Thursday, September 6, 2012

Cheap Wireless TTL? Aokatec AK-TTL Review


The Aokatec AK-TTL radio trigger is a wireless radio trigger that is supposed to be cross-compatible with Canon, Nikon, Pentax and Sony (no word on Olympus). The price for a transmitter and receiver kit: $109.99.

I've never heard of Aokatec before (until a comment posted by a reader, Ricardo Rodrigues, about Aokatec's version of the Nikon SG-3IR infrared panel). I've also been disappointed many times when buying products from unknown companies, especially when they make incredible claims, and even more so when the price is a fraction of equivalent products from more established manufacturers.
How well did it perform? Hit the jump.

OVERVIEW
Currently, there are several available systems that promise wireless TTL. First, most camera brands offer their own native wireless TTL system. Until recently, all of those systems worked through infrared light. Commander units could communicate with slave flashes through coded pulses of visible light (or infrared light). The problem with this system is that sometimes, the slave flashes could not detect the light pulses sent out by the commanders -- either because the ambient was too bright, or the flash was too far away. It's only slightly better than line-of-sight (it's better than LOS because the pulses can bounce off from nearby surfaces).

Third parties came up with radio-based wireless flash systems. At first there were just simple manual triggers which offered much greater reliability than optical systems (e.g. PocketWizard, eBay povertywizards, etc.) but could not be adjusted and were manual only (no TTL). Next came triggers that allowed manual power adjustment (e.g. Radiopopper JrX Studio). Then we had remote-adjustable radio triggers with both TTL and manual capability (Radiopopper PX, Pocketwizard FlexTT5 and MiniTT1). However, these systems were very expensive. Some companies produced less expensive TTL triggers but many of them had significant limitations (some functioned essentially like a TTL cord, except wireless). Then, a few months ago, Canon introduced flashes with a built-in radio-based wireless TTL system.
So, the market had several systems that were either cheap and didn't do exactly what I wanted, or did what I wanted but were very expensive. Then came the Aokatec AK-TTL. It was announced earlier this year but became available less than 2 weeks ago.

AOKATEC AK-TTL
The Aokatec AK-TTL works with your camera's native infrared wireless flash system. In principle, it appears to work similarly with the Radiopopper PX system. The transmitter is positioned close to the commander flash and detects the electromagnetic noise emitted by your commander flash when it flashes, then the transmitter sends out a radio signal that mimics the flash pulse pattern. The radio signal is received by the receiver unit which re-broadcasts the pulse pattern as an infrared signal, directly to the infrared receiver of the slave flash.

With the promised specs (cross-compatibility with Canon, Nikon, Pentax and Sony) and seemingly no weaknesses, the Aokatec AK-TTL seemed really fishy. There had to be a catch. So as much as I wanted to, I didn't order it. Fortunately, photographer Aaron Burns bought one to test. He was using a Nikon D5100, and tested the following commanders: Nikon SU-800 dedicated infrared commander, Nikon SB-700, and Nissin Di866 II. For the slaves, he tested the aforementioned SB-700, Di866 II and Oolong SP-660 II. To my surprise, he reported that it worked for him. The only downside he noted was that the range was lower than advertised (75m instead of 100m).

After I read Aaron's review, I ordered a set on eBay. Fortunately, one of the sellers (ebay user gpslot) is based in California, which increased my confidence because it would be easier to return the product if it didn't work (sometimes foreign-based sellers rely on the high cost of returning a product as a way of discouraging returns).

I'd like to build on Aaron's excellent review by adding some more info. Aaron's tests were very thorough but there were a few questions unanswered, such as: would popup commanders work? What about wireless HSS work?

I found out that the seller is based in Los Angeles like me, so I got the package within just a couple of days of ordering it. The kit came as a separately boxed transmitter (TX) and receiver (RX).

THE TX PACKAGE
The TX package includes the transmitter, a lanyard, 2 pairs of velcro stickers and an infrared panel with an attachment for mounting the TX unit on the IR panel.

THE RX PACKAGE
The RX package includes the RX unit, the infrared repeater, a 3.5mm to 3.5mm sync cable, a 3.5mm to PC sync cable, a lanyard and two Livestrong wristbands bright yellow rubber bands. On my package, I did not see a rubber cutout, which was included in Aaron's package. The cutout would have been a small rubber sticker to be attached to the flash to help position the IR repeater and increase the friction between the repeater and the flash.

