# The Secret Formula to Nail Perfect Exposure Every Time

## Practice This Every Time You Shoot

Nov 30, 2020 · 10 min read

You know a perfect exposure when you see one, right? But how do you achieve that with every shot?

As a beginner, you’ve probably learned about the exposure triangle; shutter speed, aperture, and ISO. And hopefully, you’ve spent some time learning the reciprocal values of each one. For instance, if you increase your shutter speed by one stop, you need to open your aperture one stop or increase ISO one stop to compensate for it.

But knowing this in theory and putting it to use in practical terms are two different things. I know, I’ve been there. You come upon a scene with f-stops and shutter speeds bouncing around in your head. You set your camera to one of the so-called creative modes and take a shot. It’s not what you wanted, so in frustration, you switch back to full auto so that at least you’ve captured something.

Or worse, you’ve listened to all the well-intentioned advice telling you to shoot in manual mode if you want a good picture and completely flub it up. Then you switch it back to full auto and give up on all this exposure triangle nonsense.

But there’s a better way. It’s not an easier way, but it is a better way. It will require patience and practice every time you go out to shoot. It’s a formula you have to learn to use and do so over and over until it becomes intuitive. Having this knowledge will empower you to take perfect exposures every time, but you have to work it.

But first, let’s break down this ‘secret formula’ nonsense. What does that even mean? Well, by formula, I mean it’s like those high school algebra equations you learned. Except you are solving for X, Y, and Z. And all three of these numbers are on a different scale. To make matters worse, there are many ‘right’ answers, but only one perfect one.

And by secret, I mean private. Only you can know the perfect answer, so only you can solve the formula. If I go to the same location with the same light, my solution will be different. My shot will be perfect for me. At least in theory.

Sound complicated? Well, it is, and it isn’t. It’s all about the light and capturing it in a way that suits you, your equipment, the scene in front of you, and your style of photography. So, what it really takes is time and practice. Don’t give up and switch to auto mode. Work through the formula every time you shoot, and eventually, it will become second nature.

If you have looked at any of the charts or tables that display the exposure triangle, you know there is an almost infinite number of combinations. The graphs may show apertures from f1 to f64 or higher. You can see shutter speeds from 30 seconds to 1/8000th of a second and ISO Speeds from 50 to 12,800. Do the math. The number of total possibilities is… I have no idea.

But more importantly, it doesn’t matter. This is because you are limited by (at least) three things, your equipment, the available light, and what you, as the photographer is trying to achieve. We can call this the reality triangle, and it will be much more limiting than the exposure triangle. So, the ‘secret’ to this formula is first to limit the range of the exposure triangle factors based on the reality triangle.

Let’s start with ISO because it is the easiest to set limits on. First, on the low end, your camera has a native, low-end ISO. On my Canon cameras, it was 100. You could change a setting to drop that to 50, but let’s keep it simple. For 99.99% of your shots, there is no practical difference between 50 and 100. On my Fuji, it is 160. The high end is 12,800.

But would I ever shoot at 12,800? Almost certainly not. It would depend on the third part of the reality triangle, what I am trying to achieve. If I need to capture something in almost total darkness and don’t have a tripod, then maybe.

Despite all the talk about how modern cameras can handle high ISO and how good the post-processing software is, there is still a practical limit that only you can decide. So, the first part of learning this formula is making that determination. Go out in various lighting conditions, take shots at every ISO setting, or at least cover the range. Post-process these images as you usually would, running them through whatever noise reduction module or software you prefer. Note: Under most conditions, you don’t want to let your camera handle noise reduction.

Take a look at the final results. Using those photos as a guide, determine three ISO settings. The highest you consider good. The highest you consider acceptable. And the highest you would want to shoot at under any circumstances. For this test to be the most accurate, you need to look at the images in the format you typically use. For me, that’s a computer monitor. For you, if you mostly post on Instagram or Facebook, it may be your phone or tablet. If you print most of your images, you will need to print them to see the effects of high ISO.

Now, you have the practical limits of your ISO. Not what your camera can do, but what you want it to do. Next, learn if your camera has auto-ISO with settings to limit it. For me, this is the ideal. I can set my camera to one of three auto-ISO settings and know that my images will be in the acceptable range based on my testing. If you prefer total control, then remember your three ISO limits, knowing that, when possible, you will shoot at the lowest ISO setting.

Next, we will dive into shutter speed. Knowing you can shoot at from 30 seconds to 1/8000th is pretty useless as you will most likely never use either of those unless you are shooting on the dark side of the moon or the surface of the sun. So, what are the practical limits? The piece of equipment that will determine the slowest acceptable shutter speed isn’t your camera but a tripod. If you are using a tripod, you are only limited by available light and desired results. But if you are shooting handheld, you are limited by how steady you can shoot. And you will only determine that by more testing.

First, learn and practice proper handholding technique. Doing the job right can give you several extra stops of light. Next, set your lenses to whatever they call their stabilization mode if they have it. If it’s in your camera body, turn it on there. Now, go out with all of your lenses and take some test shots.

