smc PENTAX FA-50mmF1.4 Classic is listed for Pentax K with Full frame coverage. Its verified front filter size is Ø49 mm. Ricoh lists KAF as the mount subtype. Check the exact body support table for electronic functions.
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Verified specifications
| Field | Value |
|---|---|
| Mount | Pentax K |
| Mount subtype | KAF |
| Image format | Full frame |
| Front filter thread | Ø49 mm |
| Model ID | pentax-smcpentax-fa50-classic |
| Optical construction | 7 elements in 6 groups |
| Closest focus | 0.45m (1.48 ft.) |
| Maximum magnification | 0.15x |
| Minimum aperture | F22 |
| Aperture blades | 8 Rounded diaphragm （50mm:F1.4-F2.8） |
The maker also lists 7 elements in 6 groups for the optical design and a closest-focus specification of 0.45m (1.48 ft.). These are lens specifications, not a guarantee of performance on every body or in every shooting mode.
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Compare the exact model code and rear mount in each listing. Amazon results may contain another mount or generation; the search is not a compatibility verdict.
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Search camera lenses on AmazonChoosing a camera
Look for the Pentax K designation on the camera specification, then verify the exact model code and mount variant against its support page. A physical mount match is a starting point; still AF, movie AF, crop behavior, stabilization and firmware need separate checks.
Choosing a filter
A circular screw-in filter with a matching documented thread size is only a mechanical candidate. Magnetic filters, wide frames and stacked rings need separate system and vignetting checks. When no front thread is specified, do not buy a size from the focal length or barrel diameter.
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Official sources and scope
Checked for this reference on October 30, 2026. Product firmware and support lists can change; inspect the current maker page for your exact revision.