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Greg_E
06-13-2006, 04:37 PM
I was cleaning up some trhings at work, and came across something that I was going to strip for parts, when I had a different idea! I have a Polaroid Freezeframe Video Image Recorder that has a 35mm camera back/thing. It's a focal plane shutter, 35mm camera with no viewfinder, but with a motor drive, and wonderful super accurate plastic film guides.

It also has some sort of multi element, multi coated close up lens.

I was going to be working on a 35mm pinhole that attached to the 35mm film back for my Mamiya 645, but this seems like it might be a better device (except for the need for a battery).

Anyone know how the really works? The user manual has the pinouts for the connector, but I haven't started to play with it yet.

ben_s
06-21-2006, 09:46 AM
I'm not sure I can help you directly, but I have a similar project on the go.
My film back was from a lasergraphics film writer that was being chucked at work. I nabbed the back and lens, and ditched the rest of it (As it didn't work)
I opened it up, removed all the un-necessary bits, and proceeded to fiddle and prod things. I now have a 35mm motor wind back that has a bulb shutter. I'm planning to add a pinhole to the front of it and possibly a 555 timer IC to add some shutter speeds other than B.

It seems like it's a case of "two minds with but a single thought" - I'd be willing to help with a circuit for shutter control, if you want one.

I was also mulling the idea of adding a light sensor of some kind to give auto exposure - I guess that would beat the old exposure conversion tables!

Greg_E
06-21-2006, 12:13 PM
This has kind of slid to long term storage for now. I've got the digital Rollei going, and need to start on my 35mm Mamiya film back pinhole. Plus restoring a first model Rolleiflex. I really want to get the Mamiya back going, then I could use the "lens" section with the 35mm back or the 645 back. I was going to start on that last night, but got side tracked. Maybe tonight while I check out a new to me Gretag Spectrolino/Spectroscan that I'm bringing back from a bad place (you should have seen how they shipped it).

That said, it is one of the things I think about on the way home from work. Some of my most "brilliant" things come from a long boring drive like that.

ben_s
06-22-2006, 05:56 AM
Sounds like you've got your work cut out!

Out of interest, which 645 do you have? I have the original M645.
Are you going down the body cap route, or machining something up nicely?
I was considering using a body cap, with different combinations of extention tubes for differing fields of view.

Greg_E
06-22-2006, 09:58 AM
No, this is the back for the Pro/Super cameras, so I am going to make something to attach to the back. With the older m645 I would still need to extend past where the body cap goes to get the angle of view that I want. The Super and Pro (and 1000s) are my complete system, including (soon) digital.

Found out that the Spectroscan still needs some repair, and it is really SLOW! I can measure, build, zip, and email a profile with a greater number of patches in less time than this thing takes to measure a single page. The best part of the Spectroscan is the very small patches, so you can either get very small tagets, and very dense pages. I'll either keep it for fade testing papers, or sell it and hopefully get a profit.

Greg_E
06-23-2006, 03:54 PM
I said I wasn't going to be working on this for a while, but I guess I was wrong.
http://img.photobucket.com/albums/v329/Greg_E/din8cm.gif is the connector that is on the camera, pinouts are as follows:
(1) +5 volts DC
(2) Film advance
(3) ground
(4) end of film
(5) 35mm camera present
the other pins are not present

pin 3 and 5 are connected together

When you short pin 2 to ground, the shutter opens and stays open until you remove the connection. Not sure what happens when/if it hits the end of film, but it probably connects pin 4 to ground, but other choices would be to connect pin 4 to +5, or open a connection to one or the other. Hard to say and I don't really care what happens, it does have a manual film counter on the body.

If you rapidly connect and disconnect pin 2 to ground, the camera counts the number of times you do this and "fires" the shutter for each time you do it. However the shutter does not close all the way when you do this, so it is something that you should try to avoid. I need to machine a tripod socket into this camera, and find some metal tubing that will fit in the lens mount. The mount takes a 1 15/16 inch (50mm) outside diameter tube, and uses locking screws to secure it. From the end of the lens mount, it is 54mm to the film plane, so wide angle is out!

