Equivalent 1/2" and 2/3" lens sizes at DVinfo.net

Geoffrey Smith · April 7th, 2006, 03:12 PM

Could someone please clarify the following; In JVC's own literature about the different lens for the HD100/101, they give equivalent focal lengths for 1/2" and 2/3" lens when compared to the two available 1/3" lens, the TH16 x 5.5 and the TH 13 x 3.5. At 5.5mm in 1/3" the equivalent 2/3" lens is 8.27mm, and at 3.5mm in 1/3" the equivalent 2/3" lens is 6.42. Does this mean that on a 2/3" lens at 6.42mm the effective through the lens angle of view is the same as 3.5mm on the wide TH 13 x 3.5mm lens? And 8.27mm the same as 5.5mm?
Lastly, if you had a wide 4.5mm 2/3" lens, what is the 1/3" equivalent?

Tim Dashwood · April 7th, 2006, 05:19 PM

Geoffrey,

The way JVC phrases the "equivalent" focal lengths is a little confusing.

To answer your question "Does a 2/3" lens at 6.42mm the same effective through the lens angle of view as a 1/3" lens at 3.5mm," the answer is yes. You have interpreted the chart correctly. The same goes for 8.27mm on a 2/3" being the equivalent Field of View as 5.5mm on a 1/3" CCD.

These numbers are only meant to give a frame of reference for camera operators used to working with 2/3" cameras.

You asked about a 4.5mm 2/3" lens. In terms of that 4.5mm lens on a 2/3" camera, you would need a 2.45mm lens on a 1/3" camera to achieve the same FOV. (Using a crop factor of 0.545) Of course the widest available 1/3" lens is the 3.5mm.

However, if you used the ACM-17 2/3" adapter on the HD100 with a 2/3" lens, then focal length is focal length. So your 4.5mm 2/3" lens used on a HD100 is still 4.5mm, no matter what mount is on the back.

Geoffrey Smith · April 8th, 2006, 02:02 AM

Thank you Tim for shedding some light on this. Away from the charts and the theory, one has to obviously use the appropriate adaptor in order to use a 1/2" or 2/3" lens on the HD101. From your last paragraph am I right in thinking that a 4.5mm 2/3" lens mounted on a 2/3" adaptor will give you 4.5mm as if it was on a 1/3" lens, ie not as wide as the 3.5mm Fujinon JVC make available, but close to it?
My reasons for wanting to know is that the current TH13 x 3.5mm lens does not suit my purposes. I make observational documentaries for the BBC here in the UK and I need a high quality lens with a wide end of about 7mm (on a 2/3" lens), but also a telephoto end of at least 180mm (usually achieved through a 2x extender). I own a DSR 450 and a Canon J17 x 7.7mm with a 2x extender which works very well for the above, hence I want to understand the real world application of 2/3" lens to the HD101 so that I can either use my existing lens or buy the right 1/2" HD lens.

Thanks again

April 7th, 2006, 03:12 PM	#1
Geoffrey Smith New Boot Join Date: Apr 2006 Location: London UK Posts: 22	Equivalent 1/2" and 2/3" lens sizes Could someone please clarify the following; In JVC's own literature about the different lens for the HD100/101, they give equivalent focal lengths for 1/2" and 2/3" lens when compared to the two available 1/3" lens, the TH16 x 5.5 and the TH 13 x 3.5. At 5.5mm in 1/3" the equivalent 2/3" lens is 8.27mm, and at 3.5mm in 1/3" the equivalent 2/3" lens is 6.42. Does this mean that on a 2/3" lens at 6.42mm the effective through the lens angle of view is the same as 3.5mm on the wide TH 13 x 3.5mm lens? And 8.27mm the same as 5.5mm? Lastly, if you had a wide 4.5mm 2/3" lens, what is the 1/3" equivalent?

April 7th, 2006, 05:19 PM	#2
Tim Dashwood Wrangler Join Date: Aug 2005 Location: Toronto, ON, Canada Posts: 3,637	Geoffrey, The way JVC phrases the "equivalent" focal lengths is a little confusing. To answer your question "Does a 2/3" lens at 6.42mm the same effective through the lens angle of view as a 1/3" lens at 3.5mm," the answer is yes. You have interpreted the chart correctly. The same goes for 8.27mm on a 2/3" being the equivalent Field of View as 5.5mm on a 1/3" CCD. These numbers are only meant to give a frame of reference for camera operators used to working with 2/3" cameras. You asked about a 4.5mm 2/3" lens. In terms of that 4.5mm lens on a 2/3" camera, you would need a 2.45mm lens on a 1/3" camera to achieve the same FOV. (Using a crop factor of 0.545) Of course the widest available 1/3" lens is the 3.5mm. However, if you used the ACM-17 2/3" adapter on the HD100 with a 2/3" lens, then focal length is focal length. So your 4.5mm 2/3" lens used on a HD100 is still 4.5mm, no matter what mount is on the back. __________________ Tim Dashwood

April 8th, 2006, 02:02 AM	#3
Geoffrey Smith New Boot Join Date: Apr 2006 Location: London UK Posts: 22	Thank you Tim for shedding some light on this. Away from the charts and the theory, one has to obviously use the appropriate adaptor in order to use a 1/2" or 2/3" lens on the HD101. From your last paragraph am I right in thinking that a 4.5mm 2/3" lens mounted on a 2/3" adaptor will give you 4.5mm as if it was on a 1/3" lens, ie not as wide as the 3.5mm Fujinon JVC make available, but close to it? My reasons for wanting to know is that the current TH13 x 3.5mm lens does not suit my purposes. I make observational documentaries for the BBC here in the UK and I need a high quality lens with a wide end of about 7mm (on a 2/3" lens), but also a telephoto end of at least 180mm (usually achieved through a 2x extender). I own a DSR 450 and a Canon J17 x 7.7mm with a 2x extender which works very well for the above, hence I want to understand the real world application of 2/3" lens to the HD101 so that I can either use my existing lens or buy the right 1/2" HD lens. Thanks again