K7 and two AF-360 Wireless

Apologies if this has been answered b/4. I have searched and searched ...

I have a K7 and two AF-360 flashes. I make night-time, outdoor glamour photographs and want to trigger both AF-360s as wireless slaves using the built-in flash in controller mode. Many shots include the moon and moonlight reflections stretched over many metres of open water, so I shoot in Manual at f/16 or smaller, for 10 seconds or more, at ISO 200 or less.

I absolutely believe I need to use trailing curtain sync for a non-tech reason. Models tend to hold a pose until after the high power flash, and then they relax or change poses. With the flash firing when the curtain opens, I tend to get ghosting due to the model moving during the remaining 99.99% of the exposure in the ambient moonlight.

With trailing sync, it seems easier to convince the model to hold the pose until after the flash, and as a result I get very little ghosting. Unfortunately, I think the only way to get trailing sync is to use just one af-360, and that one needs to be camera mounted or hard wired. Wires are a great tripping hazard at midnight and not a desirable option.
Ugh!

BTW, page 180 of my K7 manual states, " When using the built-in flash with an external flash (AF360) that is set to the Trailing Curtain Sync function, the built-in flash will also use this mode." It doesn't say wireless explicitly, but this part of the manual is right after the wireless section, and I can't imagine using the pop up as a main flash and not just as a wireless control. Whatever this section means, I haven't been able to get trailing sync work unless the AF-360 is camera mounted.

So, options???

A third AF360, camera mounted in controller mode? I don't see how that would work because I can't get trailing sync to work now with only two AF-360s. I may be setting something wrong - Lord knows with 36 menu options, it is not only possible, but highly likely.

Perhaps Slave2 mode? Never tried it, but I read that S2 seems to be prone to misfires from any number of sources (maybe including the little LED flashlights I use for AF assist, because the K7 AF assist light doesn't work very well at any distance more than 5 feet).

Some kind of RF system? (never used them myself - from watching other photographers, they seem to be trouble prone).

Poles and overhead wires? (non Pentax cables of course, because they are all too short).

Finally conform with mediocrity and switch to Nikon?

Help, please.

Ted Sandilands

Have you considered something like the Pocketwizard set of wireless triggers? If those are too expensive, you could always get the Cactus v4 wireless triggers which are about a quarter the price?

You should be able to set trailing curtain then.

If you use the built in flash as controller in wireless mode, which should not fire (just a preflash burst). Put both AF360s in trailling mode and that would work fine.
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soheil said:

If you use the built in flash as controller in wireless mode, which should not fire (just a preflash burst). Put both AF360s in trailling mode and that would work fine.

Click to expand...

Actually, this is not true : the built-in flash fires even in controller mode, to give the external flashes a sync signal.

It will supposedly fire at a really low power so as not to register on the pic, but this value has been increased on the K7 when compared to the K20, and so can ruin pics when used with large aperture/high iso...

dlacoutu said:

soheil said:

If you use the built in flash as controller in wireless mode, which should not fire (just a preflash burst). Put both AF360s in trailling mode and that would work fine.

Click to expand...

Actually, this is not true : the built-in flash fires even in controller mode, to give the external flashes a sync signal.

Click to expand...

Thats what he said just more succinct than you "Just a preflash burst"

dlacoutu said:

It will supposedly fire at a really low power so as not to register on the pic,.

Click to expand...

Not true it fires control signals outside the shutter open period , but there is some ovelap.

dlacoutu said:

but this value has been increased on the K7 when compared to the K20, and so can ruin pics when used with large aperture/high iso...

Click to expand...

What value?? I don't understand what your talking about.

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awaldram said:

Thats what he said just more succinct than you "Just a preflash burst"

Click to expand...

No, the built-in flash, when set in Controller mode, also fires during the exposure to give external flashes a sync signal so they know when to fire their main burst (used for trailing shutter, I think), just like in Master mode, but with a preset power, barely noticeable in everyday pics, but if you try a great aperture/high iso shot, you'll see its effect on your pic.

I'm not talking about the mandatory metering bursts, which are the same between Controller and Master modes, but of the main flash occurring during the actual exposure.

awaldram said:

awaldram said:

It will supposedly fire at a really low power so as not to register on the pic,.

