problem using slave flash (Vivitar 285) with *istDL

[kate_b__seattle_1]

I've read through old messages and still can't make this work. I'm

using my very old Vivitar 285 with my new Pentax *istDL. I'm using it

as a slave with an attachement to it's hotshoe. I'm trying a

technique learned in class. The Vivitar flash will fire (set off my a

low level flash from the internal flash on the camera).

 

I've read the manuals. Camera is set to manual. I've tried shutter

speeds from 1/2000 to 1/125 and can't seem to the Vivitar to synch.

 

At least I think that's the problem. The images are dark.

 

Thanks in advance for your advice. Thank you for past advice as this

forum has been helpful to me in figuring out how to use my old manual

Pentax lenses with the new camera!

[alan_gage]

I'm not quite sure I understand what you're trying to do. But from what I could get out of your post you're not physically firing the vivitar from your camera, rather trying to use the on camera flash to fire the Vivitar. And the Vivitar is actually firing, right? Just that the images are underexposed?

 

First of all it sounds like you might have a bit more learning to do with flash. You said you tried shutter speeds from 1/125-1/2000. 1/125 is the MAXIMUM shutter speed your camera should sync at. You should be working only with speeds 1/125 and slower. Also, shutter speed has little to no effect on exposure when using a flash. The aperture is what will affect exposure with flash.

Do you have the flash setup for proper exposure; do you know how to use it? Are you using the flash in one of the auto modes or manual mode? Do you have a flash meter?

 

The flash was designed to use the auto modes when it's mounted on the camera and facing the subject. You find the correct color/exposure on the dial on the side then set the dial on front to the correct color. Then set the correct aperture on the camera. When it detects enough light (based on what "color" you chose) the flash automatically stops itself. It works pretty accurately this way, but if you have the flash mounted off camera so it's not facing the subject from the same angle and distance as the camera you're going to have problems using it in this mode.

 

The other mode is "manual" where you adjust the power to full, 1/2, 1/4, etc... Now you'd want a flash meter to find the correct aperture to use. Or since you're using digital you could just experiment by adjusting the flash power or lens aperture. A flash meter is more accurate and much faster though.

 

You can find the manual for your flash on-line if you search for it. It sounds like you just need to study up a little more on using flash. You're doing the right thing be trying and experimenting though.

 

Alan

[Jochen_S]

DSLR flashes are doing some ETTL or whatever Pentax are calling it; which fires the built in flash twice; the first time just to get a idea of the required power for the serious pop. Unluckily the slave sensors are detecting these preflashes and believe them to be reason enough to trigger your external flash before the exposure.

 

Your DSLR will do fine when you use some conventional hotshoe flash to trigger the slaves.

[kate_b__seattle_1]

Thanks to both of you for answers.

 

Alan....I realize now I did not provide enough detail. I'm using the old Vivitar as a slave as I've been warned (here, in these forums, acutally) that it's likely too powerful to place in the camera's hotshoe. I only mentioned 1/2000 as that is what the Vivitar manual stated as the flash synch. I though that was odd as I am well aware that most cameras synch at about 1/125th.

 

Jochen....I was in a class yesterday and the instructor gave me exactly the same answer. This is indeed my problem. So, if I want to use the old Vivitar, I think the solution is to get a newer (but cheap) flash unit to place in the hotshoe. It will not do the preflash and will trigger the vivitar appropriately.

 

Thanks again.

[martin_fahey]

Kate

 

I'm surprised you think the 285 is "too powerful" for hot-shoe mounting. I use a 283 occasionally, with no problems. What you have to do is simply check the voltage in the firing circuit - get an electrical or electronics person to do this (a very simple task). On some older flashes it can be very high, but if its only 6 volts or so, it should not be a problem. Maybe get confirmation of this from someone else before you act on it (but as I said, my 283 shows only 6 volts from memory, and I have used it without any problem on my istDS.

[alan_gage]

Hi Kate,

 

I'm with Martin. I use my 283's and 285's with my DS. I checked the voltage on them and found it only about 6-7 volts. I don't know the exact age of mine so perhaps some of the older ones are higher voltage. Just turn the flash on and let it charge; then check the voltage between the 2 pins with a digital volt meter. If you're checking at the flash hotshoe the ground terminal is a spring loaded clip between the "channels" where it slides on the camera shoe. Or connect a PC cable to the flash and check voltage between the center pin and outer shield. Nothing to it.

 

As for the vivitar manual saying it synced at 1/2000; I think what it really meant is that the flash duration is 1/2000, that doesn't really have anything to do with the sync speed.

 

Good luck,

 

Alan

[derekb]

Kate,

 

I have an IST DS and a Vivitar 285 that I tried using with a slave eye attached to it as well and mounted it off camera. The previous posts about PTTL are correct. I have experienced the problem as well. The on camara double flashes and the slave picks up the first flash.

 

I also have a Pentax 280AF flash that I can put in the hotshoe to trigger the 285 with and it works just fine.

 

2 Solutions:

 

1. Use a secondary simple flash as a trigger

2. Buy a fancier slave eye like some made by sunpack and wein. They can sense and ignore preflashes

 

As far as the voltage of the Vivitar 285 goes, I checked mine at 8.5 volts. Not safe for a Canon camera, but safe according to all I have read with a Pentax. My Pentax 280AF rated at 7.5 so it isn't much different. Check it with a digital multimeter by connecting the terminals one to the center 286 x sync cord centre and sheild for a voltage reading.