Hejnar PHOTO F68 Dual Captive Slot QR Clamp Review

The release of the 5/8" thick Hejnar PHOTO G15/16 Series of Milti Purpose Rails a few months ago, inspired me to start studying and further improve a design of a really Heavy Duty Multi Row Panorama Head that could withstand the offset load of long and heavy lenses.

This brought up a need of a dual slot clamp in order to support the vertical bracket, larger and more sturdy than the F69 used with Multi Row Panorama Head Ver. II

The Clamp
Hejnar PHOTO F68 is a dual-captive-slot quick release clamp unique as a concept. Where other quick release clamps have a center hole, this one has two individual captive slots in line, permitting attachment and adjustment of the clamp on some rails or other support equipment.

Manufacturer Specification:
Model:	F68 Dual Captive Slot
Jaw Length:	60 mm (2.375")
Mounting Screws:	Two 1/4"-20 captive hex-socket
Mounting Slots:	Two captive
Weight:	105 gr (3.7 oz)
Material:	6061-T6 Aluminium, Black hard coat anodized
Hardware:	Stainless Steel
Made in:	U.S.A.

The F68 clamp comes in a padded package with two 1/4"-20 screws, ½" (1,27cm) long and one Allen Hex key. As all Hejnar Photo products it is machined from 6061-T6 Aluminium, nicely finished and black hard coat anodized. The F68 comes with a large black knob with a diameter of 24mm (0.95"), although there is a choice between clear, black long and short knobs. The two captive slots can accept 1/4"-20 captive screws from top.

Due to the required length of the two slots, F68 does not follow the other Hejnar clamps' design pattern but is rectangular in shape without safety stop screw relief grooves, which are anyway unnecessary for its intended task.

On the other hand, it does have the 5 laser engraved index marks on each jaw, with a Φ center mark, common to all  2.375" (6 cm) Hejnar clamps. The marks are at 1cm intervals, very useful for the alignment of the clamp on rails or vice versa.

The bottom side has a deep hole coming from the removal of any excess material in order to lower the clamp weight. The two captive slots are joined by a deep groove that permits the alignment of any bosses or anti-twist islands.

An enlarged view of the above photos, shows better the Hejnar PHOTO standard moving jaw mechanism which utilizes tongues and grooves with rounded edges and hidden springs avoiding the accumulation of dust and dirt, ensuring smooth operation.

F68 Drawing with detailed specs courtesy of Hejnar PHOTO. (Click to enlarge.) 

Used as a Panorama Vertical Bracket support & regulator.
Although this clamp may find other uses by the utilization of its captive slots, my original intention was to form an extra sturdy vertical bracket that may be detachable and adjustable.

Both 1/4"-20 captive screws and the appropriate Allen hex keys are needed for this purpose.

Pictured above is the Hejnar PHOTO G103 -90 degree- Block attached on the rear end of a prototype Hejnar PHOTO G15-80 Multi Purpose Rail. The F68 Dual Slot Clamp fits on the bottom 1/4"-20 tapped holes of the rail and block, while the anti-twist island found on the block will sit in the fore mentioned groove at the bottom of the clamp.

After the screws are inserted and tightened F68 becomes a broad and very sturdy base for the vertical rail ...

... that can now be mounted / dismounted and regulated on a horizontal base rail  at will.

Arca-Swiss® Compatibility
The F68 Dual Captive Slot quick release clamp, besides the Hejnar PHOTO own rails, was also tested with various camera plates and lens plates, as well as with multipurpose long rails of various thicknesses and widths. Plates / Rails tested were from Benro, Kiwi Fotos, Fotoporo, and Marumi with excellent results.
For the readers that like numbers, I hereunder quote detailed measurements of the clamp Jaw dimensions, so as they can decide whether this clamp is compatible with the dimensions of their plates or rails.

Clamp Jaw dimensions	mm
Jaw Length	60.30
Steady Jaw Height	05.10
Moving Jaw Height	05.08
Min Jaw Lip Opening	31.46
Max Jaw Lip Opening	38.19
Min Base Opening	39.00
Max Base Opening	46.08

All dimensions fall within the average limits, consisting this clamp compatible with almost any Arca-Swiss® type plate and rail.

Pros
Very nice sturdy and dirt-proof design.
Very precise machining, very good finishing and anodizing.
Excellent clamping strength with large clamping surfaces.
Excellent Compatibility with virtually any Arca-Swiss® type plate or rail
Good value for money.

Cons
None against the purpose of the clamp.

Conclusion
A specialized quick release clamp with a limited number of uses. However it is a very strong and sturdy QR clamp, designed to support heavy loads even on a vertical panorama-head bracket very effectively which is a quite stressful task.

Note: The F68 clamp presented in this article is a prototype / first-production unit, kindly offered for evaluation and review by Chris Hejnar of Hejnar PHOTO. Therefore, there may be some small visual or functional differences from the final production units. For final products you may visit the "Special Clamps" section in the Hejnar PHOTO online store.

I hope you found the article and ideas useful, thank you for viewing.
All Photos: © S.C.Vlachos

Price and Availability:
Current price for the F68AB Dual Captive Slot clamp is US$ 65.00 (+Shipping where applicable).
and is available from the Hejnar Photo online store
Check the Recommended Sellers page for a valid Hejnar Photo discount coupon.

Referenced Articles:
Create a Heavy Duty Multi Row Panorama Head
Create a Multi Row Panorama Head Ver. II
Hejnar PHOTO G103 -90 degree- Block
Hejnar PHOTO G15-80 Multi Purpose Rail

Relevant Articles:
Hejnar PHOTO G21-80 MPR/Vertical Rail Review
Hejnar Photo New QR clamp Series