Here is a really crumby picture of a different image recorder that uses the same 35mm film back/thing:
http://img.photobucket.com/albums/v329/Greg_E/freezeframe.jpg

Greg_E
06-24-2006, 07:04 PM
Found that a 2 inch ID to 2 inch OD exhaust pipe coupler (for automobiles) fits inside the lens mount flange if you grind a very small amount of material off the edge of the steel pipe. I now have a 138mm to 140mm FL for a 17 degree angle of view.

Greg_E
06-25-2006, 02:20 PM
Since this is an electronic camera, I thought an electronic timer would be best, so I just bought a couple of kits to operate the shutter. I chose the first and the last (just to be safe).
http://store.qkits.com/moreinfo.cfm/QK154
http://store.qkits.com/moreinfo.cfm/QK54
http://store.qkits.com/moreinfo.cfm/QK85-2

I'll try to get some pictures up tomorrow or the next day, depending on when I get the rest of the parts for the timer box (box, battery holder, switches)

ben_s
06-25-2006, 07:56 PM
Ha! this looks very similar to my unit.
I took mine to bits and removed the cable (as it was only 3 inches long). I now have much more practical wires soldered to the PCB.
As with yours, if you short two lines, the camera fires, although i've never jammed it as you report.
It is now effectively a B mode camera.

Mine has a 2x16 LCD on top, which displays various info, and a rewind button.

When I got it, I completely disassembled it, and found at the heart of it, a copal FP shutter, which I originally intended to drive directly from a microcontoller.
After powering it up, though, I decided to use the existing brains and just add some kind of timer.

When mine comes to the end of a roll, it displays (I think) "FILM END" on the LCD.
Then you can hit rewind and the camera does it's stuff in reverse.

In theory, it should be possible to multiple expose a single frame by shorting a different pin across, as the original film writer unit could produce colour images from it's mono CRT by triple exposing through it's RGB filter wheel.

Greg_E
06-25-2006, 09:21 PM
Your's must be newer. Mine is exactly like the one in the photo above except it has about a 3 inch cord. I took a female DIN connector and soldered it to a long cable last Friday. I'll probably pick up a project box and battery holder after work tomorrow. My big fear is that the control box will look like a timer for a bomb. Not much I can do about that, but it will have a nice range of shutter speeds. I hope Qkits ships quickly.

On mine, there is plenty of room under the shutter box for a 1/4-20 T nut, so I'll need to pick up a couple of those too. Then I just need to solder a plate over the exhaust pipe and paint the insides black, and wait for some pinholes to arrive.

ben_s
06-26-2006, 05:08 AM
Mine is the same unit as the back on this one
The lens you mentioned is probably an enlarger lens. The one in mine was a Rodenstock Rodagon, now transplanted onto my enlarger. Attached files http://f295.f295.org/uploads/lfrx95_300_7390.jpg (http://f295.f295.org/uploads/lfrx95_300_7390.jpg)

Greg_E
06-28-2006, 12:19 AM
Here's what's left of the control box:
http://img.photobucket.com/albums/v329/Greg_E/pieces.jpg
Most of the parts will go in a box in case I need a component here or there.
This is kind of what it might look like, I really need to find something that is eaier to work with than the steel exhaust pipe. Copper would be ideal.
http://img.photobucket.com/albums/v329/Greg_E/cam.jpg

Jim Jones
07-01-2006, 08:40 PM
If you can mount part of a PVC coupling instead of the exhaust coupler, you can easily change tubes for different focal lengths. This facilitates experimenting with different focal lengths and with zone plates.

Greg_E
07-02-2006, 12:08 AM
Thought of that, can't find anything locally that I can machine down to fit inside the mounting collar that's attached to the camera body. Haven't been able to get the camera stripped down far enough to remove that mounting collar and attach some other kind of flange.

