You’ve got a camera that can do far more than you’re asking of it, but the dial never leaves auto. Every time you’ve tried manual mode, you’ve ended up with a photo that’s black, blown out, or close enough to fine that you wonder why you bothered. Most explanations of the exposure triangle don’t help either. They make it sound like a maths problem you have to solve before every shot.
It isn’t. Photography comes down to three settings: shutter speed, aperture and ISO. Once you know what each one does, you have everything you need to make any image you want. In this tutorial I’ll show you how to read your camera’s light meter, how to get a correct exposure with each setting, and the one change I’d make on day one that takes most of the pain out of shooting manual.
If you’d rather watch, here’s the full video:
Why Bother With Manual Mode at All?
Shutter speed, aperture and ISO make up what’s called the exposure triangle. The goal is to keep the three in balance so the photo is neither too bright nor too dark. That’s all “correct exposure” means.
But if exposure were the only goal, there’d be no reason to leave automatic mode (if you’re unsure how the different modes compare, my camera modes crash course covers them). Cameras have had auto exposure modes since the 1970s, and they nail it almost every time. The real reason to shoot manual is control. Two of those three settings change how the photo looks, not just how bright it is, and auto mode makes those decisions for you.
Think of it this way. Auto mode is a driver who always gets you to the destination, but picks the route. Manual mode hands you the wheel. You still arrive in the same place, a well-exposed photo, but you choose how you get there and what the image looks like along the way.
What Each Setting Actually Does
Shutter speed controls motion. A slow shutter speed keeps the shutter open longer, so anything moving gets that dragging blur we all associate with movement. If you’re photographing people running and want the photo to feel fast, that’s the tool. A fast shutter speed does the opposite: it freezes a moment so everything is sharp with no blur at all.
Aperture controls depth of field, which is how much of the scene is in focus. If you’re photographing someone in front of a busy background, a wide aperture such as f/2.8 keeps them sharp and turns the background into soft blur. If you want more of the scene in focus, a small aperture such as f/22 gets you there.
ISO is different. It has no artistic effect at all. ISO is the amplification of the signal coming off your sensor. Think of it as a volume knob, except it controls brightness: turn it up and the image gets brighter, turn it down and it gets darker. That distinction matters, and it’s the key to the shortcut later in this article.
[IMAGE PLACEHOLDER: the camera’s manual mode screen showing shutter speed, aperture, ISO and the light meter indicator]
Reading the Light Meter
On your camera’s screen in manual mode you’ll see your shutter speed, aperture and ISO. When I started this demo, mine was set to 1/250 sec, f/5.0 and ISO 200. Your camera’s layout may look different, but the information is the same.
Underneath those settings is a small scale: the light meter indicator. It tells you whether the camera thinks your photo will be overexposed or underexposed. To take a reading, half-press the shutter button and a marker appears on the scale. Anything to the left, the minus side, is underexposed by that many stops. Anything to the right is overexposed. My first reading was just over two stops under, and sure enough the test shot was far too dark.
Remember that the meter is only an indicator. You might want a photo a little darker or brighter than it suggests, and that’s your call. But zero is a reliable starting point.
[IMAGE PLACEHOLDER: close-up of the light meter reading two stops under, next to the underexposed test shot]
Dialling In Exposure, One Setting at a Time
My recommended order is shutter speed first, then aperture, then ISO last.
Here’s the trick that makes this quick. After you half-press the shutter, the meter stays active for roughly three seconds, depending on your camera. While it’s active, turning the shutter speed or aperture dial resets that timer and updates the meter live. So you can take a reading, then turn the dial and watch the marker move until it lands on zero, without pressing the shutter again. On my camera the top dial changes shutter speed, the back dial changes aperture, and ISO lives in a menu.
Starting from two stops under, I slowed the shutter speed until the meter hit zero, and the next shot was correctly exposed. Then I reset to 1/100 sec, which read just over a stop under, and fixed it with aperture instead, opening up to f/3.2. Correct exposure again.