A good rule of thumb is to use each lens’s focal length, so if you are shooting a 200mm lens, then start with 1/250th. You may want to try a stop or two faster to make sure. Use your best handholding technique and take shots from your starting point down to 1 second. Most likely, 1/15–1/60th will be your limit, but this will give some useful comparisons.

Now, once again, go back and process these images and view them how you usually would. Unless you never use your photos on anything but a phone, I would suggest using a computer monitor and view the subject at 100% as well as normal resolution. What is the slowest that is tack sharp? What is the slowest that is acceptable to you? What is the slowest that would do in an emergency? Memorize or write down those three shutter speeds for each lens and focal length.

There is no point in testing the fastest shutter speed. That will be driven by the available light, your other settings, and your desired outcome. You can back into that number later. But first…

As you know, aperture is the size of the hole that allows light into your film or sensor. I know on some mirrorless cameras with an electronic shutter, there may not actually be an aperture, but the principles should still work the same.

Your lens will drive the outer limits of the possible apertures. It will have a minimum and a maximum. The practical limits will be driven by available light and what you are trying to achieve. But first, you should determine the optimal aperture for your camera and each lens. Lenses tend to have a sweet spot that is the absolute sharpest. Conventional wisdom places that at about two stops from wide open. So if your maximum aperture is f2, then you should try f5.6. The reality may be different, and your results may vary. So, guess what? Yep. More testing.

Take those lenses out and shoot some typical subjects. For this test, use a tripod if you have one, or a stable surface and the timer if not. Take shots at every aperture on every lens. Head back to the computer and process them as usual. Now, with the images at 100%, look at them from the center to the edges. At what aperture is everything sharpest? That’s your sweet spot.

Now, I’ll let you in on another secret. You may not be able to tell. If not, don’t worry about it. If you can’t tell the difference at a resolution that the image will never be viewed at, then it doesn’t matter. As the photojournalists used to say, f8 and be there. Under most circumstances, if I am out and about doing general photography, my camera is set in aperture priority at f8. I let the camera choose the shutter speed, and my auto-ISO settings handle that part.

Okay, so you have reduced those infinite numbers you started with down to a manageable size. But there are still a lot of variables. This is where practice and experience come in. But you still need to solve that complex equation. With time, it will get much easier. But to start with, you need to learn how to solve it quickly. And like those algebra equations, you do so one variable at a time.

First, you need to determine either the most critical variable or the easiest to solve, depending on the circumstances. If your camera has the capability, the easiest to solve is ISO, by setting and using the Auto-ISO settings.

Even before I had that, I typically set iSO at one point and left it there unless circumstances dictated otherwise. On a sunny day, that was usually 100. If I was in shadow a lot, or it was cloudy, I would go with 200–400, knowing either would give me perfectly acceptable results. If I were inside, I typically start at 800. I don’t like to go higher than that no matter what, but you got to do what you go to do to get the shot.

But usually, you need to start with the most crucial factor. Set that, and you have significantly reduced the number of variables. Do you need a great depth of field? Then go with a small aperture. Do you need to freeze action, then use a fast shutter speed. These factors will be driven in part by available light and whether or not you are using a tripod. I know that carrying around a tripod is a pain, but eliminating shutter speed from (most) equations can free up the other factors.

So, here is where that practice comes in. Go out and shoot. A lot. But don’t just point and shoot. Think through every shot. What do you need to capture the image? Start with the most important factor and set that.

Then you can back into the other two. Let’s say you are out in the desert. You want to capture this huge vista. Okay, you need to start with f16 or f22. No matter how bright it is, that will restrict your possible shutter speeds. If it’s cloudy and you are shooting handheld, you may need to bump the ISO to get an acceptable speed.

You walk into a church. There is a lot of window light, but your eyes are much better at adjusting than your camera. Go ahead and raise your ISO to your highest comfortable setting. What does that leave you in terms of aperture and shutter speed? Handheld? You may have to shoot wide open to get a fast enough shutter speed. This will significantly reduce your depth of field.

Now, let’s say that church is relatively dark, and you don’t have a tripod. The church is enormous, and you want everything in focus, from the nearest pew to the altar and stained glass at the other end. You will display this image on a large screen, so you need noise to be minimal.

Luckily, there is a magic button on the side of your camera that will let you shoot with a low ISO, a small aperture, and a fast enough shutter speed to hand-hold your camera in dark settings.

Go take a look at your camera and find that button. I’ll wait here.

Okay, I lied. Again. There is no easy button. You are going to have to make compromises. You are going to have to adjust, adapt, and overcome. But don’t just punt and switch to auto mode. If you have been practicing these techniques long enough, you will be able to solve that secret formula quickly.

Okay, 1/30th is the slowest I can hand-hold this lens. Set that. ISO 800 is the noisiest I want to get. Check. You’ve solved X, and Y. Z will solve itself. If Z isn’t a small enough aperture, you will have to raise the ISO or find something to place the camera on.

Practice these tips as often as you can until solving the formula becomes intuitive. It will raise your photography to a new level and give you the confidence to shoot in any circumstances without resorting to that little green square on the settings dial.

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