses I own are the Voigtlander 17.5, Leica DG 25/1.4, and several boosted/unboosted Leica R primes (28/2.8, 35/1.4, 50/2). Have to admit I don't use them much lately, it's too damn easy to just pack the Sigma and two adapters and have everything I need in a single 1-lb package. I use the PL25/1.4 more than the others in a GH2-based fly pack for small jobs, based its small size and quick autofocus.

[Bo Skelmose]

Hi Thanks for info here.
I miss a wide angle and I have considered the panasonic 12-38 but maybe the sigma will do almost the same. with the use of the speedbooster?

[Kevin McRoberts]

Sigma will cover roughly the same focal lengths, and be faster, but will require an adapter change to reach the upper/lower limits (13-25 with SB, 18-35 w/o). It's also much larger and has auto-nothing.

Lumix 12-35 wins from a convenience standpoint, auto features work amazingly well on GH4, I'd stick with it if I never needed to go faster than f2.8

[Jeroen Wolf]

Originally Posted by Kevin McRoberts

I use the Sigma 18-35 boosted and unboosted on GH2 and AF100... it's a very very very good bit of glass.

Caveats... it's large, so unbalances the GH cameras a bit - not unusably so. Also, make sure you get a good quality adapter. I have two glassless adapters from Fotodiox, one "pro" and one not so pro. The non-pro version renders the lens varifocal. With the Fotodiox Pro adapter and the Speedbooster, the lens is parfocal (Metabones also makes a non-boosted Nikon G adapter with a far better iris ring design than competing models). While the focus ring doesn't have hard stops (it does have 'soft stops'), it's fully manual and repeatable, and works well with a follow focus when desired.

Kevin, I just got the Sigma 18-35 f1.8 Canon mount to use with my Speedbooster on my GH4. Never even considered using a plain adapter but your post made me realize I could make this lens even more versatile with a slight investment for a simple EF to M43 adapter.

Does this work flawlessly? Do you still think the Fotodiox Pro adapter is the best way to go? No artifacts, vignetting or whatever?