Saturday, October 18, 2008

Some SB-20 Sync Problems

I set up a little studio in my garage (details forthcoming) and in doing so I learned a few more things about the SB-20 that I'd like to share. Namely, it is a little quirky when it comes to syncing, and I think I've finally figured out some of the problems.

The Multiple Trigger Problem:

First, I've known for a while that if an SB-20 gets triggered twice in a row (rapidly) it seems to dump all the capacitor charge into the tube on the second trigger. In other words, if you have it set to 1/4 power and hit the button twice very quickly, the first flash will be 1/4 power and the second will be whatever is left (3/4 power).

In practice, this is less of a problem than it sounds, because even when my 20D is at full speed (5 fps) it isn't fast enough to cause a problem. But I noticed the effect a lot when I had a crappy connection between the SB-20 and my eBay wireless trigger. To solve the problem I rewired the connection (clipping the end of the trigger and attaching a separate 1/8" plug) and it has been very reliable ever since.

In other words, don't worry about it, but understand that a poor connection or rapid cycle time can cause the SB-20 to become inconsistent.

The Chinese Optical Slave Problem:

This second problem is a bit more serious and I had to find alternate hardware to get around it.

Apparently, the cheap Chinese optical slave triggers (seen in the picture above) lock the SB-20 up after each fire. The slave will fire the SB-20 the first time, but then it won't respond. Removing the slave from the flash will reset it as will pushing the test button on the back of the SB-20. Actually, the first time you push the test button on the SB-20 there isn't a flash, but then afterward, since it has reset, it will flash each time you push it.

Once I figured this out, using all three lights (I only have two radio triggers) meant firing a single shot, manually pushing the test button on the SB-20, shooting again, etc. In other words, it very much interrupted my flow.

FYI, I verified the problem on both SB-20s yet my eBay trigger works fine with both of them. So it is definitely some sort of incompatibility between the SB-20 and this specific model of optical slave. Sadly, this unit (a boxy little guy with a hemispherical clear window and a PC connection) is the primary optical slave available at the low end of the market.

But, there's another slave out there made by Sonia, an Indian company. So I ordered one of them (including a hot-shoe mount with two extra PC connections) and I really hope it won't cause the same problems on my SB-20s. If it works, I'll probably get one or two more to have the option.

If you are interested, the current eBay listings for optical slaves are below. The sonia slaves have a clear epoxy package with some sort of color to them (from the circuit board inside). The Chinese slaves are the boxy ones. I'll review the Sonia slave once I receive it!


tws said...

hey excuse me...

did you have any follow up on your sb20? i ask since i have an old sb20 (went with my nikon f3hp) and now would like to set it up wirelessly on my new nikon D300...

any further input would be welcomed.



Sean said...

All my SB-20 stuff can be found here.

An SB20 on a D300 will probably only work manually/auto like on my Canon. The TTL on the SB-20 depends on a sensor related to the film which the D300 does not have.

Almost any wireless trigger should work (since the SB-20 has the correct port) but the more you pay, the more reliable the trigger will be.