35mm zoom and DOF at DVinfo.net

Dan McCain · November 5th, 2004, 02:39 PM

I am interested in purchasing a 35mm zooms lens, like a cooke 20-100mm. However the fastest zoom lens seems to be 3.1 . Would this lens be able to get the shallow depth of field as my 1.4 primes? Do you think a 3.1 zoom lens would be practicle in terms of exposure and DOF for this system or just a waste of money? I know that films have been shot with zooms. Any advise on zoom lenses would be appreciated.

Charles Papert · November 5th, 2004, 05:18 PM

Hi Dan,

To answer your question, an f3.1 lens will not deliver the shallow depth of field of an f1.4 lens. To evaluate whether or not you are willing to live with the compromise, you can simply dial your prime lens to that stop (call it a 2.8 and a half for all practical purposes) and see if the results are something you can live with.

Exposure-wise, you are putting yourself into a challenging situation as far as interiors go with this slow of a lens coupled with the light loss of the Mini35. Be prepared for some big lighting units!

I have used zooms with this system (see my article on the Seinfeld/Amex spots and it's great as long as you have enough light to accomodate, as well as the proper support gear (heavy-duty head/sticks, zoom motor and controller, appropriate mattebox etc).

Guy Genin · November 6th, 2004, 10:30 AM

Hi Dan,

I will have to caution you about trying to use a Cooke 20-100 zoom lens on the Mini35. This particular lens was designed before the full frame was widely used as a film format. It was designed to cover only the academy format (that preserves the optical audio on the side of the frame). On the Mini 35, the corners of the full frame will have a visible light loss. Most of the zooms except the most recent have this problem.

Guy Genin.
ZGC Inc.

Charles Papert · November 6th, 2004, 04:45 PM

Guy:

Interesting, that's news to me. I guess I always assumed the Mini35 used Academy framing. So, is it effectively the same as the Super 35 TV frame (sometimes known as BigTV?). Thus I should assume wider field of view for a given focal length than a standard TV "pumpkin"?

Dan McCain · November 9th, 2004, 11:12 AM

Guy,
Thanks as always for the great tech support and info.

Chris Rubin · December 9th, 2004, 01:44 AM

Can somebody who knows, please tell exactly what the captured image size on the mini35 ground glass is? Is it 24 x 36 mm (still) or 21 x 15,3 mm (cine)?

Barry Green · December 9th, 2004, 12:33 PM

It's cine, not still.

November 5th, 2004, 02:39 PM	#1
Dan McCain Regular Crew Join Date: Apr 2004 Location: Atlanta, GA Posts: 65	35mm zoom and DOF I am interested in purchasing a 35mm zooms lens, like a cooke 20-100mm. However the fastest zoom lens seems to be 3.1 . Would this lens be able to get the shallow depth of field as my 1.4 primes? Do you think a 3.1 zoom lens would be practicle in terms of exposure and DOF for this system or just a waste of money? I know that films have been shot with zooms. Any advise on zoom lenses would be appreciated.

November 5th, 2004, 05:18 PM	#2
Charles Papert Wrangler Join Date: Jan 2002 Location: Los Angeles, CA Posts: 6,810	Hi Dan, To answer your question, an f3.1 lens will not deliver the shallow depth of field of an f1.4 lens. To evaluate whether or not you are willing to live with the compromise, you can simply dial your prime lens to that stop (call it a 2.8 and a half for all practical purposes) and see if the results are something you can live with. Exposure-wise, you are putting yourself into a challenging situation as far as interiors go with this slow of a lens coupled with the light loss of the Mini35. Be prepared for some big lighting units! I have used zooms with this system (see my article on the Seinfeld/Amex spots and it's great as long as you have enough light to accomodate, as well as the proper support gear (heavy-duty head/sticks, zoom motor and controller, appropriate mattebox etc). __________________ Charles Papert www.charlespapert.com

November 6th, 2004, 10:30 AM	#3
Guy Genin Sponsor: ZGC Join Date: Feb 2004 Location: Mountain Lakes, NJ. Posts: 36	Hi Dan, I will have to caution you about trying to use a Cooke 20-100 zoom lens on the Mini35. This particular lens was designed before the full frame was widely used as a film format. It was designed to cover only the academy format (that preserves the optical audio on the side of the frame). On the Mini 35, the corners of the full frame will have a visible light loss. Most of the zooms except the most recent have this problem. Guy Genin. ZGC Inc. __________________ Guy Genin ZGC Technical support

November 6th, 2004, 04:45 PM	#4
Charles Papert Wrangler Join Date: Jan 2002 Location: Los Angeles, CA Posts: 6,810	Guy: Interesting, that's news to me. I guess I always assumed the Mini35 used Academy framing. So, is it effectively the same as the Super 35 TV frame (sometimes known as BigTV?). Thus I should assume wider field of view for a given focal length than a standard TV "pumpkin"? __________________ Charles Papert www.charlespapert.com

November 9th, 2004, 11:12 AM	#5
Dan McCain Regular Crew Join Date: Apr 2004 Location: Atlanta, GA Posts: 65	Guy, Thanks as always for the great tech support and info.

December 9th, 2004, 01:44 AM	#6
Chris Rubin Regular Crew Join Date: Jul 2004 Posts: 38	Can somebody who knows, please tell exactly what the captured image size on the mini35 ground glass is? Is it 24 x 36 mm (still) or 21 x 15,3 mm (cine)?

December 9th, 2004, 12:33 PM	#7
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	It's cine, not still.