Optical to MM coversion at DVinfo.net

Mack Fisher · August 5th, 2006, 08:57 PM

I read alot of nature sites for locating waterfalls and such, and many say that the falls from a certain view require a 150mm telephoto lense, or 300mm telephoto lense and Im wondering if there is a good or rough way to convert optical to milimeter or visa versa.

Barry Green · August 6th, 2006, 11:00 PM

Depends on the size of the imager you're using. For 1/3" cameras, the typical conversion factor is 7.2, meaning that you'd multiply your 1/3" video camera's focal length by about 7.2 to get an approximation of what length of lens you'd need to use on a 35mm still camera to achieve a similar field of view.

So -- a 10mm lens on a 1/3" video camera usually approximates to about a 72mm lens on a 35mm still camera.

Mack Fisher · August 7th, 2006, 10:13 AM

Do you mean a 10X optical lense? I dont need to go mm to mm Im trying to figure out what my 12X opitcal is equal to millimeters

Barry Green · August 7th, 2006, 12:04 PM

There's no way to know that just from the "10x" label. Because, it's 10x what? "10x" means that it has a zoom range that means its maximum telephoto is 10x as long as its minimum wide angle setting. But it doesn't tell you what that wide-angle is, so you have no basis for comparison.

You'd have to find out what the minimum focal length is in order to start comparing. For example, the DVX100 is a 10x lens, and its minimum wide angle is 4.5mm, so it's 10x4.5, or a total zoom range of 4.5 to 45mm.

August 5th, 2006, 08:57 PM	#1
Mack Fisher Regular Crew Join Date: Mar 2006 Location: Seattle, WA Posts: 158	Optical to MM coversion I read alot of nature sites for locating waterfalls and such, and many say that the falls from a certain view require a 150mm telephoto lense, or 300mm telephoto lense and Im wondering if there is a good or rough way to convert optical to milimeter or visa versa.

August 6th, 2006, 11:00 PM	#2
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	Depends on the size of the imager you're using. For 1/3" cameras, the typical conversion factor is 7.2, meaning that you'd multiply your 1/3" video camera's focal length by about 7.2 to get an approximation of what length of lens you'd need to use on a 35mm still camera to achieve a similar field of view. So -- a 10mm lens on a 1/3" video camera usually approximates to about a 72mm lens on a 35mm still camera.

August 7th, 2006, 10:13 AM	#3
Mack Fisher Regular Crew Join Date: Mar 2006 Location: Seattle, WA Posts: 158	Do you mean a 10X optical lense? I dont need to go mm to mm Im trying to figure out what my 12X opitcal is equal to millimeters

August 7th, 2006, 12:04 PM	#4
Barry Green Barry Wan Kenobi Join Date: Jul 2003 Location: North Carolina Posts: 3,863	There's no way to know that just from the "10x" label. Because, it's 10x what? "10x" means that it has a zoom range that means its maximum telephoto is 10x as long as its minimum wide angle setting. But it doesn't tell you what that wide-angle is, so you have no basis for comparison. You'd have to find out what the minimum focal length is in order to start comparing. For example, the DVX100 is a 10x lens, and its minimum wide angle is 4.5mm, so it's 10x4.5, or a total zoom range of 4.5 to 45mm.