Review of Strobeam D4 HSS IGBT Flash Head

What's New?

The new D4 HSS IGBT (nice catchy name) is a total revamp of the old DL4, in reality it's a completely different product. The biggest change being that it now has an ‘integral’ battery. This makes it even more portable than the old DL4 because there are no leads to an external battery pack.

The battery is mounted on top of the flash head and is unclipped with a small button at the back. I believe Strobeam are intending to sell spare batteries for less than £100, quite possibly significantly less. The claim is that the battery will be good for 300+ shots at full power, from what I’ve seen of previous Strobeam battery powered heads this likely to be easily achieved and quite possibly exceeded.

The body of the flash has completely changed and there is a smaller display on the back which at the time of writing is woefully under backlit so it’s not really possible to read in low light. Hopefully this will be rectified on newer models. The buttons are smaller than on other Strobeam heads that I’ve used but are still OK. It would be nice if the power button was significantly different in shape, size or location so it could easily be differentiated from the other buttons but that’s nothing that would cause a problem once you become used to the layout of the head. I guess the only problem I can foresee with this is the possibility of accidently turning the head on while transporting it, one of the problems of have the battery always connected. This would be easily solved by just taking the battery off the head when packing it away.

The controls are fairly intuitive; the main knob adjusts power, as shown on the display, there is a cell button that turns the internal photocell triggering off and on, a button to change the channel though 0 to 9, a power button, a test button and a line of 3 red LEDs which give a very crude indication of battery charge level.

This head is IGBT controlled, just like its predecessor. It also has a couple of other very interesting features up its sleeve, it can be adjusted down to 128th power which in my book is really useful and it can be used at any shutter speed, right up to 1/8000th second although it has to be set to full power to achieve this.

As I’ve commented before, I do like the Strobeam remotes I think they’re well designed, have a quality feel and are easy to use, baring the odd glaring design issue. The remote for the D4 HSS is no different, including the glaring design issues unfortunately. I this case it has two, the first being the usual problem which is that it only remembers one power setting rather than remembering a separate power setting for each ID. This may sound trivial but makes anything other than the trigger functionality of the remote largely useless if you’re using more than one head. This is a real pity as the head does have memory in it so I’m guessing it would only be a small tweak to the firmware in the remote to sort this out.

The second issue being that the remote for the D4 HSS is not compatible with any other Strobeam kit. This is an odd decision as it makes life more difficult for existing Strobeam customers and somewhat discourages brand loyalty.

The range of the remote is considerable, I tried it up to about 30m with me outside and the flash inside and it worked fine. I’m guessing most people won’t want to go beyond that. The new remote also has an automatic wake up function, so if it goes into sleep mode when on the camera it’ll wake up when the shutter release is partially pressed. This is better than the old remote which just turned off after an annoyingly short period of time and you had to slide the power switch off and back on to get it to wake up again. I don't know what the battery life of the remote is but I've tested a few different Strobeam heads and used a few of the remotes and I've never had to charge one yet so I'm guessing it's quite considerable.

One thing that is a little unusual is that there is no flash sync socket on the head so you have to either use the supplied remote of the optical cell trigger, you can’t wire it or use another trigger system such as Pocket Wizards.

The other design shortcoming in this remote is that, for reasons I can only imagine, it’s not compatible with any other Strobeam product! So if you have a couple of Strobeam G5s for instance and you want to add an D4 HSS to those then the D4 HSS remote won’t trigger the G5s and the G5 remote won’t trigger the D4 HSS. Great move in terms of supporting existing customers.

There is an LED modeling light, which I think is a 10W LED configuration. Although this is likely to be useless outside in sunlight it is surprisingly bright and would be more than adequate in a studio. The white balance of the modeling light is also quite close to the flash tube temperature at 4500k albeit with a bit of a green hue to it.

Build Quality And General Comments

The build quality of this head seems good. The body casing is all metal, the rear of the flash is made of a robust looking plastic. One thing I would have quite liked to have seen is a carrying handle of some sort, the flash is quite heavy (1.8kg including battery and standard reflector) for a portable unit because it incorporates the battery and there’s nowhere to really grab hold of it and carry it by other than the stand mount.

The display is quite small and has almost no backlighting which for me made it very difficult to read in a darkish studio setting. I do wear reading glasses so I’m sure someone younger with better eyesight might be fine but there’s no way you’d read the display on this head from a distance. Although the G5 display had a major viewing angle problem I’d still say the display on the D4 HSS is inferior, I certainly found it a pain in the arse to work with.

