[Spodeworld]

I was looking at the Cactus RF60 Wireless Flash With Wireless Flash Transceiver V6, and noticed it had a HSS Sympathy Mode.

Does that mean on a Pentax I can get this thing to fire over the sync speed using this? I remember hearing about certain restrictions with Pentax when you try to go above the max sync speed, but wasn't sure if it would compromise this capability.

Thanks

[Adam]

A detailed write-up on HSS can be found here:
Cactus RF60 Review - Special Features | PentaxForums.com Reviews

Basically, you can get the RF60 to work in HSS mode if you mount a P-TTL flash that support HSS on the camera. The latter will serve as a trigger.

[Spodeworld]

Thanks Adam.

I read it over a few times (still haven't fully digested it) and it looks like Pentax makes you jump a few hurdles to access this functionality. Frustrating that they just can't take the simple Nikon approach!!

A detailed write-up on HSS can be found here:
Cactus RF60 Review - Special Features | PentaxForums.com Reviews

Basically, you can get the RF60 to work in HSS mode if you mount a P-TTL flash that support HSS on the camera. The latter will serve as a trigger.

[mcgregni]

I wrote up a demo thread of a 3 flash HSS setup using the Cactus equipment and 2 Pentax flashes, here .....

https://www.pentaxforums.com/forums/125-flashes-lighting-studio/311128-pentax...-hss-demo.html

[maxfield_photo]

Thanks Adam.

I read it over a few times (still haven't fully digested it) and it looks like Pentax makes you jump a few hurdles to access this functionality. Frustrating that they just can't take the simple Nikon approach!!

Pentax, unfortunately (or maybe fortunately for some) chose to put in certain safeguards against the dreaded black bars of flash photography. Normally the pop-up flash, the hotshoe, and the PC socket all go inactive above max sync speed and so there is no way to get a sync signal to the flash equipment. The only exception to this is if the camera can detect a HSS equipped flash on the hotshoe, then it will cross the sync barrier. I agree, it's frustrating.

So the traditional way to do off-camera HSS with a Pentax DSLR (and the MZ-S) is to have a master or controler HSS flash on the hotshoe, and one or more slave HSS flashes off camera. The on-camera unit would transmit pTTL data to the off camera units during pre-flash talk and tell them when the shutter curtains were about to start moving, and therefore when to begin firing.

What the Sympathetic HSS mode on the Cactus RF60s does is it sees the pre-flash from the master/controller and then chimes in with it's own continuous burst after a predetermined delay in milliseconds which can be adjusted by the user. This all works via optical slave by the way. Even though the RF60s normally use radio communication, pTTL HSS does not, so in order to chime in the flashguns need to see the pre-flash (but we'll come back to this in a minute). The power can't be adjusted on the fly the way a true pTTL exposure can, but when dealing with HSS, usually the problem is not having enough power, so it's usually safe to just set full power on the flash and deal with exposure with aperture and ISO on the camera. The system works well, maybe not flawlessly, but it's cheaper to buy RF60s than AF540s.

There is another very sneaky trick you can do with the Cactus system though. You can actually use a V5 or V6 as an external sync source for both the camera and the flash. That way, the camera will cross the max sync barrier because it doesn't know that there is a need to activate it's black bar protection, it just thinks it's taking a normal non-flash shot. One of our members, Class A, describes the procedure in this post. He and I have taken to calling this approach "the Starter Pistol Method" because you use a hand held Cactus in transmitter mode to start a race between the camera and any number of flashes, and hopefully, they will all cross the finish line together (but you use the delay function on the flashes to give the camera a head start.) The beauty of the starter pistol method is two fold: for one thing, it actually uses radio frequency rather than optical signals, so it can work at much greater distances, and in bright daylight. The other great thing is you don't need a HSS master on the hotshoe, in fact, you don't need a HSS compatible flash at all for this trick to work.

It's all a little confusing to read it, but it makes more sense when you are actually setting it up, and it does work surprisingly well. It is a little complicated to achieve something so simple, but that's what we are stuck with for now.

[Spodeworld]

So, would your 'sneaky approach ' need more than one cactus transceiver and one cactus flash? I'm really clueless about this stuff!

Thanks

Pentax, unfortunately (or maybe fortunately for some) chose to put in certain safeguards against the dreaded black bars of flash photography. Normally the pop-up flash, the hotshoe, and the PC socket all go inactive above max sync speed and so there is no way to get a sync signal to the flash equipment. The only exception to this is if the camera can detect a HSS equipped flash on the hotshoe, then it will cross the sync barrier. I agree, it's frustrating.

