Landscape with filters

Learning goal

At sunset, you will be able to measure in the field the difference in brightness between the sky and the ground, express it in stops, and decide according to this difference whether to balance it with a filter, with several exposures, or in editing. You will choose the strength of a graduated ND filter according to the difference you measured, and place the transition line according to the horizon, the mountains and the people in the frame. You will notice that when the sun is right on the horizon the brightest strip is just above the horizon, and get to know the reverse graduated ND filter made for this situation. You will see which part of the sky a polarizer affects at sunset and which it doesn't, and that erasing the reflection on the lake or not is a choice. You will prevent the face of a person cutting the horizon from staying in the filter's dark part and going dark, especially the loss of detail on dark skin.

The question

Your friend returns to the lakeshore once more. The sun is setting over the hills opposite, the sky orange and bright, while the rock on the shore is in shadow. When they expose so the rock looks good, the sky turns into a pure white flatness. When they expose for the sky, the colors come back but the rock and the lake are pitch black. In their bag there is a polarizer and a piece of glass dark on one half; they don't fully know how to use either. How do you balance a bright sky?

Context

In the filters lesson you learned that a polarizer darkens the sky most at a right angle to the sun, can leave an uneven band with a wide angle, and cuts the reflection on a water surface (Lesson 13.2). Right after that you saw that a glass dark on one half balances a bright sky with a dark foreground, that the transition can be hard or soft, and that things cutting the horizon cause trouble (Lesson 13.3). In exposure bracketing you met shooting the same scene at different exposures and combining them (Lesson 9.8).

This lesson uses those tools in a single landscape, in order. First you measure how different the sky and the ground really are. Then you decide with which tool to close this difference. Last, you think about where to put the transition and how the person in the frame will be affected by these decisions. A filter is one solution, but not the only one; without knowing the difference, you can't choose which one suits this scene.

Simple explanation

How big is the difference?

The sky-to-ground difference is the measure, in stops, of the difference in brightness between the sky's brightest important area and the dark area on the ground whose detail you want to keep. To measure it, you set the camera to spot metering and meter first the bright sky a little away from, not right next to, the sun, then the rock in shadow. If the sky wants 1/500 and the rock 1/60, the difference between them is three stops. This number decides which tool you choose.

For small differences that stay within the range the camera can carry detail in a single frame, one or two stops, shooting raw and opening the shadows in editing is often enough. Around three stops, a graduated ND filter does the job cleanly. If the difference is bigger still, or if the horizon is cut unevenly by mountains or trees, shooting several exposures and combining them may give a better result. You don't have to close the difference completely: leaving the sky one or two stops brighter than the ground looks natural to many eyes; this is a preference, not a right answer to be measured.

What changes when the sun is on the horizon?

When the sun comes down to the horizon, the brightest place in the sky isn't at the top but in the strip just above the horizon. The dark part of an ordinary graduated ND filter is the same darkness from the top down to the transition line, and slowly becomes clear at the line. When the line is set on the horizon, the bright strip just above the horizon falls in this transition zone, where the filter darkens least, and doesn't darken enough; the top of the sky, already darker, can on the other hand darken more than needed.

A reverse graduated ND is a graduated filter whose darkness is strongest at the transition line in the middle and gets lighter going up. On an open horizon where the sun rises and sets, by the sea or a lake, it is made for these scenes because it darkens the brightest strip. If the horizon is cut by hills or mountains, a reverse graduated ND also darkens the tops of the mountains harshly; in this case a soft-transition filter, or combining several exposures, works better. At sunset, a polarizer hardly changes the sky facing the sun; its effect is in the sky at a right angle to the sun and in the reflections on the lake. Keeping or erasing the hills' reflection in the lake is a decision made according to what the photo will tell.

Where do you put the transition?

Transition placement is the decision about where in the frame to put the line between the dark and clear parts of a graduated filter. On a flat sea or lake horizon, the line is set on the horizon. When mountains and hills cut the horizon, the line is put in the middle of the mountains or a little below; otherwise the tops of the mountains darken along with the sky and an unnatural dark band appears in the frame. To see where the line falls, enlarging on the screen, or stopping down the aperture for a moment to preview, helps.

