Focal Length and Digital lenses

[kwakky]

Hello all

I have two things to ask today.

1. Out of curiosity why are Digital SLR focal lengths mulitplied by 1.5 and what is the resoning behind this?
2. Are there any specific lenses made for Digital apart from the EF-S. Wide angle is my preference.

Many thanks

[Michael Fanelli]

Hello all

I have two things to ask today.

1. Out of curiosity why are Digital SLR focal lengths mulitplied by 1.5 and what is the resoning behind this?
2. Are there any specific lenses made for Digital apart from the EF-S. Wide angle is my preference.

Many thanks

The sensor is smaller than 35mm film, hence the edges are "cut off."

Pentax and Nikon make smaller, APS-digitial only, lenses.

[straightarm]

The focal length is not multiplied. This has important implications when calculating Depth of Field.

As Michael said, the image is cropped, at the edges, thus giving a narrower angle of view. So for example, if you use a Canon EOS 10d, the cropping gives you the same angle of view as using a lens 1.6 x longer on a standard 35mm cameras.

The cropping factor varies from camera to camera. Nikon seem to have standardised on 1.5x. Canon have 1.6x, 1.3x and no cropping factor at all. Depends on the sensor size. The larger the sensor, the much more expensive it is to produce.

As well as Canon's ef-s lens(es) (There might well be more in future) Sigma make some digital only lenses. These lenses make use of the smaller sensor size and have a smaller image circle. If you tried to use them on a full frame camera, the corners of the image would be cut off.

[kwakky]

Excellent...Thankyou for clearing that up for me....

[b_nikon]

Most is already said although I am very curious about the futur (who isn't) and mainly about the ways Nikon and Canon are going. As said Nikon has chosen (apparantly) for the 1.5 cropfactor while canon has three (yes?) different CMOSchips and the impressive CMOS with no cropping at all.

Can't wait till 15/09 when Nikon introduces his new "toys" .

Bart