The head angle adjustment is done with a normal lever and was pretty easy to use. The umbrella holder is built into the stand mount rather than the body of the flash itself the reflector that was supplied to me with the flash has the usual slot in it for the umbrella shaft to fit through. The prototype unit supplied to me was not a Bowens S-type fitting but Strobeam assure me that the final product will be.

It’s worth noting that although the remote is very similar to the other Strobeam remotes, for some reason it seems to have a poorer viewing angle than the others that I’ve seen. This means when viewed at an acute angle i.e. when it’s fitted to the hotshoe on top of the camera the display is not as easily read as on the previous remotes. This isn’t a huge problem it just means you need to tilt the display a bit further towards you to see it clearly.

The controls on the remote allow full control of the head, there are direct access buttons for channel ID, all or individual ID setting and triggering, modeling light, optical cell triggering, test trigger and increasing and decreasing power level. Unlike the other Strobeam remotes there is not a group button so two sets of D4 HSSs can be used in close proximity without triggering one another. However as the D4 HSS remote isn't compatible with other Strobeam products you’ll not have an issue if you have a set of different Strobeam heads in the same location and if you have two sets of D4 HSSs then you can use the channel setting to differentiate them, just make sure you don’t set the channel switch to ALL instead of EACH or you’ll trigger all the flashes all the time.

Here are a few photos so you can get an idea of the size and build quality of the head and also of the user interface.

Power Setting Accuracy

Firstly I measured power setting accuracy. This head behaves much as I expected based on the performance of previous Strobeam products that I’ve looked at. The guide number is 42m at full power but because of the nature of IGBT switched heads the light output has a long tail on it at full power, as you can see if you look at the scope traces a bit further down the page. This means it tends to be a bit nonlinear when it goes from full power to half power and indeed it is, the flash power actually drops by just over half a stop at half power rather than a full stop. However from then onwards it’s very linear indeed and in all honesty this probably is the best compromise that Strobeam could have made so I have no complaints here.

Power Accuracy Results Table

Power	Power Setting	Quoted GN	Actual GN	% of Ideal
400W	1/1	42.0	42	99%
200W	1/2	29.7	37	125%
105W	1/4	21.0	29	138%
50W	1/8	14.9	20.5	138%
25W	1/16	10.5	14.7	140%
13W	1/32	7.4	10.4	139%
6.3W	1/64	5.3	7.2	138%
3.1W	1/128	3.7	5.4	146%

I’m not sure what Strobeam are specifying this head at in terms of guide number as I wasn’t privy to a full specification at the time of writing this review. But 42m is pretty much in line with what I’d expect.

Colour Accuracy

The next test I did was colour accuracy. Here I measured the head’s Kelvin white balance at output power settings from full power to 1/128th power. Typically IGBT designs have a tendency to give a bluer light as the power is reduced, unless the manufacturer compensates for this by reducing the supply voltage as the power is reduced as done in the Paul C Buff Einsteins. However, whether by luck or judgment, Strobeam seem to have pulled it off in the D4 HSS, the colour consistency is absolutely superb! From full power to 1/64th power I was unable to measure any colour shift and at 1/128th power the flash shifted from 5000k to 5200k which is just not going to be visible at all and I’d have to say is probably within my measurement uncertainty.

Colour Accuracy Results Table

Power	Power Setting	Red	Green	Blue	Kelvin White Balance
400W	1/1	77	76	77	5000
200W	1/2	77	76	77	5000
100W	1/4	77	76	77	5000
50W	1/8	77	76	76	5000
25W	1/16	77	76	76	5000
13W	1/32	77	77	77	5000
6.3W	1/64	77	76	77	5000
3.1W	1/128	77	76	77	5100

So to be honest I’m gob smacked at this performance, this is by far the best colour consistency that I’ve seen to date and would equal the Paul C Buff Einsteins in their colour priority mode. Whether a selection of D4 HSS heads would all be as consistent I can’t comment but I’d guess this attribute tends to be a feature of certain design attributes so I’d imagine the heads would be pretty consistent in this respect.

Power Consistency

Here I’m checking that when set to a given level the D4 HSS consistently delivers the same power. This is actually quite an important parameter as I have seen cheap heads that can vary by almost a stop, shot to shot which isn’t great.

The D4 HSS is a bit of a mixed bag on this front. If you fire off a high speed burst of flashes (say 3 fps) the head allows the next flash to be fired before the power supply has fully recharged. Hence the light level gradually drops as the burst of frames goes on. In this situation the light output of the head can drop by a stop from the first to the last frame of the burst. Bear in mind most flash heads won’t even let you do this at all so the fact that performance is less than optimum here is still tolerable.