If there is a person in the frame cutting the horizon, their head and face enter the filter's dark part and go one or two stops darker. On light skin this makes the face look dull; on dark skin, on the other hand, the detail of the eyes, lips and cheekbones can be lost completely. Bringing the person below the horizon, raising the camera to put them in front of the ground, or leaving the filter and shooting several exposures to take their face from the correctly exposed frame keeps them in their own color.

Visual evidence

With spot metering your friend meters first the orange sky to the right of the sun, then the rock in shadow. The sky wants 1/500, the rock 1/60: three stops. The sun is above the hills, the horizon isn't flat.

First they try an ordinary hard-transition graduated ND. When they set the line on the horizon, the upper half of the hills darkens along with the sky, and a dark band appears along the hills' ridge. They switch to a soft-transition two-stop filter and bring the line down to the middle of the hills. The sky is orange and detailed, the rock and lake read; the hills look natural.

They try the polarizer; the sky facing the sun hardly changes, but the hills' reflection in the lake is erased. Because they want the reflection, they take the filter off. Their hiking companion standing on the shore, dark-skinned, has his face go dark when his head rises above the horizon. Your friend raises the camera a little; the man now stands in front of the lake and his face is in the filter's clear part, in its own color.

Common mistakes

Summary

A bright sky is balanced by first finding the difference between the sky and the ground in stops with spot metering, and then choosing according to this difference between editing, a graduated ND filter or combining several exposures; when the sun is on the horizon, a reverse graduated ND darkens the brightest strip. The transition line is placed according to the horizon, the mountains and the person in the frame; at sunset a polarizer mostly affects reflections, and a face cutting the horizon isn't allowed to stay in the filter's dark part.

Mini assignment

In this assignment you will measure and balance the sky and the ground at a sunset.

1. Near sunset, in an open landscape, meter the bright sky and a foreground in shadow with spot metering, and write the difference between them in stops.
2. Shoot the same framing with a single exposure without a filter, with a graduated ND filter if you have one, and at three different exposures.
3. Compare the frames; look at where the transition falls, whether the mountains or trees darkened, and, if someone is in the frame, which part their face stayed in.

Check yourself

• Did the difference you measured really close with the tool you chose?
• Did the transition line leave a visible band in the frame?
• Is the face of the person in the frame in its own color, or has it gone dark?

Glossary

Mini quiz

1. If the sky wants 1/500 and the rock 1/60, how many stops is the difference?

• A) One
• B) Three
• C) Five
• D) Eight

2. When the sun is right on the horizon, which filter best darkens the brightest strip?

• A) A polarizer
• B) An ordinary hard-transition graduated ND
• C) A reverse graduated ND
• D) No filter

3. In a scene where mountains cut the horizon, where is the transition line put?

• A) Above the tops of the mountains
• B) At the very bottom of the frame
• C) Exactly in the middle of the sky
• D) In the middle of the mountains or a little below, with a soft transition

4. If the face of a person cutting the horizon enters the filter's dark part, what can be done?

• A) Bring the person below the line, or use the face from the correct frame with several exposures
• B) Replace the filter with a darker one
• C) Nothing, the face always reads
• D) Raise the ISO to its highest

Answers

1. B — From 1/500 to 1/60 you get there in three steps, each stop doubling the time.
2. C — A reverse graduated ND carries its strongest darkness exactly at the transition line, on the bright strip at the horizon.
3. D — If the line is put at the tops of the mountains, the mountains darken along with the sky and a dark band appears.
4. A — If the face stays in the clear part or in the correctly exposed frame, the skin appears in its own color.

Summary card

• Measure first: the stop difference between sky and ground with spot metering.
• A small difference, editing; around three stops, a graduated ND; a big or uneven difference, several exposures.
• A reverse graduated ND for the sun on the horizon.
• At sunset a polarizer cuts reflections; keeping the reflection is a choice too.
• Transition to the middle of the mountains; don't leave a face cutting the horizon in the dark part.

Bridge to the next lesson

The lakeshore frame is finally balanced. The next week your friend goes to the sea; waves crash against the rocks and foam, and in every frame there are frozen, sharp droplets. In their bag sits a very dark filter they have never used. How does the sea come to look like fog? The next lesson takes up how the shutter speed decides the water's character: from frozen droplets to silky flows, and from there to a sea surface turning to mist.