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SMC Pentax-M 100mm f/4
Macro (1977-1984)
© 2008 KenRockwell.com. All rights reserved.

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Pentax 28mm lens

Pentax 100mm f/4 SMC-M Macro. enlarge. I'd get mine at these direct links to it at Adorama and eBay. It helps me keep adding this old stuff to this site when you get yours through these links, thanks! Ken.

 

December 2008      More Pentax Reviews

 

Ideal Uses: Perfect for use on Pentax as a general purpose telephoto and portrait lens, as well as a perfect macro lens.

Not for: Autofocus. This is a manual focus lens. It works on AF cameras, but you must focus manually.

Optics:
Ergonomics: (manual focus)
Usefulness:
Availability:
Overall:

 

Introduction     top

Intro    Specs    Performance    Recommendations

This could be the only telephoto lens you ever need for your Pentax. It works on just about anything Pentax. I tried it on the Pentax ME.

It's not that common, since it cost more than the 50mm macro and it cost more than the other short teles when new, but if you can find one, it replaces several different lenses.

This 100mm f/4 can replace both 85mm and 135mm conventional lenses. A 100mm macro is much more convenient for real macro shooting than an 50mm macro because it leaves enough room between the front of the lens and you subject for both lighting ad your subject's comfort.

It is very well thought out. See the numbers on the front of the focus ring? Those are the reproduction ratios. These are much easier to read on their own scale than having them mixed in with the focus scale, as Nikon and Canon do. This makes this lens much easier to read than any of the other macro lenses.

Optics are just about perfect. If you can't make a sharp shot with this lens, you can't make a sharp shot.

Out-of-focus backgrounds are perfectly smooth and undistracting, much better than most lenses.

It's compact and takes 49mm filters.

Pentax 100mm Macro

Pentax 100mm f/4 SMC-M Macro. enlarge.

 

Specifications     top

Intro    Specs    Performance    Recommendations

Lens Mount: Pentax K.

Optics: 5 elements in 3 groups. Pentax Super Multi-Coated.

Diaphragm: 6 blades, stops down to f/32. Full, and sometimes half-stop clicks.

Filter Thread: 49mm.

Close Focus: 1.48 feet (0.45m).

Maximum Reproduction Ratio: 1:2.

Size: 2.54" diameter x 3.05 " long (64.6 x 77.5mm), rated, when focused at infinity.

Weight: 12.4775 oz. (353.75g), measured. 12.70 oz. (360g), rated.

100 4 at 1:2

Pentax 100mm f/4 SMC-M Macro at closest focus distance. enlarge.

Hood, Pentax 100/4

Hood. The same hood also fits the f/2.8 100mm and 85mm f/4.

Pentax 100/4, case and hood

Pentax 100/4, included custom case and hood. enlarge.

 

Performance     top

Intro    Specs    Performance    Recommendations

As hoped, the Pentax 100mm f/4 Macro SMC-M is just about perfect no matter what you do with it.

 

Bokeh

Bokeh is beautiful. Backgrounds are always soft and undistracting.

Out-of-focus foregrounds are always distracting, regardless of the bokeh. Bokeh for near objects is poor, but even if the foreground bokeh was great, out-of-focus objects between you and the subject are always distracting.

 

Coma

I can't see any.

 

Distortion

The Pentax 100/4 Macro has no visible (or measurable) distortion at any tested distance from infinity to 10 feet (3m).

 

Falloff

The SMC Pentax 100mm Macro has an almost invisible amount of falloff wide-open at f/4.

It's completely gone at f/5.6.

 

Focus

Focus is easy. Even with its big helicoid I can do it with one finger.

 

Lateral Color Fringes

None.

 

Sharpness

I can't recall any significantly sharper lens.

It's super sharp edge-to-edge, even wide-open, as seen on Velvia 50 with an 8x loupe.

Seen on-screen from 3,600 DPI scans, it's sharp even to the farthest corners at f/4, and gets a little sharper and contrastier at f/5.6 and f/8, with f/8 being optimum before diffraction sets in.

Rear, Pentax 100mm Macro

Rear, Pentax 100mm Macro. enlarge.

 

Recommendations     top

Intro    Specs    Performance    Recommendations

This could be the only telephoto and macro lens you ever need for your Pentax. If you find one, pick it up.

Bottom, pentax 100 4

Bottom of Pentax 100mm f4. enlarge.

 

PLUG

I support my growing family through this website.

If you find this as helpful as a book you might have had to buy or a workshop you may have had to take, feel free to help me continue helping everyone.

If you've gotten your gear through one of my links or helped otherwise, you're family. It's great people like you who allow me to keep adding to this site full-time. Thanks!

If you haven't helped yet, please do, and consider helping me with a gift of $5.00.

The biggest help is to use these links to Adorama, Amazon, B&H, Calumet, Ritz, J&R and when you get your goodies. It costs you nothing and is a huge help to me. eBay is always a gamble, but all the other places have the best prices and service, which is why I've used them since before this website existed. I recommend them all personally.

The biggest help is to use these links to Adorama, Amazon, B&H, Calumet, Ritz and J&R when you get your goodies. It costs you nothing and is a huge help. These places have the best prices and service, which is why I've used them since before this website existed. I recommend them all personally.

Thanks for reading!

Ken

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