Pentax M 40mm f/2.8 SMC

Pentax 40mm f-2.8 SMC Review Front Element Filter-1

Pentax M 40mm f/2.8 SMC. If you’re looking to purchase this lens I always check Adorama and Ebay for good deals. It helps me if you purchase it through one of these links here in this review. When you purchase through these links it financially enables me to devote time to develop this site further. Thanks for the help! -Todd

Pentax M K 40mm f-2.8 SMC Asahi Lens-1

Pentax M K 40mm f-2.8 SMC Asahi Lens Rear Mount-1

Pentax M K 40mm f-2.8 SMC Asahi Lens Pancake K1000 Body Size-2

Pentax M K 40mm f-2.8 SMC Asahi Lens best K1000 Body Size-1


3.9 oz (111g)

Focus Ring
Rubber on Metal.

Close Focus
2.1 feet (0.6 meters).

Filter Threads
49mm, Metal.

Aperture Ring

6 blades stopping down to f/22.

Pentax-M K Metal Mount.

Made in



f/2.8 | f/3.5 | f/4 | f/8


100% Crop

f/2.8 | f/3.5 | f/4 | f/8

Corner at f/2.8

Flare and Ghosting


Pentax 40mm f-2.8 SMC Review Bokeh Blur at f2.8-1

Bokeh at f/2.8

Closest Focus at f/4

A little soft with lower contrast and quite a bit of chromatic aberration.
f/3.5: Sharpens up only a little but has better contrast and very little chromatic aberration.
f/4: Sharpness is better with good contrast and color.
f/8: Very sharp with great contrast and no signs of diffusion until f/14 area.

Quite a bit of vignette and is only gone around f/7.1.

The bokeh is not the greatest feature of the lens and is pretty distracting.

Flare and Ghosting
The flare is pretty good and absolutely no ghosting at all from what I can see. Stopping down just a tiny bit reduced flare quite a bit.


Almost no Barrel Distortion.

On AF Camera
Optics:         ★ ★
Mechanics:  ★ ★ ★ ★
Ergonomics: ★ ★ ★
Usefulness:   ★ ★
Availability:    ★ ★
Overall:          ★ ★ ★

On MF Camera
Ergonomics:   ★ ★ ★ ★
Overall:           ★ ★ ★
Out of 5

This is a great little lens if you need a really tough built, pocket size tiny prime lens for hiking or street photography. The real reason you would buy this lens is simply for it’s small size and a bit faster f/2.8. Otherwise even today I believe this lens is over priced for what it does. The lens is really sharp around f/4.5 but anything before that gets a little softer. The whole point of the lens is for small size but the focus and aperture rings are pretty tiny to feel for but the rubber focus ring still works well once you find it. It is a really neat lens to hold and play with simple because it is so small. The lens does really well with not producing any ghosting, distortion and has really low flare. If you want a super tiny pancake lens this is a really swell lens stopped down. If you are shooting it on a digital camera I would check Ebay to see if your camera can take a split focus screen which makes focusing a dream.


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My hopes are to take the time to continue developing this website with more test photo based reviews. If you are ever interested in purchasing this lens or other photography equipment please do so through these links here in this review. I always check Adorama and Ebay for good deals. This helps support my family and allows me to take more time for the site. The best part is this site is free for you and I link good deals I find!

Sometimes these links will actually give you better deals then typical retail prices! I personally buy from the links I have listed whether looking for new gear or fun old stuff. I can personally attest to their good & safe service from years of experience. Thanks again to you, our readers, for supporting us! -Todd