Greg_E
07-03-2006, 02:08 PM
For now I think I'm just going to go with the analog 555 timer kit. Looks like a 100k ohm log. taper pot and a switch to change between a 220uf cap and a 1000uf cap to get somewhere in the 1/3 second to around 3 minute range. Anything longer than that will be done with a switch and a watch until I do more work on the electronic timer. I'm also going to change the relay so that it operates at around 5 volts, that way I won't be wasting battery with a 5 volt regulator for the camera.

ben_s
07-04-2006, 11:00 AM
I'm going to try and get a few bits to make the controller tonight.
Hopefully I'll get something out of it soon.

Greg_E
07-04-2006, 07:37 PM
Of mice and men...

I think mice are a lot smarter than we tend to think. They don't ever seem to make elaborate plans to do anything. They just seem to focus on a couple daily things, and never get caught short (except for the occasional cat).

Me on the other hand... I had plans. I was going to pick up the few things I needed to finish the 555 timer on my way home yesterday (having today off). Well instead I ended up having my car towed home, and spent all day chasing down a phantom wiring harness short. The only part I did manage to do was pick up the parts today, so maybe in a few days.

ben_s
07-05-2006, 03:47 AM
Of mice and men...

I think mice are a lot smarter than we tend to think. They don't ever seem to make elaborate plans to do anything. They just seem to focus on a couple daily things, and never get caught short (except for the occasional cat).

Me on the other hand... I had plans. I was going to pick up the few things I needed to finish the 555 timer on my way home yesterday (having today off). Well instead I ended up having my car towed home, and spent all day chasing down a phantom wiring harness short. The only part I did manage to do was pick up the parts today, so maybe in a few days.

Sounds like yesterday wasn't a good day for any of us.
I managed to buy the parts, spent all evening sticking it together, and now it has a wierd fault, namely things going high when they really shouldn't. I've had the 'scope across the caps, and they're charging as expected, but the output doesn't want to go low.
Possibly a duff chip, or the output transistor is shot. (kind of ammounts to the same thing, anyway)
I'll have to bung a new chip in tonight and see if that improves things.

Sorry to hear about the car, and hope it's easily fixed.

moot
07-05-2006, 03:17 PM
I managed to buy the parts, spent all evening sticking it together, and now it has a wierd fault, namely things going high when they really shouldn't. I've had the 'scope across the caps, and they're charging as expected, but the output doesn't want to go low.
Possibly a duff chip, or the output transistor is shot. (kind of ammounts to the same thing, anyway)


You can try forcing the reset pin low. It's normally pulled high for a one-shot but it will override the other inputs so it's an easy way to test the output stage. Just remember to either disconnect reset from V+ or put a resistor between V+ and reset to protect your power supply when you short reset to ground.

ben_s
07-05-2006, 07:01 PM
You can try forcing the reset pin low. It's normally pulled high for a one-shot but it will override the other inputs so it's an easy way to test the output stage. Just remember to either disconnect reset from V+ or put a resistor between V+ and reset to protect your power supply when you short reset to ground.

Thanks for the tip. I've just tried this, and while reset is pulled low, the output goes low. When it's floating or high, the output is always high.


With reset floating or high, when you press the trigger button (pulls pin 2 low), the output goes low while you hold the button in. As soon as you let go, the output goes high again.
The chip is definately timing, because the trigger button locks out for the timed interval, and a scope on the caps shows them charging.

I've checked the circuit through numerous times, and it's as it should be.
I think I'll replace the chip, as I have a few more in my box.
Failing that, I'll rebuild the whole caboodle on a breadboard and see what happens, unless anyone has any more suggestions?

moot
07-06-2006, 01:25 PM
Hmmm. When you pull the trigger pin low, the output should go high, not low. Also, the output stage has the same sense as the discharge transistor (pin 7), so if the output is low, the timing cap should be shorted and should not be charging.

My guess is that something is wrong with the RC timing network connection to pin 6 or something is happening on pin 5 (control voltage) because the upper comparator is not working correctly. The way it works is that the trigger sets an internal flip-flop, and then the upper comparator (connected to the top of the timing capacitor) resets the FF when the comparator threshold (2/3 V+) is reached. If the output is backwards (low instead of high) the upper comparator is putting the internal FF into the wrong state and the trigger can only momentarily force it into the other state. Assuming the power supply connection is right and the reset is pulled high, focus your attention on pins 5 & 6 since they are the inputs to that comparator.

