Panasonic GH4 7-14mm f/4 vs Tokina 11-16mm f/2.8 + Metabones Speedbooster,

I love my wide angles, and getting the Panasonic GH4 I opted to get myself the Widest lens it has straight away as my first lens, the Panasonic 7-14mm f/4 (which is supposedly the equivalent of 14-24mm on a full frame sensor in terms of Field of View)

This is an ultra wide angle lens and possibly the widest i have ever used, and with no distortion that can be seen on the panasonic raw files.  However it has 2 big problems.

its an f/4
and
it has a bulbous end.

A professional lens is usually considered to be an f2.8 or brighter.
Full Frame Nikons have a 14-24mm f/2.8,
 full frame Canons have a 16-35mm f/2.8
Cropped camera have the awesome Tokina 11-16mm f2.8

the difference between an f4 and an f/2.8 is "1 Stop"  A single stop means it requires TWICE as long to capture the same exposure. (or twice the iso)

Meaning a Nikon shooting at 14mm at iso-800 at f/2.8 taking a photo at a 1/25th of a second would require the Panasonic to extend its shutter opening time to 1/12th of a second.... which if doing video is not possible so would require to boost the iso up to iso-1600... which really degrades image quality and brings in digital noise.

I can get an adapter for my Tokina 11-16mm and put it onto the Panasonic.  The fotodiox adapter costs £25 and is just a simple thing but has an aperture control which is handy.  But of course with this you lose any autofocus or VR control you have with any lens. Then due to the 2x crop of the sensor means that the 11-16mm has equivalent FOV is that of an 22-32mm.

However. If I spend a painful amount of money and get myself a Metabones Speedbooster, I can get the FOV back to close to what it was on a normal 1.5crop sensor camera (i.e. nikon d3300, 5200, 7100 etc)  Metabones gives the calculation of x0.71  so my lens being 11mm goes to 22mm then is x0.71= 15.6mm
So still brighter and wider than my Canon 16-35mm

But not only that!
The Metabones Speedbooster also brings in more light via clever optics also known as witchcraft. and it increases the exposure value by 1-stop.
So now it is "15.6mm f/2 " brighter and wider than my Canon 16-35mm! and making it a whole 2 STOPS (4 Times) faster than the Panasonic)
However I am still restricted to manual focus but if doing filming that is what you want anyway.

so here are screen grabs from the tests,
Camera set in the same position, set at maximum aperture size) 1/25th of a second iso 400

First shot Panasonic 7-14mm @ 7mm (14mm equiv) f/4

Tokina 11-16mm with Photodiox adapter

@11mm (22mm equiv) f/2.8

Tokina 11-16mm with Metabones speed booster

@11mm (15.6mm equiv) f/2

The third and final bonus is that the Tokina has a flat end, meaning in can put circular polarisers and ND filter grads on the front. BOOM WIN!

Doing the maths.
Tokina 11-16mm + Speedbooster = Manual focus, 15.6mm f/2 @ Around £800
Panasonic 7-14mm = Autofocus, 14-24mm f/4 (Around £800)



Links

Speedbooster   Metabones Nikon G to Micro Four Thirds Speed Booster   http://amzn.to/1ztQGCY (£400)

Fotodiox adapaters http://amzn.to/1Bl6k65  

Tokina 11-16 (nikon mount) http://amzn.to/173LBuw  around £490

Canon mount http://amzn.to/173LGyg (around £580)

Nikon 14-24mm http://amzn.to/1y4cTw2 (£1200)

Canon 16-35m http://amzn.to/1rxBDKM (£1100)

Panasonic GH4 http://amzn.to/1y4d6zx

panasonic 7-14mm f4 http://amzn.to/173McfN (£800)