The Porst Compact Reflex OS is a SLR camera. It is a re-labelled model of the Japanese camera producer Cosina. The model designation of Cosina was “Cosina CS-1”.
The Porst Compact Reflex OS features exchangeable lenses. For this purpose the camera is equipped with a Pentax K bayonet. There is no autofocus with the 35mm camera. You have to focus manually on the subject.
The 35mm camera has an exposure meter. It was designed for films with a speed of ISO 25 to ISO 3200. The SLR camera determines the correct exposure when it measures through the lens (TTL). The aperture and shutter speed can be freely set by the photographer.
The camera has a bulb mode. A external flash can be connected via the PC flash port or Hot Shoe.
Films for the Porst Compact Reflex OS
The Porst Compact Reflex OS exposes 35mm films. For this film format, there is still a good selection of material for color and black and white images. Possible films for the Porst Compact Reflex OS are the Fujifilm Superia 400* for color shots and the AgfaPhoto APX 400* for b/w photos.
The Porst Compact Reflex OS has a thread for a tripod and a connection for a cable release. In addition, there is a self-timer. The dimensions of the 35mm camera are 13,65 x 8,32 x 5,1 cm. The weight of the Porst Compact Reflex OS is 530 g. The needed energy for the camera is provided by two S-76 1.5V batteries (eBay / Amazon*).
The Porst Compact Reflex OS is no longer in production. The value of a used copy is primarily determined by the condition and functionality.
Technical datasheet
| Attribute | Specification |
|---|---|
| Type of Camera | Single lens reflex camera |
| Film format | 35mm |
| Picture format | 24 mm x 36 mm |
| Lens mount | Pentax K lens mount |
| Focus | Manual |
| Viewfinder | Pentaprism finder |
| Exposure times | 1/1000 second to 4 seconds, Bulb |
| Bulb mode | Yes |
| Light meter | Yes |
| Built-in flash | No |
| Flash Connection | Hot Shoe, PC-Flash |
| Flash sync speed | 1/60 s |
| Tripod mount | Yes |
| Cable release thread | Yes |
| Self-timer | Yes |
| Power supply | 2x S76 batteries |
| Size | 13,65 x 8,32 x 5,1 cm |
| Dimensions in inches | 5.37 x 3.28 x 2.01 inches |
| Weight | 530 Grams |
| Company name of the brand | Photo Porst |
| Manufacturer | Cosina |
| Country of production | Japan |
| Estimated value / Used price | 71,66 Euro Estimate based on used prices of 3 offers (possibly with different scope of delivery and/or condition). As of June 15, 2026 |
| Average used price in the year 2023 | 43,29 Euro (46.54 US-Dollar) |
| Average used price in the year 2025 | 98,80 Euro (106.08 US-Dollar) |
FAQ about the Porst Compact Reflex OS
Is the Porst Compact Reflex OS an automatic camera?
No, it's a manual focus camera. You have to manually adjust the focus yourself. It doesn't have autofocus capabilities.
What kind of lenses does this camera use?
It uses interchangeable lenses with a Pentax K bayonet mount. This means you can switch lenses to achieve different effects.
What type of film does the camera take?
It takes standard 35mm film. You can use both color and black and white 35mm film rolls in this camera.
Can I use a flash with the camera?
Yes, it has both a PC flash sync and a hot shoe for connecting external flash units for better lighting in low-light situations.
How big and heavy is the camera?
It's relatively compact, measuring 13.65 x 8.32 x 5.1 cm and weighing 530g. It's a reasonably portable 35mm camera.