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Old May 3, 2008, 2:40 PM   #11
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Your comments make no sense to me, please consider my confusion.

I understand that ---- If a film lens has a field of view of 90 degrees (24mm lens) then the 90 degree view light transmitted will cover the 35mm film

I understand that------ If a Digital ONLY smaller circle lens has a field of view of 90 degrees 24mm then the light transmitted will cover the smaller sensor with no "cropping" due to light being off the sides of the sensor.

What I do not understand is how the UNCROPPED - USING SMALLER CIRCLE DIGITAL LENS 24mm 90 degree field of view in a digital camera somehow magically becomes a 36mm equivalent as if a non digital lens had been cropped.

Think about it. How can a 24mm smaller circle digital lens with the light/image falling entirely on the sensor become a 36mm?

Are the digital only Len's actually 36mm but advertised as 24?

Signed quite baffled.
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Old May 3, 2008, 4:29 PM   #12
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J-R-S wrote:
Quote:
I understand that ---- If a film lens has a field of view of 90 degrees (24mm lens) then the 90 degree view light transmitted will cover the 35mm film
Actually, a 24mm lens wouldn't have a 90 degree angle of view with 35mm film.

A 24mm lens would have an angle of view closer to 84 degrees (measured diagonally) on a 35mm camera (using 24 x 36 cm film). But, if that 24mm focal length lens was designed for a 6 x 4.5 cm film size, you'd have a wider angle of view of around 115 degrees. On a camera with a smaller APS-C size sensor, that 24mm lens would give you a narrower angle of view of around 61 degrees.

The angle of view you see in lens specs assumes a given sensor or film size (the film or sensor size the lens was originally designed for). Don't confuse image circle size or angle of view with focal length.

If you use a smaller sensor or film size, the angle of view will be narrower (more apparent magnification) for any given focal length.

If you use a larger sensor or film size, the angle of view will be wider (less apparent magnification) for any given focal length.

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