UPDATE, JUNE 2024: Strobist was archived in 2021. Here is what I am up to now. -DH


RadioPopper JrX: Questions and Answers

About a gazillion RadioPopper JrX questions came in while Ben and I were enjoying our three-day mancation. I wanted to hit as many of them as practical before getting onto Boot Camp Assignment 3, which is in the on-deck circle.

Lotsa answers -- and some test results -- after the jump.


Before the Q&A, just a note that continued shooting with the RadioPopper remotes has only increased my confidence in the units.

Their initial reliability is holding up in multiple environments, and I would feel very comfortable taking them out on assignment.

Can the JrX's fire remote cameras?

Yes. You will need to purchase an adapter cord for your particular camera, which will need to have a remote jack on the body. Connection is the same as with PocketWizard remotes, so there are several types of cords available for most popular camera brands.

Are the JrX's compatible with my Cybersyncs/PocketWizards/Cactus/whatevers?

No. You cannot mix and match them (except with other RP units) because the operate on different frequencies and/or with different digital protocols.

In the Article, you say, "Nikon switched into a new system with the '900's, so they are out." Does that means they wont work under SB-900?

They will fire an SB-900 in dumb sync mode, but will not remotely control the power level using the (upcoming) RPCube module. This is true for all flashes which are exclusively iTTL. The restriction also apparently includes some Nissin model flashes, and/or any other model which does not support analog quenching of the flash pulse.

What kind of speedlights will be compatible with the remote power level adjustment?

In addition to immediately supporting the ABs and WLs (the ones with telephone jacks in the backs, at least) Kevin at RP says that most any TTL flash designed to work with Nikon or Canon should be remotely adjustable. Except the SB-900, of course, and any other off-brand flashes which do not support analog quenching. You will need the appropriate brand-fitting RPCube, of course.

There is talk of establishing a crowd-sourced compatibility table (or wiki) on the RP site. I think this is perfect, as RP could not possibly acquire and test every legacy flash -- especially the third-party flashes. I think this is a great idea.

Advice: If you are going this route and find a cheap model of flash that works in variable mode (i.e., some Acme Nikon/Canon equiv. TTL flash) snap up a few on eBay before including that model in the wiki. Just sayin'.

What about high speed sync?

I am reluctant to even bring this up, given the variable quality of info and claims floating around, but here goes.

First, the JrXs as a standalone system are max 1/250th on SLRs. And some SLRs cut it close enough to where you may have to lose the error correction to get your top sync speed. (This is mostly a Canon thing, as they tend to cut it very close on the second curtain at max sync speed.)

As for true, HSS -- no. The RP PX's will, by bridging the signal of the standard, time-pulsed Nikon and Canon protocols, but only for HSS-enabled flashes. The RadioPopper/AlienBee high-speed sync is not true HSS. Here's what is happening:

The flash pulse in some circumstances on an AB is long enough to exist for the entire time the "slit" is traveling across the frame during a high shutter speed exposure. So, yes, while you can technically sync a frame, there are two problems.

One, a tremendous amount of light is wasted, in that it falls on the blackened-out part of the frame while that slit is traveling. That is why your high-speed synced AB looks a lot more like an SB-800 in the power output department. But that is also true with pulsed HSS.

Two, the evenness of coverage is related to the shape of the flash pulse as distributed over time. Which is to say, it is not even at all. The flash pulse ramps up very quickly, and trails off more slowly as the capacitors in the flash discharge over time. (That's why Nikon and Canon pulse the flash signal -- for evenness.)

This will manifest itself as a light variance across the frame that would be brighter at the top or bottom -- depending on the direction the shutter travels in your model of camera.

What about point and shoots?

Ahh, different story there! Point and shoot cameras are more like leaf shutters than SLR shutter. And there is no "traveling slit," which means no worries about the evenness issues. But you have a separate set of concerns.

One, the speed of the remote electronics and trigger protocol. Here, the RP wins over the PocketWizard Plus II's for manual firing of flashes via remote. With my Canon G9 and an SB-800, I max out at just about 1/500th with the PWs but can go much higher with a PC cord (or off-camera TTL cord).

The RP JrXs split the difference -- faster that the PWs, but slower than a cord. All in all, very fast for wireless and with great range.

The other factors are shutter duration and flash pulse length. No matter what, you cannot cram a full-power flash pop (which lasts about 1/1000th of a second) into a 1/2500th of a second shutter exposure.

As you go up in shutter speed, you proportionately lose power settings on the flash. I was getting solid 1/8 and (almost) solid 1/4 power pops wirelessly at 1/1250th of a sec with the Canon G9 and JrX's. That's enough to do some cool things at midday.

FWIW, both equipment shots on this post were done with a Canon G9, at 1/1250th of a sec with flashes at 1/8 and 1/4 power. They were synced with an RP JrX.

Can it remotely adjust my LP120/Vivitar 285/Pile of Magnesium Powder?

Alas, no.

The variably timed "quench pin" approach basically hijacks the TTL protocol and gives you control of when the flash pop is quenched. Which varies the power of the pop. You need that underlying TTL system in the flash for it to work.

