Exposure Summary

So, let’s start to bring things together. Although we’ve got quite complex, we still can’t escape the fact that exposure is made up of 3 components, that the 3 are linked, and that each has a creative effect on the image that we eventually shoot. Anything beyond this – whether metering modes, exposure modes or anything you like – is essentially just supporting those 3 fundamentals. Before we move on to other technical aspects of photography, let’s have an exposure summary!

You should also by now start to understand that the actual concept of “the right exposure” is a bit misleading. Yes, images look better when everything is nice and clear, but some subjects will come across much better if you let their natural darkness come through, or deliberately over expose them to make them brighter. Yes, it’s “correct” to get everything in the shot nice and sharp, but sometimes it can be very effective to have an element of blur in the image somewhere to convey a sense of movement. Beyond the basic rule of “one stop in one direction, means you’ll have to allow one stop in the other direction” any photographic “rule” is totally open to interpretation. Since you now understand the basics of exposure, you’re in a much better place to make these choices.

Choosing the best exposure for the shot

So how do you know if you’ve got the “best” exposure for the shot you’re trying to create? Well, when you’ve balanced all the various creative choices against the limits of what your equipment can accomplish, along with the actual amount of light you’ve got to deal with, the best exposure will simply be the combination of aperture, shutter speed and ISO that you feel looks best.

These two, very different looking images, will help me to illustrate how you can’t escape the constraints of those three aspects, but that you can learn to make informed choices about them.

Francesca - Exposure Summary

The first looks fairly simple – just a nice, relaxed lifestyle image of a woman enjoying a cup of coffee.  I wanted a very light, airy feel to this shot, to maintain this atmosphere. In exposure terms, there’s a fair bit of light around, as there’s a large window behind the model, and white walls on all sides of her, which help to bounce the light around a lot.

Francesca setup shot
The room this image was taken in, from roughly the same angle, but higher, with a darker cover on the bed, and the pictures removed from the back wall.

I want a shallow depth of field, so that just the model is in focus, and there are no distracting details in the background.  I’m on a 50mm lens, whose widest aperture is f1.4, and I settle on f2.5 as a good choice between shallow depth of field and image quality (the image quality of a lens deteriorates at extremes of the aperture scale – either fully wide open, or fully stopped down)  At ISO 100, for maximum image quality, f2.5 only gives me 1/40th second shutter speed. You may recall the rule about avoiding camera shake from when we talked about shutter speed – one over the focal length for the minimum safe shutter speed to avoid shake – so I need a shutter speed of at least 1/50th second.  All I do is push the ISO up to 200, and that allows me to shoot at 1/80th second, and avoid any camera shake.

All in all, a very simple looking image, but still with a quite an involved thought process to arrive at the result I was looking for.

Puma Glow - Exposure Summary

This second image is obviously much more complicated, and has much more going on.  My brief was to show off this new “glow in the dark” running gear, so as a starting point I know I can’t shoot in a bright environment, as the glow won’t show up.  I still need to see the runner inside the gear though – there’s no point making it look like the clothing is just floating in thin air!

So, I shoot in a blacked out studio, and experiment with the gear until I arrive at a shutter speed of 1 and a half seconds – this is long enough for the glow to shine through.  I’m at f5.6 on the aperture, as I want sufficient depth of field to get the whole runner sharp. ISO 100 gives me the best image quality, which is needed, as these images are going to be blown up large.

Puma Glow setup shot
The setup for the above image. Note the glow in the dark tape on the floor, and the totally black studio.

So, how come with a one and a half second shutter speed the runner isn’t just a blur?  Surely with the shutter open for that long her movement should be totally blurred? Well, there’s also a flash in use – in fact something called a ring flash which sits around the lens of the camera – and the fact that the flash only fires for a brief instant (roughly 1/1000 s or less) means that her movement gets frozen.  Since the room is dark, the only light on the runner is coming from the flash, that flash happens in a very short space of time, so she’s frozen. The direct light from the flash also helps to pick out the reflective strips on her gear, which is another plus. The shutter stays open longer than the duration of the flash, to allow the light from the glow in the dark bits to shine through.

A close up of the camera mounted in a ring flash – that big black circle around the lens.

In both of these images, no matter how complex they get, I’m still just dealing with aperture, shutter speed and ISO.  Yes, there are more factors that get added to the mix such as the daylight in the room, and a flash, but all my creative choices start from a position of how much light I’ve got to deal with, and then how I can adjust those three controls to create the shot I’m looking for.

As you know by now, each of the 3 scales only has a certain amount of range – there are only so many apertures, shutter speeds, and ISO settings to play with – so you don’t have an infinite number of combinations you can play with. In difficult circumstances you may well be pushed all the way to the limits on some, or all, of these scales. Don’t be afraid of this – yes, there will be trade-offs in image quality – but realistically these matter far less than getting the shot you want.

When you’re forced to choose

There’s one last area I want to cover now that you’re fully versed in how exposure works. Having this insight is vitally important when you’re forced to make a difficult choice – usually due to the amount of light you’ve got to deal with, either too much, or more likely, not enough.

Think of a dark indoor situation like a sports hall – an example we used in a previous video. The overall amount of light won’t be great, but if you’re trying to freeze some sports action you know you need a decent shutter speed – say 1/250s or faster. The lens you’re using has a maximum aperture of f4, so you can’t get any more light in than this, and all the camera is letting you have is a measly 1/30s. Of course, you know the answer to this – turn up the ISO until you get a decent enough shutter speed. The trade off will of course be a bit of noise in the image, but since you know you can remove much of that in software, it’s not a big concern.  As your photography develops you’ll get more and more comfortable making these choices, and accepting which aspects you may want to sacrifice. Just like most things in life, there’s rarely a perfect situation, the skill lies in making wise compromises.

Exposure Summary

Hopefully after all that, the mysterious numbers on your camera are starting to make sense. Likewise, magical creative effects such as freezing motion or having a very shallow depth of field should no longer be arcane tricks pulled by professionals, but something you can incorporate into your own work.

We’re now coming on to the rest of the technical basics – things like different types of camera, focusing, resolution, and all the rest. You might want to take a little breather at this point – I would if I were you, but before you pause, remember: Keep your camera in manual mode, get lots of practice, and revel in the fact the your photography is improving by leaps and bounds.

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