When using FX lenses on a DX camera, we use the crop factor to ensure we are choosing the best lens for the job. However, if a lens is labled DX, do we take the focal length at face value, or do we have to apply the crop factor as well?

> However,
>if a lens is labled DX, do we take the focal length at face
>value, or do we have to apply the crop factor as well?

Actually you do both. The AFS 35mm f1.8 DX lens is a 35mm lens no matter what camera you put it on. However on a DX camera body it will have the same view angle as a 52.5 mm lens on a FX body.

Len

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The short answer is the crop factor applies to both FX & DX lens.

When I shot film I had a 24mm lens for landscapes. Now that I shoot digital and use a DX camera, I bought a 16-85VR lens so the 16mm will give me the field of view that I got on the 24mm film camera.

Jerry Jaynes
Great Smoky Mountains
of North Carolina

http://www.flickr.com/photos/by_jerry_jaynes/

Hi Demetrius,

Welcome to Nikonians!
The focal length of FX lenses and DX lenses are the same.
DX lenses project a smaller image circle at the sensor plane than FX lenses.
Since the sensor plane is in the same location on both FX and DX bodies as well as film bodies the "1.5 X crop factor" applies to All lenses when they are mounted on a DX body.
Good Luck and Enjoy your Nikons!

Best Regards,
Marty

I think in terms of a 35mm film camera (135 format) with a negative of 36mm x 24mm. When I think of lenses and focal lengths, I think in terms of what that lens will give me as an angle of view with respect to a 35mm film or FX digital camera:
24mm = 84 degrees
35mm = 62 degrees
50mm = 46°

In DX format:
24mm = 61°
35mm = 44°
50mm = 31°30'

But I'm not comfortable learning the angle of view for DX focal lengths, so I translate to FX angle of views with the 1.5x crop.

In FX, a normal lens is the 50mm lens with 46° angle of view in DX, a 35mm x 1.5 = 52.5mm whic is pretty close to 50mm and has an angle of view of 44° ... making it a "normal lens" for DX bodies.

Long story longer, yes, do the crop factor thing if you think in terms of film/FX lenses and are comfortable with it.

I hope that makes sense.


Anthony

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