If the wiring is correct, since the timing cap is charging the only guess I have is that something is wrong at pin 5. That is an external connection to the threshold voltage divider and it should stay at 2/3 V+. There is normally a bypass cap to ground on pin 5 to improve noise immunity. If you put the scope on pin 5 and it isn't at 2/3 V+ or if it is noisy, that might cause the problem. I'd also check the voltage directly at pin 6, instead of across the capacitor. If pin 5 is at 2/3 V+ and pin 6 sees the charge ramp the upper comparator should work.

I'd put the circuit together on a breadboard. My gut tells me you have a wiring error. Having made lots and lots of them, my gut has had some practice :-/

BTW, before anyone gets the wrong idea, the 555 is the *only* chip that I know at that level of detail. The others are for the most part black boxes to me. I use 'em, but I don't know much about what's inside. Except for the smoke, that is. All chips have smoke in them. Ask me how I know...

Greg_E
07-06-2006, 04:42 PM
That's why I bought a kit. Now I have a good basis for mods to meet my needs. For the $10 plus shipping it turned out rather nicely. The next one I'll build from scratch, but a lot can be said for having a pre-etched board so you can just plug the components in. The only thing I wish I had done is scan the board before I started stuffing it. It's kind of too late now.

As far as my timer goes... It's all modified, and stuffed in a box. Switches and lights are mounted, and it's been tested with the camera. All I need to do now is sit and measure different times so I can label where the knob needs to point. I'll have a couple of pics later after I edit them and shrink the size.

I also found out something odd about the camera... You need to hold the rewind button until it finishes rewinding. If you don't it will forward wind when the button is released.

Greg_E
07-06-2006, 09:11 PM
Please forgive the background mess, though I cropped out most of it.
inside:
http://img.photobucket.com/albums/v329/Greg_E/timer1.jpg
outside:
http://img.photobucket.com/albums/v329/Greg_E/timer2.jpg

moot
07-07-2006, 12:42 AM
Looks great, greg! There is something to be said for a tested pc board.

ben_s
07-07-2006, 04:16 AM
Moot; Thanks again for your help. it's odd, as the output isn't inverted. It only goes low while you pull the trigger pin low, which is what I would expect - it should start timing when you release the switch.
I've checked the circuit through times, and I can't see anything wrong. I can't see (or meter) any shorts anywhere, so I'll be inclined to go the route of complete rebuild on a breadboard.

All electronic components have smoke in them. It's a vital ingreedient of electronics.
I know some people who build Tesla coils with semiconductors. Their bangs are most impressive. When their big transistors and IGBTs blow up, you tend to find the bits in the next county ;) . One managed to blow a fuse *completely* ie. to glass powder - And the fuseholder went too! :o

Greg; Nice job! Have you brought the rewind etc controls out to the box too?
Mine only has a dial, range select switch and fire button. What do all the other buttons and switches do?

I almost got off my backside and made a PCB, but i eventually decided it wasn't worth the effort. I'm now thinking otherwise!

Greg_E
07-07-2006, 11:05 AM
Switch for power (below the green LED), red LED for shutter open (from the timer board). Next row is a range switch between 220uf and 4000uf and the 100k ohm pot. Third row is stop button (red), start button (black), and longer exposure switch (anything over 10 minutes). I left the rewind up on the camera, it feels like you need to move some gears to make it rewind, so I probably can't move it. In the future I might add a yellow LED for film end, but not sure if I'll bother for this timer.

I'm still going to get the digital timer working so that I have a little more precision. This analog timer has a bad habit, if you hold the start button, the shutter will remain open for as long as you hold the button. That renders fast shutter speeds pretty much useless. I just need to work with the digital timer a little more to get it where I need it to be. The analog timer was just the quickest way to functional, which is good because the pinholes are here.

Greg_E
07-07-2006, 11:12 AM
You know, I'm just sitting here thinking.... Isn't this kind of like anti pinhole in the entire concept. Short of a digital capture camera, these must pin the next most complex pinhole cameras. Is it really worth all the effort? Hopefully the results will be worth something, or at least someone else will get something from all this.

