Sigma 30mm f/1.4 DC HSM Art

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Prime lens

A prime lens by Sigma for APS-C cameras, 30mm f/1.4.

What it frames like

Its full-frame-equivalent focal length on the sensor it was made for.

How wide 30mm sees on each sensor it covers.

f/1.4 wide open, to scale against f/1.4.

On APS-C (Nikon F, Pentax K): like 45mm on full frame; f/1.4 gives about the depth of field of f/2.1 there.
On APS-C (Canon) (Canon EF): like 48mm on full frame; f/1.4 gives about the depth of field of f/2.2 there.
Not usable on the larger-sensor bodies of Canon EF: they have no crop mode (and Canon's EF-S lenses don't even mount on them), so it is for APS-C bodies only.
On the larger-sensor bodies of Nikon F, Pentax K: it works with the camera in a APS-C crop mode, at fewer megapixels.