THE TX UNIT AND RX UNIT
Externally, the transmitter and receiver appear identical. The only difference externally appears to be the label. I attached the lanyard to the receiver to make it easier for me to distinguish between the two in the field when it's dark or I'm in a hurry. Physically, the triggers are reasonably small (about the size of a pack of TicTac candies) and very light.
On the face of the unit is an LED light, a test button and a 16-channel switch.
- When the unit is turned on, the LED pulses with a green light every 4 seconds or so. When the TX transmits or the RX receives a signal, then light becomes red. The red light seems brighter than the green light, although both are visible to me in daylight.
- Besides being used to confirm that the units are communicating, the test button can be used to wake up your slave flash if it goes into standby or sleep mode.
- The channel selector has clear detents. It is not likely to be nudged accidentally into a different channel. One issue is that the arrow for the channel selector is tiny, so it may be hard to see whether a channel is set to a particular number or the number on the opposite side.
At the top of the unit is a cover for the battery. It feels secure, though as noted in Aaron's review, the clips for the cover are very thin and could easily snap off. Both TX and RX are powered by two AAA batteries each. On my package, batteries were not included. The labels for the required polarity for the batteries are a little hard to see. I just have to remember that the battery closer to the middle has the + end pointing inside the unit.
The bottom is a plastic foot for a regular ISO hotshoe with a flash triggering pin. (I don't have a Sony version but to my understanding it has a foot for the Sony/Minolta hotshoe.) The foot has no collar or other mechanism to lock it in position on a hotshoe other than by friction. However, when attached to a hotshoe, it felt snug, not like it was going to fall off.

On one side of the unit is a switch between manual mode, off, and auto (i.e. wireless adjustment mode). On the other side of the unit is a 3.5mm jack. The switch is ok although there is a bit of 'play' so the switch feels slightly flimsier than the rest of the unit.

INFRARED PANEL
The TX package includes an IR panel, which at first glance looks like a clone of Nikon's SG-3IR infrared panel. If you're new to wireless flash, the function of the IR panel is to block the visible light from the commander's pulses while allowing the infrared spectrum of the signal to pass through. For conventional wireless flash systems, this makes sure that the popup commander is not contributing to the exposure. Another benefit is that it blocks the flash pulses that often cause subjects to blink. (With the IR panel blocking the visible flash pulses, all the subjects will see is that the panel will flash a bit red, which in my experience doesn't cause them to blink.)
With the Aokatec AK-TTL system, the panel arguably should block all of the light (even the IR portion) so that the receivers won't get confused with competing signals from the repeater and the popup commander. However, the Aokatec panel does allow the IR portion to pass through. I am considering sticking something at the back of the Aokatec panel to block even the IR portion. However, by allowing the IR portion to pass through I can mix the radio-based AK-TTL triggering and the regular optical triggering.
The Aokatec panel (left, with attachment shown) and the Nikon SG-3IR
Notwithstanding the many similarities between the Aokatec and Nikon panels, there are a few significant details that distinguish the Aokatec panel from the SG-3IR:

1. One of the first things I noticed is that the Aokatec panel has a more flimsy movement compared to SG-3IR. It is possible that if the Aokatec panel is flipped many times repeatedly, the hinge might get worn to the point that the panel might not stay up by itself. However, I'm just speculating - it hasn't happened yet and I suspect it would take a while for that to happen.

