by Tim Gander

The Rise (and Downsides) of LEDs

On a ‘lighter’ note from my previous post, this week I wanted to bring up one of the daily scourges of the working photographer; that of LED lighting.

Of course I’m a huge fan of energy-saving devices, and I appreciate the part LED lighting plays in this (though I do have some questions around that – perhaps best saved for another day), but they can cause issues for photographers.

What most people don’t realise is that LEDs are not constant lights in the way halogen lamps are/were. LEDs have a frequency, that is to say they pulse on and off. For the most part the human eye cannot detect this, but cameras, because of the way they work, can.

Each frame is 1/800th of a second, but slowed down here so you can see the changes more easily.

The Invisible Flicker

If you look at the video above, it shows a sequence of images taken at high speed over the course of a few seconds. This is not a light being dimmed up and down, it’s the LED effect. The camera settings haven’t changed from one frame to the next, but you can see how the light dims on a cycle. You wouldn’t see this when you look at the light, but the camera’s sensor is recording the variable output of this light source.

What you’ll also notice is that the ‘bulb’ isn’t changing all at once. That’s because these LED bulbs consist of clusters of LEDs, each with their own frequency. If they’re not in sync with each other you get this wave effect of light brightening and dimming.

The issue this can cause to photographers is seen as banding in images (see image below) where horizontal strips of the image are darker than the rest of the picture. It looks horrible and can’t be corrected in post-production, at least not easily. The effect in the example here is exacerbated by my use of the electronic shutter function of the camera.*

 

Two young male school students are seated in blue lecture theatre seats. They are casually dressed and looking towards something or someone we cannot see. One has his hands in his lap, the other is resting his chin on a hand. They both look thoughtful. The photo shows the 'banding' of lighter and paler areas caused by the LED lighting on the camera's sensor.
Heavy banding ruined a few of these images.

Note how the banding affects the background wall, the seats and bench in front of the students. It’s less visible in the subjects, even so I rejected it.

LEDs Everywhere

LEDs are now ubiquitous in our everyday lives. They’re in all our workplaces, shops, homes, cars; basically, they light our lives. Better quality LED lamps will cause fewer problems than cheaper ones. However, even expensive LEDs can cause issues, especially if they’re dim-able.

When an LED light is dimmed, it isn’t actually dimmed, so much as its frequency is extended. In other words, the moments when the LED is off are extended. We’re talking microsecond differences here, which is why the human eye doesn’t see more flicker, just a dimmer light.

As of writing this article, I believe there is still only one photo-centric (not video-centric) camera with a sensor design which eliminates this issue completely, and that costs almost £6,000.00 just for the body. Other slightly cheaper cameras use faster processors to try to mitigate the effect, but it’s still an issue to be aware of.

My cameras don’t show banding when I’m using the default Mechanical Shutter mode. In some situations it would be preferable to have the camera operating completely silently (by using the Electronic Shutter setting), but if banding is ruining the photo then there’s no choice but to allow the shutter to click. It’s not exactly loud, but can be noticeable in certain situations.

LEDs Triggering Issues

The flicker of LEDs can have other detrimental effects too. If I’m setting up portable studio lighting for a photo session, I’ll often use a handheld flash meter to set the output (brightness) of my flash units. To do this, I press a button on my flash meter which is then waiting for my flash to fire so it can measure the intensity of the flash. But the flicker of an LED light is often enough to fool the meter into thinking it’s detected the flash, when all it’s detected is the pulse of an LED light.

This can make it incredibly difficult to get an accurate flash meter reading. I can try shielding the flash meter from the LED light source, or I can plug the flash meter into the flash unit and not use the non-cabled setting (apologies if this is getting technical!) Unfortunately, not all modern flash units have a flash cable socket, so this often rules that option out. It’s also not always possible or desirable to switch off all the LED lights in a space to prevent the interference.

There have been occasions where I’ve just had to set the flash output by taking a series of test shots until I’ve got the correct exposure. It’s not ideal, but it gets job done eventually.

