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# Lenses for Digital Cameras

Discussion in 'Through-the-Lens Club' started by Eagle78101, Aug 27, 2005.

1. ### Eagle78101

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Could somebody tell me if ratios are the same for lenses in digital as they are for film cameras? IOW, is 200mm still a telephoto, is 35mm considered a wide angle and so on?

Thank you.

2. ### nipperwolf

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on average, the gain in focal length. 1.5

the 200 becomes a 300, the 35 becomes a 52, etc....

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4. ### scowan007memberrific!!!

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Are you talking about DSLRs or just regular digital cameras?

5. ### hwyhobo

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Generally speaking, yes, but the exact measurements will be different. It all depends on the size of the sensor in your digital camera, and it's fairly easy to calculate. Currently there are several different sensor sizes:

1. 1/1.8 - 7.176 mm x 5.319 mm (diagonal 8.933 mm)
2. 2/3 - 8.8 mm x 6.6 mm (diagonal 11 mm)
3. 4/3 - 18 mm x 13.5 mm (diagonal 22.5 mm)
4. APS-C - 25.1 mm x 16.7 mm (diagonal 30.1 mm)
5. 35mm - 36 mm x 24 mm (diagonal 43.3 mm)

So, to know the appropriate factor, you need to divide the diagonal of your sensor into the diagonal of the 35mm frame. For instance, if you have a sensor designated as "4/3", your would do: 43.3 / 22.5 = (ca) 2. Your factor would be 2. That means that a 35mm lens with a focal length of 100 mm when mounted on a 4/3 digital camera would behave like a 200 mm lens on a full frame (35mm) camera.

The above measurements are close enough but now always exact. For example, Canon 20D, designated as "APS-C", really has a factor of 1.6, not 1.5, but it is not enough to cause confusion or serious miscalculation.

Hope that helps.

6. ### hatidua

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you don't say what kind of digital camera you are referring to in your initial question. My 1:1 DSLR camera bodies interpret focal length the same way my analog bodies did: a 15mm lens now shows exactly the same field of view as a 15mm lens did "back then".

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