Spyderman
Well-known
IMHO it's not important whether the curtain is complete grey (Bessa), white or it looks like on OM-2. The important thing is that it reflects light to the metering cell.
DIY project: simple TTL metering
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IMHO it's not important whether the curtain is complete grey (Bessa), white or it looks like on OM-2. The important thing is that it reflects light to the metering cell.
Murray Kelly
Well-known
I don't think you'd want something brilliant white inside the camera during exposure. That would contribute to flare? OTOH that would be the best color for low light sensitivity.
The Bessa has the outer shutter to play with. It folds away before the main shutter fires. (Hence all the noise).
It will have to be able to work with a 'spot' or similar.
My son is coming to dinner tonight - I will run it all past him then.
As I look at the PCB it looks like you've made space for the LEDs even tho they will live elsewhere?
Murray
The Bessa has the outer shutter to play with. It folds away before the main shutter fires. (Hence all the noise).
It will have to be able to work with a 'spot' or similar.
My son is coming to dinner tonight - I will run it all past him then.
As I look at the PCB it looks like you've made space for the LEDs even tho they will live elsewhere?
Murray
Murray Kelly
Well-known
I had a quick look at that Russian sitewith its very elegant multi resistor arrangement for shutter speeds. I think the 'sunny 16' rule would be easier in the long run.
1. If you want to look back at the shutter a brilliant white line down the edge that retracts into the blind roller first would cause as little flare as could be expected. Say, the width of the gap at highest speed?
2. I looked at my collection (FED1thru 3 and Zorkii-4 and Kiev4 & 4A) The Feds and Zorkii have, as been pointed out, a flat area above the film frame where a CdS cell could live, pointing forward. Very sensitive, too. Problem is, it's out of the frame when you shoot. You'd have to meter with the camera pointing down slightly before actually shooting.
3. The Russian has a bridge with a long-tailed pair consisting of darlington transistor pairs as the detector. Could be made smaller but the bridge and comparator sounds better. What intrigued me was the arrangement of the detector. It faces forward and must flick down as the blind crosses over?
My Russian is confined to yes/no/g'day/goodnight/ thanks. Does it explain how they accomplish this?
4. Nearly all the old cameras (not the Kiev) have this space above the frame and the oldest have this big space below the frame where a SMD PCB could live. No need to gut the selftimer. I think that is where you propose to put the battery? Such a little board could live there, too, possibly?
Just some thoughts.
Murray vk4aok
1. If you want to look back at the shutter a brilliant white line down the edge that retracts into the blind roller first would cause as little flare as could be expected. Say, the width of the gap at highest speed?
2. I looked at my collection (FED1thru 3 and Zorkii-4 and Kiev4 & 4A) The Feds and Zorkii have, as been pointed out, a flat area above the film frame where a CdS cell could live, pointing forward. Very sensitive, too. Problem is, it's out of the frame when you shoot. You'd have to meter with the camera pointing down slightly before actually shooting.
3. The Russian has a bridge with a long-tailed pair consisting of darlington transistor pairs as the detector. Could be made smaller but the bridge and comparator sounds better. What intrigued me was the arrangement of the detector. It faces forward and must flick down as the blind crosses over?
My Russian is confined to yes/no/g'day/goodnight/ thanks. Does it explain how they accomplish this?
4. Nearly all the old cameras (not the Kiev) have this space above the frame and the oldest have this big space below the frame where a SMD PCB could live. No need to gut the selftimer. I think that is where you propose to put the battery? Such a little board could live there, too, possibly?
Just some thoughts.
Murray vk4aok
Murray Kelly
Well-known
As promised I spoke to my son, the electronics engineer.
Firstly he said that modern devices would show little if any drift with the sort of temperatures we're likely to meet.
As for a PCB it would be trivial to design and what you have done is fine, even over done with the LEDS mounted on the board.
I still haven't worked out quite where to put the LEDs.
The hard part would be getting them made (the boards) as commercial houses would expect to make a whole sheet of them. That would be hundreds, they are so small. Not inexpensive, however - some hundreds of dollars. Better learn to etch your own. Fiddly but not impossible.
My sugestion is to make the prototype in 'dead bug' style. Hotglue the IC onto a piece of copper clad upside down and solder the components to the legs. Cut little squares for islands where components are not connected to the ground plane or the IC. Just make sure you mark, clearly, which is pin #1. When its upsidedown it's easy to lose track of the pinout.
Use the smallest resistors you can find. Once upon a time you could get 1/10 or 1/20th watt devices but they have given way to SMDs. I see one can get 1/4 watt resistor that looks as big as 1/8th watt.
I am mulling over the idea of using a 2n5777 transistor - I have some if I can only find the darned things after moving house 5 years ago.
Other devices like diodes and LEDs are photosensitive. The green are best, IIRC. Some very early transistors were in a can to keep out the light. They were mounted in a glass capsule. Take off the can and you have a very sensitive detector. Some were only painted black - scratch the paint off.
I once removed the top of a TO18 transistor and it was very sensitive but it deteriorated over time as the air got at it. Seal a clear window over it and it might last years.
