smc Pentax-DA 645 25mm F/4 AL [IF] SDM AW

Ultra-wide angle prime lens • Digital era • Discontinued

SMC The multi-layer coating is applied to the surface of lens elements. It boosts light transmission, ensures sharp and high contrast images, minimizes ghosting and flares.
DA Autofocus lens optimized for Pentax digital SLR cameras.
AL The lens incorporates aspherical elements.
[IF] The lens incorporates internal focusing.
SDM The lens is equipped with Supersonic Drive Motor.
AW Dust-proof and water-resistant lens.

Model history

smc Pentax-DA 645 25mm F/4 AL [IF] SDM AW44x33A12 - 80.4m-- 2012 
smc Pentax-D FA 645 25mm F/4 AL [IF] SDM AW6x4.5A12 - 80.4m-- 2011 

Designed for

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Features highlight

44x33
Extreme AoV
1 Bi-ASPH
1 ASPH
9 blades
IF
SDM
QFS
DP/WR
SP
Drop-in filters
Built-in hood

Specification

Production details
Announced:March 2012
Production status:Discontinued
Production type:Mass production
Original name:SMC PENTAX-DA 645 1:4 25mm AL (IF) SDM AW
Optical design
Focal length:25mm
Speed:F/4
Maximum format:Medium format 44x33
Mount:Pentax 645
Diagonal angle of view:95.2° (Medium format (cropped frame))
Lens construction:12 elements - 8 groups
1 Bi-ASPH, 1 ASPH
Convex protruding front element
Diaphragm mechanism
Number of blades:9
Focusing
Closest focusing distance:0.4m
Maximum magnification ratio:1:9.1 at the closest focusing distance
Focusing method:Internal focusing (IF)
Focusing modes:Autofocus, manual focus
Manual focus control:Focusing ring
Autofocus motor:Supersonic Direct-Drive Motor
Focus mode selector:AF/MF
Quick-Shift Focus System (QFS):Yes
Shake Reduction (SR)
Built-in SR:-
Physical characteristics
Weight:1040g
Maximum diameter x Length:⌀90×148.5mm
Weather sealing:Dust-proof and water-resistant barrel
Super Protect (SP) coating:Front element
Accessories
Filters:Removable front filters are not accepted
Additional features:Drop-in filter holder (40.5mm)
Lens hood:Built-in petal-shaped

*) Source of data: Manufacturer's technical data.

Manufacturer description

PENTAX RICOH IMAGING COMPANY, LTD. is pleased to announce the launch of the PENTAX-DA645 25mm F4AL [IF] SDM AW.

Designed for exclusive use with the PENTAX 645D, this unifocal, ultra-wide-angle lens features PENTAX-original optics optimised for high-quality digital photography to ensure exceptional high resolution images. The sturdy construction of the lens, which is dustproof and weather-resistant, makes it ideal for outdoors photography.

Major Features:

1. Unifocal, ultra-wide-angle lens

When mounted on the PENTAX 645D medium-format digital SLR camera body, this ultra-wide-angle lens offers a focal length of approximately 19.5mm in the 35mm format, providing the widest perspective of all the lenses compatible with the PENTAX 645D. Creating visual effects unique to ultra-wide-angle lenses, such as exaggerated perspective and extra-wide depth of field, it can be effectively used for a wide range of subjects and situations, including spectacular landscapes and indoor shooting within a confined space. This lens gives the PENTAX 645D greater photographic freedom and flexibility.

2. State-of-the-art optics

Incorporating two high-performance a-spherical optical elements within its optics, this ultra-wide-angle lens provides exceptional image-resolving power with outstanding brightness levels even at the edges, whilst keeping any aberrations to a minimum. All lens characteristics are optimised for digital photography, for instance - exclusive lens coatings are applied to optical elements, while anti-reflection materials are applied to the interior of the lens barrel. The result is a lens that brings out the full potential of the PENTAX 645D medium-format digital SLR camera.

3. Aero Bright Coating to dramatically improve transmittance

This lens is treated with a PENTAX-original Aero Bright Coating, which ensures outstanding anti-reflection performance over a broader wavelength range to deliver images that are brighter and of higher quality. Created using PENTAX’s advanced nanotechnology, this exclusive coating reduces lens reflections and greatly improves light transmittance by forming a silica aerogel layer with uniform pores on the surface of the optical elements.

4. Dependable dustproof, weather-resistant construction

As the newest model of the dependable AW (All Weather) series, the lens comes in a highly dependable dustproof, weather-resistant construction with 11 special seals to effectively prevent the intrusion of dust and water into the lens interior. By coupling this lens with the PENTAX 645D camera body, the user is assured of a durable, reliable digital imaging system that performs superbly in demanding outdoor settings — even in rain and mist, or locations prone to water splashes or spray.

