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06-05-2013, 09:28 PM   #1
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How to trigger and optical flash

What's the best way to trigger an optical flash with the built-in flash? I'm using a K5 IIs, and the pre-flash sets the slave off too early. I could put an external flash on the body to do that, but would prefer to use the built-in flash.

06-05-2013, 09:32 PM   #2
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The slave flash has to be P-TTL compatible
The Definitive Guide - Pentax P-TTL Flash Comparison
06-05-2013, 10:12 PM   #3
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The slave flash doesn't have to be P-TTL compatible, although that makes things a whole lot easier.

Some flash units support an optical slave mode that can ignore pre-flash, and fires only on the main flash. But you need to adjust your power settings carefully so you achieve the proper overall exposure. (In this setup, when using such an optical slave, make sure the on-board flash on your K-5iis is set to normal flash mode, NOT wireless mode, which will fire more than two pulses.)

Another option is to set your slave flash down to 1/16 power, then it might be able to keep up, and fire twice. Once with the on-board metering pre-flash, and once with the main flash pulse. (Again, set the K-5iis to regular flash mode, not wireless mode.)

Yet another option is to use a non-A lens, which should trick the K-5iis to fire in full manual mode, with a single pulse.
06-06-2013, 02:39 AM   #4
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I hoped there was a mode, like "manual", that wouldn't use a pre-flash.
A flash with "P-TTL" ?
Hah !!
I'm trying to work as cheaply as possible. The most expensive parts of my lighting are the optical triggers! I have 3 Sunpak "potato mashers", a Sunpak 30DX, a Sunpak 8R ring flash, and a no-name swivel & tilt flash; each cost less than one of the optical triggers. Except for the "no-name" flash, they all have a manual power adjustment.

06-06-2013, 05:26 AM   #5
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I hear you. As far as I know, there is no way to fire the on-board flash in a fully manual mode, except to use a non-A lens, and then it completely discharges. I should have mentioned that I haven't actually tried this myself, because a full discharge really isn't too useful for what you (and I) would like to do.

It would also be particularly useful for those cameras which don't have a hotshoe to begin with, like the MX-1 in particular, but also the bridge cameras like the X-90 and X-5. I don't think the MX-1 or X-5 has any manual flash controls for the on-board flash, and I know for certain the X-90 doesn't.
06-06-2013, 06:53 AM   #6
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Add a Seagull SYK-5 optical slave to your external flash. They cost less than US$20. This optical slave has a red-eye reduction timer to ignore pre-flashes. It can also be adjusted to ignore the P-TTL pre-flash. I frequently use mine with an off-camera Vivitar 550D in autothyristor mode. You will find a couple posts in the flash and lighting sub-forum describing how to do this, and a translation of Seagull's instructions from Chinese into English.
06-06-2013, 12:36 PM   #7
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QuoteOriginally posted by JimJohnson Quote
Add a Seagull SYK-5 optical slave to your external flash. They cost less than US$20.
I was going to suggest the same gadget. I bought it from Deal extreme for 12USD with free shipping:
Seagull Remote Slave Trigger for Digital Camera SYK-5 - Free Shipping - DealExtreme

I am waiting for it to arrive.
Jim, can you post a link to the explanation of how to set it right? thanks
06-06-2013, 12:51 PM   #8
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In the "Search the Forums" block at the top right corner, just key in syk-5

06-07-2013, 11:04 AM   #9
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I have a couple of these Adorama house-brand wireless triggers:
Adorama Electronic Slave Unit PSL15 1315
Despite the image on-line, the units I received look exactly like the Seagull SYK-5, except they don't have the preflash suppression option. I did a test with these this morning, and wanted to share my results.

I mounted one of these on an old flash unit set to manual discharge and 1/16 power. Watching carefully in a mirror, with the K-5 on-board flash set to regular auto mode (as opposed to wireless) both the on-board flash and the slave flash fired twice: once for the K-5's pre-flash metering, and then once again for the main flash. The exposures were excellent! The K-5 sees the combined illumination from the on-board flash and the external flash, meters accordingly, and then fires the main flash at the appropriate power to work with the second external flash pulse.

