Pro 35 vs Digi Primes

[James Mann]

I will be shooting a music video in a month and have decided to work with the CineAlta. The video has a bit of greenscreen work in it and so my primary concearn is resolution and sharpness. In trying to put together a package I stumped myself on the issue of lens selection.

 

What are the inherent (visual not phsyical) differences between using a set of digi primes and a set of (for example) Zeiss Super Speeds through the Pro35 adapter?

 

I like the idea of a shallow depth of field but how drastically different would that be between the two options.

 

Also, in taking into consideration the light loss with the adapter, is there a danger (while attempting to produce a clean and sharp image for compositing) in shooting wide open?

 

Is there anything else that I should be taking into consideration?

 

Thanks,

 

James Mann

[David Mullen ASC]

You should first consider that the Zeiss Digi-Primes shot wide-open (f/1.6?) will give you the same depth of field in HD as shooting around an f/2.8 or f/2.8-4.0 split (more or less) in 35mm, so the only point in using the Pro-35 and 35mm cine lenses instead is if you want even LESS depth of field, like more in the f/1.4 to f/2.0 range -- which is pretty shallow-focus... and may not be recommended for greenscreen work.

 

Plus the Pro-35 rig acts as a mild diffusion since the image is being rephotographed off of a groundglass. Which may look great for your needs but again, I'd feel safer using the Zeiss Digi-Primes if doing greenscreen work since the edges would be cleaner and sharper.

 

Just my opinion, not having much practical experience with the Pro-35 rig. I just feel that since the fast Digi-Primes allow a moderately shallow-focus look if shot wide-open (except maybe the widest angle lens), the only reason to use the Pro-35 is if you want REALLY shallow focus, and you'd have to ask yourself if you'd really want to be shooting everything at an f/2.0 or less if this were a 35mm shoot...

[Tomas Koolhaas]

Hello,

The last two shoots I have shot have been on the cinealta. For one I used the Pro-35 adaptor (with Zeiss superspeeds), and the other Digiprimes. Let me start by saying that anything I say about either setup is based solely on what I felt from seing the images on the HD monitor on-set, and on HD monitors in post production. Since the differences in images is such a subjective thing to describe or compare my advice is only based on my opinion and in no-way is meant to detract from anyone elses advice or opinion on this forum. Having said that, I would say that although both the pro-35 and digiprimes yeilded excellent results, I felt that the images I created with the pro-35 adaptor were much more beatiful, and also looked alot more like 35mm film than those I achieved with the digiprimes. This would be attributed by most people to two things; the shallow depth of field allowed by the Pro-35 adapter, and also the slight diffusion given by the ground glass to the image (similar to a 1/8 black promist according to most people) which helps take the edge off harsh highlights which is a tell-tale sign of video formats. I used a black promist 1/8 on my digiprime shoot and felt that (even excluding the D.O.F advantages) the images from the Pro-35 adapter still had a more pleasing "filmic" look. The pro-35 images seemed to have a sharp feeling, while also having a softness in tonal gradation that looked more like 35mm than HD. I feel that there is more advantage to using the Pro-35 adaptor than simply having less D.O.F and a slight diffusion effect. It seemed to me that using the pro-35 and super-speeds allowed me to retain a bit more information in the highlights than using the digiprimes. I know this is unprovable and somewhat implausable but again, I only know what I felt like I was seeing on HD monitors (I used the same exact monitor on-set for both shoots). I had the DCC switched ON for both shoots so that cannot be the explaination for the extra information in the highlights (internal menu settings were also indentical on both shoots).The digiprimes were excellent lenses but produced a slightly too harsh image for my likeing (even when used in conjunction with a 1/8 black promist), but again that's just me. Also, to compare the lenses based on these two shoots is slightly unfair as one shoot (pro-35) was well organized and afforded me adequate time for lighting, while the one with digi-primes was rushed and I was given a ridiculously small amount of time to light each scene, and as we all know good lighting makes a massive difference to image quality, especially for video. Neither of my shoots included green screen work, and I would assume whoever is doing your greenscreen work would preffer keying from an image shot with Digiprimes, so that's another concern you will have to take into account. I also found from testing on the pro-35 that I preffered the look of the image when at a 1.6 on the superspeeds as opposed to all the way open-1.3 (seemed to have slightly better sharpness and contrast). Good luck making your choice.

Cheers.

Tomas.

[Jayson Crothers]

I just completed a 2 camera shoot with the 900's and pro-35's.

 

A few thoughts:

 

We chose it because the director very much wanted that extremely narrow depth of field look (we were usually at a T1.4 or T2). Had we not been after such an extreme focus look, I would have pushed for digi-primes.

 

The light loss is around 1 2/3 stops - that means the camera is working at an efefctive asa of around 100 (in our case anyways - your camera will vary with whatever menu selections you make).

 

There are aberations inherent to the adapter - you need to carefully test your lenses during prep since the adapter will only enhance any aberations in the taking lenses. We'd originally planned on using zeiss standard speeds because there was a better deal on them, but during our prep we found that in combination with the adapter we were getting a weird pin-hole look (SERIOUS vignetting around the edges) and we swapped to super-speeds.