And sitting here looking at the 8banners shutter assembly... For such a simple thing, it really is pretty nice! I'll probably buy a few more if I decide to make a camera. The one I bought is a factory second, the words on the front are mis-spelled, and for that he knocked off $10. Personally, I don't care if it says "shutter", or "shuffer", it seems to work pretty well.

ben_s
07-07-2006, 08:36 PM
You know, I'm just sitting here thinking.... Isn't this kind of like anti pinhole in the entire concept. Short of a digital capture camera, these must pin the next most complex pinhole cameras. Is it really worth all the effort? Hopefully the results will be worth something, or at least someone else will get something from all this.

Kind of anti pinhole I suppose, but it fits with the homebrew model...
Next up - microprocessor control with motorised zoom, filter wheel and built in AE metering (?!)....Or maybe I'll just get it working at all first.

The basic idea can't be too flawed if two of us have come up with it independently!

With regard to my problems, I'm just breadboarding the 555 now.

Greg_E
07-07-2006, 09:52 PM
The AE meter would be kind of neat! I may or may not work on this over the weekend... My sheet metal shear finally arrived, and I want to do a little work on the D-Rollei. I also received a new project camera that I need to make a few notes on.

ImageMaker
07-08-2006, 07:34 PM
This analog timer has a bad habit, if you hold the start button, the shutter will remain open for as long as you hold the button. That renders fast shutter speeds pretty much useless.

Seems to me there's a way to convert any switch close into a pulse of arbitrary duration -- IIRC (as one for whom ICs run on magic and transistors are voodoo devices), you'd use a 555 in astable mode, holding a switching circuit "open"; when you press the button switch, a second 555 detects the state change of the astable 555, and (in monostable mode) outputs a single pulse to the trigger of the timing 555. By "short", depending how you build the circuit, the trigger pulse could be as short as a millisecond. Given the prices of modern 555 (or multi-555) chips, this would increased the value of your blue box to around $8... ;)

moot
07-08-2006, 08:46 PM
There's an easier way to get around the problem of short exposures - put a differentiator on the trigger line. All you are doing is making sure the timer sees a short pulse, no matter how long you hold the button down.

Just add a capacitor in series with the trigger switch as shown in the sketch. The effect is that you can push and hold the trigger button, but the only thing that gets through the capacitor is the falling edge. The cap then rapidly recharges through the pullup resistor and effectively shortens the trigger pulse. The diode protects the trigger line against any transients by shunting them to the positive supply. It can be a little switching diode like a 1N914 or similar. Attached files http://f295.f295.org/uploads/555_2936.jpg (http://f295.f295.org/uploads/555_2936.jpg)

ImageMaker
07-09-2006, 02:48 PM
Aaaah, same effect, and MUCH simpler...

Told you transistors were voodoo to me... :P

Greg_E
07-14-2006, 09:58 AM
One note, I'm not at all happy with the log taper pot... There is no rhyme or reason to the spacing of the times. There is very little space between 1 and 2 seconds, yet a huge amount to get to 4, then another huge amount to 8 and a very small amount to 16, then another large amount to 30 seconds. The desire was to have the fast speeds be a little more controlled, but it kind of went over the top. I get about 1/4 second shortest time with this set-up. But because of the lack of consistancy, I'm going to have to move to the digital timer.

I'm trying something different... Instead of a regular flat black paint, I ended up with Krylon flat Blackboard paint. They say you can paint it on all sorts of things to create a flat black chalk board. It is fairly flat, but I wonder if a regular flat black would have been better. Had to buy an almost 2 pint container because that's all they had, all the little 8 ounces cans of flat black were gone. So I think I have plenty of paint, maybe I'll refurbish the old chalk board we have at work.

And today is picture day. All I have to do is add a tripod socket, and give it a go. If anything comes out I'll post and image or two. I have some ideas, but who knows if they will be good enough for me to bother scanning and posting. I'm very critical of my work, most never sees the light of day after it get exposed and developed.

ben_s
07-14-2006, 10:20 AM
This problem is why I went for a rotary switch - I have a resistor chain for each time on each position of the switch.
It's still not massively accurate though. - The perils of analog circuitry I guess.

