The flashtube is probably bad
I wound some extra coils of wire around the original flashtube and still was not able to get good ignition.
I did have an old Rollei E36RE flash with a bum/shorted capacitor. I took the tube out of this unit and jumped it to the back of the tube socket on the EG&G and it works perfectly. Fires every time!!
This tells me the flashtube that came with the device is worn out.
One remaining problem is that the flash intensity on the settings 10-2 and 10-3 is almost exactly the same. 10-4 is much less intense to the eye and is probably working correctly.
Radio Shack Flash Tube Makes Good Replacement
I wound up just going to Radio Shack and I got the Flash Tube replacement they sell. I re-soldered this to the base that the original flash tube was connected to. Making shure to get the polarity correct. The Radio Shack tube has a little red dot on it. This flashtube cost less than $10 USD. Now my unit fires perfectly.
Last edited by ic-racer; 04-08-2007 at 01:02 AM. Click to view previous post history.
Comparison of Wejex and EG&G
Eventually I would like to compile all this info into a buyers guide. But for now I will just post some things as I think of them.
Wejex-incandecent small bulb running off of about 5 - 10 VAC
EG&G-xenon flash tube
Wejex-one second, controlled by a shutter driven by a clockwork motor.
EG&G-1/100, 1/1000, 1/10000, controlled by fixed capacitor size and fixed resistors.
Wejex-sturdy metal, but spring loaded so need 3 hands to load film. Opens TOWARD the operator.
EG&G-flimsy plastic, connected to trigger so chance of premature firing. Opens AWAY from the operator. Stays open for loading.
Place to put filters:
Method of adjusting exposure:
Wejex-variable resistor for light intensity
EG&G-3 choices of exposure duration. Intensity must be controled with ND filters
Wejex-simple transformer, runs from alternating current.
EG&G-complex 700volt filtered and regulated AC power supply with a rectifier circut. Unfiltered DC output (no filter capacitors to replace or to blow up)
Wejex-now made by Tobias; still in buisness, though support for the older white light models may be NA.
EG&G- still in buisness(?), though support for the, no longer made sensitometer may be NA.
Shop manual or owners manual on the internet:
Wejex- built in
What I like best:
Wejex- I like the fact that it is so simple. It can be copied or rebuilt from simple components (older white light model). Newer models may be more complicated.
EG&G- Excellent workmanship and circuit layout. More complex than the Wejex, but still primitive enough to be fun to work on.
What I don't like:
Wejex- little light bulb may be too yellow even with 80A filter in place. Color temp probably changes with lamp voltage. Though, these factors probably don't matter much in real life film testing for gamma.
EG&G- some components are specific to this unit and are probably unobtainable (like the monster super-fast discharge capacitor). Suitable replacements ARE available, but may alter the function of the unit. Though, who really needs exposures of 1/10,000 sec in fine art photography. Those fast speeds were for matching film sensitivity data to high-speed xenon flash subject matter.
Why you need a sensitometer
The need for a sensitometer is similar to the need for an exposure meter. One does not really NEED it but it can help out. With experience its use becomes less important, but when faced with the unnusual or out of the ordinary, it is a neccessity.
People learned photography years ago with instruction on how to use a light meter. Sensitometers were not deemed neccessary (in my opinion) simply because they were so EXPENSIVE. A current unit from Agfa cost $24,000. They are so expensive because they can be calibrated for ISO standard determination. Unless one is running an ISO standards laboratory, this is unneccessary.
THE MAIN REASON THE FINE ART PHOTOGRAPHER NEEDS A SENSITOMETER IS TO DETERMINE A STARTING POINT FOR DEVELOPMENT TIME.
If you use the same film and developer combination all the time you DON'T need a sensitometer. Likewise if you shoot in bright sun all the time you DON'T need a light meter. I was like this for many years, however, the film and developer that I like may soon be extinct.
UNKNOWN FILM/DEVELOPER COMBINATIONS ARE THE MAIN INDICATION FOR SENSITOMETER USE
For generations one had to guess at a starting point based on mfgs tables or the experience of others or trial and error.
Use of a sensitometer (and densitometer) puts some order into the process and allows one to zero in on a development time by comparing the slope of the new film with the slope of a known good film/developer combination.
How To Do It...
If one has never processed film or printed film, a sensitometer can give some guidance, but perhaps not much more than tables or experince of others.
The main utility is to answer the question of how long a new film developer combo needs to be developed WHEN ONE HAS ALREADY PROCESSED A FAVORITE FILM IN A MANNER THAT GIVES EXCELLENT PRINTS.
