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Pentax Auto Bellows 645

Reviews Views Date of last review
1 2,971 Wed January 3, 2018
Recommended By Average Price Average User Rating
100% of reviewers $640.00 9.00
Pentax Auto Bellows 645

Pentax Auto Bellows 645
Pentax Auto Bellows 645
Pentax Auto Bellows 645
Pentax Auto Bellows 645

An Auto Bellows for the Pentax 645 that allows extreme magnification with 645 system lenses. Very rare on the second-hand market.

Pentax Part Number: 38421

New Price (1999): $999.95 (US)

-Minimum 54mm
-Maximum 180mm

Dimensions (WxHxD): 3.9" x 7.8" x 8.4" (100mm x 197mm x 213mm)

Weight: 3.6 Pounds (1.6 kg)
In Production: No

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Registered: August, 2007
Location: Coquitlam, BC, Canada
Posts: 426

1 user found this helpful
Review Date: January 3, 2018 I can recommend this item: Yes | Price: $640.00 | Rating: 9 

Pros: Excellent Build, Streamlined design, smooth functions, pleated bellows protected when closed
Cons: Shorter extension range than the 6x7 Auto Bellows

The Pentax Auto Bellows 645: This bellows unit is similar in basic design to the other auto bellows units, utilizing the strong, well-engineered, single “X” rail configuration. It also incorporates a geared tripod mounting block. This block can be positioned along the bottom of the X rail to properly balance your camera/bellows/lens combination. The operation of the bellows unit is smooth, with front lens board, rear camera board, and movable tripod seat gear operated with micro-action control knobs. The movement of all three components are precise, allowing no creep, and has a locking knob on the opposite side to the control knobs.

The bellows is sleek; round cornered, with a satin black finished, a more modern looking design than the earlier “35mm” bellows units. With the front lens board and the rear mount board completely closed, the pleated bellows is inside the mounting boards, which protects it and keeps it dust free. The bottom plate has a generous mounting surface and includes a threaded 1/4 -20 (UNC) mounting hole as well as a 3/8-16 (UNC) threaded hole to accommodate larger tripod studs. There was no slide copier made for this auto bellows.

This bellows allows Aperture-Priority AE and Metered Manual operation with an extension range from 54mm to 180mm. This medium format auto bellows does not have as wide a magnification range as the “35mm” auto bellows units. The attainable magnification range it allows is only from 1.0x to 4.3x with the 55mm f2.8 lens. The Pentax Auto Bellows 645 is usable with all 645 lenses below 300mm, with the exception of the zoom lenses. In an early brochure it states that it is not usable with the leaf-shutter lenses, but in the bellows operating manual it includes these lenses and their accompanying magnification tables.

In reviewing the lens tables in the bellows manual it would appear that the most optimal lens would be the SMC Pentax-A 645 55mm F2.8, or the SMC-D FA 55mm F2.8 in that it achieves 1.0x to 3.2 times life size in normal mode to a magnification of 4.3x in reverse position. The SMC Pentax-A 645 Macro 120mm F4.0, or SMC Pentax-FA Macro 120mm F4.0 would also be good choices. As well as achieving slightly more working distance from your subject, this lens can be used in two different modes with the bellows unit. One by using the bellows set at the minimum 54mm and then setting the lens to the various lens extension scales, and the other by setting the lens to its minimum setting and then extending the bellows to reach 2.7 times life size. This gives a moderately wide range of magnification from 0.44x to 2.7x while allowing a comfortable working distance.

Unlike the other Pentax Auto Bellows Units, the front lens board is not reversible and requires a reverse adaptor to enable the lenses to be mounted in reverse position. When doing so, keep in mind that the 645 series lenses do not have a manual, or non-automatic aperture setting and cannot be stopped down without externally engaging the aperture mechanism. The lens is reversed by using a set comprised of two components, a Reverse Adaptor 645 (58mm) for mounting the lens using the filter thread, and a Reverse Attachment 645 which mounts on the exposed lens flange, engaging the aperture components and allowing the lens aperture to be operated manually. The Reverse Adaptor 645 (58mm) has a locking set screw that allows the lens to be rotated after mounting to orientate the aperture control markings so that they are clearly visible, from any viewing position.

The bellows has a cable release socket on the front board, connecting to a stop down mechanism for the lens. On the other side of the front lens board there is an optional, manual, lockable plunger for stopping the lens down. As well there is an electro-magnetic release socket that was designed to connect to the electro-magnetic shutter on the on the 645 film camera bodies. This requires the Infrared Remote Release Cord 2P, which is included with the bellows. This cable is shown iin the illustration. Also included is a single mechanical cable release.

Either the Pentax 645D or 645Z digital camera bodies can be used with this bellows. To coordinate the synchronized release of the camera shutter and the lens stop down, a Pentax Double Cable Release A must be used with a modified Canon T3 Cable Release Adaptor to connect to the body. Another alternative would be to modify the Infrared Remote Release Cord 2P with a 2.5mm Stereo plug on the camera connection end.

When mounting the camera body, it is advisable to mount the bellows unit securely on a tripod before attaching the camera body; otherwise the weight of both units can make this operation awkward and accident prone. To mount the camera body you simply line up and engage the mounting flange, or remove the camera mounting ring and connect it to the camera body first. To remove the camera body from the bellows, loosen the fixing screw on the rear board and remove the camera body and camera connecting ring as one piece and then remove the camera connecting ring. Note:The lens release button is not accessible with the body mounted on the bellows.

As the maximum extension is only 10mm longer than the 35mm bellows units more lens extension may be needed for additional magnification. This bellows can be used with both the Auto Extension Tube-A 645 Set and the Helicoid Extension Tube 645 for extensions beyond the maximum allowed by the bellows. Keep in mind that the Auto Extension tubes are better mounted between the lens and the bellows to allow the lens to stop down automatically. On the camera mounting board there is no auto aperture connection and the Helicoid Extension Tube 645, which has no aperture components, may be used for additional extension.

Of course Pentax SMC Takumar 6x7 and SMC Pentax 67 lenses can also be used on the Pentax Auto Bellows 645 with the Pentax Adaptor 645 for 67 Systems and still maintain auto diaphragm operation.
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