If you leave the head to fully recharge, and fire at more sedate frame rates then the shot to shot variation is within 0.2 stops which I’d say is fine for most uses. This head is not as good as say the Strobeam G5 in terms of high speed burst rates. The most I managed to get out of it was 6fps and that had to be at 1/16th power or less, still as I said a moment ago it’s pretty amazing that you can do this at all so…

Flash Duration

On to flash duration, arguably one of the key attributes of the D4 HSS. Well it does what it says on the tin basically. At full power you get a normal exponential decay of light stretching out over 10ms (1/100th second) or so but as soon as you reduce that power you get a sharp cut off of the light output which is very good for freeze action, in a way that most studio flash heads do not. Realistically you have to drop to 1/4 power and below to get much action freezing potential but the head gets gradually faster until at 1/128th power the flash duration is only 90us (12000th second). You’re not going to freeze a speeding bullet with that sort of flash duration but it will stop pretty much anything else in its tracks.

I’ve shown here oscilloscope waveforms of the output power at the various settings so you can see how pronounced the reduction in flash duration is, to the point where the 1/64 (6W) flash pulse is so small you can barely see it.

	Strobeam D4 HSS
400W
200W
100W
50W
25W
13W
6W
3W

Note: Oscilloscope traces showing the variation in flash duration (rollover the power values to show the different scope traces)

I’ve measured the D4 HSS head at 1 stop intervals from full power down to 1/128 power and noted the t=0.5 and t=0.1 times. t=0.5, the time when output power has dropped to 50%, is what most manufactures quote because it makes them look good and is the industry standard, even though it’s not terribly useful. t=0.1, the time when output power has dropped to 10%, is a more practical figure if you want to compare it to an equivalent shutter speed, at this point the light level is just over 3 stops down so what little light is still coming out of the flash is not going to show very much on your moving subject.

Power	Power Setting	t = 0.5	t = 0.1
400W	1/1	3.0ms (1/330th)	8.2ms (1/120th)
200W	1/2	1.9ms (1/500th)	1.9ms (1/500th)
100W	1/4	0.9ms (1/1100th)	0.9ms (1/1100th)
50W	1/8	0.48ms (1/2100th)	0.48ms (1/2100th)
25W	1/16	0.30ms (1/3300th)	0.30ms (1/3300th)
13W	1/32	0.20ms (1/5000th)	0.20ms (1/5000th)
6W	1/64	0.13ms (1/8000th)	0.14ms (1/7200th)
3W	1/128	0.09ms (1/12000th)	0.10ms (1/10000th)

Note: The flash durations are shown in ms and in brackets as fractions of a second

Flash Recycle Time

Flash recycle time is a bit of a week point for this head. The sample I had took between 5 and 6 seconds to recharge at full power. Because of the nature of IGBT heads this recharge time does drop, roughly in proportion with power level. So at half power the D4 HSS takes about 3 seconds to recharge, at quarter power about 1.5 seconds and at 1/8th power less than a second.

See my note about Strobeam’s expected recharge time under ease of use.

Battery Life

I tested this a couple of times and got 300 full power flashes from a single charge of the battery on both occasions. This is actually really good compared with old fashioned lead acid battery powered flash heads. This should increase roughly proportionally as the power is lowered, although bear in mind that when dropping from full power to half power the head only drops about half a stop so in reality you’re likely to get about 450 flashes at half power, but quite possibly 900 at quarter power. This is quite a bit less than I saw using the D4 HSS with an external battery but then the D4 HSS’s battery is a bit smaller so this is only to be expected. I think the main point is it would be adequate for most shoots and if you really need more you can buy a second battery.

It’s worth noting that the battery seems to take about 3 to 4 hours to fully charge from flat. Rather annoyingly there seems to be no indication on either the charger or the battery that it has charged so you just have to allow 4 hours, a minor oversight.

Also bear in mind that if you use the modeling light extensively the battery life will come down. To give you a feel for that I’m guessing the battery would power the modeling light on its own for about 6 hours.

High Speed Sync Mode

The remote that comes as standard with the D4 HSS allegedly supports use at shutter speeds up to and potentially beyond 1/8000th second. When ordering an D4 HSS you will need to specify whether you want a Nikon or Canon compatible remote. I was supplied with a Nikon unit as I shoot Nikon. Strobeam assure me this functionality works fine with a Nikon D90, D700 and several Canon cameras. However I tried it on a Nikon D60 and a Nikon D7000 and it worked with neither camera. The behaviour of the remote was somewhat different in both cases so I'm not sure what was going on. Strobeam assure me they've tested this on a D7000 and it works fine so it may well be I had a faulty remote. I'll give them the benefit of the doubt on that one. I believe Strobeam are going to come up with a list of compatible cameras so you might want to check that if this functionality is important to you.