Click to expand...

Not true it fires control signals outside the shutter open period , but there is some ovelap.

Click to expand...

Overlap from the approx 1/10000 bursts of the metering? Kidding, right?

awaldram said:

awaldram said:

but this value has been increased on the K7 when compared to the K20, and so can ruin pics when used with large aperture/high iso...

Click to expand...

What value?? I don't understand what your talking about.

Click to expand...

When you set your camera to Controller mode, it will fire during the exposure. This can be easily seen if you try this in front of a mirror.

The power level of this sync burst is set by the camera to a (usually) low level. This level is model-dependent, and while quite low on both K10 and K20 (so low as to be virtually invisible in pics), this is not the case anymore with the K7.

I guess they increased its power so as to have a better sync in broad daylight (must have been misfire reports with Controller mode in this scenario), but for low-light situations, it's a real disaster...

Anyway, just try it, you will see by yourself... With a fast lens (say 1.4), 800 iso, try Master mode, then Controller.

The camera mounted flash preflashes first to alert the remote that it's using wireless mode , the remote fires a preflash to confirm this and to get exposure setting.

Then the camera mounted flash preflashes again to transmit the exposure info to the remote flash, The shutter is tripped and the exposure is taken.

There's another preflash from the camera mounted flash for flash duration if HSS is being used.
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awaldram said:

The camera mounted flash preflashes first to alert the remote that it's using wireless mode , the remote fires a preflash to confirm this and to get exposure setting.

Then the camera mounted flash preflashes again to transmit the exposure info to the remote flash, The shutter is tripped and the exposure is taken.

There's another preflash from the camera mounted flash for flash duration if HSS is being used.

Click to expand...

Well, if you have a look to the Pentax flash system patent (have the exact patent number somewhere... wait... US 6,826,364 B2 here: http://www.freepatentsonline.com/6826364.pdf ), it does not work like this...

If you have a look to Fig. 17, you'll see that in Wireless mode (S425, WLint=1), regardless of Controller or Master modes, the camera does fire a low-power built-in flash burst (S426)...

Every camera I tried (K10, K20, Kx and K7) did fire a burst even in controller mode during the exposure , except, as you stated, for HSS (called "flat emission" in the patent, S402 in the Fig. 17) where the sync signal is being sent beforehand.

Again, just try it (you don't even have to actually use an external flash for this, just set your camera to Controller, and happily snap a pic of a mirror...).

The amount of light produced by the built in is insignificant due to the distance from the subject I need to obtain the necessary DOF. Actually any little bit helps to force the models irises to contract.

The problem is that sliding the switches on the AF-360s to rear curtain does nothing when the units are off the camera. The displays on both flashes revert to front curtain, and they actually fire at the opening of the shutter instead of at closing. I am shooting in regular P-TTL mode.

I can't seem to make the rear curtain sync setting "stick" when the units are off camera.

It appears from most of the responses that this is not a problem for you folks. Have I set something wrong, or in the wrong sequence that causes the flashes to set themselves back to front curtain regardless of the position of the switch?
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Ted Sandilands

Well, I've never tried this, but looking at the K7 manual I'd say it is possible, but not sure.

The K7 manual never mention trailing curtain sync in the wireless pages, but says, the following about Trailing curtain sync:

sandilands said:

When using the built-in flash with an external flash [...] that is set to the Trailing curtain sync function, the built-in flash will also use this mode.

Click to expand...

But it doesn't say if this works in Wireless (it sure works with an extension cord). It's a little bit vague about this possibility, in fact, so I'll have to try...

Don't remember exactly what does the AF360 manual say, but that flash doesn't work on trailing curtain sync off the camera, if the camera are set to another mode than Program (at least on my K10D).

Yes, please do try it. I can't seem to make it work. And as you say, the K7 manual is very vague about it. I also think it will work wired to the hot shoe, but in my shots the camera is usually > 6 metres away from the light stands therefore excluding Pentax brand cables.

Ted Sandilands

I'll try P mode, but that kind of defeats the purpose I think. The idea is to get a bright burst at the end of a very long exposure. I usually use M mode, and have never used P - but at this stage anything is worth a try.