So the traditional way to do off-camera HSS with a Pentax DSLR (and the MZ-S) is to have a master or controler HSS flash on the hotshoe, and one or more slave HSS flashes off camera. The on-camera unit would transmit pTTL data to the off camera units during pre-flash talk and tell them when the shutter curtains were about to start moving, and therefore when to begin firing.

What the Sympathetic HSS mode on the Cactus RF60s does is it sees the pre-flash from the master/controller and then chimes in with it's own continuous burst after a predetermined delay in milliseconds which can be adjusted by the user. This all works via optical slave by the way. Even though the RF60s normally use radio communication, pTTL HSS does not, so in order to chime in the flashguns need to see the pre-flash (but we'll come back to this in a minute). The power can't be adjusted on the fly the way a true pTTL exposure can, but when dealing with HSS, usually the problem is not having enough power, so it's usually safe to just set full power on the flash and deal with exposure with aperture and ISO on the camera. The system works well, maybe not flawlessly, but it's cheaper to buy RF60s than AF540s.

There is another very sneaky trick you can do with the Cactus system though. You can actually use a V5 or V6 as an external sync source for both the camera and the flash. That way, the camera will cross the max sync barrier because it doesn't know that there is a need to activate it's black bar protection, it just thinks it's taking a normal non-flash shot. One of our members, Class A, describes the procedure in this post. He and I have taken to calling this approach "the Starter Pistol Method" because you use a hand held Cactus in transmitter mode to start a race between the camera and any number of flashes, and hopefully, they will all cross the finish line together (but you use the delay function on the flashes to give the camera a head start.) The beauty of the starter pistol method is two fold: for one thing, it actually uses radio frequency rather than optical signals, so it can work at much greater distances, and in bright daylight. The other great thing is you don't need a HSS master on the hotshoe, in fact, you don't need a HSS compatible flash at all for this trick to work.

It's all a little confusing to read it, but it makes more sense when you are actually setting it up, and it does work surprisingly well. It is a little complicated to achieve something so simple, but that's what we are stuck with for now.

[maxfield_photo]

So, would your 'sneaky approach ' need more than one cactus transceiver and one cactus flash? I'm really clueless about this stuff!

Thanks

Yes, you need one Cactus unit set to transmitter mode that you hold in your hand, a.k.a. your "starter pistol." It could be a V5 or V6 (it might even work with a hand held RF60)

Then you need one Cactus unit set to receiver mode that you attach via cable to the remote shutter port on your camera. Again, it could be a V5, or a V6 (I don't think the RF60 will work here).

Finally you need flashgun(s), at least one, but you can have as many as you want. I would highly recommend Cactus RF60s for this purpose because they have HSS sympathetic mode. (With other flashguns you can still achieve faster-than-sync speeds, but it is something that PocketWizard would refer to as "Hypersyncing". It relies on capturing the long tail of the flash from a full power burst. The illumination isn't as even as with the RF60s.) You set the flashguns to a certain delay, I find that 91ms is a good starting point, but you may need to adjust it. Then you fire both the camera's shutter and the flashguns with your hand held transmitter.

So at a minimum, 3 units, 2 transceivers and a flashgun. And a simple 3.5mm to 2.5mm audio cable to connect the receiver unit to the camera. And a camera. And some batteries.

---

Last edited by maxfield_photo; 03-03-2016 at 05:34 PM.

[Spodeworld]

Thanks Max.

Sounds so convoluted for something that should be so simple!


It also sounds like this is what happens when solutions are over-engineered. I know there was a purpose, but I think the obstacles it poses were not worth the advantages.

Yes, you need one Cactus unit set to transmitter mode that you hold in your hand, a.k.a. your "starter pistol." It could be a V5 or V6 (it might even work with a hand held RF60)

Then you need one Cactus unit set to receiver mode that you attach via cable to the remote shutter port on your camera. Again, it could be a V5, or a V6 (I don't think the RF60 will work here).

Finally you need flashgun(s), at least one, but you can have as many as you want. I would highly recommend Cactus RF60s for this purpose because they have HSS sympathetic mode. (With other flashguns you can still achieve faster-than-sync speeds, but it is something that PocketWizard would refer to as "Hypersyncing". It relies on capturing the long tail of the flash from a full power burst. The illumination isn't as even as with the RF60s.) You set the flashguns to a certain delay, I find that 91ms is a good starting point, but you may need to adjust it. Then you fire both the camera's shutter and the flashguns with your hand held transmitter.