Irritation and Mitigation

I say the human eye can’t detect the flicker of LEDs, but that isn’t always true. I used to work in an office which had LED strip lights, and they irritated my vision and fatigued my eyes. Some people are more sensitive than others and you can even buy special glasses to counteract LED lighting.

The trickiest thing about LEDs is you can’t easily predict when they’ll be a problem. I’ll take test shots or look through the electronic viewfinder of my camera, but neither of these is a 100% reliable predictor of when banding will wreck a photo. A different angle, moving from one location to another or someone making changes to the lighting can all have an impact.

Many audio visual engineers have moved to LED stage lighting and this can be brilliant or a disaster depending on their system.

So next time you’re at an event and the photographer’s camera is clicking away, even if you know they have a silent function on their camera, perhaps now you’ll understand why they might not be using it.

Sorry about the length of this article, but I do hope it’s shed some light (see what I did there?) on a mostly invisible issue.

*Electronic shutter setting means the camera is completely silent, however the imaging chip is more prone to recording banding because it exposes the sensor by scanning in lines from top to bottom. The example photo I’ve used was shot at 1/200th of a second which shows just how fast the frequency of the LED cycles is.

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 by Tim Gander

Back to the Future

While Marty McFly’s time-traveling DeLorean might still be a thing of science fiction, there’s still plenty of scope for Doc Brown-style WOWs! at IAAPS, including a gull-winged test car. This time though, it’s a BMW. Probably somewhat more reliable than a DeLorean, albeit lacking a flux capacitor.

Instead of Doc or Marty though, it was the turn of Helen Godwin, West of England Mayor, to be wowed by the work going on at the propulsion systems research centre near Bristol.

No Need for Roads

The purpose of Helen’s trip was to discover more about how IAAPS and University of Bath work to connect research with industry, creating real-world benefit from what could otherwise be siloed into pure academic study. Also to then explore how this work can be used to help promote the region to the wider country and indeed the world.

My humble task, as I have done on previous occasions, was to document the visit and generate media-ready images to help get IAAPS’ and the Mayor’s message out there.

With this kind of event it isn’t always easy to encapsulate the entire message into a single image, or even a handful of them, but it’s also not good enough to just hang around with a camera and hope something presents itself.

So my strategy on this kind of job is to be the fly on the wall, but with an eye for an opportunity to step in and arrange (with the lightest possible touch) a picture which looks natural, includes key people while also helping to tell the story.

Of course moments such as when Helen was in the driving simulator always make for a good photo, but it’s in the test cells that the story becomes somewhat clearer, visually at least.

A woman with shoulder length straight hair and wearing glasses and a blue suit laughs as she holds the steering wheel of a driving simulator with large monitor screens showing a simulation of city streets. A bearded man in a white shirt and chinos is standing next to her, smiling.
Helen Godwin enjoys her time on the simulator.

Back to the Future, or Back of the Heads?

The only problem with taking photos of people looking at things is that you either end up with photos showing the the they’re looking at (but you just get the backs of heads of the on-lookers), or you see the people doing the looking, but now you can’t see what it is they’re looking at.

On this occasion I stepped in and asked that for a few moments at least, they discuss the car and the test cell, while pretending there was something more interesting than an observation window behind me. With the cell and test vehicle behind them, I could get a photo that made it look as though they were engaged in lively discussion, I could see their faces and gesticulations, but also that sense of what it was they were talking about because the background is part of the illustration.

Beware the Brand Hammer™

There was also a handy bit of branding in there too (note the number plate), but the branding is there without being ‘in your face’. Too often PRs will insist on plastering their client’s branding all over a photo, but this often dilutes the impact, and a picture without impact will be ignored. So beware the Brand Hammer™!

