HD PENTAX-DA 21mmF3.2AL Limited is listed for Pentax K with Unknown coverage. Its verified front filter size is Ø43 mm. Ricoh lists this in its K-mount lens catalog; the electronic subtype is not stated on this page. Check the exact body support table for electronic functions.
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Verified specifications
| Field | Value |
|---|---|
| Mount | Pentax K |
| Mount subtype | Unknown |
| Image format | Unknown |
| Front filter thread | Ø43 mm |
| Model ID | pentax-hdpentax-da-21 |
| Optical construction | 8 elements / 5 groups |
| Closest focus | 0.2m |
| Maximum magnification | 0.17x |
| Minimum aperture | F22 |
| Aperture blades | 7 |
The maker also lists 8 elements / 5 groups for the optical design and a closest-focus specification of 0.2m. These are lens specifications, not a guarantee of performance on every body or in every shooting mode.
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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.