Digital back for M film cameras

Let me preface this by saying that my knowledge of digital hardware design is limited, and what I propose may be out of the realm of possibility.

There seems to be a somewhat firm belief that this unit needs to be a single, unified piece of hardware. It does not.

I propose a 2-piece construction. A backdoor replacement, and a baseplate unit.

The digital backdoor obviously holds the sensor, and attaches on the preexisting hinge mechanism--folding up and down in the same way that original door does. Easy on/easy off--easy cleaning. At the bottom of the door, where the original door extends into the baseplate, and is secured, the digital back will have a long, thin digital connecter strip.

This this thin plug, as it were, will connect to the baseplate unit. Think modified USB.

The baseplate will contain the power supply, and the majority of the hardware including card slot(s). The baseplate will attach in the same manner that the traditional baseplate does.

This has distinct advantages concerning battery life, because larger batteries could be attached without having to change the sensor unit.

The film canister cavity could be utilized to the full extent possible, but only as additional space for the baseplate unit--perhaps a portion of card slot could extend into the body.

This way--the unit does not extend out from the back of the camera, but the primary volume of the hardware would extend down--like a leicavit.

Other considerations:

An LCD would be nice, but is certainly not required.
Perhaps a small screen that displays histograms and iso.
Again, not required.

iso selection could have dedicated dial--perhaps on the baseplate unit.

Pirate's idea about the takeup spool trip is viable.
Two different attachments for each type of takeup spool.

In order to avoid "eating" batteries--have optional controls for the sensor--perhaps a type of auto-off that can be manipulated or disabled--some type of manual override.
Again--a switch or button on the baseplate unit.

Perhaps a fine-tune adjustment for focus--a concealed screw on the sensor unit would work--this would allow for focus compatibility across models.



You know--something like that.



Also, it sounds like Frankie knows what he's talking about.
 
NathanJD said:
i think that would work - i think the camera could do with a main on/off switch as well then so that your 'ready and waiting' CCD isn't just eating your batteries.
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Use the shutter "B" setting as on/off switch...just like an M-6; or an uncocked shutter functioning as default "off" position.

On another note:

Recently, I purchased a shutter speed tester on eBay. A solid-state device hand-built by a Romanian and only $15. Works brilliantly with freeware from Audacity.

The unit is essentially a LED-like light sensor ~2mm in diameter with related circuitry all housed in a plastic box...a match-box size thing that happened to fit right into the rail-cavity of an M. That light sensor is the very type-thing Brian Sweeney talked about as a tripping sensor for the retrofit.

Brian knows I have been at this a while.

My latest design evolution avoids outward clues that the M2/3 camera has been retrofitted...no on/off switch, no WB window, the rewind knob now a 2/3 position toggle switch for something (perhaps daylight, A, tungsten), no LCD, no frame counter needed [use the existing one], and the "Bulb" socket converted into a steady/blinking "ready" and "low battery" warning light; ...except, perhaps a mini-USB hole somewhere for the iPod LCD. [A design tradition started in my stereo plotter digital-retrofit old days of mounting encoders onto existing holes...cheap and easy too.😀]

Gutting a Sony NEX to try out ideas is well within my budget. An APS-C size Leica-M retrofit might just work out...and my CV 25/4 and 50/2.5 lens pair for my RD-1 is ready.
 
wilonstott said:
There seems to be a somewhat firm belief that this unit needs to be a single, unified piece of hardware. It does not.

I propose a 2-piece construction. A backdoor replacement, and a baseplate unit.

The digital backdoor obviously holds the sensor, and attaches on the preexisting hinge mechanism--folding up and down in the same way that original door does. Easy on/easy off--easy cleaning. At the bottom of the door, where the original door extends into the baseplate, and is secured, the digital back will have a long, thin digital connecter strip.

...Also, it sounds like Frankie knows what he's talking about.
Click to expand...

Your idea is not strange at all. In fact, one of my old gang champions that idea...also opens the door for easy sensor upgrades [but removes the option of motor drive or rapid-winder] Thin and calibrated shims are easy to obtain and Leica M8/9 use shims to adjust for perfect focus anyway.

The removable back door is thus replaced by a thin box containing the sensor chip-set unit. Perhaps needs to stick out 1 or 2mm more.

The base units styled and sized like a rapid-winder houses the rest. [TomA and myself both live in Vancouver. We know each other and have mutual friends.🙂]
 
Are we still talking about a camera that is switchable from Film to Digi anytime we want? Frankie, it sounds like your mods make the camera more of a permanent digi?
 
Pirate said:
Are we still talking about a camera that is switchable from Film to Digi anytime we want? Frankie, it sounds like your mods make the camera more of a permanent digi?
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Making it a two-way switchable unit is one of the ideals I am striving for. If I had to pick, I would go permanent digital. Buying a companion film-M will soon be very cheap.
 
Ok, got it. All my thoughts on this are geared toward a switchable unit. I can't see changing an older M into a completely digi camera. There's just too many digis out there if that's all you want, even though I understand the appeal of the M... that's why I own them for sure.
 
wilonstott, the 2-piece idea is great. I don't know why I didn't see that before, I was only thinking to use the door or a remade door for the pressure plate of keeping the sensor in place. Using the 2-piece idea and having the door house the sensor and other stuff is great.

You guys think this will be eventually doable in Full Frame sensor?
 
Pirate said:
This is a quick mock-up of what my system would look like, all parts being on a new baseplate. Stow the original base until you go back to film. The sensor would be suspended in the middle - stiff suspension so it doesn't flop all over the place, and when loading everything with the door opened, you can make sure it sits properly in place and close the door on it, securing it down with the pressure plate on the door.