Just some ideas. I feel I haven't helped much. Sorry.
Murray
Firstly he said that modern devices would show little if any drift with the sort of temperatures we're likely to meet.
As for a PCB it would be trivial to design and what you have done is fine, even over done with the LEDS mounted on the board.
I still haven't worked out quite where to put the LEDs.
The hard part would be getting them made (the boards) as commercial houses would expect to make a whole sheet of them. That would be hundreds, they are so small. Not inexpensive, however - some hundreds of dollars. Better learn to etch your own. Fiddly but not impossible.
My sugestion is to make the prototype in 'dead bug' style. Hotglue the IC onto a piece of copper clad upside down and solder the components to the legs. Cut little squares for islands where components are not connected to the ground plane or the IC. Just make sure you mark, clearly, which is pin #1. When its upsidedown it's easy to lose track of the pinout.
Use the smallest resistors you can find. Once upon a time you could get 1/10 or 1/20th watt devices but they have given way to SMDs. I see one can get 1/4 watt resistor that looks as big as 1/8th watt.
I am mulling over the idea of using a 2n5777 transistor - I have some if I can only find the darned things after moving house 5 years ago.
Other devices like diodes and LEDs are photosensitive. The green are best, IIRC. Some very early transistors were in a can to keep out the light. They were mounted in a glass capsule. Take off the can and you have a very sensitive detector. Some were only painted black - scratch the paint off.
I once removed the top of a TO18 transistor and it was very sensitive but it deteriorated over time as the air got at it. Seal a clear window over it and it might last years.
Just some ideas. I feel I haven't helped much. Sorry.
Murray
Murray Kelly
Well-known
Found the 2n5777 light transistors. They are darlingtons too, and will be harder to test than just with the multimeter. More and more voltage needed.
Still don't know where you plan to install the leds.
Murray
Still don't know where you plan to install the leds.
Murray
Spyderman
Well-known
Thank you for your ideas.
The manufacturing of the PCB is not a problem - there is a guy here that makes them in small batches - price based on size and number of holes to drill. Together up to $ 10 for one.
I'm not that much affraid of the white painted curtain... maybe I'll make it gray. Leica also uses something similar in M6 and newer.
And considering that the CdS are very sensitive to red light, maybe blue-ish spot on the curtain would compensate for the higher red sensitivity...
The project is sleeping at the moment, because both I and my friend have lot of work for school. But I hope I'll be able to work on it during the summer.
I'd be most grateful if you could design a PCB for me. I know the one from my friend is far from perfect. We could work on it a bit more, but we're both just beginners at this.
BTW: if I put the board between the lens and film gate, where could I place the battery ? Any ideas ?
The manufacturing of the PCB is not a problem - there is a guy here that makes them in small batches - price based on size and number of holes to drill. Together up to $ 10 for one.
I'm not that much affraid of the white painted curtain... maybe I'll make it gray. Leica also uses something similar in M6 and newer.
And considering that the CdS are very sensitive to red light, maybe blue-ish spot on the curtain would compensate for the higher red sensitivity...
The project is sleeping at the moment, because both I and my friend have lot of work for school. But I hope I'll be able to work on it during the summer.
I'd be most grateful if you could design a PCB for me. I know the one from my friend is far from perfect. We could work on it a bit more, but we're both just beginners at this.
BTW: if I put the board between the lens and film gate, where could I place the battery ? Any ideas ?
Murray Kelly
Well-known
A quick reply - your friend's board is fine if you just allow for pads to solder leads to the LDR and LEDs instead of mounting on the board. That would save a little space. 'Dead bug' is a very viable substitute for a board. Not in this case, but at high frequency it often performs better than a PCB.
Batteries are a bit of a problem. Maybe (I haven't checked) there's enough room in there for a battery pack with flying leads? Solder directly to the cell?
Or, maybe, on the bottom plate, covered by the carry case. Especially OK if the camera has a hinged back. Excludes the one I want - the FED-2. :-(
I still can't figure where the leds will go. Haven't been into the top plate of any of these. Only the Bessa-R, and that was 'packed'!
Murray
Batteries are a bit of a problem. Maybe (I haven't checked) there's enough room in there for a battery pack with flying leads? Solder directly to the cell?
Or, maybe, on the bottom plate, covered by the carry case. Especially OK if the camera has a hinged back. Excludes the one I want - the FED-2. :-(
I still can't figure where the leds will go. Haven't been into the top plate of any of these. Only the Bessa-R, and that was 'packed'!
Murray
Spyderman
Well-known
There's plenty space for the LEDs 🙂 FSU tops are almost empty...
Especially on a FED-2 I was thinking the LEDs could go beside the viewfinder on the right-hand side. That way it would be visible even when not looking into the viewfinder, but still visible with your peripheral vision when you're looking through it. Also a red-green LEDs would make it easy to distinguish the moment when they're switching...
So basically I've got it all in my head, now just make it real 🙂
Especially on a FED-2 I was thinking the LEDs could go beside the viewfinder on the right-hand side. That way it would be visible even when not looking into the viewfinder, but still visible with your peripheral vision when you're looking through it. Also a red-green LEDs would make it easy to distinguish the moment when they're switching...
