Points in Focus Photography

An Idea, LED Modeling Lights in Speedlight Flashes

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For the last year or so I’ve been talking about features I’d love to see implemented in camera gear. This time I want to talk about having a proper continuous modeling light built into a hotshot flash.

Before I get into the meat of my idea, the first question one might ask is simply, what’s my problem with the status quo?

After all, most hotshoe flashes in addition to being a flash, have some form of modeling capability (by strobing the flash tube) along with some form of autofocus assist capability (typically with red or near-IR LEDs). After all they do provide the intended functionality to a large degree.

So what does having an actual LED modeling light enable that having IR autofocus LEDs or strobing the flash tube doesn’t?

I have two main use cases where I think this would be a beneficial idea. First is for people who need to shoot video. Specifically I’m thinking about photojournalists, who are increasingly being asked to get video clips for their publication’s website, but the idea applies elsewhere too. With things as they are now, you ideally need a speed light for stills in a wide range of conditions, and a separate video light of some sort — at least potentially — for video. With my idea, you’d just have your speed light.

The second case where I think it would be useful is in strait up using speed lights as a replacement for studio strobes. Admittedly this is also a personal point for me. I have nothing against studio strobes, I just never went down that path. However, I do a lot of product photography for this site, where I use speed lights in various modifiers (e.g., the Lastolite EzBox Hotshoe).

The thing with studio shooting is that you don’t want ambient light contaminating the colors in the images you make. That means generally you keep the studio dark so the only light comes from the strobes themselves. With speed lights, that also means you don’t have much if any light illuminating the subject matter for focusing and composition.

Okay, so clearly the idea here is that I’d like to see a continuous LED modeling light in a flash. Canon already did something kind of like this in their Speedlite 320 Ex. Well except not really. Yes, they put an LED on the light, but it’s not integrated with the zoom head, so it doesn’t actually model what the flash would do. Moreover, as far as I know it doesn’t track flash power, or have any kind of power adjustment at all.

What I’m envisioning is integrating the LEDs into the flash head in the same area as the flash tube. Perhaps off to a side or both sides. This would then allow the LEDs to use the same zoom head, and therefore mirror the behavior of output of the flash tube.

Moreover, I would want them to be able to track the power output of the flash as well. If you’re going to do modeling lights, you should at least be able to see what the ratios will look light too.

Okay, so let me wrap this up with a bit of back of the napkin engineering.

I don’t see why a high power LED or two couldn’t be put in the flash head. The issues are mounting location, heat, power consumption, and brightness. I’m not going to comment on mounting since I’ve not spent any time digging around in the zoom head of a flash.

Heat, power consumption, and brightness are all related. The brighter the light is the more power it draws and the more heat it dissipates. An LED like the Cree XP-G2 can produce 172 lm/W and can be driven at up to 5W (for a max of 586 lm output). A reasonably good set of 4 NiMH AA batteries can provide up to 12 Wh. So some quick math says a single XP-G2 LED running off 4 NiMH batteries worth of energy could deliver 172 lm for 12 hours, or 586 lm for a bit more than 2 hours. Of course, the trick/trouble with driving the LED at 5W would be dissipating the heat it produces.

One up side, since the LEDs don’t produce infrared light (i.e., heat) there shouldn’t be much concern in overheating and melting the plastic Fresnel lens elements in the zoom head. The only heat concern is how to safely dissipate the heat of the LED itself.

Anyway, I’ll leave the actual engineering for the camera makers, I don’t think I’ll be trying to hack LEDs into my 600Ex-RT anytime soon. But it would be nice to have.

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