Prism 'hump' not required to be SLR. Minolta did it first, or how Pentax K-S1 could be even smaller

Started Aug 22, 2014 | Discussions thread
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Broken Hill Regular Member • Posts: 215
Prism 'hump' not required to be SLR. Minolta did it first, or how Pentax K-S1 could be even smaller

The leaked images of the new Pentax K-S1 has aroused a lot of curiosity and not a little surprise at the size of the camera. It's unlikely to have an EVF but why do some people seem to think that a viewfinder has to be ' in line ' with the lens to be considered an SLR?

Quite simply it is wrong. An optical viewfinder does not have to be in direct axis with the lens to work and work well and it was proved and introduced by Minolta in 1996 in it's flagship Minolta Vectis S-1 SLR using the new Advanced Photo System film format. the camera was compact and offered a range of V System interchangeable lenses.

To make the camera as compact as possible Minolta designed a radical viewfinder where the light travelled up and then sideways through a number of prisms making the camera very small. Not only is the viewfinder very bright but it has an extraordinarily large eyepice. Bigger than many 35mm SLR's and fully justified in being call a ' High Eyepoint ' viewfinder.

These links give some indication of the way the optical system worked and also the large eyepeice


Though i've tried i cannot find an image of the schematic of the viewfinder arrangement online though Minolta were proud enough of their achievement to show it in the brochure for the camera. Unfortunately my treasured brochure is in London or i would have scanned the image.

Ever since the introduction of the Pentax 'M' series of film SLR's Pentax have pursued a policy of reducing and making their cameras more compact. The K-S1 could well be one of the smallest DSLR's to date but how much smaller could the camera have been if Pentax had been bolder with the design? Could we have seen a radical design which though sporting an optical viewfinder actually looked like a mirrorless camera?

Perhaps one of the the ways for Pentax to differentiate themselves against the other brands is by a totally new style of body design for the entry or enthusiast level cameras. Less looking like a Canon or Nikon but distinctly Pentax.

It's been done before, both the Minolta Vectis S-1 and S-100 were compact and light SLR's and the very first Minolta DSLR, the Minolta RD3000 was based on a Vectis body design. Advanced Photo System film format was better know as APS and guess where the term and the digital format size we use today comes from.


Broken Hill

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Pentax K-3
Kodak Pixpro S-1 Minolta RD-3000
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