So basically I've got it all in my head, now just make it real 🙂
Murray Kelly
Well-known
Found some really tiny LEDs for surface mounting today. Also tracked down the 2n5777 s. Will visit a better store tomorrow if possible for more stuff.
Just because I have them, I am tempted to go the darlington transistor circuit as at the russian site. Your'e right - the batteries are the headache.
Murray
Just because I have them, I am tempted to go the darlington transistor circuit as at the russian site. Your'e right - the batteries are the headache.
Murray
Azaroth
Newbie
Hello Ondrej,
So, what happend with the project? Did you finished it?
I'm working on a TTL meter for a Zorki 4, but i'm using a different approach (more complex sensor & microcontroller). Your project is much simpler and I would like to know if i overcomplicated things 🙂)
So, what happend with the project? Did you finished it?
I'm working on a TTL meter for a Zorki 4, but i'm using a different approach (more complex sensor & microcontroller). Your project is much simpler and I would like to know if i overcomplicated things 🙂)
kotokot21
Wrenchfinder
Maybe now things are easier when you can just buy an dirt-cheap module like this, with little work after? Still it's very interesting to make such a meter, even in one of the smallest cameras like Zorki/Barnack.
I'm completely not confident in creating electronics, hence I'm bumping this 6 years old thread — maybe someone will have more ideas on this.
I'm completely not confident in creating electronics, hence I'm bumping this 6 years old thread — maybe someone will have more ideas on this.
Murray Kelly
Well-known
Thanks for the input Kotokot, it certainly is a neat solution. The price is right! I couldn't buy the parts for that . I can't see the light sensitive components but there may be 2 in the white boxes on top. Could be diodes in clear encapsulation.
I cut a piece of card 3.2 x 1.4 cm and it won't fit above the gate in a FED II but just (and only just) goes below. May need a teensy reduction of the width of the PCB. It will fit if sloped back a little but I wonder where the sensitive components are?
In my ramblings I never did think of where to put a power source. (Battery)
BTW this thread is 8 years old so you aren't a mathematician either😀
Good luck
I cut a piece of card 3.2 x 1.4 cm and it won't fit above the gate in a FED II but just (and only just) goes below. May need a teensy reduction of the width of the PCB. It will fit if sloped back a little but I wonder where the sensitive components are?
In my ramblings I never did think of where to put a power source. (Battery)
BTW this thread is 8 years old so you aren't a mathematician either😀
Good luck
kotokot21
Wrenchfinder
My mistake, I was just counting years from the last comment. There is a CdS cell with short legs, that red thing. It could be easily resoldered or changed to another one. The power source would be better to live underneath the bottom cover of the camera, wouldn't it?
Murray Kelly
Well-known
kotokot21, I think you are right. I mistook it for a capacitor. In that case it could be unsoldered and mounted anywhere you like as you said, and the rest of the board similarly. A couple of fine wire leads to link the one to the other.
I do believe I've never had the top or bottom plate off - well not recently anyway. The most I had to do was adjust the curtain tension.
Good luck and thanks for that.
I do believe I've never had the top or bottom plate off - well not recently anyway. The most I had to do was adjust the curtain tension.
Good luck and thanks for that.
Alfonso B
Established
While prototyping is easier and cheaper than ever, it is still hard to make electronics usable. Reading the shutter speed is one of the major difficulties, you might consider taking apart a bunch of old cameras and finding the best donor for a potentiometer that fits inside the top plate, around the ss dial shaft. You also need a way to set iso and an on/off switch implemented on the camera body. Choosing the right microcontroller is also crucial, you need a couple of analog inputs for reading shutter speed and iso and 2 digital outputs for indicator lights. Power consumption needs to be absolutely minimal so Arduino is pretty much a no-go. You need to fit a 2-cell power source if using leds for indication so mc needs to operate at ~2,8v. The subject is pretty interesting, if I had to have a meterless Leica I would surely do something like this to it 🙂
kotokot21
Wrenchfinder
I guess, the best victim for this job would be a Zorki-C or a Zorki-2C. They are rather ugly (compared with regular Zorkis or barnacks), but they're still small, however with enlarged top plate, perfect to accomodate all the electronics. There's an additional selector around the shutter speed dial, which is a delay selector (used for flashbulbs). It could be remade to become an ISO selector. Also there's plenty space there, and it's possible to cut a bigger finder window and put a better finder there (Leica IIIg style). Perhaps it's more difficult or impossible to use the russian scheme for Zorki-4 ttl (the shutter speed dial part), because the speed dial is rotating and can be set both after and before cocking the shutter. I need to investigate this and first get a proper Zorki-C.
Alfonso B
Established
Iso selector on the same axis would be great as you could possibly cope with one potentiometer for both functions. I'm not familiar with zorkis and totally forgot about the selector rotating while winding thing, could make things a lot harder.. If you 3d print a thicker baseplate, you could possibly fit a cut down small prototype board there so there's no need for custom pcb.
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