Re-adjusting the AGFA Microflex 200

[mad*one]

Hi there,


i just wanted to share my newest adventure with you, i don't know yet if it finally worked, but i'll post it here, when i've got the first results.

I have no idea if i did everything right, or of this method is the most effective one. But I don't have light metering equipment, no lightbox, and i didnt want to waste a film.

My aim was to use a Microflex (that i've bought recently) with 100 ASA stock and without wratten filter, for example the new 100D or Plus-X Carts that i still have around here.

I did the following:

I've build a little amplifying circuit around a photocell to measure the light intensity directly in the cartridge compartment of my camera. Its as simple as it can be, its just an amplifier with a whole lot of gain. Just one OpAmp and some resistors, and capacitors for stability. It runs on a 9V Battery, and is connected to a voltmeter.

I then made a very little Cube made of black card paper for the fotoresistor to fit in. Just one side of this cube consists of normal copier paper, and has the size of slightly above the Super 8 image size, and will later be pointed at the film gate. This paper side is meant to simulate the "film", thus the fotocell is looking at the projection thats coming from the main lens, and is projected to a small piece of white paper.

This little unit i made didn't have to be calibrated because my procedure doesnt require that. Well the truth is, I didn't have any idea how to calibrate it, and thought about how to do it without calibration. So my solution was to just compare the light to another camera, so it was only of importantance to know whether or not the incoming light is equal, and if its higher or lower.

At first, I permanently disengaged the wratten filter inside of the microflex camera, but i didn't want to destroy something. I succeed with a small piece of plastic to block the switch underneath the tripod mount. It was a bit complicated to get it in position, but it finally worked. The spring that "tries" to engage the filter is quite strong, so if the plastic is in position, it will stay there as it is hammed in very well, and the tripod mount stills remains fully usable.

Good to know: The disengaged wratten filter also disengages the influence of the R5 Potentiometer, so i could leave it out in the adjustment procedure later.

I opened the unit up, and disengaged the motor by unsoldering one of its connections. I just guessed, as one of the cables was thicker than the others, and it turned out to be the "-" Connection of the Motor.
Then i turned the shutter to its "open" position. There is a little relay inside that stops the shutter at a defined position, so its important to press the trigger first, (unit needs to be powered!) when moving the shutter disk. After this procedure, the exposure circuit can be powered and works with a stopped motor in "open shutter" position.

Then I installed my little measurement unit in my other camera, the Beaulieu, of which i know that it exposes properly. I disengaged its wratten filter and adjusted 150 ASA instead of 100 ASA to compensate for the faster shutter of the microflex. Thus, the beaulieu *would* underexposure a 100 ASA film by the amount, that the "wider" shutter of the microflex will compensate later.

I installed my little measurement unit in the beaulieu, pointed it at the sky, and adjusted the aperture to correct exposure.
Its was important here, that every position in the image shows the same brightness, as I did not know how the "weighting" of my unit is, compared to the internal meter. (Thats the reason why I just used the sky, and applied filters lateron.)
I then upowered the unit, pulled the trigger and turned the shutter to its open position. I noted the value, that my little unit returned from the cartridge compartment for reference.

In my microflex, there is a little filter in front if the CdS Cell that is connected to the mechanical 160 ASA notch probe. After a long period of trying with the Potentiometers, i finally removed it, and succeed in getting the right settings shortly afterwards. Procedure:
I installed the measurement unit in my microflex, that was half opened to get access to the trim potentiometers. I again pointed it to the sky, and used several filters (some sheets of a very light paper, probably suboptimal, but i didnt have real grey filters) to adjust the "compensation amount" that is adjusted by R4. If its influence is too high (=R4 resistance is too low), the exposure will get darker, if the scene gets brighter. So its necessary here to find the spot where it just compensates, and the amount of light at the cartridge chamber stays the same when applying one or more filters at the main lens.
Then i adjusted R3, which seems to be the ASA Pot, to a position where my meter showed the same amount of light at the film gate that i've previously noted on my Beaulieu. I then readjusted R4 again like the procedure above, and repeated all this several times. As a result, regardless which or how many "filters" were applied, my unit showed the same amount of light at the gate, except for getting into the range where it can't compensate, because the aperture is at its limits.

