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Optical viewfinder for camera

Application of viewfinder

The optical viewfinder is a tool to composition and review images before shooting. It also helps the photographer to choose the focal length of the lens. Also, when the light is low, it is a great help to image composition.

The ALVANDI new optical viewfinder is redesigned. It has a 120° angle of view, with spirit level, that can be seen from the viewfinder. You can change a variety of masks based on lens and format. It has the ability to adjust the diopter. Read more

ALVANDI optical viewfinder with spirit level
ALVANDI optical viewfinder with spirit level
optical viewfinder and 4x5in mask
Optical viewfinder and 4x5in mask
optical viewfinder back view
Optical viewfinder back view

Viewfinder structure

An important part of this device is the optical system. This tool should be able to create an image of super wide-angle at least 140 degrees, directly (no reverse). For this purpose, I used WinLens 3D software for basic design. And according to the patents, and study them, I have created a sketch. This lens is comprised of three elements in the two groups. The front section containing two negative lens and a positive lens is included in the back section.

Optical viewfinder lenses 2 group-3 element - section view
Optical viewfinder lenses 2 group-3 element - catia software section

The next step was cutting and polishing glass lens according to the design. After a long time search, I found artisan it, I ordered for the production. Next step, collection lens is built based on the design, should be assembly inside a chamber. Thus, external body of viewfinder, also designed and were made.

Optical viewfinder with 4x5 in mask - section view
Optical viewfinder with 4x5 in mask - catia software section

The composition system

But, for composition in landscape,with a variety of formats and lenses, I made special frames (mask) for it, which will be installed in front in viewfinder. To make this part, I used from a glass transparent plastic (Plexiglas). By using machines, according to lenses angle of view, I've carved frame with very thin lines. In this regard, I have tried as far as possible do remove error parallex. Table below shows selected format, compared to the focal lens in optical viewfinder.

film format-focal lenght
focal lenght of large format lens  
210 150 90 75 65 47 film format
ok ok ok ok ok ok 6x6 cm
ok ok ok ok ok ok 6x9 cm
ok ok ok ok ok ok 6x12 cm
ok ok ok ok ok ok 6x17 cm
ok ok ok ok ok ok 4x5 in
Optical viewfinder masks
Optical viewfinder masks

Optical viewfinder by using standard flash mount, can be installed on a variety of cameras.

Technical Specification

Viewing Angle: 140°

Masks: 5 Piece, 6X6cm – 6X9cm – 6X12cm – 6X17cm – 4X5in

Material: Aluminum Alloy 7075

Coating: Anodizing

Internal Paint: Anti-reflective black

External color: Semi-gloss black coating

External dimensions: W:77, H:87, D:80 mm

Weight: 300gr

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