1/3" equivalents

[egproductions]

What is the equivelent for a 28mm focal length of a 35mm lens when dealing with 1/3" lenses?

[Barry_Green]

Well, you have to define whether you're talking about 35mm movie lenses, or 35mm still-camera lenses.

For movie lenses, the typical multiplication factor is around 4.4, and for still camera lenses it's between 7.2 and 7.8.

So 28mm / 7.2 = 3.9mm

Meaning a 3.9mm lens on a 1/3" video camera will about match the field of view of a 28mm lens on a 35mm still camera.

[egproductions]

thanx for the multiplication factors that makes sense now...one more question though since you broght it up. Why is the multiplication factor diffrent for movie lenses if the size of the sensor/film plane is 35mm diagnol is it actually smaller than 35mm and if so wouldnt 35mm adapters give you shallower depth of field since most people use still photo lenses?

[Petrus]

35mm still camera frame is placed along the film (24x36mm), 35mm movie frame is sideways, plus there is space for the audio track, thus 35mm movie frame is much smaller than 35mm still frame. For that reason shorter focal lengths are used for film for same angle.

Easy math: 35mm still frame is about 43mm diagonal. 1/3" frame should be about 8mm diagonal (1/3"!). 43/8 = 5.3 which should be the ratio between 35mm and 1/3" focal lengths for the same angle. But in truth 1/3" sensors are even smaller. But basically the math holds, just insert the correct sensor/film size into the equation.

And yes, 35mm still camera lens gives less DOF than a cine lens, but only because the focal lengths used tend to be longer. It is ONLY the focal length (and F-stop used, of course) that matters here, not what camera the lens was made for.

[egproductions]

Very informative, so since 35mm adapters dont need that extra space for audio etc you can use still photo lenses and get a wider FOV while maintaining the Shallow DOF. Very clear now thanx