Thyristor based flashes

[captlen]

Mark, I have noticed you mention the metz thyristor based flashes. What exactly does that mean and what is the benefit of them. I shoot a canon 10D at the moment

[Mark McCall]

Captlen,
The advantages are huge.

TTL was great when the latitude of film gave you some flexiblity with regard to exposure, but it's the worst when trying to get consistent exposures digitally, where exposure is everything.

A thyristor based works by means of a sensor on the front of the flash.
All thyristor based flashes allow you to dial in the ISO, then the desired aperture. This give the flash a reference point.

When fired, the flash emits it's light.
The light is bounced off the subject, and reflected back toward the sensor.
When the circuitry in the flash "collects" enough light, it's shut down immediately.
If the subject is farther away, the flash will automatically compensate.
It all happens in a millisecond.

For the record, some thyristor based flashes are more consistent than others. Every Vivitar I've owned would not give me consistent exposures. I switched to Metz about 10 years ago., haven't looked back.

The beauty of the thyristor system is that it will expose correctly, regardless of how far away your subject is, although most will overexpose if you get too close.

No TTL, ETTL or DTTL modes in Canon, Nikon, Kodak or Fuji are accurate enough for CONSISTENT digital capture, and does not afford the control a Thyristor does.
I expect some flak for that statement, but read up on TTL on the Shoot Smarter University website.
Jim Tweedie can dispell any opinions you have about TTL's consistency.

[deluco]

The term, "Thyristor" has nothing to do with the accuracy of the flash. Thyristor is a means to turn off the flash before all power is used, therefore conserving power. Non-thyristor flashes would dump the power not used, therefore it used up your battery power much faster. Flashes that have thyristor circuitry also can provide TTL and Manual features. It has nothing to do with the ability to shoot in Auto, TTL or Manual modes.

The mode that Mark is describing is not a "Thyristor" mode....it's generally stated as Auto mode where the flash makes the decision regarding when to shut off..not the camera. TTL mode is when the camera decides.

That said, the more expensive strobes will generally have more accurate circuitry that does provide more accurate and consistent results, but even that isn't a given. The Metz is widely considered one of the best out there.

[Mark McCall]

Thanks for clarifying, Jim.

[scoundrel1728]

Thyristors are a specific kind of electronic switches. In particular, they are comparatively small, fast, and inexpensive for the amount of power they can swing. For this reason, even electronic flashes that don't have a special "thyristor" mode usually have thyristors.

In your basic electronic flash, a fixed amount electrical energy stored in a capacitor is simply dumped through the flashlamp. This gives a specific amount of output whether or not you actually need that much light.

In a somewhat more elaborate version, the electrical energy is dumped through the flashlamp but the amount needed is monitored. One of the limitations of thyristors is that they are easy to turn on but, once they turn on, they are relatively difficult and slow to turn off again. Less expensive flash units get around this limitation by diverting the energy from the flashlamp and dissipate the excess as heat once the correct amount of light is put out. Even the full-powered flash is over in a thousandth of a second or two, so a thyristor, which can turn on in a very few millionths of a second, is needed to pull off this switching trick.

In more elaborate (and expensive) designs, the circuitry is arranged to turn off the drain from the energy storage capacitor rather than simply wasting the extra energy. This saves on battery power. Also, because the energy storage is usually only partially discharged, the energy can be replenished in a shorter time and the flash can cycle and be ready for the next picture sooner.

[captlen]

Thank you all for your input. This site makes me challenge my knowledge and have found I am a better photographer just from browsing the information. Thanks all.

If I understand correctly I would be shooting on manual or apeture priority and not usingt ttl for best results,* is this correct?* If I were to purchase the Metz MZ54 that is compatible with my 10D do I then have more flexability in use then I do with my 550EX. If I am correct the 550Ex does not let me use f stops.* If I were to use* the metz off camera using a Microsync to triger it what type of adaptor do I need would it be a specils shoe that I would attach to the reciever?

[rpcrowe]

Just a cavaet regarding non-EOS flashes including thyristor flashes.

Some thyristor based flashes have a very high sync voltage some actually in the 400-600V range. This doesn't have anything to do with them being thyristor, just is the way some of them were designed. Some like the Vivitar 283-285 series flashes have several voltage ranges depending on the specific model and where it was made. The 10D is limited to a sync voltage of 6V and the very high voltage flash unite could fry that cameras electronics. The 350D has a more liberal sync voltage ability but, a 500-660V shot might damage that camera's circuitry also.