The Pentax 40mm glass is one of my favorite glass in their “Limited” lens lineup. I like this glass better than the other Limited lenses because it offers sharper image quality, solid build, smaller dimension and the best value for money.

This is probably the best pancake lens that they have ever made.

Pentax 40mm

Lens Score (APS-C Sensor)
Optical Quality: (4.5 / 5)
Build Quality: (5 / 5)
Value for Money: (4.5 / 5)

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The primary purpose of this glass is for street photography. Photographers who are looking for a “slightly longer than normal” glass will also benefit from this glass as well.

Many people will find the joy of using this compact, light, tough and sharp glass.

If you belong to one of those group, then by all means, get this glass.

See my complete Pentax 40mm review below to learn more about this glass.

Technical Specs

Official Name:
Pentax SMC DA 40mm f/2.8 Limited

Focal Length Markings:

SMC – Super Multi Coating – Minimizes flare in the glass.

DA – Only compatible with cropped sensor DSLR camera.

Limited – Limited Edition. A label that is put for great performance in a compact package.

Full Technical Specs

Technical Specifications
Groups / Elements 4 / 5
Angle of View 39°
Number of Blade Diaphragm 7
Minimum Aperture f/22
Minimum Focusing Distance 15.7in. (0.4m)
Filter Thread 49mm
Weight 3.2oz. (90g)
Dimension (Diameter x Length) ø2.5 x 0.6″ (63 x 15mm)
Macro Magnification Ratio 0.13X

Optical Performance


On the center this glass is very sharp, even at the widest aperture of f/2.8.

Border sharpness are also great at any aperture.

To get the maximum sharpness on this glass, shoot at f/4.

Sharpness Scale (from Best to Worst):
(5) Excellent
(4) Great
(3) Good
(2) Fair
(1) Poor

Center Sharpness

Focal Length / Aperture f/2.8 f/4 f/5.6 f/8 f/11
40mm Great Excellent Excellent Excellent Great

Border Sharpness

Focal Length / Aperture f/2.8 f/4 f/5.6 f/8 f/11
40mm Great Excellent Excellent Excellent Great


Being a length on this normal focal length, distortion is very well controlled. It is not visible on this glass and you can ignore it.

See the distortion grid test below.

Distortion Test

Distortion Test


Vignetting is apparent at f/2.8. Stop down to f/4 or smaller aperture to greatly reduce it.

Besides f/2.8, vignetting is no problem at any apertures.

See the vignetting test result below.

Vignetting Test

Vignetting Test

Chromatic Aberration

Chromatic aberration control is very good on this lens. It is negligible at any aperture.

See the test table result below.

Chromatic Aberration Scale (from Best to Worst):
(5) Negligible
(4) Very Low
(3) Low
(2) High
(1) Very High

Chromatic Aberration

Focal Length / Aperture f/2.8 f/4 f/5.6 f/8 f/11
40mm Negligible Negligible Negligible Negligible Negligible

Build Quality


This is a Limited lens, which means that this lens is made from very high quality metal parts.


Focus ring is quite small because the lens dimension itself is small, but it is smooth.

This lens has no internal autofocus motor (which is typical for any DA lens) so it has to rely on the camera’s drive. This generates a mild autofocus sound.

Autofocus speed is very fast and accurate.

Also, the front element does not rotate during focusing, so you can use polarizing filter easily.

Image Stabilization

The Image Stabilization feature is installed in the camera body, not on the lenses. Check your DSLR camera if it has Image Stabilization feature.


The DA designation means that this lens is only compatible with cropped sensor DSLR only. It should not be used with a full frame DSLR or 35mm film SLR camera.

Sample Image

Below are some sample shots that I took using this lens. Click on any thumbnail to open the image.

Sample Image 1

Sample Image 1

Sample Image 2

Sample Image 2

Sample Image 3

Sample Image 3

Sample Image 4

Sample Image 4

Sample Image 5

Sample Image 5


Below is the summary of the Pentax 40mm lens review.

As usual, being a Limited lens, the optical quality is very good.

It is very sharp both on the center and on the borders at any aperture. Distortion and chromatic aberration is very well controlled.

The only downside is the visible vignetting at f/2.8. At other apertures, vignetting is not a problem.

Although this glass is a small one (hence the name “Pancake”) the build quality is very good. It is made out of metal and was a joy to use.

There is a slight autofocus noise due to the lack of autofocus motor on the glass, but this should not be a problem for most shooters.

The 40mm focal length is an ideal lens for street photography as well as photographers looking for the normal glass with extra reach.

If you are one of those, this glass will not disappoint.


  • Visible vignetting at f/2.8
  • Moderate degree of autofocus noise


  • Very sharp on the center and borders
  • Superb chromatic aberration control
  • Great distortion control
  • Vignetting is well controlled except at f/2.8
  • Tough and solid build
  • Fast and accurate autofocus
  • Good value for money

Good For

  • Street photography
  • Slightly longer normal lens

Not So Good For

  • Wide angle or landscape photography

What Others Are Saying…

by “James Lin”

After using the old Pentax-M 40mm pancake for a while, I decided to get this DA Limited version. 40mm on a Pentax dSLR is a great focal length for portraits and for regular walk-around use. The 1.5x multiplier of Pentax dSLRs makes…
Click here to see the full review

by “A. Adamson”

I just purchased this lens this week, so this is something of a preliminary review. My initial impression of this lens is very positive. It focuses faster than any other Pentax lens I’ve tried, including the DA* zooms with the hyper-sonic…
Click here to see the full review

Where to Buy

Pentax 40mm

Lens Score (APS-C Sensor)
Optical Quality: (4.5 / 5)
Build Quality: (5 / 5)
Value for Money: (4.5 / 5)

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Below are links to reputable sites where they offer the best deal online:

Thanks for reading this Pentax 40mm review and I hope you’ll be able to make a good purchasing decision based on this.