This is the third chapter of the series Long Exposure Photography. A new post is published every Wednesday.

We already know what a long exposure is and why this technique is so awesome. And we know the camera gear and equipment we need. In this week's chapter, we'll talk about how to actually use that gear to take a long exposure.

Note: long exposures on film are a little bit trickier. We have to take other factors into consideration and that deserves its own chapter.

I'll show you how I take a long exposure with my Sony a6500 step by step. The controls on your camera might have a different name, but the process should be pretty similar. If you have any questions, leave a comment or contact me.

Meter the scene as usual

Let's forget for a second that we are taking a long exposure. Compose your shot as usual and either meter the scene manually or let the camera work its magic. Try to use an aperture between f/6.3 and f/11, more or less.

I use P mode most of the time, but it doesn't really matter how you do it. The goal is to get an accurate reading of the scene.

In the example I'm going to be showing, we have an initial settings of ISO 100, f/7.1 and 1/20th.

Think of the long exposure time FIRST

What most photographers do here is to take that reading and increase it accordingly to match the ND filter they are using. This is a mistake and it should be done the other way around.

In order to create the image you have in mind, you need to know -more or less- how long the exposure will be. A 5-second exposure will result in a dramatically different image than a 30-second exposure.

We will talk about how to choose the right exposure time for different subjects in a future chapter.

In our example, I'm looking for an exposure time of around 15 seconds. That's more than enough to smooth the water out without creating excessive blurriness on the sticks. We will work with these settings to get the exposure time we are looking for.

Tables

Your ND filters should have come with exposure guides like the one above from Lee.

As I mentioned, instead of reading the table from left to right, we'll do it the other way: from our desired exposure time to the shutter speed we need in our camera.

Highlighted, our options to get those 15 seconds:

The easiest way would be to use the 10-stop ND filter and a shutter speed of 1/60th. A slight increase in the ISO should move our original shutter speed from 1/20th to 1/60th.

We could use the 6-stop ND filter as well, almost 3 stops away from our original shutter speed. This would require stopping the lens down to f/16 or so.

It's not pictured on the table, but we have a third option if we wanted to use the 15-stop ND filter. In this case, we'd need to dramatically increase the ISO: we need a shutter speed of 1/2000th, 7 stops away from our original shutter speed of 1/20th. We could keep the aperture of f/7.1 by increasing the ISO to 12800. If we can afford to change the aperture, something like f/4 and ISO 3200 would be more reasonable.

Let's stick with the 10-stop ND filter. After adjusting the exposure, our new settings are ISO 400, f/8 and 1/60th, exactly the shutter speed that will give us 15 seconds when using the ND filter.

Switch to manual mode

Switch from P (or whatever mode you were metering on) to manual and make sure to dial the settings we got in the previous step.

If our exposure is longer than 30", we need to select BULB, use a cable release and stop it when the time is up.

Focusing

Depending on the camera, you might be able to auto-focus and lock it in place during the whole exposure. My Sony camera is supposed to do that, but it's not the first time that it decides to refocus during the exposure.

To avoid this, I auto-focus and then switch to manual focus. That way I make sure the camera won't be changing the focus and the final image will be sharp where I wanted it to be.

Put the filter on

Now it's time to put the filter in front of the lens -make sure no light can go through the corners. Other than that, this step is pretty simple.

Avoid camera shake with shutter delay

I usually use a shutter delay of 2 seconds. That means that the camera will wait for 2 seconds after I press the shutter before starting the exposure. This way, I make sure there will be no camera shake.

Fire!

We are ready: press the shutter and wait for the exposure to finish.

If it's raining or snowing, you'll need to clean the ND filter every once in a while or the drops will show up on the frame.

Take another one, or two

No matter if I'm shooting digital or film, I like to take at least a couple of long exposures of the same composition.

This is even more important when there are elements in the photo that are constantly moving. See this post for an example of what I'm saying.

Conclusion

The technical aspects of long exposure photography are easy once you get familiar converting shutter speeds to exposure times. Over time, you'll even memorize them and you won't need any tables.

Avoiding camera shake and keeping the filter clean are key aspects to long exposure photography, along with of course having enough power to keep the camera alive!

In the next chapter of this series, we'll dive into what makes good subjects for long exposure photography and how long they should be.