Yoshizen's Blog

Save a junk (replace a Prism of Pentax)


In our network, I seems to be a man, the most hopeless junk would end up.  May be because I could find a way to repair or utilize it = not just I got some skills but also I’m keeping many junks which could be used as a spare to repair.  So, people described me a resourceful man —– then I gave a thought or two

—– May be the matter here was not what I got for spare or a skill to use but the way of thinking. = I got very flexible way of thinking, — or more precisely I never trained to follow the standard or regular method, therefore I may conceive totally different approach and able to find a fancy solution.  This is a freedom to be an outsider.  😀

One typical sample is the Tilting Macro Bellows of which I made the orignal nearly 50 years ago.  Only a small cost of lens and camera body caps + straight bracket etc, (and some cut and grue works) = what I got was a device which can make a close-up photo up to 1:1 + tilting adjustment.  Simply the reason to make such adapter was, I needed to have a macro lens though, I didn’t have a money (I was a Uni’ student and my saving had gone to Nikon F body and 50mm F2 already). —– If it was the situation, the answer and the solution was, why not to make one myself !  The requirement for close-up photo was, to hold the lens further away from the body, and how far from the body correspond to the magnification = 50mm extension for 50mm lens would create 1:1 / life-size close-up. —– And what I made, Tilting Macro Bellows, was good enough, and worked exactly what I expected.  In there, there was no jump of thinking = everything was pretty rational and simple —– yet still, as no body ever made like this before indicates, there was a kind of blockage in thinking that the camera device must be very rigid and elaborated. (to be a good salable commodity —– no solution for homemade poor man’s choice can be existed) 

A Pentax film camera brought by somebody got hopelessly heavy black fungi in the center of the finder prism.   In normal sense, the prism may be replaced (by Pentax or somebody keeping a spare parts) but the cost of the repair would be no less than £50 or even more, while the value of such old camera would be less than £50.  It’s no worth to consider. = so, the camera came to me.  —– I was thinking to use its mirror to make a side view adapter etc. 

Then somebody need a film camera for Pinhole photo, I thought this camera can be a good candidate.  For hours of ultra long exposure (use dark ND filter together) view finder has to be blacked-out too. —– but, to frame a direction, finder would be useful. —– To remove the fungi, peel off the paint and coating then clean the glass — is a straight forward procedure though, — wait a moment, the prism of the 35mm film camera must be all same size (as the image size is the same 36×24 mm) the prism doesn’t need to be the same Pentax. = Why not Canon. (as I happen to have a disassembled Canon body, it was easy to get a prism out of its frame.

So, I disassembled the Pentax K1000 body to remove the fungi infested Prism. (It’s alway the case, — I know from the past 40 years experiences — a screw fixing the wind-up lever is the most awkward to Remove.   Some of them were CCW screw and break-off, or using screw lock grue = needed to heat-up and melt) 

Once the top cover was removed, the prism is easily accessible.  Behind the prism (alongside the view finder) mounted CdS are for measuring the exposure. (Photo Right)  Pentax is doing exactly the same since their SP, but later addition of the top (smaller) CdS is to compensate the strong back (sky) light.

(Photo left was Pentax prism.  Photo middle was Canon Prism.  Photo right = Canon prism was happily settled on the Pentax head. )

On the end, the Prism swap operation was a great success.  Leaving an empty Canon junk frame behind,  the Pentax K1000 got new lease of life.     🙂


9 Responses

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  1. An Anonymous Pentaxian said, on February 5, 2018 at 00:15

    Hi Yoshi,

    Excellent work you’ve done. Can you tell me which Canon camera you cannibalized to save this K1000?

    best regards 😀

    • yoshizen said, on February 5, 2018 at 02:43

      Hi Mr.Pentaxian It was the EOS 50E. ( I think, any one but expensive 100% view type could be used, though 50E Prism was a bit larger than Pentax (about 0.5mm)
      therefore the Pentax housing became a bit tight.)

  2. Joey said, on July 28, 2019 at 06:12

    What Cannon did you use for the prism swap?

    • yoshizen said, on July 28, 2019 at 06:43

      It was a Canon 50E. Though, I think any cheap model would do the same.

  3. Wim HH van Heugten said, on January 23, 2021 at 16:18

    You mention that the third sensor is to compensate for the sky light. It is not. It’s the (in)famous photo-switch that switches on the light meter when enough light shines on it. If you use a prism without light exit to this sensor, the meter will not switch on.

    • yoshizen said, on January 23, 2021 at 22:14

      Thank you Wim for you to educate me. In fact, my use of the Pentax was SP (M42) in my High-school time and the
      ME many years later for fun. The K1000 was given by a friend of my friend, and I have had no knowledge of the function of the third CdS. (So far, I haven’t have tested the K1000 with a film yet)

  4. Miguel said, on April 17, 2021 at 00:52

    Hello Yoshizen.
    I have an chinese K1000 model with the prism infested with mold. Is there any change of cleaning it or I must change the entire prism?
    Thank you

    • yoshizen said, on April 17, 2021 at 01:14

      Hello Miguel.
      There is almost no chance to clean the prism = interesting charenge though. Find a junk SLR would be much easier and a cost almost nothing.
      I wish you have good luck.

      • Miguel said, on April 17, 2021 at 13:26

        Thank you! Best

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