[tallison]

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Does anyone know of an optical trigger that ignores the preflash from a pttl flash?

Thanks

[matiki]

Does anyone know of an optical trigger that ignores the preflash from a pttl flash?

Thanks

Look for a "digital" optical slave trigger - for some reason the marketing gurus decided that being selectable to ignore pre-flash (e.g. sync with the second flash) makes it "digital" compatible/etc.

Like this:

Amazon.com: Morris DS-1 Digital Slave Trigger with Hot Shoe Mount.: Camera & Photo

[GerryL]

If you are using the built-in flash though and that flash suddenly goes to focus assist (strobes), then it would still be a problem as the strobe function does a couple of bursts.

[matiki]

If you are using the built-in flash though and that flash suddenly goes to focus assist (strobes), then it would still be a problem as the strobe function does a couple of bursts.

Yes, this is a problem and one of the reasons I went to a PTTL compatible cable myself. I still chuckle thinking about this time my wife was my guinea pig and successive blasts of light fired rapidly without a single photo being taken.

[ma318]

Even if you can delay your "dumb" optical slave flash so it ignores the pre-flash, your photo with p-ttl flash and the optical "dumb" slave flash would most likely be overexposed. Your camera uses the pre-flash to figure out the flash power level for its onboard or mounted p-ttl flash. That means the light from the p-ttl flash alone would be enough to expose the photo correctly. If you add more light from your optical slave flash, you will get overexposure. p-ttl can not take into account of the additional light provided by your "dumb" delayed optical slave. I suppose you can dial the p-ttl flash compensation down but you must configure your slave flash and your camera's aperture first - the flash configuration is no longer fully automatic.

If you use a p-ttl compatible slave flash that communicates wirelessly with the camera then you would fine. Or you could use a P-TTL cable if your slave flash is a p-ttl flash.

Or you can disable p-ttl, by mounting an older auto-thrysitor flash on the camera and have it trigger your opitcal slave flash. But you would have to understand how to configure the setting on the flashes and the aperture on your camera.

Note: this also explains why one would get dark photos when one tried a "dumb" non-delayed optical slave with p-ttl. The slave got trigger during the pre-flash. The camera think there is a lot of light so it will dial its onboard flash power level way down for the real flash. But your optical slave flash can not flash again quick enough (it needs time to charge up) when the real p-ttl flash goes off (probably at its minimum flash power level).

[GerryL]

Even if you can delay your "dumb" optical slave flash so it ignores the pre-flash, your photo with p-ttl flash and the optical "dumb" slave flash would most likely be overexposed. Your camera uses the pre-flash to figure out the flash power level for its onboard or mounted p-ttl flash. That means the light from the p-ttl flash alone would be enough to expose the photo correctly. If you add more light from your optical slave flash, you will get overexposure. p-ttl can not take into account of the additional light provided by your "dumb" delayed optical slave. I suppose you can dial the p-ttl flash compensation down but you must configure your slave flash and your camera's aperture first - the flash configuration is no longer fully automatic.

If you use a p-ttl compatible slave flash that communicates wirelessly with the camera then you would fine. Or you could use a P-TTL cable if your slave flash is a p-ttl flash.

Or you can disable p-ttl, by mounting an older auto-thrysitor flash on the camera and have it trigger your opitcal slave flash. But you would have to understand how to configure the setting on the flashes and the aperture on your camera.

Note: this also explains why one would get dark photos when one tried a "dumb" non-delayed optical slave with p-ttl. The slave got trigger during the pre-flash. The camera think there is a lot of light so it will dial its onboard flash power level way down for the real flash. But your optical slave flash can not flash again quick enough (it needs time to charge up) when the real p-ttl flash goes off (probably at its minimum flash power level).

Actually, the one with the optical slave still works without blown exposure as long as the slave flash can be set to automatic or is the auto-thyristor kind.
I have this such flash and have use it to shoot macro at times (just using on board flash to fire the slave with the slave actually doing the lighting).
I had this type of flash when I was using my Canon S3 IS which didn't have a hot shoe.
I still have the flash and still use it at times with my K100Ds with good results.
Only beware of the auto-focus assist of the built-in flash itself.

[GerryL]

Yes, this is a problem and one of the reasons I went to a PTTL compatible cable myself. I still chuckle thinking about this time my wife was my guinea pig and successive blasts of light fired rapidly without a single photo being taken.

Blinded guinea pig I should say!

[ma318]

Actually, the one with the optical slave still works without blown exposure as long as the slave flash can be set to automatic or is the auto-thyristor kind.
I have this such flash and have use it to shoot macro at times (just using on board flash to fire the slave with the slave actually doing the lighting).
I had this type of flash when I was using my Canon S3 IS which didn't have a hot shoe.
I still have the flash and still use it at times with my K100Ds with good results.
Only beware of the auto-focus assist of the built-in flash itself.

When you use your optical slave flash with the Canon S3 IS, did you put the S3 in Manual mode? Is your optical slave a delayed slave?

I use a non-delayed optical slave with my Canon A570 IS too but I always have to put it in Manual mode and dial down the manual flash power to minimum. With the A570, the build-in flash does not do pre-flash when the camera is in manual mode only. In any other mode, it would do pre-flash and I would always get an underexposed photo - as expected with a non-delayed optical slave and pre-flash. I had tried a manually adjusted delaying optical slave with my A570 in AV or P mode but I was never able to get it to work. Others might have gotten it to work but not me - I could not get the amount of delay right.