Jim Jones
07-14-2006, 10:58 AM
One note, I'm not at all happy with the log taper pot... There is no rhyme or reason to the spacing of the times. There is very little space between 1 and 2 seconds, yet a huge amount to get to 4, then another huge amount to 8 and a very small amount to 16, then another large amount to 30 seconds.

When I designed and built a 555 enlarging timer many years ago, a Radio Shack pot had close to the right taper. The short speeds were expanded; the long speeds appropriately compressed. Space permitting, two or three decade switches would be a practical alternative. They are even better for a darkroom timer, since they can be set by feel.

Greg_E
07-14-2006, 11:30 AM
Those tricky people put a tripod socket in the "grip". All I had to do was drill a hole in the bottom of the case.

I thought about using something like a decade box for the timing, but decided a pot would be decent enough. I had expected that the short times would have a large space between them, ever decreasing until it hit the slowest speed. I also have to wonder if what I'm seeing has something to do with leakage in the cap. Anyway, after I see the first roll, I'll know if I want to bother geting the digital timer configured.

Greg_E
07-26-2006, 09:09 PM
Finally took some film for processing, all I can say is that I'm not at all happy with the results.

The first images were a studio step up with a single bright continuous light source, camera on tripod, nice short 1 and 2 second exposures on Kodak BW400CN film. Started with a .4mm hole, then .3mm and then .2mm. The .4 was extremely soft, the .3 worse, and the .2 was almost like a zone plate. With a user constant of 1.5 Pinhole Designer says it should have a .41x diameter hole (FL is about 140mm), I guess I'm going to have to try a larger pinhole to see where things go. I also noticed that the angle of view seems to be much wider than calculated.

And really disappointing was that lightning strikes don't even show up of the film. I should have had a couple from a storm last night, but not even the faintest trace. I'll revisit this as the summer goes on (if I can get the hole diameter worked out). Guess I better order some drill bits in the morning.

ben_s
08-06-2006, 06:34 AM
Greg: sorry to hear about the problems. Good luck in finding a better pinhole.

An update from my project:
Bah!
I've finally got round to debugging my circuit - it's perfect.
I really need to learn to check the simple stuff first.
It was the switch:
Generally, when you ask for a single pole momentary push to make switch, that is what you want.
Evidently Maplin think you'd really be better off with a push to BREAK instead!

I've decided to rebuild it anyway, and make a proper PCB, rather than using stripboard.
I'm also going to go for a bigger case, as the current one is somewhat cramped.
There are a few additions I want to make as well, like having an output indicator on the box, and also a manual B setting on a switch.
I'll post again when I have more progress

ben_s
08-09-2006, 06:39 PM
Well, I got the box of tricks finished, and it works well. :)
However, in the time since I last tried the camera, it has developed a terminal fault. >:(
I powered it up (on it's own, not connected to my circuit), and got a load of random garbage on the screen, followed by "Checksum Failed"
I powered it off and back on again, this time with more success, in that I managed to load a roll of film, which it duly began to wind on. about 3 seconds later, it stopped, and the screen went dead.
Now it won't work at all. :'(
It really failed very unspectacularly. I was watching the meters on the PSU, and it didn't even draw any extra current, nothing got hot, and certainly no smoke.

It must be a manufacturing defect - they even forgot to put the smoke in it! :D

So, I guess I need to start fiddling with programming a new micro to drive it.
To date, I've only used Basic Stamp micros. I think this could be an excuse to try and learn how to program a real PIC.