 

Zooms can be tricky, both for size (with our 10-1 zoom the camera was nearly four feet long), but the deeper the stop on the taking lens, the more risk you have in seeing the ground glass in the adapter. It's suggested that you not set your taking lens at deeper than a T4, but I found anything over a T2.8 was cutting it a bit close for me.

 

I refer to "taking lenses" because the stop you set on the lens is different to the "stops" you set on the back of the adapter. Essentially, you set one stop on the actual lens, but any adjustments you make (ie, closing down, opening up) are done on an ND wheel at the back of the adapter - for example, if your lens is set at a T2.8, but you want to stop down one stop, you wouldn't set the lens to a T4, you'd instead leave the T2.8 on the lens and dial in .3 on the rear ND wheel of the adapter - it's a bit confusing until you see the actual device. It should also be noted that adjusting one stop on the taking lens doesn't translate to the camera as a one stop change (another reason you make adjustments to the adapter's ND wheel) - I don't understand the specific "why's" though.

 

The adapter, in my opinion, was equivalent to a 1/4 pro-mist - you don't really need any more diffusion unless you're after a heavily diffused look.

 

Back focusing the adapter is a wee bit funky - with digi-primes or any HD lenses, you have a focus chart you can use; with the Pro-35, you're back focusing by using the grain on the ground glass as a reference - the focusing rings on the adapters are a little sticky, so back focus can take a few minutes and can be a little frustrating.

 

There's a resolution loss as well, so for green-screen work I'd be careful and perhaps even hesitant to employ the adapter.

 

I enjoyed using it, but as with anything, it's not for every project. Test, test, test (this boards common mantra).

[Tomas Koolhaas]

Hello everyone,

Jayson, you bring up a good point about the back focus of the pro-35 adaptor it is somewhat subjective and a bit annoying on-set, However the original question was about the 'visual' differences between the Por-35 adaptor and Digiprimes, not the practical differences. You spoke mainly about the practical issues that you encountered while using the adaptor but you didn't mention which project or footage gave you the best looking results. When I used the adaptor none of these issues bothered me at all, except the back focus, but even this was a minor issue which only took a few minutes longer than a normal back focus.

In my reply I spoke about the differences I percieved in the images from one monitor to another, this subject (the difference in look between different systems) is such a difficult one to address because, as with any artistic format, the results are totally subjective, and as Jayson rightly says the only way for anyone to decide which look THEY prefer is to test both systems (I would suggest testing them in various identical or very similar lighting set-ups in order to get the most accurate idea of which look you actually prefer). Then you also have the issue of green-screen, you should confer with however is doing it and preferably do some tests with them (but obviously the Digi-primes would be prefferable for keying from).

Jayson, I would be interested in knowing how you felt about the results you got with the two different systems, just in terms of the visual look of each, as I felt that although the Digiprimes looked good, the footage I shot on the Pro-35 looked much better, and was worth the slight inconviniences it incurred.

Cheers.

Tomas.

[Jayson Crothers]

A tough question to answer because it's all based on taste, but I felt like the Pro-35 had an organic feeling, but the inherent diffusion and slight grain/noise look felt strange (not digital noise, not grain, but some kind of "thing" across the image - not distrating, but certainly there).

 

The digi-primes feel very clean and sober to me - crisp and maybe even a bit clinical.

 

The biggest visual difference that's quick and easy to point out is the focus, but if you're smart about it, the digi-primes can be very selective in focus as well.

 

Having shot with them both, I can't say if I prefer one over the other - depends on story, director, budget, etc.

[Elhanan Matos]

James,

 

Personally I prefer the DigiPrimes, theyre sharper, crisper, faster, and easier to use than the Pro-35. Obviously working for the worldwide exclusive distributor of the Digiprime lenses theres a bit of a bias, but you should test the lenses out for yourself. If youre in the LA area feel free to give me a call and come by to check out the Digiprimes and Digizoom, I also have a prototype 3.9mm right. You can reach me at (818) 841-9655.

[Landon D. Parks]

I always thought that if your going to shoot blue/green screen, more depth of field was better. If your shooting non-chroma, less depth of field is better.

 

The Pro35 has to be bulky and it adds an extra $400.00 day onto your price tage. If your shooting chroma screen, go wth the digiprimes. They will provide you with a clearer and shaprer image (which is better for keying).

 

Just my non-professional adivce...

[Keith Mottram]

from a visual effects point of view, shooting with the pro35 would be a daft idea. If you are only shooting green screen then any diffusion or softness in the back of the image will seriously screw up the key. Dont forget that if you want any form of diffusion you can always add it after the composite (if you do shoot diffused then you'll also have a nightmare matching background plates). Similarly if, and i have not tested the pro 35, there is any grain like structure as an artifact your compositor will have to be quite skilled (and have the right tools) to match that on the back plates/ cgi. If you want to guarantee a good key then keep it sharp - no DOF, no Motion blur. If you have people at different distances from the camera consider shooting them on two or more passes and let the compositor sort the DOF and motion blur out.

 

Keith