So at a minimum, 3 units, 2 transceivers and a flashgun. And a simple 3.5mm to 2.5mm audio cable to connect the receiver unit to the camera. And a camera. And some batteries.

[maxfield_photo]

It's definitely a very complex way of achieving something that should be simple. "Should be" is the key here, unfortunately, as you observed at the beginning of this thread, Pentax has chosen to make things more complicated than they need to be. If you shoot a Pentax camera, and you like to use flash in bright sunlight, your options are somewhat limited:

• use several HSS flashguns and use optical pTTL HSS (expensive and not reliable in bright sunlight or at long distance)
• use one HSS flash and hardwire it using Pentax's proprietary system of cords and adapters (hotshoe adapter, cord, and off camera shoe) (also expensive, and creates clutter which can be tripped over)
• use a strong enough ND filter to get your shutter speed down to max sync speed thereby allowing you to use normal sub-sync flash, (simple, effective, but robs you of flash power)
• use an pTTL repeater like the Aokatech or Acon (still a bit buggy and complicated from what I understand)
• use a Priolite studio strobe and transmitter (very expensive)
• use the Cactus system and the "starter pistol method" (a little complex, moderately expensive)

You can take your pick of evils (or switch camera brands). The nice thing about using the Cactus system is it also adds flash groups to the Pentax system which it currently lacks.


The other unfortunate thing about the Pentax flash system is people don't realize how complicated it's going to be be until they start actually trying it for themselves. What should be simple is not. I'm sure some people will feel I'm bad-mouthing the brand, but anyone who has tried to use HSS in a real-life shooting situation will understand that this criticism is well-earned.

[MadMathMind]

use a strong enough ND filter to get your shutter speed down to max sync speed thereby allowing you to use normal sub-sync flash, (simple, effective, but robs you of flash power)

Why does this rob you of flash power? I pack 2, 4, and 6 ND filters and that covers it well. I can reduce to almost anything I want to.

1/8000 -> 1/4000 -> 1/2000 -> 1/1000 -> 1/500 -> 1/250 -> 1/125
1/6400 -> 1/3200 -> 1/1600 -> 1/800 -> 1/400 -> 1/200 -> 1/100
1/4000 -> ... -> 1/125 through 1/60 by slightly bumping ISO bump for the higher shutter speeds
1/3200 -> ... -> 1/200 through 1/60

Anything less than 1/60 I consider too slow for humans, for the most part. Done some at 1/30 but I prefer to stay over 1/60. With the three filters, the only issues really come at 1/4000 or higher. If you're less than 1/2000, then you can hit any shutter you want and have any flash you want. It really comes down to not insisting that you shoot at f/1.4 in the brightest sun you can find. Just stopping down to f/2.2 or so can get you everything you need.

[maxfield_photo]

Why does this rob you of flash power?

By that I mean the 6 stops of light you are cutting from your ambient exposure is also 6 stops that you are cutting from your flash exposure. I don't deny that you can get down below max sync speed, but if you have a GN 60 (meters) flash, set to 1/4 power (quarter power is better than full power if it can be helped due to better color consistency and faster recycle times), then your flash will have an apparent GN of 0.94m. Put that in a softbox and you'll lose another stop or two of light.

In a lot of ways, it's the easiest solution, but it's far from ideal. Ideally Pentax would implement a hybrid electronic shutter like in the D70s where: the shutter is pressed>the first curtain fully opens>the sensor turns on>the flash fires>the sensor turns off>and the second curtain closes. The fact that the K1 has electronic first curtain (at least in PS mode) gives me some hope, but I'm not sure the engineers at Pentax/Ricoh give much thought to daylight flash photography. Otherwise why not make ever new lens for the 645Z a leaf shutter?

[Spodeworld]

Maybe this is the easiest solution. Unfortunately, it seems like Pentax overengineered the flash solution to 'save' folks from the dreaded black bar....but you would think that people would figure it out quick enough and work with its limitations. And, most importantly, the added flexibility would mean that you wouldn't have to find all these sub-optimal work arounds.

Just venting.....

Why does this rob you of flash power? I pack 2, 4, and 6 ND filters and that covers it well. I can reduce to almost anything I want to.

1/8000 -> 1/4000 -> 1/2000 -> 1/1000 -> 1/500 -> 1/250 -> 1/125
1/6400 -> 1/3200 -> 1/1600 -> 1/800 -> 1/400 -> 1/200 -> 1/100
1/4000 -> ... -> 1/125 through 1/60 by slightly bumping ISO bump for the higher shutter speeds
1/3200 -> ... -> 1/200 through 1/60

Anything less than 1/60 I consider too slow for humans, for the most part. Done some at 1/30 but I prefer to stay over 1/60. With the three filters, the only issues really come at 1/4000 or higher. If you're less than 1/2000, then you can hit any shutter you want and have any flash you want. It really comes down to not insisting that you shoot at f/1.4 in the brightest sun you can find. Just stopping down to f/2.2 or so can get you everything you need.