Thanks for the idea and getting my brain out of a rut.
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Ted Sandilands

I gues that happens because the system needs to use P-TTL to correctly calculate the amount of flash power to do a correct exposure.

Me to, would like to use the wireless flash with trailing curtain sync in manual mode, and get frustrated to the impossibility to do so, but even "locked" to P mode, i think the system works fine.

Well, I tried P mode and just about every other mode I could think of. The only way I can to get rear curtain sync is with the af-360 mounted on the hot shoe, and that does not fire the second slave flash. I think I will try some of the Pentax short cables

If anyone has anymore ideas, I am all ears.
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Ted Sandilands

You were right, one can't use slow sync with wireless flash, but I tried something odd on my k7+ 540 and it almost worked. I put my 540 on stobe2 mode and the built in flash on slow sync. whenever the built in flash fires (unfortunately it fires twice: one at the start and one at the second shutter) the 540 fires too. So, I think you might give it a try and see it works for your case.
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Actually, a pretty good idea. I'll place a hangman's mask over the control flash for the first burst, and remove it before the second. It just might equal wireless trailing curtain sync.

Thanks for continuing to experiement
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Ted Sandilands

Well, maybe using flashes set in M mode would be the solution, then...

One flash on the camera (mandatory if you want to use trailing sync and not trigger your slaves on the pre-flashes), the others in dumb flash mode (Slave 2).

You lose P-TTL, but with such controlled environments, it's a piece of cake to set up your flashes.

I've had a more in-depth reading of the flash patent by Pentax, and I believe that it is indeed impossible to have wireless trailing curtain sync...

The diagram is correct for TTL circa 2001 the mirror must be up and the flash fired to assess light as the ttl sensor is a photo diode measuring light reflected off the film.

But that patent/diagram does not seem to be for P-ttl where the Flash output is assessed by the exposure sensor that lives in the mirror down light path.

If that diagram was correct for current P-ttl then how is the light level assessed whilst he mirror is up.??? There is no sensor available to take readings.

dlacoutu said:

awaldram said:

The camera mounted flash preflashes first to alert the remote that it's using wireless mode , the remote fires a preflash to confirm this and to get exposure setting.

Then the camera mounted flash preflashes again to transmit the exposure info to the remote flash, The shutter is tripped and the exposure is taken.

There's another preflash from the camera mounted flash for flash duration if HSS is being used.

Click to expand...

Well, if you have a look to the Pentax flash system patent (have the exact patent number somewhere... wait... US 6,826,364 B2 here: http://www.freepatentsonline.com/6826364.pdf ), it does not work like this...

If you have a look to Fig. 17, you'll see that in Wireless mode (S425, WLint=1), regardless of Controller or Master modes, the camera does fire a low-power built-in flash burst (S426)...

Every camera I tried (K10, K20, Kx and K7) did fire a burst even in controller mode during the exposure , except, as you stated, for HSS (called "flat emission" in the patent, S402 in the Fig. 17) where the sync signal is being sent beforehand.

Again, just try it (you don't even have to actually use an external flash for this, just set your camera to Controller, and happily snap a pic of a mirror...).

Click to expand...

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awaldram said:

The diagram is correct for TTL circa 2001 the mirror must be up and the flash fired to assess light as the ttl sensor is a photo diode measuring light reflected off the film.

But that patent/diagram does not seem to be for P-ttl where the Flash output is assessed by the exposure sensor that lives in the mirror down light path.

If that diagram was correct for current P-ttl then how is the light level assessed whilst he mirror is up.??? There is no sensor available to take readings.

Click to expand...

Well, of course it's dated from 2001, for a film camera with a TTL sensor, as the first implementation of P-TTL was in the MZ-6 and MZ-S film cameras...

If you look at Fig 10b (which is the overall behavior of the camera), you'll see that it indeed covers P-TTL (S125 is the Pre-flash emission process of P-TTL), TTL being hinted at by PreNeed=0.

Anyway, TTL had no wireless feature, so it would be quite strange to have wireless mentioned in a patent for TTL only...

This patent was quite helpful to really understand what does P-TTL, and I've found that digital versions of P-TTL are in fact crippled compared to what it did on those film camera : for example, HSS (and trailing curtain, IIRC) are available in wireless mode on the MZ6, but not anymore on the *istD line or the K line.