All this is done now, I soldered the motor to work again, and i will give it a try with real film material. I think it should work fine, but I will report my results here in any case.

For everyone who needs it, I made a "back-engineered" schematic from its exposure circuit. I can't guarantee that its 100% correct, i've not taken it fully apart, but maybe it is useful for someone.

http://filebeam.de/temp/MICROFLE.JPG


Many greetings!
mad*one

[etimh]

Hey mad*one, this is really interesting. Thought I'd tell a somewhat related story.

I've always loved these little Microflexes (have several 100s, 200s, and 300s in various states of functionality). A couple of years ago I bought a pristine, fully working 300 that a guy had "recalibrated" for the "new" 64t. I was skeptical at first, but went ahead and took the plunge. It turned out great--the camera was in perfect shape and produced fantastic images with the 64t (the guy had even placed a very professional looking "64t" sticker inside the camera door).

Now I don't really know much about the technical insides of cameras so I'm not even sure what was done. The guy who sold it had evidently had some camera tech somewhere do the modification. I was interested in knowing the contact because I thought I could have other "non-useable" cameras recalibrated for the 64t stock. But the seller was not that interested in connecting me with the camera tech directly, so I let him know if I needed any more cameras worked on I'd contact him.

Jumping ahead, I never got back to him to do any additional work but have been recently thinking about having the little 300 converted to the new "New" 100D. I've yet to track down the guy as I seem to have lost his email. But I'm just wondering if it was as easy to recalibrate my camera (as it apparently was for the 64t), then maybe it is not that difficult of a job and someone else might be able to do it? Regardless, I sure hope it is not as tough as your procedure was! That sounds like some serious fiddling around in there.

Anyways, thanks for the great report, and definitely keep us updated on how everything works out.

Tim

[mad*one]

Hey Tim,


i think, seriously every professional camera technician should be able to make this modification. It is basically just trimming some pots in the inside, and (i'm not 100% shure if its necessary) removing the filter glass from the CdS Cell. You don't have to do all the hassle that I had, when you have professional equipment at hand.

I just think those microflexes look terribly cool, thats why I wanted one, together with the fact that they are so damn small, and i wanted something portable. They really do not look like there from the early seventies, its such a classic design, it does not look "old" at all.
They have all metal housing that is basically made out of a middle cast part (!) and two thinner side panels, a rock solid and seemingly expensive construction. The cameras body is smaller than two Carts, and isn't even thicker than a (packed) Super-8 Cart.

From what I can say for now... Ahm, well, just to be fair, I can't say anything to image quality ;) But I just *assume* that these cameras make good images. The construction is well done, there are a lot of clever details in the inside. I dont know, but I expect that those things must have been expensive when they were sold in the past. But we will see if the results meet my expectations ;)

I keep you updated!


Many greetings,
mad*one

[mad*one]

Just wanted to share this with you: I got my Plus-X test cart back, and am very pleased by the results. The autoexposure worked well, and the images are perfectly sharp and steady. I'm happy with my Microflex. This will be my point-and-shoot camera.

[granfer]

Interesting "modification" which illustrates the truth of the often ignored fact that when attempting a "calibration" of ANY sort, the calibration of the device used for measuring need not be known accurately as long as it can be used to "compare" the device to be calibrated to a known accurately calibrated device, and to adjust until both devices give the SAME indication.
This applies in almost any field, not just optics and light measurement; a crude "transfer " device is often all that is required.
Good thinking, Kemo Sabe!

[ewanuno]

i was tryinfg to do this with a microflex 300 last year sometime, but i never got it finnished.

i got some good advice here: for a much simpler way.

viewtopic.php?f=1&t=20555&p=190236&hili ... ex#p190236