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Another option I'm thinking of....

Also a replaceable baseplate model, but a thicker base plate to house a proper battery, removeable SD or micro-SD card. A base of about 3/4 inch thickness that would attach just like the original base yet give you all the room needed for extra electronics. The two film spool areas would still be utilized for the main components as in my first idea, but now the base would let us add anything we want without adding much weight to the camera.
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I love this discussion, and I'd be willing to shell out $1500 or so for a unit that would plug right into my M2 and give me 1.3x or less crop. All the better if I could also pop out and replace with film without a major operation. I'd pay more for that.

Maybe it's just a failure of imagination on my part, but does anyone see a mechanical issue with a design such as the one pictured? I don't know about you guys, but I have to hold the baseplate at an angle to get the hole in the baseplate hooked over the lug on the body that secures the non-clamp side. It would be impossible to tilt the pictured arrangement that way if it were a one-piece affair.
 
Details. It's all in the Details. That was just a quick mock up of a general idea.

The end tab you are referring to is quite easily solved. I have two ideas already, but it's not worth putting in here yet.
 
My initial idea was to house the sensor/chip-set in a thin box [45 x 90mm and up to 10mm thick; making the outrigger thickness no more than 3mm additional], replacing the back door.

Two tab-like flexible circuit board extends from the box: one connecting to the battery in the film cartridge chamber and the other to the take-up spool chamber where a micro-SD reader like device mounted on a semi-cylindrical pillow-block slots into place.

With no external mod involved [listed previously], and no chassis surgery involved, reverting to original condition is easy.

This idea also works for my Nikon F, F2, FM and FM3A (the favourite).

As I had long said: the biggest problem is packaging the thin box...and working on it.
 
Pirate said:
Details. It's all in the Details. That was just a quick mock up of a general idea.

The end tab you are referring to is quite easily solved. I have two ideas already, but it's not worth putting in here yet.
Click to expand...

Oh, I thought it was ready to sell (except that the sensor already has an image on it). 🙂

Looking forward to more.
 
I agree that such a unit would have to fit within the door space lest it require severe and irreversible changes to the camera. A unit inserted as film would surely risk sensor damage. At the same time a door unit would require some pretty strict tolerances to position the sensor properly. I don't know about you, but my M3 door has the slightest touch of play - probably enough to induce CA on a sensor.
 
flip said:
I agree that such a unit would have to fit within the door space lest it require severe and irreversible changes to the camera. A unit inserted as film would surely risk sensor damage. At the same time a door unit would require some pretty strict tolerances to position the sensor properly. I don't know about you, but my M3 door has the slightest touch of play - probably enough to induce CA on a sensor.
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No. The sensor cannot be inserted as if it is a piece of film. The package cannot even be mounted via the hinge pins. The only thing that can be rely on is the top surface of the inner film rails, which supposedly would be precise to the flange to film plane specifications of the M-mount (28mm less 2 thousand's or 50u). Leica made them...no? 😀

The back door is merely a convenient opening...already cut and nicely finished.

To get a batch of CCD with substrates at precisely 35mm wide is no problem. The front bezel of the CCD (where the UV/Bayer filters and cover glass is mounted) could even be custom ordered with only a 1mm rim all round, making it a 22 x 34mm net opening size or a 1.06X crop-factor. The front bezel will now fit into the format opening and simply drops in. Affixing and shimming the CCD to the chassis is a different matter.

And to order panchromatic version (meaning no Bayer filter at all) is also doable...and common in all digital aerial cameras. [I am in the know for some time before digital aerial cameras were commercially introduced in ISPRS 2000.]

At 1.06X crop-factor, and given the M-framelines are always loose (~85%) anyway, no frameline modifications are necessary. I couldn't care less if my 35mm lens is now a 37mm equivalent...do you?
 
Would it be possible for a hobbyist to build something like this from the ground up?

* purchase FPGA
* purchase DRAM
* purchase ADC
* purchase SD card reader
* purchase full-frame sensor with electronic shutter (CMOS/CCD)
* Design and prototype the main PCB
* Design and prototype the sensor board
* solder everything together
* write the firmware to initialise and self check
* write SD card driver
* write control firmware for varying the ISO
* CAD design to design the housing for the electronics
* design a battery system

Anyone recommend a resource/forum to read up more and the likely cost of such a project?
 
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Hobbyists can build everything, it's all matter of cost, skill and time involved. Also I think it will cost quit a few times more then commercially available products (like M9). But if you really want to take a plunge (since at least it will teach you a lot) I would recommend you to pay a visit to local hacker space and see who's around your area with skills, if any. I'm not knowledgable enough to give you insight on exact costs, time or skills required but I know it will be a huge project, actually if your asking you most likely don't want to spent all the time required in learning everything, but I might be wrong on that one.
 
Santtu Määttänen said:
Hobbyists can build everything, it's all matter of cost, skill and time involved. Also I think it will cost quit a few times more then commercially available products (like M9). But if you really want to take a plunge (since at least it will teach you a lot) I would recommend you to pay a visit to local hacker space and see who's around your area with skills, if any. I'm not knowledgable enough to give you insight on exact costs, time or skills required but I know it will be a huge project, actually if your asking you most likely don't want to spent all the time required in learning everything, but I might be wrong on that one.
Click to expand...

Thanks for replying. Here is a block diagram showing what's involved..It is definately a huge project like you say..

http://focus.ti.com/docs/solution/folders/print/80.html
 
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