zarek rahman © 2011
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Combining flash with a wide aperture lens

When you refer to a wide aperture lens, you are generally talking about a lens with a maximum aperture of f2.8 or more, with the most popular maximum aperture lenses being f2.8, f1.8 and f1.4. Canon users can choose from a variety of f1.2 lenses, while Micro Four Thirds users also have the extremely fast but manual focus only f0.95 lens available.

The wider the aperture of your lens, the more light you can let into your camera. You might therefore assume that such a lens lets in so much light that flash is no longer required, but I don’t think so and today I’ll explain why.

[box_grey]“I don’t need to use flash because I have a fast lens so I can shoot natural light“[/box_grey]

Everyone knows someone who loves to shoot natural light only. That’s not a bad thing, and that is what can dictate a person’s style of photography. For me though, natural light alone does not suffice, especially when you’re shooting people at events or parties.

1. You control the light instead of the light controlling you.

Available light might be beautiful, and shooting in it might be less intrusive and more memorable. But more often than not, the light that you’re dealing with generally isn’t best placed for shooting people. Here are some photos of my buddy who I was at a party with:

On the left, available light:

• With an aperture of f1.7, I had a pretty fast lens on my camera. The party was in a dark bar with a some horrible purple and red lighting. The walls were dark and didn’t really reflect any light into the room. So there was plenty of available light, but it was a nasty colour.
• The lighting was only coming from above, so there were shadows being formed on the left side of his face simply because he tilted his head.
• If I had chosen a higher ISO, noise would have started to show up. This is a factor you need to consider if you’re using a non-pro camera, like I was on this day. The best Nikon and Canon cameras can go up to 6400 and would have fared much better here, but not everyone has one of those. Even so, a higher ISO still wouldn’t have cured the purple light problem.
• The solution was to pop on my external flash gun and bounce it off the wall behind me, but still shoot wide open so as to let in as much available light as possible

On the right, with flash:

• Taken only a few seconds later, notice the huge difference in sharpness, clarity and skin tones which I managed to achieve simply by bouncing my flash at a low power level.
• I had placed a 1/4 CTO warming gel on my flash, with the white balance on my camera set at tungsten. That combination allowed me to retain the mood lighting in the background, but retain a realistic flesh tone for my subject.
• You might be thinking that I’ve killed the mood by changing the colour. Well no, I don’t think so. The available light photo is indeed available light, but only as the camera saw it – not my eyes. My memory of the party is much more like the second photo than the first.
• The point is that while there was plenty of available light, by adding the flash I was able to add to that available light to get a photo that works a little bit better.

 

2. If you use flash, you can freeze movement with ease.

 

In this photo we have Spider-Man jumping around in his living room. Spider-Man’s living room was bright, with a bunch of downlighters in the ceiling and nice white walls to bounce the light around evenly. I could have got some really nice natural light photos of him spinning his web by changing my camera settings to 1/80 and ISO 2000. If I had done that though, this photo would have been a blurry mess.

No amount of natural light is enough to freeze the movement of a crime fighting superhero, especially when he’s 5 years old. In fact, even at 1/250s (the max sync speed for my camera), you can see that he is still too quick for me – check out his left hand.

Again, in this situation the wide aperture lens has put some separation between Spider-Man and the cluttered background, as well as taken in the available light in the room to retain the mood.

3. A wide aperture is tied to a shallow depth of field.

It’s all good to shoot wide open in a dark room without flash, so long as you’re not taking photos of groups. A wide aperture not only lets a lot of light into your camera, but it also gives you a shallow depth of field. This is how you get background blur and separation between your subject and whatever is going on behind then. The wider your aperture, the shallower your depth of field will be.

If you are photographing an event and going around asking for couples to pose, f2.8 or so works pretty well. But sooner or later you’re going to get asked to photograph a big group together, and in those situations shooting at f2.8 means that you won’t get everyone in focus and you will need to stop down to f8 or so (depending on your camera).

Shooting at f8 means that you are letting in 3 stops less light than you were at f2.8 – and if the light is already dim, you probably aren’t going to get much of a picture at all. In fact, in this photo even f8 wasn’t enough (but you can’t tell because it’s so small):

Having the flash to add to the available light was the only way I could have got this group photo and increased the depth of field.

In short:

• Shooting with a wide aperture lens will help your flash. The flash will need to use far less power when the lens is wide open. This means it will recharge quicker so that you can fire off shots more quickly. It also means the batteries will last longer, and your flash won’t overheat.
• I generally try to expose for the ambient light, so that I can retain the mood of the venue. This usually necessitates a slower shutter speed, often as low as 1/60s. No matter how fast your lens is, that won’t be fast enough to freeze motion if people are moving around.
• Shooting natural light only can certainly work, but you have to be aware of the limitations that face you if you do this.
• So my advice is to always have a flash gun handy, even if you are a natural light shooter.