2. The Aokatec's panel seems to be made of a different kind of plastic, although it appears just as opaque as that of the SG-3IR. I haven't seen any difference in ability to block visible light.
3. A distinct feature of the Aokatec panel is that it includes a removable attachment that allows an AK-TTL TX unit to be mounted on the panel.
4. A plus for Canon shooters is that the Aokatec foot has a thinner portion designed to avoid pushing down the TTL pins on Canon hotshoes. (Otherwise when those pins are pushed down, Canon cameras think there is a Canon TTL flash attached.) By contrast, Canon shooters wanting to use the SG-3IR have had to shave off a portion of the SG-3IR's foot to avoid pushing down the Canon TTL pins.
5. Another difference is that the Aokatec's locking pin is rounded, whereas that of the SG-3IR is sharp. Some SG-3IR users have commented that the SG-3IR is hard to remove from a hotshoe (in fact some users have removed the locking pin). With the Aokatec's rounded pin, it is easier to remove from a hotshoe, while still being secure.
USING THE AK-TTL SYSTEM
To use the AK-TTL system, you first attach the TX unit close to the commander. If you're using a popup commander, then this is done by mounting the TX unit on the included IR panel.
If your commander is instead an external flash or dedicated IR commander, you can attach the TX unit to your commander flash using the included velcro pads.
As previously mentioned, the RX unit includes an IR repeater. The repeater is quite small though somewhat thick. The side with the emitter has rubber padding to increase friction with the flash surface.
You plug one end of the repeater to the sync port of the RX unit. You then locate the IR sensor of the slave unit. The sensor is not always facing the front. On the SB-800, it is a small round and dark window on the side of the flash, near the battery door.
You attach the repeater over the IR sensor using the included rubber band.
Personally I don't like the rubber band because it looks way too conspicuous. I am also concerned that the rubber may dry out and snap. Instead of the rubber band, I used two velcro cable ties linked to each other. The cable tie is attached to the cable, making it less likely that I'll lose it. I think it also looks better than the rubber band.
From there all you have to do is put the slaves on wireless mode. Some reminders
- The slaves should be in the same channel (1, 2, 3 or 4) as the commander, and note the group (A, B or C).
- The TX and RX units have to use the same radio channel (1 through 16).
- Make sure the slaves aren't asleep or in standby.
- Some 3rd party slave flashes don't have HSS. If you exceed the sync speed, the commander will use the HSS protocol which the slave won't understand so it won't fire.
The AK-TTL can also be used as a simple manual radio trigger. To do that, you just switch both units to M mode and connect the receiver to the slave using the 3.5mm to PC cable or the 3.5mm to 3.5mm cable. I tested the PC cable and was able to trigger the SB-800.
COMPATIBILITY TESTS
I tested the AK-TTL system with the following commanders:
- Nikon D70 popup (note: the D70 wireless flash is limited to channel 3, group A only. You cannot change the channel or control any other group).
- Nikon D90 popup
- Fuji S5 popup
- SB-800 as commander
I tested them with the following slaves:
- Nikon SB-800
- YongNuo YN-560EX
Based on my tests, the AK-TTL does work just as well as Nikon's CLS (Creative Lighting System) AWL (Advanced Wireless Lighting). With two caveats (discussed below), the slaves functioned to the same extent as if they had been controlled by the optical signal from the commander. I could use TTL mode, adjust FEC up and down, change to manual mode, and adjust manual power levels.
Among the tests I did, which worked (feel free to check out the exif on the samples):
Yongnuo YN-560EX. The fact that this worked was a relief, because I want to use the YN-560EX as an inexpensive wireless adjustable slave.
Wireless HSS: I tried Wireless HSS at 1/8000 shutter speed and it worked. I tested it with the Fuji S5 popup as commander and a Nikon SB-800 as slave.
Non-HSS sync speed: I tested up to 1/500 shutter speed (using Nikon D70).
Mixed optical with AK-TTL radio:
I tested the SB-800 as commander, with another SB-800 as AK-TTL radio slave in Group A and YN-560EX as Nikon CLS AWL optical slave in Group B.
Inline image 1

Panasonic Lumix LX-5: :Just for fun, I experimented with the LX-5's popup flash as well.  I used an SB-800 as a slave in SU-4 mode.  I covered the SB-800 with a thick comforter to make sure it was not receiving an optical signal from the popup flash.  When I mounted the TX unit on the hotshoe using the Aokatec panel, the system did not trigger (the TX unit probably could not detect the electromagnetic noise from the small popup flash).  However, when I held the TX beside the popup flash, it was able to trigger the SB-800 all the way to the maximum 1/2000 sync speed.

In short, as far as I can tell, the AK-TTL performs just as promised. About those caveats I mentioned earlier:
1. Interference. If the slave receives a signal from the repeater as well as the optical signal of the commander, it might not fire. One solution is to face the sensor away from the commander.
2. Repeater placement. On my first couple of tries with the YN-560EX, it did not fire. I don't know for sure if it was partly caused by interference but one thing I did is to adjust the IR repeater position slightly to the left of center, and from there the 560EX worked fine. The 560EX's sensor is a large opaque panel, so it's hard for me to tell the optimal position for the repeater.
If I had to nitpick the AK-TTL, I think the weakest part of the system is how the IR repeater attaches to the slave flash.
- First, it might not completely block the flash from still receiving the optical wireless signals, resulting in failure due to interference.
- You also need to know where the sensor is on the slave flash. On the SB-800 it's easy. On the YN-560EX, I am hoping I have it figured out. I would hate to be on an assignment and have the triggering fail because the repeater is slightly out of position.
- Placing the repeater can take a few seconds. I think the velcro cable tie makes this a bit easier.
- The IR repeater might be moved out of position if the flash is jostled hard enough. Besides losing the signal, the RX unit could fall if it is just dangling from the IR repeater.
- It's possible you might forget, lose or break the rubber band that you're using to secure the repeater, which could make the system temporarily unusable (then again, gaffer tape could come to the rescue).
Also, pls. note that I have not yet tested:
- long term durability
- battery life in the field
- multiple RX units (I have another RX unit on order and will be posting about this soon)
- whether it works on Canon, Sony, Pentax or Olympus.
You can tell that those are really minor gripes, and those are the worst things I can say about the AK-TTL. In other words, I FRIGGIN LOVE IT. It works as well as I hoped and the price is just right. This is now my preferred radio flash trigger and would recommend it. I previously envied Canon shooters for having a radio-based wireless flash system. Now? Not as much. :) Coupled with the availability of inexpensive wireless-capable flashes such as the Yongnuo YN-560EX, adjustable radio-based wireless flash systems are now accessible to virtually everyone [even Pentax shooters :) ]!