5. Mountable circular polarising filter

The lens features a built-in, pull-out-type filter holder in its barrel. By placing the C-PL (circular polarising) filter (40.5mm in diameter; included as an exclusive accessory) on this holder, the user can easily rotate the filter to obtain the desired polarising effect.

6. Smooth, quiet SDM autofocus operation

The advanced SDM (Supersonic Direct-drive Motor) autofocus mechanism has a supersonic motor installed inside the lens barrel which ensures a smooth, quiet autofocus operation.

7. Other features

  • High-quality machined aluminium parts, including the lens barrel, hood and cap
  • The built-in lens hood is optimally shaped for the angle of view when the lens is mounted on the PENTAX 645D camera body
  • Quick-Shift Focus system for instant switching to manual-focus operation, after the subject is captured in focus by the AF system
  • Rounded diaphragm to produce a smooth, beautiful “bokeh” (out-of-focus rendition), while minimising the streaking effect of point light sources
  • SP (Special Protect) coating applied to the front surface of the lens to effectively repel dust, water and grease

Typical application

landscapes, interiors, buildings, cityscapes

smc Pentax-D FA 645 25mm F/4 AL [IF] SDM AW

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35mm full frame

43.27 24 36
  • Dimensions: 36 × 24mm
  • Aspect ratio: 3:2
  • Diagonal: 43.27mm

Travellers' choice

Note

Among autofocus lenses designed for 35mm full-frame mirrorless cameras only. Speed of standard and telephoto lenses is taken into account.

Professional lens (Top class)

One of the best ultra-wide angle prime lenses

According to lens-db.com; among lenses designed for the same maximum format and mount.

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Image stabilizer

A technology used for reducing or even eliminating the effects of camera shake. Gyro sensors inside the lens detect camera shake and pass the data to a microcomputer. Then an image stabilization group of elements controlled by the microcomputer moves inside the lens and compensates camera shake in order to keep the image static on the imaging sensor or film.

The technology allows to increase the shutter speed by several stops and shoot handheld in such lighting conditions and at such focal lengths where without image stabilizer you have to use tripod, decrease the shutter speed and/or increase the ISO setting which can lead to blurry and noisy images.

Supersonic Direct-Drive Motor

AF/MF

AFAutofocus mode.
MFManual focus mode.

Drop-in filter holder

A drop-in filter holder with a neutral filter comes with the lens. The holder accepts 40.5mm filters. The filter holder must be always in place because the filter is a part of the lens optical system.

Aspherical elements

Aspherical elements (ASPH, XA, XGM) are used in wide-angle lenses for correction of distortion and in large-aperture lenses for correction of spherical aberration, astigmatism and coma, thus ensuring excellent sharpness and contrast even at fully open aperture. The effect of the aspherical element is determined by its position within the optical formula: the more the aspherical element moves away from the aperture stop, the more it influences distortion; close to the aperture stop it can be particularly used to correct spherical aberration. Aspherical element can substitute one or several regular spherical elements to achieve similar or better optical results, which allows to develop more compact and lightweight lenses.

Use of aspherical elements has its downsides: it leads to non-uniform rendering of out-of-focus highlights. This effect usually appears as "onion-like" texture of concentric rings or "wooly-like" texture and is caused by very slight defects in the surface of aspherical element. It is difficult to predict such effect, but usually it occurs when the highlights are small enough and far enough out of focus.

Low dispersion elements

Low dispersion elements (ED, LD, SD, UD etc) minimize chromatic aberrations and ensure excellent sharpness and contrast even at fully open aperture. This type of glass exhibits low refractive index, low dispersion, and exceptional partial dispersion characteristics compared to standard optical glass. Two lenses made of low dispersion glass offer almost the same performance as one fluorite lens.

Low dispersion elements

Low dispersion elements (ED, LD, SD, UD etc) minimize chromatic aberrations and ensure excellent sharpness and contrast even at fully open aperture. This type of glass exhibits low refractive index, low dispersion, and exceptional partial dispersion characteristics compared to standard optical glass. Two lenses made of low dispersion glass offer almost the same performance as one fluorite lens.

Canon's Super UD, Nikon's Super ED, Pentax' Super ED, Sigma's FLD ("F" Low Dispersion), Sony' Super ED and Tamron's XLD glasses are the highest level low dispersion glasses available with extremely high light transmission. These optical glasses have a performance equal to fluorite glass.

High-refraction low-dispersion elements

High-refraction low-dispersion elements (HLD) minimize chromatic aberrations and ensure excellent sharpness and contrast even at fully open aperture.