One needs to expose the KNOWN film with the sensitometer, and process it in a KNOWN manner. The results are read with the densitometer and plotted. Then, using some indicator of slope or gamma (many ways to do it, just be consistent) find the slope or gamma for the known film.
Then expose (with the sensitometer) and process the unknown film and measure its slope or gamma. Then alter one's development time to adjust the slope or gamma to match that of the known film. More development to increase slope/gamma and less development time to decrease slope/gamma.
The utility of these methods will become more important as we photographers are forced into unknown film/developer combinations by market availability of products.
There are many, many other uses of sensitometers and densitometes in fine art photography, but the above mentioned testing sequence is the main reason why I think almost everyone would probably benefit from a sensitometer.
As an analogy, if one is taking pictures in the bright sun without a light meter and then one wishes to photograph inside a dark building, one does not NEED a light meter to get good exposures, but having one can really help. In a similar manner, when moving into an unknown film developer combination, one can get by without a sensitometer, but having one can really help.
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I am looking for an X-rite blue/green sensitometer to compare with the Wejex and the EG&G. I am starting to beleive that these relatively small battery operated, LED driven devices may have some advantages for B&W testing. The main drawbacks are that I think the exposure time is long (like a second or so, like the Wejex) but I am not shure. The on line PDF file for the 393/394 indicates that there are 7 different exposure settings but does not list the times in the specs.
I even refreshed my memory on reciprocity by looking back at the Zakia and Todd book on Sensitometry and I still think that when one is just interested in "process control" information (specifically DEVELOPMENT TIME), the duration of exposure in the sensitometer does not make much difference.
I guess there is a point that I wanted to make clear again when I make the statement that I believe that all 3 types of sensitometers are probably going to work fine. The point is that I would never consider trying to mathematically match film data to a scene to be photographed. That is , I would not measure the 'range' of the scene and then look at sensitometric data to find out which curve will 'fit' that range. These 'process control' sensitometers are not going to be accurate in that type of setting.
My method implies that one uses 'trial and error' to find out which film curve (ie which development time) fits the scenes range. THEN when one wishes to try a new film or developer on a similar scene, the 'process control' curves of the known and unknown film can be matched. This saves re-doing the 'trial and error' again with the new film or developer. Another way of putting it is that the sensitometric data that one is able to easily obtain is going to be too far removed from the actual scene to do a 'mathematical' matching of scene range to film curve. If one wanted to do a 'mathematical' matching one WOULD need to be concerned with spectral composition of the sensitometer light source, sensitometer exposure time etc. And even then one may need a different sensitometer and different test exposures for different scenes. Furthermore, the range of the scene is not consistently related to the range of intensities behind the lens, because of flare and such. So, some type of film plane reading would be needed. Again, at this point one is 'way out there' in unneccessary complexity.
Last edited by ic-racer; 04-09-2007 at 03:07 PM. Click to view previous post history.
I have the manual in-hand and will attempt to scan it tonight. IC-RACER, please PM me your email address so I can send you a PDF.
UPDATE: OUCH! It is 20 MB! Be forewarned!
UPDATED UPDATE: Just found out my email server won't transmit anything more than a 15 MB attachment, so I had to do an ugly compression job on it for now. If anyone would like to host it on a site, I can ftp it to you @ 300dpi and 20 MB.
Last edited by Kino; 04-09-2007 at 10:49 PM. Click to view previous post history.
Reason: update info
Thanks for the EG&G manual. It did confirm some thing and clear up some confusion on my part.
First, in the troubleshooting section, under "Intermettent Flashes" the first thing mentioned is "Flashtube FT-118 at end of life, hard starting." This was indeed the case, as replacement with the Radioshack tube cured it. I did find a place on the internet with a real FT-118 for about $30.
Second, it was curious that the 10-3 position seemed brighter than the other two. My usual experience with almost all 'automatic' photoflashes for photography is that they use flash DURATION to control the light output. So I figured the brightest flash was the longest duration.
This was NOT confirmed by the circuit which shows the 10-3 circuit discharging through a 2 ohm resistor and the 10-2 circuit discharging through a 50 ohm resistor. So the discharge through the 2 ohm resistor IS Faster, but it also burns the lamp brighter.
This is all confirmed in the manual:
10-2 light output = 800
10-3 light output = 4000
10-4 light output = 70
Therefore the need for some special filters to even things out.
Just for the record, the Wejex that I have has an exposure duration of 2.5 seconds.
Originally Posted by ic-racer