Testing the sharpness of the Rokinon Cine 85mm with Lens Turbo on the Pansonic GH4
Since I last posted a review of the Lens Turbo, a cheap Metabones Speed Booster clone from China, my kit has undergone some big changes. I’ve upgraded my trusty GH3 to the Panasonic GH4, and instead of a motley collection of old Canon FD lenses, I’ve invested in a complete set of Rokinon Cine lenses.
The main reason for switching lenses had little to do with image quality … I’ve always liked the “classic” look from my old Nifty Fifty … and everything to do with practicality. DSLR’s and the still lenses that accompanied them radically changed the low budget film landscape. Enthusiast filmmakers like myself could work with an image quality that was unimaginable a decade ago…but at a price. Usability. If you’ve never shot with geared lenses with a long throw and a solid follow-focus, well, you need to try it.
That said, there was no way I could afford one Zeiss cine lens, let alone a full compliment of primes. I had been following discussions about the Rokinon cine lenses online for some time. As with almost any topic on the Intarwebs, opinion ranged from ‘godsend‘ to ‘unusable.‘ I needed to rent one for myself. So I did. I was sold. Period. `Nuff said.
I now own the full compliment from the crazy wide 8mm the whole way up to the 85mm (which is more than long enough for the narrative style of work I do.) In addition to the aforementioned benefits of any cine style lens, it’s also really nice to have a matched set of lenses. The images belong together, the handling works the same. It’s just makes things simpler, and on set, simpler is better.
When renting the Rokinon (from the great guys and gals of Lensrentals.com), I also rented the Metabones Speed Booster. Which is a “lovely bit of kit“, as Master Philip Bloom would say, but $500 for an adapter just isn’t in my budget. $100 for a Lens Turbo is more compatible with my wallet. I had read online that these knock-offs couldn’t focus wide open and would be a disaster. Since I had good luck with a cheap Chinese knock-off for my Canon FD mount, though, I decided to try one out to match the Nikon mount of my new Cines.
What’s the verdict? Can this budget combo stand-up to 4K pixel peeping? Let’s go to the instant replay!
Wide open at T1.5 (if you’re not familiar with the term, a t-stop is simply a truer indicator of the light making it through a lens than an f-stop as it includes transmission loss. It is common for cine-style lenses to be marked this way.) there is very clearly a lot of bloom. How much of this is from the lens, and how much is exacerbated by the adapter, I can’t say. I do have a simple mechanical adapter on it’s way, so I’ll update this post when I can say for sure. What I can say, is that this level of blooming is consistent with how many fast lenses perform wide open. I dare say its a hair better than my personal standard, the Canon 50mm 1.4. Also note the fine detail being resolved through the diffusion/glow? I think its important for people to understand that wide open these lenses – while very “diffused” – are not “unfocused.” I’m not trying to apologize for the image, and I’m not saying that I would want images to look like this in normal circumstances, but I do think it is worth noting that a diffused image is not the same as saying the image is “soft“.
Stop down to T2.8, ISO 400 and the bloom goes away (actually, it’s gone by T2.) This is an image I’m happy to work with any day of the week. It’s plenty sharp, even at 4K.
T4. ISO 800. A tad sharper perhaps, basically the same image.
T8. ISO 1600. Technically, this may be the sweet spot for sharpness, but to me the difference between 2.8 and 8 is negligible. ISO 1600 is where I start feeling the need to apply Neat Video to tame the noise. I did not do so in this case in order to not distort the comparison. (For those looking at the GH4, note the somewhat natural look to the 4K noise…it’s not nearly as ugly as traditional video noise.)
- Why Nikon mount? Simply because it’s the most future proof, adaptable mount. No matter what camera I move to in the future, it’s likely I’ll be able to bring these full frame lenses forward. Glass is an investment that should outlast any one camera.
- Highly recommend the Spydercheckr and Spydercube to everyone. Would never shoot without one. Makes color correcting a breeze. Makes matching cameras less of an exercise in frustration.
- My lighting was a bit crazy…okay it was totally crazy. It was a mix of tungsten kitchen fixtures, a daylight balanced fluorescent flower, an Alzo 3000 LED spotlight bouncing off the ceiling and a super-cheap LED panel hitting the bottles. Not the way to get good color. I just needed to get light in a dark kitchen since I was only testing sharpness.
- I’ve done a lot of testing on the GH4’s picture profiles, and I can say with some confidence that the combination of CineD (-5,-5,0,-5,2) with a slight shadow/highlight curve (+2,-2) gives the most “gradable” image. It will hold up in post as good as any 8-bit image can. It’s not the most natural image…there are better profiles for that…but the settings do store the most usable information.
- I did light color correction to all of these images, equally. What I consider the level of “finishing” that I do to even the simplest, fastest job. This does include detail enhancement (as sharpening was completely off in camera.) Again, exact same amount done to all images.