EX-3 with Zeiss digiprimes: crop factor question

R

raijin

New member
Hey guys,

I'm doing a short on my friend's EX-3 and this will effectively be my first time shooting video. I've been considering the possibility of using an adapter and shooting with Zeiss prime lenses for the project. But I'm still not clear on the whole sensor size vs. focal length problem. I would be using lenses designed for a 2/3" sensor on a camera with a 1/2" inch sensor. So what physical focal lengths would I need to achieve (35, 50, 100) on the EX-3?
 
Depends on what you mean by 35, 50, and 100...

Do you mean you want to achieve the same field of view as a 100mm lens when used on a 35mm still camera? Or the same field of view as a 100mm lens on a 35mm movie camera? Or, the same field of view as a 100mm lens on a 2/3" video camera, which the lenses were made for?

If compared to a 35mm still camera, the "crop factor" is about 5.1, meaning a 20mm lens on the EX3 would about equate the field of view of a 100mm lens on a 35mm still camera.

If compared to a 35mm movie camera, the "Cinema Crop Factor" is about 2.93, meaning a 35mm DigiPrime on an EX3 would about match the field of view of a 100mm lens on a 35mm movie camera.

If compared to a 2/3" video camera, the crop factor would be about 1.4, meaning a 70mm lens on an EX3 would about match the field of view of a 100mm lens on a 2/3" camera.
 
Raijin,
Thought I would share some real world experience here: I just shot a feature with the EX3 / Pro35 + Zeiss super speed primes. Great image and decent low light capability for an adaptor setup. There was definitely a crop factor. My go-to lens was 18mm on interiors. The field of view of the 25mm was just too small for the majority of the interior work. MCUs and CUs looked great with 35mm or 50mm. I used an 85mm only a handful of times (even though I generally love 85mm), it was just too telephoto.

As for the Digi-primes on an EX-3, I do not have any experience.


Jason
 
Okay, well, there's a difference between using a mechanical mount adapter (EX3 to B4) and using a Pro35 adapter. The Pro35 changes the field of view, whereas a B4-to-EX3 adapter doesn't. So we'd have to know for sure which way you were planning on going, before being able to answer.
 
Thanks for the responses everyone!

I'm thinking that I will just be using a mechanical lens adapter (B4) and mounting the digiprimes directly onto the EX-3. I would like the added dof that the Pro35 enables, but seeing as the majority of this film is going to be shot handheld, using that adapter seems like it's not an option. Though now that I see that the hand-grip comes off with the stock lens, I could be out of luck either way.

So correct me if I'm wrong... I still can't get a handle on this. To get approximately the same field of view as an 100 mm lens on 35 (cine) I would stick a 70mm digiprime on the EX-3?
 
No no no. That would give you the FOV of a 100mm lens on a 2/3" camera.

If you want to match a 35mm cinema camera's field of view when it's using a 100mm lens, you'd need to use a 35mm DigiPrime.
 
I shot a film last year with an EX3 and a P+S Pro 35 for EX3, http://www.pstechnik.de/en/digitalfilm-pro35-ex3.php " The PRO35 projects the 16 x 22mm (academy format) image produced by a 35mm lens onto an especially designed, eccentrically moving ground glass. This image is then relayed onto the 1/2 ” sensor of the electronic camera on a reduced scale while maintaining 35mm depth-of-focus and angle-of-view. Contrast is improved and colors have a more natural appearance."
I was happy with it overall, enjoyed the workflow cause I was used to it. Here's a clip http://vimeo.com/8737926 - In saying that however, we're shooting a follow up in a few weeks and we'll be using a 7D and a set of Zeiss ZF.2s we've just bought. Though I have to say, I'll miss the back Iris on the P+S.
 
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