Actually with a delayed slave and an auto-thyristor type flash, I can see that it could work as long as you get the delay right. The auto-thyristor flash would measure the light from the p-ttl flash and would simply output whatever additional light that is required. In most cases, it would not output much light at all because it has determined the light from the p-ttl flash is sufficient. Unless you dial the p-ttl flash compensation down, much of the subject will still be lighted by the p-ttl flash which kind of negates the point of using a slave flash. The amount of delay must also be very accurate otherwise it might get a wrong measurement of the amount of light from the p-ttl flash.

Canon actually used to sell an optical slave flash that can handle pre-flash by delaying precisely the amount of time required to ignore the pre-flash. The duration of each brand's x-ttl pre-flash appears to be fixed but the camera manufacturers do not seem to publish it - at least openly.

http://products.howstuffworks.com/canon-hf-dc1-digital-slave-flash-review.htm

[GerryL]

The slave flash was specifically made for this type of P&S (S3 IS) cameras to deal with the pre-flash of the camera.
The flash was an auto-thyristor and it adjusts it light output depending on what it sees.
If the on-board flash of the camera is strong, then the optical slave flash adjusts to get the correct exposure.
I still use it to do macro shots or put fill-flash on my K100Ds.
It would be kind of hard to put the S3 on manual if you don't get the settings right.
Anyway, with digital, you can see the results immediately so, you can adjust where the throw of light is or other camera settings.

[GerryL]

The auto-thyristor detects its own flash output and reads the final flash of the camera and not the P-TTL flash.
It automaticall cuts off its output if it detects the camera flash as sufficient enough.

[ma318]

GerryL, looks like your slave flash works a lot like the Canon HF-DC1. Yes, slave flash like these that are manufactured by a major brand vendor specifically designed to handle pre-flash will work.

I think in a previous post, the OP asked about the cheapo manually adjusted optical delay trigger. My experience with this type of cheapo optical delay trigger is that they do not work with pre-flash. I was unable to manually adjust the delay to ignore the pre-flash accurately.

(I ended up putting an old auto-thyristor flash on my camera, which disabled pre-flash, to trigger my non-delayed optical trigger.)

https://www.pentaxforums.com/forums/camera-studio-accessories/87123-seagull-syk-5-trigger.html

[Russell-Evans]

Does anyone know of an optical trigger that ignores the preflash from a pttl flash?

If you already have optical slaves, it will be cheaper to buy an old manual flash to use as a trigger. This will also be the more likely to work all the time solution as well.

If you need to buy optical slaves, it probably wouldn't be much more expensive to buy poverty wizards off ebay instead.

Thank you
Russell

[tallison]

I have a Bower SFD926P and a Pentax af240z. I would like to use the Bower in p-ttl mode with an off camera cable on a stand triggering the af240z in auto mode as a fill flash. I had planned on dialing down the p-ttl flash compensation down on the Bower to see if I can get a good exposure. I was willing to loose $12 on the Seagull trigger just to see if it would work. I'm not sure if I want to loose $30 just to play arround. You guys seem to know a lot about this stuff. Do you think that it would work?

Thanks

[ma318]

Whether you mounted your Bower directly on the camera or off-camera with a p-ttl cable, it will still generate a pre-flash. So you still have the same problem in getting the af240z to ignore the pre-flash and only trigger on the real flash. I don't think there is any way around it. I think your choices are:

1) if you must use p-ttl, then ensure all your flashes are p-ttl capable and all can be wirelessily (or wired) controlled by the camera.

or

2) if you must use p-ttl, you can get something like the Canon HF-DC1 as the slave flash.

or

3) forget about p-ttl, put a cheap auto-thyristor flash on the camera and uses all your flash in manual mode and/or auto-thrysitor mode. You can use regular optical slave triggers.

or

4) get an old istD* and use an external TTL flash which does not do pre-flash as your main flash and you can use regular optical slave trigger.

(You can also replace the optical triggers with radio triggers if you want.)

[Russell-Evans]

I have a Bower SFD926P and a Pentax af240z. I would like to use the Bower in p-ttl mode with an off camera cable on a stand triggering the af240z in auto mode as a fill flash.

The Bower has a built in optical slave. Just use the AF240Z on the camera in A mode and it will trigger the Bower for you. No cables, but also no P-TTL.

I remember a post a long time ago with someone saying the delay optical slaves didn't work, so that is why I am suggesting doing something else. I can't remember the post or the poster. I'm not even sure it was here, it might have been at DPR.

Do you have the K20D or K-7 with the sync port? You could use that for your setup as well. P-TTL cable and remote Bower, PC sync cord and pc sync hot shoe with the AF240Z.

The other option would be a Pentax P-TTL adapter F, Pentax P5 cord, and another P-TTL adapter F to connect the Bower. Then on the Pentax adapter F on the camera, as it is also a hot shoe, add a PC sync hot shoe and cable, and another PC sync hot shoe on the other end for the AF240Z.

You could also go with the Pentax P-TTL adapter FG, a Pentax P5 cord, and a P-TTL adapter F and just use the on board flash as fill for a completely P-TTL solution.



You probably don't want to buy the "off camera adapter F" as it is a lot more expensive than the "adapter F" for some strange reason. You can spend $3 on ebay to get a remote flash stand with a tripod mount, save money, and have a more useful set up.

If you already have a P-TTL cable, it isn't a Pentax cable, and you don't own the K20D or K-7, you could open the cable up and add a PC port to it to make this all work.

Thank you
Russell