Finally, at f/5.6 and 1/125 sec I was two stops under, so I raised the ISO. On my camera that’s done in a menu, and there’s no live meter while you change it, so I bumped it up about two stops, checked the meter, and nudged it a little higher because the light was fading. Three different settings, same result.
[IMAGE PLACEHOLDER: side-by-side of the underexposed shot and the corrected shot after adjusting shutter speed]
Using Aperture to Shape the Image
Getting exposure right is the mechanical part. The creative part is choosing which settings to use to get there. I couldn’t demonstrate motion blur because nothing in my scene was moving, but depth of field was easy to show.
From my balcony there’s an electricity pole with boats in the background. To blur the boats, I opened the aperture to f/2.8. That let in too much light and the meter read overexposed, so I made the shutter speed faster to compensate. The result was correctly exposed, with the pole in focus and the boats melted into blur. That blur is the bokeh.
[IMAGE PLACEHOLDER: the pole shot at f/2.8, zoomed in, showing the pole sharp and the boats blurred]
To bring the boats into focus, I closed the aperture to f/20. Now the meter showed more than three stops under, with an arrow off the end of the scale. About 1/6 sec would have balanced it, but at that speed even pressing the shutter on a tripod can shake the camera. So I raised the ISO to 3200, which let me use 1/20 sec at f/20 for a correct exposure. Same focus point on the pole, and the boats were now much sharper.
I then went to f/32, the smallest aperture on that lens, with a shutter speed around 1/6 to 1/8 sec. The first shot had camera shake, so I switched on the two-second self-timer and shot again. That one had both the pole and the boats in focus.
[IMAGE PLACEHOLDER: the pole shot at f/32, zoomed in, showing the boats in focus]
The Easier Way: Manual Mode With Auto ISO
That’s how manual mode is usually taught. Here’s the approach I’d actually recommend when you’re starting out.
Shutter speed and aperture are your creative choices. ISO isn’t; it just turns brightness up or down. In the traditional workflow you pick your shutter speed and aperture for the look you want, then adjust ISO to get the meter back to zero. So why not let the camera handle that last step?
Go into your ISO setting and scroll to the lowest value. On many cameras, including mine, there’s an Auto ISO option there. Select it, then set your shutter speed and aperture. I chose f/5.6 at 1/60 sec, which had read as overexposed with a manual ISO. With Auto ISO, half-pressing the shutter updates the display and actually sets the ISO needed for correct exposure. The shot came out correctly exposed. I changed to f/8 and shot again: correct. Then 1/40 sec: correct again.
You still choose everything that affects how the photo looks. You’ve just handed off the one setting that doesn’t. When you’re comfortable, you can go back to setting ISO manually if you want to.
[IMAGE PLACEHOLDER: ISO menu with the Auto option selected, and the display showing the ISO the camera chose]
Common Mistakes to Watch For
Forgetting about camera shake. Small apertures need slow shutter speeds, and slow shutter speeds show any movement, including from your finger pressing the button. Raise the ISO to get a faster shutter speed, or use a two-second self-timer on a tripod. For more on this, see my tips for getting sharper images.
Treating the meter as the final word. Zero is a starting point, not a rule. If you want a darker, moodier image or a brighter one, adjust away from zero on purpose.
Assuming Auto ISO has no limits. Every camera has a highest and lowest ISO. If Auto ISO hits either end, it can’t compensate any further, and you’ll need to adjust shutter speed or aperture yourself. Most of the time, though, it works very well.
Give It a Go
The key takeaway: you don’t need to control everything manually. Set your shutter speed and aperture for the creative look, and let ISO handle the exposure. Switch your ISO to Auto, try a few different apertures and shutter speeds on your own scenes, and see how you go.
Have you tried Auto ISO in manual mode, and where did it work or let you down? Let me know in the comments.
Free Reference Guide
If you want something to keep in your bag, I’ve made a free exposure reference guide you can print or save to your phone. It’s in my free resources pack, along with a bunch of other free downloads.