zoom question at DVinfo.net

Ron Edwards · September 29th, 2004, 08:48 PM

General question. Lets say my GL2 with 20x lens is sitting side by side with a JVC 5000 and a 16 X lens. Both cams focus on news print at 20 feet. Which cam will record the largest print? Does the fact the lens of the JVC is physically much longer than the GL2 play a part in the equation? Thanks in advance!
Ron

Ken Tanaka · September 29th, 2004, 09:25 PM

The physical sizes of lens designs is not material to their optical performance, per se. Not being a "measurebator" myself I have never performed such a side-by-side comparison between my XL1S' 16x and my GL2's 20x lenses. But I'm quite confident that the 20x will produce a higher degree of magnification in the image.

You should, however, also understand that you must also consider the size and resolutions of the lenses' targets; i.e. the CCD's. You're comparing a (nominal) 1/4" target on the GL2 to a 1/2" target on the JVC camera.

Why do you ask this question?

Ron Edwards · September 29th, 2004, 09:36 PM

Thanks Ken,
Just trying to get a better understanding. I did not know if the physical length of the lens played a part or not. My little part time video work may allow me to "move up" some day in equipment. I am considering the JVC 5000, but not totally convinced this is the right choice. The standard lens is 16X. The 20x cannon is several more $$$. My GL2 20x is about right for my work.
Ron

Jeff Donald · September 29th, 2004, 10:43 PM

The zoom ratio of a lens is irrelevant in determining subject magnification. You need to compare the focal length of the lens in mm to determine the magnification.

Ken Tanaka · September 29th, 2004, 10:54 PM

Indeed. And in this regard, the GL2's 20x lens is spec'ed at a 35-mm-equivalent focal length range of 39.5mm-790mm.

Alan Craven · October 1st, 2004, 10:09 AM

When comparing digital camera focal lengths with 35mm cameras, the difference in image aspect ratio can be a factor.

Strictly one should compare angle of view (which is format independent), but some manufacturers take advantage of the 3:2 ratio of 35mm and compare horizontal field of view.

Jeff Donald · October 1st, 2004, 11:16 AM

Unfortunately, few people understand or care about field of view. But almost everyone cares about how big their subject is. There is no avoiding it. Hence the need to educate people about the various factors that effect the image size of the subject, including formats, lens focal length and distance to subject.

September 29th, 2004, 08:48 PM	#1
Ron Edwards Regular Crew Join Date: May 2004 Location: Fairview Heights, Illinois Posts: 148	zoom question General question. Lets say my GL2 with 20x lens is sitting side by side with a JVC 5000 and a 16 X lens. Both cams focus on news print at 20 feet. Which cam will record the largest print? Does the fact the lens of the JVC is physically much longer than the GL2 play a part in the equation? Thanks in advance! Ron

September 29th, 2004, 09:25 PM	#2
Ken Tanaka Retired DV Info Net Almunus Join Date: Dec 2001 Location: Chicago, IL Posts: 6,943	The physical sizes of lens designs is not material to their optical performance, per se. Not being a "measurebator" myself I have never performed such a side-by-side comparison between my XL1S' 16x and my GL2's 20x lenses. But I'm quite confident that the 20x will produce a higher degree of magnification in the image. You should, however, also understand that you must also consider the size and resolutions of the lenses' targets; i.e. the CCD's. You're comparing a (nominal) 1/4" target on the GL2 to a 1/2" target on the JVC camera. Why do you ask this question? __________________ Lady X Films: A lady with a boring wardrobe...and a global mission. Hey, you don't have enough stuff! Buy with confidence from our sponsors. Hand-picked as the best in the business...Really! See some of my work one frame at a time: www.KenTanaka.com

September 29th, 2004, 10:43 PM	#4
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	The zoom ratio of a lens is irrelevant in determining subject magnification. You need to compare the focal length of the lens in mm to determine the magnification. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

September 29th, 2004, 10:54 PM	#5
Ken Tanaka Retired DV Info Net Almunus Join Date: Dec 2001 Location: Chicago, IL Posts: 6,943	Indeed. And in this regard, the GL2's 20x lens is spec'ed at a 35-mm-equivalent focal length range of 39.5mm-790mm. __________________ Lady X Films: A lady with a boring wardrobe...and a global mission. Hey, you don't have enough stuff! Buy with confidence from our sponsors. Hand-picked as the best in the business...Really! See some of my work one frame at a time: www.KenTanaka.com

October 1st, 2004, 11:16 AM	#7
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	Unfortunately, few people understand or care about field of view. But almost everyone cares about how big their subject is. There is no avoiding it. Hence the need to educate people about the various factors that effect the image size of the subject, including formats, lens focal length and distance to subject. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

September 29th, 2004, 09:36 PM	#3
Ron Edwards Regular Crew Join Date: May 2004 Location: Fairview Heights, Illinois Posts: 148	Thanks Ken, Just trying to get a better understanding. I did not know if the physical length of the lens played a part or not. My little part time video work may allow me to "move up" some day in equipment. I am considering the JVC 5000, but not totally convinced this is the right choice. The standard lens is 16X. The 20x cannon is several more $$$. My GL2 20x is about right for my work. Ron

October 1st, 2004, 10:09 AM	#6
Alan Craven Major Player Join Date: May 2003 Location: York, England Posts: 518	When comparing digital camera focal lengths with 35mm cameras, the difference in image aspect ratio can be a factor. Strictly one should compare angle of view (which is format independent), but some manufacturers take advantage of the 3:2 ratio of 35mm and compare horizontal field of view.