DIY Projekt stealing a Pentax ME its Mirrorbox

[Alexander Seidler]

There are so many different cameras out there, perfect designed little miracles of engineering.
One of them must fit anybodies preference. Yes? No? except maybe you want a 24 x 24 mm square format film camera ?
For interchangeable lenses ? Auto exposure ? and a flange focal distance as short as possible for being able to use modern " mirrorless " lenses ?

So here is a little story of my DIY project unSLRing a Pentax ME.

As i already use a Pentax ME with a 24x24 modification, i knew how to do the changes for the film advance.
So as a new step for me the mirrorbox had to be removed, but some functions had to be replaced by custom mechanics, including an electrical contact.
The original electronics for metering and exposure were to big and could not be used.
When the camera was stripped to the main body with the film advance and the shutter, it was possible to make some decisions:
Lens mount M42 (big enough for huge rear lenses but also small enough to fit the camera)
Flange focal distance: 23,8 mm (+4mm for adapting LTM)



Here is a first picture with the modified top cover. I decided to engrave it my family name.

 

[Pete Askew]

What an interesting project, Alexander. Looking forward to seeing how it progresses.

 

[Stevenson Gawen]

Wow, that looks like serious re-engineering! Looking forward to more updates

 

[Chris Bennett]

Fascinating!

 

[Brian Moore]

It's a Seidler ME! Not many of those around. Impressive work, Alexander.

 

[Alexander Seidler]

Thank you folks !

As i knew allready, i could not keep the ME electronics, i had to create a simple analogue circuit. (audio circuits are my profession)
The plan was to do it with only one transistor, a capacitor and two light dependent resistors (LDR)
Mounting the LDRs in a way they measure the reflection of the film - which is a very small amount of light.
The circuit works. Powered by the original battery.



The LDR mounting plate.

For this circuit the original ASA-Potentiometer was not usable.
It had to be a switch. 100 to 1600 ASA in 5 steps will be good for me, including one stop exposure compensation from 200 to 800.
Lots of work - but the best way to keep the pentax ASA wheel - i made a new PCB to fit the original part.





All functionality seems to be prepared.
Looking forward to putting it together !

 

[Alexander Seidler]

Ready for some test shots:

 

[Chris Bennett]

Wow! That looks really good.

 

[Alexander Seidler]

It took me two rolls of "garden gnomes and parked cars" ( www.leicalensesfornormalpeople.com )
for evaluating basic things like light tightness and metering - i will not share with you.

But the first "realworld" photos with the Ricoh GR 28 shot on Ultramax 400.
Exposure is on the long side, but decreasing with lower lighting. I am happy with it for the moment.
It works

​

 

[Pete Askew]

Looking good, Alexander: a really impressive conversion and some damn fine shots too. What did you use to machine the new 'circuit board" ? I was looking forward too the gnomes!

 

[Alexander Seidler]

Thank you Pete. I used my brave CNC mill. No way for the gnomes ;-)

 

[Rob MacKillop]

Wow. My first reading of this thread. Amazing work, Alexander. Love those shots! Especially the chairs and the woman.

 

[Stevenson Gawen]

Amazing work! Great pics too.

I had a bit of a chuckle at the (slightly irreverent) thought of a camera collector finding that camera in say 100 years - wouldn't they be puzzled! It looks completely factory, yet it's a complete one-off. Terrific.

 

[Alexander Seidler]

Thanks Rob and Stevenson !
Three more shots of difficult to impossible metering situations.
I thing the metering circuit did it well.

 

[Rob MacKillop]

Excellent exposure on all three!

 

[Pete Askew]

Absolutely. Very nice shots too.

 

[Murray Leshner]

Very cool.

I end up with parts saved for big ideas I rarely get close to finishing.

I have a cannibalized pentaprism set aside for an imagined pseudo TLR-style viewfinder project. I don't remember what format because I have three piles somewhere of TLR-themed projects, 6x4.5 cm, 6x6 cm and 5"x7". I think the pentaprism one might assure I'm pointing the camera toward the subject. I haven't raised the bar for goals for that yet.

I think the pentaprism donor might also have contributed a 35mm louver focal plane shutter. I'm pleased it is still functional but that's how far I got.

I admire completion of projects.

I tell people I rarely complete mine because there is a brief sentiment that a piece of my soul has died until I remember another project I can resume. Sometimes it feels like the journey is more important than the destination (or I'm rationalizing).