===== Pentax-A SMC 100mm f/4 Macro ===== 
{{ :lens:pentax-a_smc_100mm_f4_macro.png?250|}}
==== Summary ====
The SMC Pentax-A 100mm f/4 Macro is a manual-focus macro prime introduced in 1984 for the Pentax K-mount, and produced until 1989. It was designed as a compact, affordable alternative to faster macro lenses, offering 1:2 magnification without extension tubes. Though modest in aperture, it delivers excellent close-range performance, making it a favorite among vintage macro enthusiasts and collectors. Optically, it uses a 5-element, 3-group design with Super Multi-Coating (SMC) and a 6-blade automatic diaphragm, stopping down to f/32. The lens focuses as close as 45cm, yielding a 0.5× magnification ratio, and uses a 49mm filter thread. It weighs 340g, measures 65 × 78mm, and includes a manual aperture ring with an “A” setting, enabling full program and shutter-priority modes on compatible bodies. There’s no internal focusing or weather sealing, but the deeply recessed front element eliminates the need for a hood. A rare Dental Macro variant was also produced, featuring specialized distance markings for clinical photography.
==== Tech Specs ====
| Manufacturer    |Pentax|
| Series          |A Series Macro|
| Model           |SMC|
| Focal Length    |100mm|
| Max Aperture    |f/4|
| Min Aperture    |f/32|
| Format          |Full-Frame|
| Image Circle    |-|
| Minimum Focus   |45cm|
| Focus Rotation  |°|
| Iris Blades     |6|
| Optical Design  |5/3|
| Squeeze         |none|
| Front Diameter  |65mm|
| Filter Thread   |49mm|
| Focus/Zoom Rod  |none|
| Native Mount    |Pentax K|
| Data Protocol   |none|
| Length          |78mm|
| Weight          |340g|
| Body Telescope  |-|
| Body Material   |-|
| Focus Drive     |-|
| Iris Drive      |-|
| Zoom Drive      |-|
==== History ====
Country of Origin:  \\
Release Date: 1984 \\
Launch Price:  \\
Design Revisions:  \\

==== Service ====
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Service Manual: (Insert link to manual here) \\
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Full CLA: **TBD hrs.**\\
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==== Cine-Mod ====
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Focus Ring O.D.: -\\
Zoom Ring O.D.: -\\
Iris Ring O.D.: -\\
De-click Y/N: -\\
Additional Notes: \\
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==== Notes ====
==== Media ====