RED Lens Test: Zeiss SLR VS Zeiss Cinema
Testing and comparing Zeiss SLR lenses and Zeiss Cinema Lenses on the Red.
For the last two years I have been using a set of Zeiss ZF SLR lenses and various 35mm adapters on projects that have smaller budgets, but still want the cinematic look of film. For the projects that can afford it, I have been renting the cinema lenses. Having used both styles of lenses I have seen the mechanical differences between the two, and now with this opportunity with the RED I had a chance to see how big of a difference, if any, there is in the image quality of each set of lenses.
To highlight the potential differences between the lens sets I settled on the following tests: sharpness, color, breathing, vignetting, and the mechanics. To keep the results consistent I decided to shoot both charts as well as a real world test. Charts are helpful for consistency and measurements, where as the real world test will show you what you actually get. The cinema glass used for this test was a set of Zeiss Superspeed Lenses (MKIII) with a T-stop of 1.3 and the SLR lenses were the Zeiss ZF lenses with a T-stop of 1.4. To keep as many of the variables out of the equation as possible, the footage was all processed through RED Alert using the same settings. See the picture below for the settings used. The only change made to the real world footage was a change to 709 Gamma in the Output LUT.
All of the still frames have been left unprocessed and have not been graded, while the sample footage has been graded using the same settings in each set of clips in Color. You can download the Color project files, as well as the full res sample images and footage at my web site, by going to the resource page. In the download you will find this review in PDF form as well as the setup notes for the tests which details out the various settings used, and lighting setups. So lets take a look at what the tests yielded.
(What follows below is excerpted from my full review notes. If you would like to read the full text, you can download the PDF’s here:
REW-ZeissLensTest-Results.pdf
REW-ZeissLensTest-Setup.pdf
REW-Zeiss-Breathing-H264.mov)
CHARTS:
Resolution / Sharpness @ Wide Open.
Resolution / Sharpness @ T4.
Vignetting @ T4.
Color Fidelity @ T4.
REAL WORLD:
Resolution / Sharpness @ Wide Open.
Resolution / Sharpness @ T4.
(The breathing and mechanics tests are detailed more in the PDFs, and the breathing test video can be downloaded at the link at the beginning of this article.)
After processing the footage, and reviewing the results, I was surprised to find that the SLR lenses were holding their own against the cinema lenses. I would even say that they were out performing the cinema lenses, as the SLR’s felt a little more sharp then the cinema lenses. Not only do the SLR’s feel more sharp, but they are completely color matched with each other and the cinema lenses, and there is no vignetting either.
The results of this series of tests was very surprising to me, and it was very welcome news as well. It was great to find out that the set of SLR lenses that I have will be able to get the job done. My only hunch as to why the lenses perform as well as they do on the RED, is that the film plane on the SLR is larger then the film plane on the RED. So the SLR lenses have to be able to resolve a larger image, and due to the increased image, the breathing in the lenses is probably falling outside of most of the RED’s sensor.
So what does a good set of Zeiss Super Speed lenses costing well over $20,000 get you that a good set of Zeiss ZF SLR lenses costing just under $6,000 can’t get you? Cinema style mechanics. The last series of testing that I did related specifically to the mechanics of the lenses, and this is where the rubber meets the road and the differences really stand out. And it is these differences that will be the deal breaker for many- especially those who have been around for a while.
The first major difference in is the size and weight of each set. The cinema lenses weight almost a full pound more then their SLR counterpart, and they are about twice the size as well. The second difference is the most important difference in my opinion- the SLR lenses rotate backwards. On the cinema lenses, to focus close to the lens you turn the lens counter clockwise, and for the SLR lens you turn it clockwise. The reason this is such a big issue is that an AC (Assistant Camera) has learned their trade very carefully and precisely in order to do there job well. A good AC is worth their weight in gold. Having learned their craft on cinema lenses, if they were to use an SLR lens, all of their natural reflexes will now be backwards, making their job much more complex. To further complicate the issue the third major difference between the two sets of lenses has to do with the degrees of rotation to get from one end of the lens to the other. On the cinema lenses the shortest throw was on about 300 degrees on the 35mm lens, where as on the SLR lens it was about 115 degrees. That means that there is less movement between distances on the SLR, making the AC’s job that much more challenging. The last mechanical difference is in the aperture. On the cinema lenses the aperture rolls smoothly all the way through the range, allowing for smooth transitions. On the SLR lens, there are hard stops at each half and full stop, with no smooth adjustments possible.
In the end, having a set of SLR lenses may save you a chunk of change on buying lenses, but it may end up costing you more in the long run depending on the application you are using them in. For myself, I’ll be hanging on to my SLR’s to use in applications where small form factor, and lightweight portability are needed. And then I’ll continue to rent the cinema lenses for the projects that require them. Either way I can see a need and application for both sets of lenses.
Cheers,
Ryan E. Walters, Cinematographer