Film Style Lenses

Stav Bhuna · July 17, 2004

Good day to you all,

I am about to shoot a commercial on the Sony DVW-790 and I am very keen to experiment with a diferent type of lens other than the standard Canon J series. I am especially interested in knowing more about the "electronic cinematography lenses" that are available at present.

1. With the so-called "film style" lenses, for example the Optex 7.8 - 164mm, would the characteristics of the depth of field be similar to that of an Angenieux (11.5 - 138mm) or a Zeiss (11 - 110mm), given that all our conditions are identical? Are the digital lenses responsible for video's apparent infinite depth of focus and therefore, with me using the J20a (Optex conversion) or the Cooke Videtal, my depth of field would be greatly reduced?

2. Some of the shots involved in the job have the camera tracking in from about 20ft to filling the frame with a beermat. Unfortunately it seems the budget cannot afford for me to have too many lenses and therefore I am trying to find a lens that is roughly 8-60mm with macro capability. Could anybody advise me on a lens that might fit these specifications?

3. If one was to pull focus from 20ft to 10" how much barrel shift can one anticipate?

4. I have also become aware that the lens measurements on a digital lens are slightly different to those on a film lens. 8mm on a J16 ain't 8mm on a Zeiss Distagon. Could somebody please explain to me the reasons why?

Ideally I should go into a hire company and check all this out for myself but there is not too much time left.

Finally, if there are any unforeseen points that I should know I would greatly appreciate them. Your advice and suggestions are much anticpated.

Martin Radich.

Phil Rhodes · July 17, 2004

Hi,

> 1. With the so-called "film style" lenses, for example the Optex 7.8 - 164mm,

> would the characteristics of the depth of field be similar

Depth will be identical for the same stop and focal length for any lens on a given sensor. Falloff characteristics could change, but this is subtle. Exceptions include macro lenses and of course groundglass projection devices.

> 3. If one was to pull focus from 20ft to 10" how much barrel shift can one

> anticipate?

Depends on the lens, and the focal length you're using it at if it is a zoom.

> 4. I have also become aware that the lens measurements on a digital lens are

> slightly different to those on a film lens. 8mm on a J16 ain't 8mm on a Zeiss

> Distagon. Could somebody please explain to me the reasons why?

There doesn't appear to be any very good reason why the marks on some video lenses are inaccurate. They just are.

Phil

David Mullen ASC · July 18, 2004

"Cine-style" just means that there's no zoom motor / hand grip / auto iris / macro attachment, it takes a longer rotation to pull focus from near to far, allowing bigger and more detailed distance marks, and generally the lens has a larger barrel all around, making all the marks easier to read and reducing some of the breathing problems. So the lens can be used more like how it would be used on a movie camera.

The depth of field is the same as for video lenses of the same focal length on the same camera.

I'm not sure about this one, but I believe that the distances on cine lenses assume you are measuring from the film / CCD plane while video lenses assume you are measuring from the front of the lens. Could be wrong.

Mitch Gross · July 18, 2004

I'm not sure about this one, but I believe that the distances on cine lenses assume you are measuring from the film / CCD plane while video lenses assume you are measuring from the front of the lens. Could be wrong.

That used to be true but no longer.

Stav Bhuna · August 4, 2004

Many thanks for your replies guys. It is much appreciated.

Martin Radic.

:ph34r:

Sam Wells · August 4, 2004

That used to be true but no longer.

Because of the prism block and it's refractive index, the physical and "in air" distances to the image plane are not exactly the same. I think BandPro has a sticker with the in air distance offset marked on it, if you're in gnat's eyelash mode......

-Sam