Problem with two flash guns

I'm trying to fire two flashes simultaneously to improve modelling and practicing on my chessmen (they don't complain about the flash in their eyes).

I have a AF240Z and a AF260As each mounted on an Ishoot radio receiver.
The radio transmitter is mounted on my K10D which is set to X.

If I switch off the left hand flash, the right hand one always fires and vice versa, and gives the effect shown in my avatar
If I switch both on sometimes the left fires and not the right, sometimes it's the otherway round. It's almost as if they don't like each other. But occasionally (about once in eight) all works fine

I'm running the AF240Z flash gun in manual and I've tried covering both the sensors with black tape. All batteries are fully charged. Exposure is about right when both fire (ok on the side of the flash when only one fires)

Any ideas about what might be going wrong would be most welcome

Bernard

If the iShoot transmitter has a test button, what happens when you press it? Do both flashes fire OK?

Have you tried changing the radio channel?

My guess is the fault lay with the radio tx/rx's rather than the camera/flash.

One review says:
( http://dptnt.com/2009/12/ishoot-wireless-flash-trigger-pt-04-cn-review/ )

From memory, I think some Nikon or Canon triggers will work a bit with Pentax, but some require a minor mod to work properly with Pentax...

Matt

Peter
The tx has a test button and more often than not both flashes go off (to my eyes) simultaneously, but not when initiated by the camera???.
I've run through all the combinations of channels and it's the same. I've swapped rxs and flashes over to try and isolate anything

Matt
Thanks for the link - I've made a copy of the text to a PDF file.
The set (1tx + 2rx) were bought via Amazon but are identical to the review and Pentax was specific in the Amazon write up (otherwise I wouldn't have bought them)
Not sure what is meant by flash in standby- my flashes are yesterdays technology (the 260Sa is on or off - the 240Z has off/P/A/M) both have a sensor on the front which I've blacked out to enable the flash to ignore my diffusers. I note the comment in the review that rechargeables shouldn't be used ----- I wonder if this is the problem, I'm using Uniross Ni-MH----- I'll have to buy some ZnC's and try those.

It's just perplexing that they rarely fire together .


The following shots show the problem (the last being a good one albeit I've yet to get the exposure correct)
[IMG]http://i1236.photobucket.com/albums/ff444/Frogherder/IMGP7954.jpg[/IMG]
[IMG]http://i1236.photobucket.com/albums/ff444/Frogherder/IMGP7956.jpg[/IMG]
[IMG]http://i1236.photobucket.com/albums/ff444/Frogherder/IMGP7957.jpg[/IMG].


Thanks and regards
Bernard

I hate flash,

for this sort of subject I would try a couple of tungten lamps, you can see the shadows your creating and only take the shot when your happy, I find the K10D, as with all the Pentax DSLRs I've owned quite capeable of getting the colours right even with the camera set to AWB, and of course the shutter speed should'nt be a problem if your using a tripod.

The subject chosen was to save blasting a human subject over and over when it wasn't working right.

In a sentence - I was practicing for when I get a human to sit long enough to get a good portrait, usually anything longer than 1/180 causes boredom to set in

Bernard

If we postulate, for a moment, that the iShoot kit is the problem.
What would be a suitable replacement (Don't bother putting expensive kit forward-I can't afford it)

Bernard

I use cactus V4's... Get the occasional misfire but nothing like you describe... They're pretty reliable...

Cactus now sell V5's which get great reviews also...

I'd consider replacing the AF240z for a more 'controlable' unit too...

Gadget Infinity (who supply the cactus triggers) do a clone of the Vivitar 285hv... It has no swivel feature but on a stand that make no difference...

I am not very experienced with flash use, but wanting twin flashes for Macro work thought Flash-trigger and Receivers would be the cheapest way to go,using two Panasonic Flashes about 30 years old fixed on a length of steel, bolted to tripod-socket and holes on flat steel,these receivers
have thread in the base for 1/4in bolts

Checking Ebay came across these, NEW★Wireless Flash Slave Trigger✚❸Receiver►PENTAX◄PT-04 (270646375502).

For the sum of $AU39.99,from lilyrst,I have used them for a couple of months without any problems.

Cactus V5's should suit your requirements.

With my studio flashes I use one radio trigger and any head that doesn't have a built in sensor is fired optically with this sort of thing: link

Simple and virtually nothing to go wrong.

Actually, they do go wrong eventually, being made very cheaply, but if you buy two you'll have a spare if one packs up.

Beer in my local pub is now nudging its way over the £4.00 barrier. Makes lots of things look cheap.

G

Point taken, George, but I was actually meaning nothing to go wrong in the way that more complicated radio systems are frequently problematic.

Beer is £2.70 a pint in the pub nearest my studio but I haven't been in since someone was shot

Thanks to all who've taken the time out to comment.
All noted and stored for reference- I'll probably try Gartmore's cheapie option first as V5's don't appear to be freely available in the UK (I found a couple of sites selling V2 and V4 but only the US sites were into V5s) They could well be on my Christmas wish list when my son asks.

Update.
I've discovered that using Zn-C batteries works well, almost problem solved.
Ni-MH, whilst having a similar terminal voltage, appear to act up a bit (I'm curious as to why). I thought my batteries were fully charged, but two were a tad low - I didn't check whether they were out of the same Rx or there was 1 in each Rx
Ni-Cd work, but only just.

My conclusions are that the Rxs are sensitive to battery voltage and start to fail when it starts to drop off, why both work when the partner is off is a mystery, but I think it might be down to timing ie when messing about trying to figure the problem the 'off' one is resting and therfore works best when the other starts to fail.

Tests in the garden at night appear to infer that the range falls quite dramatically as the batteries slightly age (several shots in quick sucession causes shortened range - let the battery rest a minute or two and the range is extended again),

I suspect the circuitry is deigned using 3v chips, so 3 AAA's and a voltage reg would have worked better (but cost much more)

Bernard