FWIW, here's a pic of the controller.
The LED in the middle is an orange power/ready light
The red dial is a 12 position rotary switch that selects the shutter speed. This selects a resistor from a bank of 12. I personally find it has greater repeat accuracy than using a pot.
The left toggle switch is a 3-position type; up is on, middle is off, and down is "B" - this operates the relay directly, without powering the rest of the circuit.
The right toggle switch selects the range; up - short times on a 220uF cap, down - long times on a 1000uF cap. I use the terms long and short loosely - the fastest shutter speed is about 1/4 sec, the longest is several minutes.
Finally the blue button is the fire button, which lights up during exposure.
Attached files http://f295.f295.org/uploads/controller_7504.jpg (http://f295.f295.org/uploads/controller_7504.jpg)

Greg_E
08-10-2006, 04:45 PM
I bet you can find one of the ones that I have pretty cheap if you look around. And of course you could use the timer on other solenoid driven shutters.

ben_s
08-10-2006, 07:05 PM
I'll have to have a look at good old ebay!


And of course you could use the timer on other solenoid driven shutters.
I'm currently working on a shutter similar in design to a copal, but actuated by a solenoid.
The other use I have in mind for this device is stereo photography, as I gave it two no-volt outputs, which I could interface to a pair of EOS's, for example.

Greg_E
08-10-2006, 08:37 PM
I'm going to do some testing on mine tomorrow. If it goes as poorly as it did the first roll, I might have one for you. Going to try a different size hole, and try some filters. I might also try a shorter FL too, just to see what happens. Thought I would put a hole at the old mount flange which is about 40mm from the film, and try that with filters too.

Greg_E
08-11-2006, 08:54 PM
OK, I tried this again, and the results are still not what I'm looking for. I'll have to try and scan some of the film to see if anyone has seen this and can help with suggestions. I tried the .4mm hole with several filters. I also tried a larger .53XXmm hole (#75 drill bit) which is closer to the 1.9 user constant for that FL, same filters again. I also tried a shorter FL of about 44mm with a .2mm hole and a bunch of filters. On all of them, I'm getting extremely soft images, the filters don't really seem to do anything except make the exposure more difficult to get. I used and orange, yellow, IR block and IR block with blue light (because that's all I had on hand. Now what really bothers me is specular highlights. They have a pattern that looks like several concentric rings, broken by other rings. I assume this is some kind of diffraction, and may be the cause of my woes.

Looking and the film, I'm also seeing something very strange! All the images taken with the 140mm FL all too small on the film, they do not fill the frame. The images taken with the shorter FL all fill the film frame. They are all "perfect" rectangles, so it isn't like I am getting vignetting. This is seriously strange!!!

http://img.photobucket.com/albums/v329/Greg_E/edit.gif I know what it is now... The shutter is up near the front of the camera, and there is a small mask up there. The light rays are coming in so straight, that they are masked and fail to fill the entire frame. With the closer pinhole, the image circle can wrap around that mask to fill the frame. I wonder if this mask is killing my resolution by causing some sort of odd diffraction patterns?

I have a feeling that this may spell the end of this camera unless I can mount a pinhole right next to the shutter, or about 24mm FL.

Greg_E
08-12-2006, 06:46 PM
Some images here:
http://f295.f295.org/uploads/Blah.pl?b-cm/m-1155354692/

Greg_E
08-12-2006, 09:04 PM
I think I am going to bin this camera and try again with something else. i just ordered some plywood to build a lens for my 645 and 35mm film backs. Hopefully I can get better results with something that I build. While I wouldn't mind having the odd diffraction on specular highlights, I really need something that will give me a little more detail in the images. I look through the galleries and keep seeing other images that have the amount of detail I want, so it must be possible.

ben_s
08-13-2006, 06:33 AM
Greg;
If you have/can get access to one, try putting the pinhole under a microscope.
I did this with my 5x4", and found my drilled hole was triangular (!?)
I carefully eased the edges out with a fine pin, until it was nominally circular.
Then I blackened the film facing side of the pinhole plate with a marker.
Results improved quite a bit.
I'd recommend giving it a try.

Start off with around 50x pmag, then if you feel like it, go to between 100 and 450x and inch round the edge and check for any sharp spikes.
Use a diffuse light source behind the pinhole.

Greg_E
08-13-2006, 12:30 PM
I have a 100x microscope from Radioshack that I use on ground glass to check the focus of TLRs before calling them finished, I'll have to take a look at the holes I have. Though I would expect that the 2 holes I bought would have been round. And I'm fairly certain that the hole was aligned to the film plane.