High Index, High Dispersion elements

High Index, High Dispersion elements (HID) minimize chromatic aberrations and ensure excellent sharpness and contrast even at fully open aperture.

Anomalous partial dispersion elements

Anomalous partial dispersion elements (AD) minimize chromatic aberrations and ensure excellent sharpness and contrast even at fully open aperture.

Fluorite elements

Synthetic fluorite elements (FL) minimize chromatic aberrations and ensure excellent sharpness and contrast even at fully open aperture. Compared with optical glass, fluorite lenses have a considerably lower refraction index, low dispersion and extraordinary partial dispersion, and high transmission of infrared and ultraviolet light. They are also significantly lighter than optical glass.

According to Nikon, fluorite easily cracks and is sensitive to temperature changes that can adversely affect focusing by altering the lens' refractive index. To avoid this, Canon, as the manufacturer most widely using fluorite in its telephoto lenses, never uses fluorite in the front and rear lens elements, and the white coating is applied to the lens barrels to reflect light and prevent the lens from overheating.

Short-wavelength refractive elements

High and specialized-dispersion elements (SR) refract light with wavelengths shorter than that of blue to achieve highly precise chromatic aberration compensation. This technology also results in smaller and lighter lenses.

Blue Spectrum Refractive Optics

Organic Blue Spectrum Refractive Optics material (BR Optics) placed between convex and concave elements made from conventional optical glass provides more efficient correction of longitudinal chromatic aberrations in comparison with conventional technology.

Diffraction elements

Diffraction elements (DO, PF) cancel chromatic aberrations at various wavelengths. This technology results in smaller and lighter lenses in comparison with traditional designs with no compromise in image quality.

High refractive index elements

High refractive index elements (HR, HRI, XR etc) minimize field curvature and spherical aberration. High refractive index element can substitute one or several regular elements to achieve similar or better optical results, which allows to develop more compact and lightweight lenses.

Apodization element

Apodization element (APD) is in fact a radial gradient filter. It practically does not change the characteristics of light beam passing through its central part but absorbs the light at the periphery. It sort of softens the edges of the aperture making the transition from foreground to background zone very smooth and results in very attractive, natural looking and silky smooth bokeh.

Original name

Lens name as indicated on the lens barrel (usually on the front ring). With lenses from film era, may vary slightly from batch to batch.

Format

Format refers to the shape and size of film or image sensor.

35mm is the common name of the 36x24mm film format or image sensor format. It has an aspect ratio of 3:2, and a diagonal measurement of approximately 43mm. The name originates with the total width of the 135 film which was the primary medium of the format prior to the invention of the full frame digital SLR. Historically the 35mm format was sometimes called small format to distinguish it from the medium and large formats.

APS-C is an image sensor format approximately equivalent in size to the film negatives of 25.1x16.7mm with an aspect ratio of 3:2.

Medium format is a film format or image sensor format larger than 36x24mm (35mm) but smaller than 4x5in (large format).

Angle of view

Angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view.

As the focal length changes, the angle of view also changes. The shorter the focal length (eg 18mm), the wider the angle of view. Conversely, the longer the focal length (eg 55mm), the smaller the angle of view.

A camera's angle of view depends not only on the lens, but also on the sensor. Imaging sensors are sometimes smaller than 35mm film frame, and this causes the lens to have a narrower angle of view than with 35mm film, by a certain factor for each sensor (called the crop factor).

This website does not use the angles of view provided by lens manufacturers, but calculates them automatically by the following formula: 114.6 * arctan (21.622 / CF * FL),

where:

CF – crop-factor of a sensor,
FL – focal length of a lens.

Mount

A lens mount is an interface — mechanical and often also electrical — between a camera body and a lens.

A lens mount may be a screw-threaded type, a bayonet-type, or a breech-lock type. Modern camera lens mounts are of the bayonet type, because the bayonet mechanism precisely aligns mechanical and electrical features between lens and body, unlike screw-threaded mounts.

Lens mounts of competing manufacturers (Canon, Nikon, Pentax, Sony etc.) are always incompatible. In addition to the mechanical and electrical interface variations, the flange focal distance from the lens mount to the film or sensor can also be different.

Lens construction

Lens construction – a specific arrangement of elements and groups that make up the optical design, including type and size of elements, type of used materials etc.

Element - an individual piece of glass which makes up one component of a photographic lens. Photographic lenses are nearly always built up of multiple such elements.

Group – a cemented together pieces of glass which form a single unit or an individual piece of glass. The advantage is that there is no glass-air surfaces between cemented together pieces of glass, which reduces reflections.

Flange focal distance

The flange focal distance (FFD), sometimes called the "flange back", is the distance from the mechanical rear end surface of the lens mount to the focal plane.