I think that this might be better than suppressing the initial flash, because you retain the metering. While the external flash is at a fixed power, the on-board flash will meter correctly, assuring the overall illumination is correct.

Next, I tried this on my X-90 which uses an electronic shutter. As it turns out, the duration between the pre-flash and the main flash is really, really short, due to the lack of a mirror. And too fast for the external flash unit to react to the second flash twice. Every image that I took through the mirror only showed the on-board flash was illuminated. So, I'd say that using a dumb optical trigger probably won't work for some other cameras, such as the X-5, or the MX-1 which don't have a mirror to flip, which is a shame because they don't have any hotshoe either.
06-07-2013, 11:37 AM   #10
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QuoteOriginally posted by Tanzer Quote
I have a couple of these Adorama house-brand wireless triggers:
Adorama Electronic Slave Unit PSL15 1315
Despite the image on-line, the units I received look exactly like the Seagull SYK-5, except they don't have the preflash suppression option. I did a test with these this morning, and wanted to share my results.

I mounted one of these on an old flash unit set to manual discharge and 1/16 power. Watching carefully in a mirror, with the K-5 on-board flash set to regular auto mode (as opposed to wireless) both the on-board flash and the slave flash fired twice: once for the K-5's pre-flash metering, and then once again for the main flash. The exposures were excellent! The K-5 sees the combined illumination from the on-board flash and the external flash, meters accordingly, and then fires the main flash at the appropriate power to work with the second external flash pulse.

I think that this might be better than suppressing the initial flash, because you retain the metering. While the external flash is at a fixed power, the on-board flash will meter correctly, assuring the overall illumination is correct.

Next, I tried this on my X-90 which uses an electronic shutter. As it turns out, the duration between the pre-flash and the main flash is really, really short, due to the lack of a mirror. And too fast for the external flash unit to react to the second flash twice. Every image that I took through the mirror only showed the on-board flash was illuminated. So, I'd say that using a dumb optical trigger probably won't work for some other cameras, such as the X-5, or the MX-1 which don't have a mirror to flip, which is a shame because they don't have any hotshoe either.
The units from Adorama are just as expensive as the SYK-5, and you get more functionality out of a SYK-5.

You ran your external flash at 1/16th power. That's not much range. What if I wanted more power? Would there still be enough there to fire twice, and would the external flash still do it fast enough? With the SYK-5, your external flash can use up to full power.
06-07-2013, 12:48 PM   #11
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I agree, however, the OP indicated he is trying to work with his existing optical triggers, and implied that he might not want to buy new ones. I'm not recommending the Adorama units, rather I already have them, like the OP does. Wish I had seen your posts earlier.

If my math is right, 1/16 power will give you 1/4 the GN. So an old flash good for 100 ft can still cover 25 ft, or 10 ft at f/2.5 (and this is outdoors). Plus the on-board flash. Since the on-board P-TTL flash can't be suppressed, I'd be more concerned about overexposure, than underexposure.

The real solution is to use an external flash on the hotshoe, so that it can be manually controlled, and both flashes balanced.
06-07-2013, 01:20 PM   #12
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QuoteOriginally posted by Tanzer Quote
I agree, however, the OP indicated he is trying to work with his existing optical triggers, and implied that he might not want to buy new ones.
OP owns a K-5IIs and is worried about less than US$20 to test a SYK-5? To each his own I guess.
06-07-2013, 02:49 PM   #13
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I thought my Adorama units were so cheap at $15, I bought 3 of them. That's what I thought at the time ... wish I knew about the SYK-5 earlier.

Hey, maybe that deserves an entry in the accessories database ...
Flash Accessories (Third-party) - Pentax Camera Accessory Review Database
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