Waveform on 3a Folding Brownie

[peter k.]

A friend of my wife an I, gave me her grandfathers 1914 3a folding brownie, that is in excellent shape, and so did a lens test on it.
Got a weird waveform... taken @100.
Someone give me a clue... on what's happening with this lens... with the two lower peaks, the second larger than the first.
Perhaps its my DYI setup.. or .. ? the lens, bad dog .. no bone

Yet, took the lenses off, and looked directly at the shutter, both sides, and its clean, no oil, but understand through archives that the lens, a Brownie Ball Bearing, was a 'dry' lens.
Firing the lens, its sounds good to me, but then we have very little experience in this.
The camera is very clean and in good shape. Keep, for many decades, in the top of her closest.



Took a black and white 4x5 (Arista400@200) that metered (Weston Ranger 9) directly, and gave indication of 15.5. ... Couldn't get an incident meter reading exposure as I wasn't into getting my feet all wet in the new soft silt, created by the earlier Slide Fire of Oak Creek Canyon, Sedona Az

Shot it f16 (U.S.) @100, focus set at 50' (the lit rocks), and here is a quick scan with nothing done to it.

Which looks good to me... bright light to deep shade..

 

[shutterfinger]

Connect your tester and with the recording program running quickly illuminate the sensor with the test light. If you get an erratic pattern its the tester, If you get sharp on off peaks then the shutter leaves are not laying flat against one another or there is bounce in the leaves on the close causing a secondary reading. The photo looks over developed, reduce your development time by 10% or drop your developing temperature by 2°F.

 

[peter k.]

Perhaps using wrong light source..
Tried with three light sources.. inexpensive 9 bulb led flashlight.. which was used in test
Regular flashlight and halogen desk lamp.. all give sharp peaks, up and down ..

Here is the Led used in test... turned on only...

 

[summicron1]

what exactly are yu measuring with this instrument -- the light passage, lens performance or shutter? Sorry, ur talking tech here.

In any event, it's a Brownie. The optical system in it is about on the level of a Holga and not too far removed from the bottom of a coke bottle. Let's keep our expectations real.

Having said that, those cameras actually do pretty well. Millions of photo albums around the world are filled with their treasured product.

 

[Pioneer]

Yep. My Brownie takes amazingly good pictures. I play with lots of old cameras. It is amazing how many of them won't even work any longer, or if they do, they don't provide very impressive photographs. But that Brownie is so simple it just keeps ticking away with no dramas.

 

[shutterfinger]

Sensor test: connect sensor to stupid high speed switch machine and start recording program in record mode. turn the device producing photons of energy on then move it over the sensor then back off repeating several times at a quick rate. stop recording and inspect waveform, it should be sharp peaks that correspond to the photons of energy exciting the sensor then not exciting it.
Shutter testing: Same as sensor testing but put shutter with lens opening centered over the sensor then stop down to f22 to f32 to cut the angle of view error of the sensor down. Start the recording, turn on the photon of energy producing device then position it over the shutter, trip the shutter after setting it, turn the photon of energy device off, stop the recording, and inspect the waveform. The time interval between the rise from 0 to positive peak back to 0 to negative peak back to 0 should be the shutter marked speed ± 20% to 30% of the speed.

If using CFL or LED source for the photons of energy it will be best to energize them and leave them energized until the end of testing. I use an incandescent 2 AA mini mag for leaf shutter testing and a clear 60W ceiling fan lamp fpr Focal Plane Shutters in large format SLR's.

 

[Regular Rod]

Looking at the timelessness of the photograph you made, complete with all the foibles the camera produces, I'd simply pack in testing stuff and go out and make some more photographs with it!

Tremendous potential...


RR

 

[CJBo001]

The additional "squiggles" in your waveform are artifacts introduced by the fact that your waveform recording device is not dc-coupled. That is, the electrical signal from the sensor must pass through a capacitor which will not pass dc. The width of the initial peak should still give a good indication of the time the shutter is open.

Chuck

 

[peter k.]

Summiccron1.. testing the shutter.. and your right, "Let's keep our expectations real."

Shutterfinger.. Thanks for more clarity.. and believe now its the shutter, with a bounce in the shutter leaves because they are not laying flat as you suggested in your first post. So this morning we went and tested some more, with some tons of photons hitting against a roll of 120 Tri-X. ;-)

CJBo001 ... a thought but there is not a capacitor in the circuit...

Off to develop... thanks everyone for all your encouragement and replies ...

 

[shutterfinger]

1/2 second in tolerance shutter using the mini mag.


1/125

I correct my previous statement, on shutter opening the sensor goes to a positive peak then drops to near zero and remains there until the shutter closes then, when the photons of energy are cut off it goes to a negative peak. The curvature from the negative peak back to zero is the device fall time and not part of the shutter's time. The point from which the device just starts to rise above zero is part of the shutter's time.

 

[cliveh]

Waveform on 3a Folding Brownie

 

[Jim Jones]

. . . In any event, it's a Brownie. The optical system in it is about on the level of a Holga and not too far removed from the bottom of a coke bottle. Let's keep our expectations real. . . .

Around a hundred years ago some 3A Brownies were fitted with simple meniscus lenses, some with the obsolescent Rapid Rectilinear, some with the still highly regarded Dialyte formula, and some with Bausch & Lomb or expensive Zeiss Anastigmats. There was about a 1:3 ratio in price between similar cameras with meniscus and Zeiss lenses. Even the Rapid Rectilinear could produce sharp enlargements when stopped down.