[mcgregni]

The power loss with HSS is significant, but its convenience value is also. I certainly find it convenient to flick into HS mode, far more so than I would find fitting an ND filter plus holder. The Pentax HS system works well as the on-camera flash (or controller) will automatically switch into and out of HS mode as you adjust the shutter time up and down around 180th sec .... no need to change the mode yourself.

There are ways of dealing with the power loss, such as using something like a Gary Fong powersnoot or reducing the distances, increasing ISO eg.

[MadMathMind]

By that I mean the 6 stops of light you are cutting from your ambient exposure is also 6 stops that you are cutting from your flash exposure. I don't deny that you can get down below max sync speed, but if you have a GN 60 (meters) flash, set to 1/4 power (quarter power is better than full power if it can be helped due to better color consistency and faster recycle times), then your flash will have an apparent GN of 0.94m. Put that in a softbox and you'll lose another stop or two of light.

I don't quite get this. Can you explain it more? (Not being snotty. Really want to know.)

The ND filter would cut down the total light, ambient and flash, by the same amount. Thus, the ratio remains the same. But how does this affect the guide number any more than leaving the aperture where it is?

Let's suppose you get to choose between all of these:
1) No filter: f/8 at 1/180
2) No filter: f/2.8 at 1/1500
3) 3 stop ND filter: f/2.8 at 1/180

Of these, #2 crushes your flash the most, since HSS kills the power output rather dramatically. Let's use the FGZ540 as an example. It has a GN of 56. HSS at 1/1500 and ISO100 gives a GN of about 12, according to the tables. At f/2.8, that leaves you at 4.3. #1 is simpler: GN is 7.

But for #3...the ND filter has not changed the exposure, which is what matters, right? The dividing by f stop is a measure of the amount of light let in, which is why GN is divided by it. So shouldn't the GN still be at least 7?

[maxfield_photo]

I don't quite get this. Can you explain it more? (Not being snotty. Really want to know.) [trimmed for brevity]

Well there are a few things missing from your calculations if this is to be a real world shooting scenario. First, your figures are correct for certain light levels, but they are a bit too optimistic. Basically you are calculating the exposure for an overcast day. If we assume "Sunny 16" conditions, which is where the rubber meets the road, f/8 at ISO 100 would require a shutter speed of about 1/500th or 1/4000th at f/2.8.

Secondly, I don't know if the AF540 is tuned a little better to the Pentax shutter curtains than my Metz 58 (it's possible), but in HSS mode the Metz, which has a full power GN of 58m, calculates a working GN of 2.4m (at 1/1500, f/2.8, ISO100, 105mm zoom position) on an overcast day, but that drops to 0.9m at 1/4000th on a clear, sunny day. The reason for this is that there is a lot of light that gets wasted bouncing off the back of the shutter curtains in HSS mode and never reaches the sensor as the shutter speed gets higher.

Now on the sub-sync side, if thing weren't complicated enough, many speedlight have long flash durations at full power (another reason I like to shoot at quarter power). If you close the shutter before the flash has completely discharged, you end up losing some of that GN horsepower. Manufacturers seldom publish the t.1 times, instead they quote the t.5 times to make their lights seem faster, but for a lot of speedlights t.1 is in the neighborhood of 1/125th at full power.

So I would amend your table to say (under Sunny 16 conditions, ISO 100):
1) No filter: f/16 at 1/125th (normal sub-sync flash)
2) No filter: f/2.8 at 1/4000th (HSS Flash)
3) 4.5 Stop ND filter: f/3.5 at 1/125th (normal sub-sync flash)

All this is before we add any light modifiers. Don't forget that at the end of the day we want this light to be attractive. So if we're trying to shoot a portrait, which is why most people choose to shoot at f/2.8, power snoots and better beamers are the wrong way to go, we need a softbox or an umbrella. So you can probably bank on a working flash-to-subject distance of less than a meter on a bright, sunny day if you're using just one flash in a softbox, whether you use HSS or ND filters.

So, if you have the flash equipment to do it, HSS is probably a slightly better way to go. Not only will your AF sensors work better without a strong ND filter in place, but there is also less risk of ghosting and flare associated with filters, especially multiple stacked filters.