Slave Flash Trouble: Turning off Pre-flash

I am wishing with all my might right now that someone is going to be able to help me with this!

Today I bought an AC slave as well as a sigma EF-500 super. I set them both up, with the AC on a light stand and the sigma shooting through an umbrella. My problem is this: They aren't synching. I suspect it's because of a pre-flash firing from the Pentax for metering purposes. If this is the reason, is there any way to turn off the pre-flash? I can't seem to find any way. If not, is there some other way I can sync these off-camera flashes? I'm so disappointed right now.

Please, someone help!

You'll have to use manual mode. In a static situation, it's the best mode to use anyway.

G

I agree with George, but I should elaborate...

You neglected to mention which camera you're working with!

You can't disable the preflash of the popup flash because there's no way for a DSLR to meter when the mirror is up, and although the *ist-D and *ist-DS did have TTL metering off the CCD it was a bit hit and miss (probably down to the reflectivity of the CCD compared to a matt film surface).

However, you can increase the time between preflash and main flash by enabling red eye reduction.

For brolley work, do this:
* Put the flash in fullly manual
* Set the flash to something like 1/8 power
* Put the camera in fully manual
* Select 1/125s
* Pick an aperture, start with f/8, take a test image and adjust until the histogram is ok
* Now, lower the shutter speed if you want the background/room to be exposed correctly (use the manual metering in the camera and adjust only the shutter speed until it shows about -1 or -2)

* Oh, and set the pop-up flash exposure compensation to -2 so it just signals and doesn't add too much to the exposure.
* And finally, don't forget to put the brolley really, really close. Ideally it should be no further away from the subject than the diameter of the brolley, but preferably just (and I mean just) out of camera view. Putting it 4 or 6 feet away is a complete waste of time (unless you've got a very very big brolley )

Sorted

What you should find is that the flash will trigger on both the preflash and main flash (assuming you're using the popup flash), and as long as the power of the flash is lower than 1/2 it should be able to cope with both without fully discharging.


Using automatic modes in a studio environment is frustrating, unpredictable and a waste of your time. The above method takes just a minute to set up and then all the shots will be just fine.

If you were expecting to use the Sigma EF-500 Super in wireless remote flash you'll find that you need two Sigma guns to do this! One on the camera as a controller or master, and second (or third) as a slave. This is true for all combinations except for the *ist-D/AF360/AF540 - but the manual method is still best for static scenarios

Hope that explains it!
Matt

Sorry, I'm using the DL.

This IS what I was hoping to do. Are the 500 Sigmas and the new Pentax flashes the only ones that are compatible with the DL? If I could just put a cheap flash on the hotshoe to trigger the slaves then the problem would be solved. But I'm thinking that a flash compatible for use with this camera's hotshoe is going to run another $300 or so. Which just isn't feasible.
I'm screwed.
And I was hoping to use this setup for living things (people, animals, etc.).

Oh, and I don't know what "brolley" means! hahaha

You need to read the manual (again). I know it's not that obvious but if you want wireless P-TTL then you have to have TWO flashguns that support wireless. No question.

You cannot use the pop-up flash as a controller or master in a wireless configuration.

BUT, as I mentioned, you can use wireless manual slave flash between the popup and a remote flash. And it works for people, animals, etc, just as long as the room and setup don't change too much (which is the case for a studio). You are not "screwed" - you just need to understand what you have available.

With the Pentax AF360 and AF540 they have two modes of wireless slave - either P-TTL or "dumb". You need the "dumb" mode (because the pop-up can't do wireless P-TTL). I'm not sure what the Sigma provides, but a little slave cell will do the job if it doesn't have the facility built in.

So, to recap. With your Sigma and *ist-DL you have two choices:
1. Mount the Sigma on the camera and use whatever mode you want.
2. Mount the Sigma on a tripod and use dumb slave, and the method I gave you.

(The pop-up flash will trigger the slave, if the slave is in dumb mode, and as long as the slave flash is set to manual power below 1/2.)

If you're not sure - print out what I said, try it, and come back if you have any probs.

Matt

Just reading the Sigma manual... and thought a couple of things need explaining.