Three people stand talking in a high-tech testing room for cars. A bearded man in white shirt to the left of the photo is gesticulating towards a BMW car on a test rig while a woman in suit, trousers and glasses listens, smiling. Another man on the right of the photo, wearing a suit and open-neck shirt and glasses is also listening to the first man.
Branding doesn't have to be brutal.

All of this is to say that with an event such as a VIP visit, it’s worth thinking ahead about how key images might be engineered to happen. Of course you can’t always plan things to the smallest detail, and sometimes I’ll need to step in and gently guide people to make a more complete picture, but having a key moment or two when the proceedings can be paused and adjusted to make more compelling images is never a bad thing.

It’s always a balance between micro-managing and under-planning, but if in either case the pictures don’t happen, you can’t get into your DeLorean to zoom back and do the job again. Even IAAPS aren’t working on that!

 

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 by Tim Gander

A Couple of Pointers

Many of my photographic jobs involve covering conferences, seminars and general get-togethers of science and industry leaders. The brief will usually involve fly-on-the-wall photography of delegates networking and exchanging ideas during the registration and coffee reception, followed by shots of the key speakers presenting their thoughts.

The spaces I’m working in can range from big lecture theatres with a capacity of 300+ to rooms barely large enough to hold 20 people, which can be a challenge when I’m trying to be discrete.

Lighting will also be mixed – it’s almost always terrible! I rarely get sufficient soft daylight to make the shots easy to edit, so I work with whatever is there. Then I go into battle at the edit stage to ensure skin tones don’t, at the very least, leave people looking ill. Sometimes I’ll use flash, but this can open a whole new can of worms and is often best avoided.

Regardless of the nature of the event, the size of the room or the lighting I’m working with, this work always boils down to ensuring I capture the speakers in a flattering and/or engaging way. One of the keys to this is the gestures people use as they speak.

My preference is to spend a minute observing the speaker to work out which area of the room they tend to address (there’s no point me taking a position to the speaker’s right when they only ever look left). I’ll try to work out if there is a pattern to when they look up and with their eyes open. And I’ll be watching to see if they make interesting hand gestures; again, I’ll look to position myself to capture this the best way possible.

A slim white male in a fine plaid shirt gesticulates with open hand towards a screen the viewer cannot see.
This tight space limited my options.
A young male academic in glasses, dark T shirt with pale green shirt over the top points as he looks to the top left of the image.
A nice strong pointing shot.
A balding white male in navy blue shirt speaks at a lectern while is image is mirrored by a large TV monitor to his side.
Using reflection to create interest.
A Japanese man in dark blue suit gesticulates with his hands up, palms forward in front of his face, towards a projection screen in a lecture theatre.
Enthusiastic gesticulation.
A white male academic speaks in front of a projected slide about his research. He is looking up and making a circle with the fingers of one hand. He wears glasses and a pale blue shirt under a dark blue sweater.
That hand gesture...
A white male with curly hair, a light beard and moustache wearing a mid-blue sweater lifts his hands, palms-up, as he speaks to his audience which we can't see.
Another expression.

Some people aren’t so easy to capture: They might only read from notes with their head down, or they might only look up with their eyes shut. If they move around a lot in a space that is dimly lit, keeping focus on them can be a challenge.

When it all comes together though, the speaker shots can work really well. They might never qualify as art, but since they’ve been taken to support on-going amplification of the event, they really should be as interesting and engaging as possible. Reaching and grabbing audience attention after the event is one of the hardest tasks for the communications manager, but it’s made all the more dispiriting if the photos are poor.

One other thing I try to ensure is that across the set there will be a variety of shots with emphasis to left and right of the frame, as well as some with design space should the client wish to drop text or a graphic into the image. It’s also important to have a mixture of upright and landscape formats for different publications and platforms.

So while this isn’t the most glamorous genre of photography, it’s interesting for me precisely because good results rely on some quick thinking and problem-solving. Sometimes an image will have an additional spark, which is usually down to the speaker’s gesticulation in the split second that I captured the image. That’s when I know all my calculations have paid off.

 

 

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