However for whatever reason with the two cameras I tried to use high speed sync mode (Strobeam refer to this as FP mode on this head) on the function did not work, the flash head did not trigger at all. So I'm unable to report on it.

Update 25th Feb 2013
I probably should have made it clearer that the head can only be used in HSS mode when it's set to full power. This means what you get, in terms of light power, is what you get, so you need to adjust your aperture to take up the slack, so to speak. Also, and this may not be immediately obvious, the guide number will drop as the shutter speed is increased beyond 1/250th second, so at 1/500th second the effective guide number will drop from 42m to about 30m and so on and so forth, so at 1/8000th second you'll be down to a GN of about 7.5m. Which is not going to light too much up in all honesty.

Ease of Use

That is always a subjective area. Generally I’d say the head is pretty good and pretty easy to use. The most annoying things from my point of view would have to be the small display with inadequate backlighting that makes it difficult to use in low light, that and the slow recharge times. The latter may be less of a problem because I’m guessing most people will probably not use the head at full power a lot of the time, unless of course you’re working outside and need to overpower the sun in which case a 5 to 6 second recharge time would be quite annoying.

In the interest of fairness Strobeam tell me that they expect the D4 HSS to only take about 4.5 seconds to fully recharge but on the sample I had it was about 5.5 seconds. Maybe there’s a level of variation in batteries, which would not bode particularly well if that is the case.

Conclusion

This is a bit of a difficult one. I think maybe the first thing to do is to list the good and the bad points of the head so you can see if any of these things are significant in your application.

Pros

1. Decent GN of 42m
2. Integrated package with no trailing leads
3. Good modeling light
4. Excellent colour consistency
5. IGBT, so very short flash durations
6. Good battery life
7. Good remote
8. Can fire multiple frames per second at lower power

Cons

1. Poor rear display
2. Slow recharge time at full power
3. High speed sync mode (FP mode) may not work with all Nikon bodies, and didn't work on either of the bodies I tried it on

As you can see from above there are a lot of positives and not many minuses. I’m guessing most people don’t need FP mode and it’s likely that Strobeam will sort this inconsistency out with a firmware upgrade to the remote although this would undoubtedly require returning the remote to the factory to have it done.

The slow recharge time is only likely to be a problem if you’re shooting at full power, which let’s face it for many applications a GN of 42m is quite a lot, and I’m thinking for reasons of practicality as much as anything else photographers rarely use large lossy modifiers in field situations so dropping to half power and getting a GN of 37m is probably more than adequate in most situations. In which case a recharge time of 2.7 seconds, or there abouts, is probably going to be fine.

The display is an annoyance because the one on the G5 and DL250 is actually really good, apart from the viewing angle issue, it’s large and brightly lit so you can read the power level from a distance. Trust me you’re not likely to read the D4 HSS display at anything more than a couple of feet because it’s so small. I struggled to read the smaller information on it, such as channel ID, however close I got but then I’m old and my eyesight isn’t perfect at close range. But actually I think that’s true of quite a lot of photographers.

I guess one question would have to be would you prefer a pair of D4 HSSs or a pair of Strobeam DL250s for field use? They’re not a dissimilar price if you get a pair of batteries for a pair of DL250s. The DL250 only has a GN of about 34m and will not accept any modifiers other than an umbrella, and you have the trailing cables to worry about which maybe a problem if you’re photographing children. The DL250 has a slightly faster recharge time and better battery life. I don’t know, it would be a hard call. Likewise you could consider the Lencarta Safari Li-on if you didn’t need the fast flash durations and wanted more power. Or if you were prepared to spend a bit more you could buy a Strobeam G5 and separate battery pack. Lots of options all of which are valid and have their attractions.

All in all these are good heads, there are a few niggles with them but then show me a product that doesn’t have a few of those. I’d say you won’t be disappointed if you buy a D4 HSS, they work well and do what they’re intended to and that's pretty good in my book.

Update 25th Feb 2013
I should point out that the head I evaluated here was a prototype and there may be a few changes to the final article. I've seen comments saying that a flash sync socket has been added to the head, which would be a good thing if one wished to use an existing triggering setup.

About the Author

By trade I’m an electronics design engineer hence the quite technical nature of this review. I like to know exactly what a product delivers so I know how I can rely on it and how I can use it. I hope this review is of assistance to anyone else who is considering buying one of these heads