Is there a formula to convert digital lens focal length to 35mm focal length ?
 

Does it relative to CCD size?

"narke" wrote in message
ups.com...
Does it relative to CCD size?
Yes it is entirely dependent on CCD size. For DSLR's, most are close enough
to 1.5x. The Olympus E1/E300 are the only lowish-priced SLR's that are
significantly different, with a 2x equivalence factor.

In article . com,
narke wrote:
Does it relative to CCD size?

Yes. To a first approximation, divide 43 by the diagonal of the sensor in
millimetres. This will give you the multiplication factor for field of
view/focal length (differing aspect rations will make this something of an
inexact sicence, but it should be close).

(43mm is the diagonal of a 35mm frame).

narke wrote:

Does it relative to CCD size?


The focal length does not change at all.

The 'cropping' factor gives a final image similar to the effect of using a
longer lens of FL * cropfactor.

So, a camera with a 50mm lens and a 1.5 cropped sensor is said to be equivalent
to a 75mm lens. (But the focal length does not change, the sensor is just smaller.)

Cheers,
Alan



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Chris Brown wrote:

In article . com,
narke wrote:

Does it relative to CCD size?


Yes. To a first approximation, divide 43 by the diagonal of the sensor in
millimetres. This will give you the multiplication factor for field of
view/focal length (differing aspect rations will make this something of an
inexact sicence, but it should be close).

(43mm is the diagonal of a 35mm frame).

Just divide 36 by the width of the sensor. eg: the Canon 20D at 22.5 mm (x):

36 / 22.5 = 1.6

(Quicker than (36^2+24^2)^0.5 / (22.5^2+15^2)^0.5 and same result).

Cheers,
Alan.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.

understand. Thank You All