So, can my Canon remotely control Nikon flashes?

Triple aces here -- absolutely. ("Nick Turpin, white courtesy phone, please...)

The remotes are working with the TTL (and, in AB's case, variable power circuits) in the flashes themselves. It does not matter what kind of camera the transmitter is sitting on -- so long as you are operating within normal sync speed constraints.

You could set up an SB-800 on group "A", a Canon 580 on group "B" and an AlienBee on group "C" and control the power on each all independently with a Holga if you wanted to. Which is pretty damn cool.

How do the units connect to the hotshoe of your camera? Are they the same as Skyports or do they have a locking mechanism like the PW's?

No lock, but very solid. No exposed antenna to worry about, either. I have absolutely no concerns about the mount or stability. They are very small, and the mount is robust. Still would like to see some sort of lug on the recievers, to keep the sync cords from becoming the strap ...

Just Nikon & Canon? What about us Sony shooters?

Um, you can get a D3X chip on a Sony for under $3k USD. You knew you were going to have to give up something, right?

How do these compare with the new Control TL's from PocketWizard? If money was not an issue, what would the choice be? I want to make the right decision now instead of change my mind at a later date and make an additional purchase.

Lot of variables there. If you are Nikon and you need it now, for instance, it's a no brainer.

But rather than the JrX's, I would consider the RadioPopper PX to be in direct competition with the ControlTL-enabled PWs (TT1, TT5 models). The systems operate in different ways and I would decide based on which features are more valuable to you.

RP's PX system is getting very good user feedback. PW TTL range has been affected by Canon RF interference from some models of flashes, but PW have created workarounds. Upcoming Nikon versions are said to be unaffected by any flash RF issues. (Essentially, the Canon flashes emit far more RF interference than do the Nikon flashes.)

On the other hand, the PW system also nets you about a full stop faster sync. Which is the equivalent of doubling all of your flashes' power rating. Which is nice. And there are increased efficiencies in high speed sync with PW because of the "HyperSync" protocols. In short, faster recycle times and/or more power.

The JrX's fit into another niche -- dumb sync and remote manual control. A completely new branch on the flash remote tree. In present form, I would compare them more to the upcoming Paul Buff remotes which have similar capabilities. RPCubes will greatly increase the universe of remote controllable flashes. But, like the PW Nikon models, they are not available yet.

CR123a Battery Solutions

I figured this was important enough to where it deserved it's own section. So here goes.

CR123A batteries are pretty common, but not so much so that you can expect to pick them up anywhere you need them. And if you buy them at a 7-11, it will be a painful lesson. So, you are either going to have to hoard disposable batts or go with nickel-metal hydride rechargeables (NiMH) rechargeables.

I have tried the Tenergy NiMH's and charger pictured above and they work great. Unlike AA NiMH's, which run at 1.2v (vs. alkalines' 1.5v) these put out the full 3v of the CR123A's lithium version. Additionally, RP says that the JrXs run just fine down to 1.9v, with no real loss in range.

[NOTE: Do not get all fancy and hotwire a (cheaper) 9v battery in there. You will not triple your range -- you will fry your JrX.]

Capacity in the NiMHs is 750MaH, compared to 1300MaH in the lithium CR123A disposables. As a quick test, I left them on overnight (on the receiver -- the transmitter has 1 hr. auto-off) and they worked just fine the next day. This was about a 20-hour test, and RP says the receivers run down just about as fast, whether you are shooting or not.

From what I can tell, there is no reason to believe these are anything other than garden-variety NiMHs. Which means that they will self-drain over a few weeks. Think of a nice, big cup of water -- with a small hole in it.

[UPDATE: Robert, in the comments, says, "Just for clarity, the Tenergy rechargeable cells you show are actually LiFePO4 (lithium iron phosphate) not NiMH (nickel-metal hydride) which is why they are 3.0v (actually ~3.2v) compared to the 1.2-1.5v we are use to with NiMH. The good news is that LiFePO4 tend to have less self-discharge than NiMH."]

Logical solutions:

A) One set of NiMH's, and charge before assignments. (Tenergy supplies both AC and 12v cords for the charger so you can keep them tricking in the car if you want.)

B) Buy one NiMH for each unit and keep a (~92-cent) spare lithium as a backup in case you get caught with your pants down. Lithiums hold their power on the shelf (or in your bag) for a very, very long time.

C) Buy twice the batts you need in NiMH's, and just rotate them out of the chargers before shooting. That way you always have a set charged. I chose this method, as it also gives me double capacity in case of a very heavy shooting session -- and spares in case a battery heads south.

The site I recommended in the initial JrX post was just fine -- and very fast shipping. But I have since found that Amazon sells packages very appropriate to a typical shooter's needs for significantly less.

Example: You can get 6 7NiMH CR123A batts and a dual-source, two-cell smart charger (same Tenergy brand) for $26.99. That's the equivalent of a free charger, compared to the other site.

There are lots more choices on Amazon -- just search "Tenergy" and "CR123A".

For More Information

As of today, the full RadioPopper JrX manual is here.


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