Every Canon EF Lens: Read the Reviews, See the Specification & Check the Price
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EF 40 f2.8 STMCanon EF 40mm f/2.8 STM

Overview

Canon's first pancake lens in the EF range. The somewhat unusual 40mm focal length gives 64mm equivalent on a 1.6 crop sensor body.

First introduced in 2012, the lens features a quiet STM (stepper motor) drive for AF and 'Movie Servo AF' for smooth, quiet autofocus when filming on compatible Canon DSLRs.

Initial indications are that the lens is very good optically

Available from: Amazon.com | Amazon.co.uk | B&H | Adorama

Lens specifications

Focal Length & Maximum Aperture 22mm, 1:2
Lens Construction 7 elements in 6 groups
Diagonal Angle of View 63°30'
Focus Adjustment Inner Focusing System
Closest Focusing Distance 0.49 ft. / 0.15m
Filter Size 43mm
Max. Diameter x Length, Weight 2.4 x 0.9 inch, 3.7 oz. / 60.9 x 23.7mm, 105g

Construction

lens construction EF40

MTF compared to 50/1.8 and 50/1.4

40mm MTF charts

A quick guide to MTF charts (which only measure contrast and resolution. Canon's guide to their MTF charts)

Black lines reflect lens performance at widest aperture.
Blue lines show the performance at f/8

Thick lines indicate lens contrast
Thin lines indicate lens resolution

Dashed lines: Lens performance with meridional lines.
Solid lines: Lens performance with sagittal lines

Closer sagittal and meridional chart lines indicate more 'natural' out of focus areas.

Remember that MTF charts are good for comparing similar lenses, so comparing ones from the 14mm f2.8L and 300mm 2.8L won't tell you much at all, whilst comparing the EF14 2.8L with the EF14 2.8L II will show meaningful differences. Note that other manufacturers may have different ways of displaying such information that may or may not match up with the Canon figures.

Which 400mm? - a list of all versions

Canon EF 400mm
Attribute f/2.8 USM f/2.8 II USM f/2.8 IS USM f/2.8 IS II USM f/4 DO IS USM f/5.6 USM f/4 DO IS II USM
Key features
Full-frame compatible Yes
Image stabilizer No Yes No Yes
Ultrasonic Motor Yes
L-series Yes
Diffractive Optics No Yes No Yes
Technical data
Aperture (max-min) f/2.8-f/32 f/4-f/32 f/5.6-f/32
Construction 9 groups / 11 elements 13 groups / 17 elements 6 groups / 7 elements 12 groups /18 elements
Aperture blades 8 9 8
Closest focusing distance 4m 3m 2.7m 3.5m 3.3m
Max. magnification 0.11x 0.15x 0.17x 0.12x 0.11x
Diagonal viewing angle 6 °
Physical data
Weight 13.44 lb / 6.1 kg 13.03 lb / 5.91 kg 11.83 lb / 5.37 kg 8.48 lb / 3.85 kg 4.27 lb / 1.94 kg 2.8 lb / 1.25 kg 2.1 kg
Maximum diameter 6.57" / 167mm 6.41" / 163mm 5.03" / 128mm 3.54" / 90mm/ 5.04" /128mm
Length 13.70" / 348mm 13.74" / 349mm 13.50" / 343mm 9.16" / 232.7mm 10.09" / 256.5mm 9.16" / 232.7mm
Filter diameter 48mm 52mm drop-in filter 77mm 53mm drop-in
Accessories
Lens hood ET-161B II   ET-155 ET-155 (WII) ET-120 Built-in
Case     400 400C 400B  
Retail information
Release date April 1991 March 1996 September 1999 August 2011 December 2001 May 1993 September 2014

EF 40mm f/2.8 STM reviews and articles

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Product Advisory notice (August 2012)

To Users of the EF40mm f/2.8 STM Interchangeable Lens for Canon Digital SLR Cameras
Thank you for using Canon products.

It has been confirmed that the autofocusing function of the EF40mm f/2.8 STM lens, which was released in June 2012, may not operate correctly.

The details of this phenomenon are described below.

Affected Product
EF40mm f/2.8 STM

Phenomenon
If pressure is applied to the lens barrel while the lens is mounted to the camera (pressure can be applied even while attaching the lens cap or while carrying the camera with the lens attached in a bag), the autofocusing function of the lens may stop working.

*This phenomenon does not occur during normal shooting.
*This phenomenon does not result in a malfunction of the lens.

Workaround
When the above phenomenon occurs, detach and reattach the lens, or remove and reinsert the camera battery to restore the operations.

Market Support: The firmware to address this phenomenon will be available for download in late August, 2012.

Firmware update via Canon USA

Comparison of size between 40mm and 50mm Canon lenses

40mm and 50mm comparison

Used Canon Lenses
• UK: MPB
• USA: B&H | Adorama
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