1. The Sigma manual mentions wireless P-TTL with the pop-up. However, if you follow the instructions you'll find you can't quite follow through with them exactly. That's because the original *ist-D did have wireless P-TTL with the popup flash (which initially was a bit of a disaster, and probably why it was dropped on all subsequent Pentax DSLRs.)
However, your *ist-DL manual makes it clear that you need two external flashguns for wireless operation.

2. Page 25 of the Sigma mentions the "Normal Slave" function. In that mode the flash is using its built in slave cell to trigger off any flash unit. However, they mention that it won't work with preflash... I can confirm that the Pentax flash guns will work with preflash just fine, but you'll need to try it out with the Sigma.

If the preflash causes a problem, there are two possibilities:

A. Enable red-eye reduction. This will give about a 1 second pause between preflash and main flash, which should be enough for the Sigma to recover and fire again.

B. Mount any cheap, modern, manual flashgun on the camera hotshoe, set the Sigma to the "Normal Slave" and fire away. If the cheap flash has a manual power adjustment, set it as low as possible (or just wrap some cloth over the front to reduce its effective power so it just signals to the Sigma).


Does that make sense?
Matt

To point #1: I know this but the reason I need two external flashes is only because of the pre-flash, isn't it? Which is why I was hoping there was some way to turn off the pre-flash, which, obviously, isn't the case. Which is why I said I was screwed. Because that was how I'd hoped I could do it and now I've realized that I can't.

To point #2: I was using the Sigma on the slave setting and am aware that it doesn't work with pre-flash. That's the whole reason for my post. haha.

I'll work on trying what you've mentioned above and see how it goes.

Thanks!

No, it's not because of the preflash that you need two Sigmas.

There is a difference between the *ist-DL preflash and a true wireless preflash (whether using two Sigmas or two Pentax flashguns). The wireless P-TTL preflash is a burst of pulses that includes information for the remote. The *ist-DL preflash is just a straight flash. You see, wireless P-TTL is much more complex than just preflash/no preflash (which is why it wasn't included in the *ist-DS/*ist-DL/K100D/K110D/K10D).

That is also why you have two slave modes in the flashgun. P-TTL wireless (the complex, digitally signalled mode) and "normal" (or "dumb". To be honest, the Pentax flashgun manuals aren't that clear, and the Sigma manual is terrible!


I understood your reason for posting, that's why I'm helping you out
Let us know how you get on.

Matt

Nothing can be simple, can it? haha

Thanks a bunch!

I'm not sure if you're sorted now or not - that last message was a bit ambiguous.

Just to repeat what Matt said, you can do the above - so if you just need a flash to trigger the AC and EF-500, then stick anything on the hotshoe. You'll have to work out the correct exposure by varying the power and position of the flashes, and the aperture of your lens. A few test shots and you should be sorted. If you want the camera to do the thinking for you, you will need another EF-500 to use P-TTL metering.

Dan

I've read that some older flashes can harm newer digital cameras. Something to do with too high voltage? Someone said something about how using an old flash can "fry" your camera, which I really don't want to happen. I can get a used flash, I actually have one here but am worried that it's going to do something to my camera. Perhaps I'm wrong on that though. Is any flash okay?

I'm also having trouble finding an infrared filter to cover the flash I'll be using as a trigger. Where might one find those?

Thanks so much for all your help!! It's taken me some time to figure out what you all mean by some of the things you've said but I think I'm starting to get it now.

The issue of old flash units and their possible effect on new digital bodies has been covered before, and a comprehensive answer can be found here: https://www.pentaxuser.com/forum/viewtopic.php?t=418&highlight=flash+voltages

I've used a Centon FG-30 on my istD for the last two years, and never had a problem. Looking at this long list of trigger voltages - http://www.botzilla.com/photo/strobeVolts.html, the voltage for this flash is around 200V.

I might suggest you have a look through the list, see what low trigger voltage ones you could get cheap (or if you have one already, what it's trigger voltage is), and go from there. I guess there's no harm in going for a low voltage one, and potentially some harm from the higher ones. As I say, there's never been a problem with my Centon, but then there's nothing to say the flash circuits in the DL are rated the same as the D.

Dan