Is there any way to "test" if a thyristor flash is quenching the flash?

[Forest_rain]

I have a couple of old "auto" thyristor type flashes, and wanted to test if they are actually "automatic" in terms of varying the flash output, but I can't find any info online about having to do so.

Theoretically, if the sensor senses a large amount of light, it would quench the flash, so if I put a flashlight up to the sensor, wouldn't the flash fire less brightly? And if I block the sensor with my finger, it should fire at full voltage.

I tried this, but I couldn't really tell any difference, perhaps this is not noticeable to the naked eye? The durations and intensities of the light may be very fast/slight.

Any info would be helpful on how to test this accurately.

 

[Chriscrawfordphoto]

Yes, you need a handheld flash meter. Set the flash to manual full power mode and take a measurement. Then set it to auto and take another. The automatic one should show the flash was dimmer.

 

[Matthew Runkel]

I believe it is the flash duration rather than the intensity that changes, with all durations being extremely short.

Take a look at the flash manual online to see how really “automatic” the functionality is. The classic Vivitar 283 just has a photocell under a rotating turret with about 5 grades of ND filter. Something that basic is probably still working as it always has.

The standard warning is that the high sync voltage of some old flash units can destroy modern camera circuitry. I assume this is true.

 

[wolves3012]

You can do a crude test to see if the output is varying: fire the flash fairly close to a white piece of paper. Then fire it again with your finger or some black tape over the sensor. The difference in the sound should be very obvious, the 'pop' sound should be much quieter at low power.

Auto-flashes quench the flash-tube when they've detected enough light, so the light output is of constant brightness but of varying duration.

 

[nikon_sam]

You can do a crude test to see if the output is varying: fire the flash fairly close to a white piece of paper. Then fire it again with your finger or some black tape over the sensor. The difference in the sound should be very obvious, the 'pop' sound should be much quieter at low power.

Auto-flashes quench the flash-tube when they've detected enough light, so the light output is of constant brightness but of varying duration.

I agree with listening to the "Pop" as you can hear a difference, you can also tell by the recycle time as to how much power was used...

 

[Forest_rain]

I agree with listening to the "Pop" as you can hear a difference, you can also tell by the recycle time as to how much power was used...

Yes this seems to work. Definitely a larger pop when I cover the thyristor sensor. Seems to work fine! Thanks a bunch, nice trick!

 

[charjohncarter]

Now that you know it works, you can learn to use it for fill flash and regular flash. And you don't have to do all that math for manual flash.

 

[Bill Clark]

This should be easy to understand with a digital camera because you can see your results immediately.

You can move your camera settings around shutter and aperture, including iso, and see what’s going on. Shutter makes no difference with flash but it does change ambient light that might be in what you are photographing.

Are you using a digital camera?

I used a flash when I was film based with a thyristor circuit. Once I went digital and also off camera flash using Pocket Wizards, I only used flashes and camera in manual mode. I would operate the flash at one constant setting while making photos I could change the settings on the camera to get what I wanted. At an event it can rather hectic at times. I didn’t use a flash meter but, instead, relied on the histogram.

I wanted to keep it simple. But I wanted to be in control.

 

[charjohncarter]

This should be easy to understand with a digital camera because you can see your results immediately.

You can move your camera settings around shutter and aperture, including iso, and see what’s going on. Shutter makes no difference with flash but it does change ambient light that might be in what you are photographing.

Are you using a digital camera?

I used a flash when I was film based with a thyristor circuit. Once I went digital and also off camera flash using Pocket Wizards, I only used flashes and camera in manual mode. I would operate the flash at one constant setting while making photos I could change the settings on the camera to get what I wanted. At an event it can rather hectic at times. I wanted to keep it simple.

Yes, if you use RAW you don't even have to be close with digital processing.

 

[Bill Clark]

Yes, if you use RAW you don't even have to be close with digital processing.

That’s not how I operated.

Sorry.

Pro photography was a great business for me. I really enjoyed it and I think clients that hired me could tell it.

At any rate, I needed to get it right in camera, first time. The files were the best when made properly in camera. Too busy back then to spend a lot of time during the process stage (on the computer) with ACR.

 

[charjohncarter]

That’s not how I operated.

Sorry.

Pro photography was a great business for me. I really enjoyed it and I think clients that hired me could tell it.

At any rate, I needed to get it right in camera, first time. The files were the best when made properly in camera. Too busy back then to spend a lot of time during the process stage (on the computer) with ACR.

That's not how I operate either, but in the real world people end up using digital editing for all kinds of nefarious manipulations: HDR, changing hair color, narrowing or widening people, making day look like night, using a make up plugin, AND read this: https://www.thephotoargus.com/40-masterful-examples-of-photo-manipulation/.

So a simple exposure adjustment with levels is the least of the 7 deadly sins if it is even in the top 20. I have not been to confession for 15 years after I had first tried HDR and realized that it was an impure thought. My penitence was really a minor inconvenience as I only did it once. I, of course, sagaciously remitted an indulgence, so I feel I'm safe now.

 

[Bill Clark]

sagaciously remitted an indulgence, so I feel I'm safe now.

Did you light a votive candle?

Ha!

 

[charjohncarter]

Did you light a votive candle?

Ha!

At the time I considered it but 15 years on I have other reasons to light a candle. Best to you and your family Bill; let's hope and pray they/we are all safe.

 

[nikon_sam]

I have a couple of old "auto" thyristor type flashes, and wanted to test if they are actually "automatic" in terms of varying the flash output, but I can't find any info online about having to do so.

IF you do any testing with a digital camera check the triggering voltage of the Flash unit first...make sure you don't damage anything...but I'm sure you know this already...😱😀