Focal length

The focal length is the factor that determines the size of the image reproduced on the focal plane, picture angle which covers the area of the subject to be photographed, depth of field, etc.

Speed

The largest opening or stop at which a lens can be used is referred to as the speed of the lens. The larger the maximum aperture is, the faster the lens is considered to be. Lenses that offer a large maximum aperture are commonly referred to as fast lenses, and lenses with smaller maximum aperture are regarded as slow.

In low-light situations, having a wider maximum aperture means that you can shoot at a faster shutter speed or work at a lower ISO, or both.

Closest focusing distance

The minimum distance from the focal plane (film or sensor) to the subject where the lens is still able to focus.

Closest working distance

The distance from the front edge of the lens to the subject at the maximum magnification.

Magnification ratio

Determines how large the subject will appear in the final image. For example, a magnification ratio of 1:1 means that the image of the subject formed on the film or sensor will be the same size as the subject in real life. For this reason, a 1:1 ratio is often called "life-size".

Manual focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Manual focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Electronic manual focus override is performed in the following way: half-press the shutter button, wait until the camera has finished the autofocusing and then focus manually without releasing the shutter button using the focusing ring.

Electromagnetic diaphragm control system

Provides highly accurate diaphragm control and stable auto exposure performance during continuous shooting.

Convex protruding front element

The convex front element protrudes from the lens barrel, making it impossible to use filters.

Fixed focus

There is no helicoid in this lens and everything is in focus from the closest focusing distance to infinity.

Overall linear extension

The entire lens optical system moves straight backward and forward when focusing is carried out. This is the simplest type of focusing used mainly in wide-angle and standard prime lenses. It has the advantage of introducing relatively little change in aberrations with respect to change in focusing distance. With telephoto and super telephoto lenses this method becomes less beneficial in terms of operability because of the increased size and weight of the lens system.

Front group linear extension

The rear group remains fixed and only the front group moves straight backward and forward during focusing. This method is primarily used in zoom lenses and allows to design comparatively simple lens construction, but also places restrictions on zoom magnification and size reduction.

Front group rotational extension

The lens barrel section holding the front lens group rotates to move the front group backward and forward during focusing. This method of focusing is also used only in zoom lenses.

Internal focusing (IF)

Focusing is performed by moving one or more lens groups positioned between the front lens group and the diaphragm.

Methods of internal and rear focusing have the following advantages:

Rear focusing (RF)

Focusing is performed by moving one or more lens groups positioned behind the diaphragm.

Methods of internal and rear focusing have the following advantages:

Number of blades

As a general rule, the more blades that are used to create the aperture opening in the lens, the rounder the out-of-focus highlights will be.

Some lenses are designed with curved diaphragm blades, so the roundness of the aperture comes not from the number of blades, but from their shape. However, the fewer blades the diaphragm has, the more difficult it is to form a circle, regardless of rounded edges.

At maximum aperture, the opening will be circular regardless of the number of blades.

Weight

Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

Maximum diameter x Length

Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

For lenses with collapsible design, the length is indicated for the working (retracted) state.

Weather sealing

A rubber material which is inserted in between each externally exposed part (manual focus and zoom rings, buttons, switch panels etc.) to ensure it is properly sealed against dust and moisture.

Lenses that accept front mounted filters typically do not have gaskets behind the filter mount. It is recommended to use a filter for complete weather resistance when desired.

Fluorine coating

Helps keep lenses clean by reducing the possibility of dust and dirt adhering to the lens and by facilitating cleaning should the need arise. Applied to the outer surface of the front and/or rear lens elements over multi-coatings.

Filters

Lens filters are accessories that can protect lenses from dirt and damage, enhance colors, minimize glare and reflections, and add creative effects to images.

Lens hood

A lens hood or lens shade is a device used on the end of a lens to block the sun or other light source in order to prevent glare and lens flare. Flare occurs when stray light strikes the front element of a lens and then bounces around within the lens. This stray light often comes from very bright light sources, such as the sun, bright studio lights, or a bright white background.

The geometry of the lens hood can vary from a plain cylindrical or conical section to a more complex shape, sometimes called a petal, tulip, or flower hood. This allows the lens hood to block stray light with the higher portions of the lens hood, while allowing more light into the corners of the image through the lowered portions of the hood.

Lens hoods are more prominent in long focus lenses because they have a smaller viewing angle than that of wide-angle lenses. For wide angle lenses, the length of the hood cannot be as long as those for telephoto lenses, as a longer hood would enter the wider field of view of the lens.

Lens hoods are often designed to fit onto the matching lens facing either forward, for normal use, or backwards, so that the hood may be stored with the lens without occupying much additional space. In addition, lens hoods can offer some degree of physical protection for the lens due to the hood extending farther than the lens itself.