Panorama

Learning goal

You will be able to turn a wide landscape that doesn't fit within a single lens's angle into a high-resolution, unbent panorama by combining frames you shoot side by side. You will explain why holding the camera vertically gains both resolution and cropping room, and why you need to leave an overlap between frames. You will keep exposure, white balance and focus fixed across the frames, prevent a wavy horizon line by leveling the tripod, recognize the parallax error that rotating the camera around the wrong point creates in a close foreground, and remove it by rotating around the lens's entrance pupil. You will compare how the projections a stitching program offers affect straight lines and the horizon, manage the breaks created by clouds and people moving between frames, and check in a group panorama that each person appears single and unbroken.

The question

From the top of the bridge the whole valley can be seen: a green hill on the right, the winding stream and the town's tiled roofs in the middle, a slender minaret on the left and the mountains stretching behind it. Your friend from the club wants this scene in a single photo. Even the widest lens they have takes in only half the valley; either the hill or the minaret stays outside the frame. When they try with the ultra-wide camera on their phone, everything fits, but the houses at the edges have stretched sideways, the horizon has curved slightly, and the minaret has drawn away from the frame and become tiny.

Your friend holds their camera vertically and shoots the valley in seven frames from right to left, and when they get home they combine the frames. The result is a long, narrow image, but sharp everywhere, in which the roof tiles can be counted one by one. How do you shoot a landscape that will not fit in one frame? How do seven separate frames turn into a single scene?

Context

In the HDR lesson you saw how to widen a scene's light range by gathering separately exposed frames into a single image. A panorama applies the same logic to space: it widens the angle of view by combining frames looking in different directions. In the compositing lesson, too, we discussed that a panorama is a technical combination that doesn't change the scene but completes what the camera couldn't capture in one go (Lesson 21.11).

A panorama gains two things. The angle of view widens: a breadth no lens can fit shows in a single image. Resolution increases too: the combination of seven frames carries far more detail than a single frame and stays sharp even in a large print. But these advantages come when a few simple rules are followed during the shoot; otherwise the frames don't fit together, the horizon waves, or objects in the foreground look broken.

Simple explanation

How are the frames shot?

A panorama is turning several frames looking at different parts of a scene into a single, wide image by combining them at their edges. When shooting a horizontal landscape panorama, holding the camera vertically gains two things. Because the long side of each frame is on the vertical axis, the panorama's height increases and the total resolution rises. It also leaves room at the top and bottom to crop the irregular gaps that will form at the edges during stitching.

Overlap is the part two frames shot one after another show in common. The stitching program aligns the frames by matching the same details in this shared part; if there is no shared part, or it is too narrow, the frames don't fit together. A common suggestion is for each frame to show again about a third of the previous one. In areas with few details to match, such as the sky or flat water, leaving a wider overlap makes the job easier.

Everything needs to stay fixed across the frames. In automatic exposure the camera meters each frame separately, and the frame facing the sun comes out dark while the frame facing the shadow comes out bright; bands form in the combined panorama. That is why exposure is metered for the brightest part of the scene and fixed in manual mode. White balance, too, is set to a fixed value so that there is no color shift between frames. Focus is switched to manual and fixed; autofocus may focus on a different point in each frame.

Why must the camera rotate at the right point?

The most overlooked problem of a panorama is the horizon and the rotation point. If the tripod isn't level, the horizon rises and falls from frame to frame as the camera rotates, and the horizon waves in the combined panorama. Many tripod heads have a small spirit level; leveling the head before starting the shoot prevents this problem.

Parallax error is near and far objects shifting relative to each other when the camera is rotated around the wrong point, and breaks, double lines or bends forming in the foreground of the combined frame. When you turn your head left and right, you see a nearby post change place relative to the mountain behind; the same thing happens when the camera rotates. In a distant landscape this shift is very small and often goes unnoticed; but if there is a bridge railing, a tree or a fence in the foreground, these objects look broken or repeated in the combined frame.

The entrance pupil is the point where light appears to enter the lens when looking from the front of the lens, and when the camera is rotated exactly around this point, parallax disappears. This point is usually not in the camera body but inside the lens, near its front; the tripod's screw, on the other hand, is under the camera. That is why in panoramas with a close foreground, a panorama head or a rail is used that slides the camera forward and brings the entrance pupil over the axis of rotation. A simple way to find this point is to line up a nearby post with a distant object, rotate the camera left and right, and look for the position where the post doesn't shift relative to the object behind.

How are the frames combined?

After aligning the frames, stitching programs spread them out onto a plane; this way of spreading is called a projection. A projection that preserves straight lines keeps the edges of buildings straight in narrow panoramas, but stretches the edges excessively as the angle of view widens. A cylindrical projection keeps the horizon straight in wide horizontal panoramas and preserves vertical lines, but bends horizontal straight lines slightly. A spherical projection is used for very wide, even full-circle panoramas. Which projection is chosen depends on the lines in the scene: an architectural facade and a mountain range look good in different projections.

Anything that changes place while the shoot is going on causes problems in stitching: a cloud, a car or a person standing in one place in one frame and somewhere else in another can look broken or doubled. That is why you need to shoot the frames fast, make sure a moving subject doesn't stay in the overlap area of two frames, and check the combined panorama by enlarging it.

In group panoramas the most delicate area is people. A person who moves between frames can appear with a half or broken face where two frames join; someone who changes place while the frames are being shot can appear twice in the panorama. To prevent this you need to ask everyone to stay in place until the shoot is over, and make sure people don't fall on the boundary between two frames. White balance that isn't kept fixed also shows a person's face warm in one frame and cool in the neighboring frame; this shift stands out as a boundary line, from brown to gray on dark skin and from pink to yellow on light skin. Keeping white balance fixed and examining faces closely in the combined panorama catches the shift.

Visual evidence

In the middle of the bridge you set up the tripod and level it with the spirit level on the head. You hold the camera vertically, meter the exposure for the brightest part of the sky and fix it in manual mode, set the white balance to daylight, and fix the focus manually on the town in the middle of the valley. Starting from the hill on the right, you shoot seven frames toward the left, as far as the minaret, each frame showing again about a third of the previous one.

In the first stitch, the bridge's railing looks broken and repeated at two places where the frames join; the railing is very close and the camera rotated around the screw. With a rail you slide the camera forward a little, line the railing up with the minaret behind it, and find the position where the railing doesn't shift when you rotate the camera. In the sequence you shoot again, the railing is unbroken. When you stitch with a cylindrical projection, the horizon is straight and the minaret stands upright. The old woman leaning on the railing isn't standing on the boundary between two frames; her face appears in a single frame, in her own warm brown under the fixed white balance.

Common mistakes

Summary

A panorama widens the angle of view and the resolution by combining frames looking at different parts of a scene; holding the camera vertically gains height and cropping room, an overlap of about a third is left between frames, and exposure, white balance and focus are kept fixed. If the tripod isn't leveled the horizon waves; if the camera is rotated at the wrong point, parallax error forms in the close foreground, and this is removed by rotating the camera around the lens's entrance pupil. The projection chosen in stitching preserves straight lines and the horizon in different ways; clouds and people moving between frames create breaks, in group panoramas people are kept away from frame boundaries, and with a fixed white balance it is checked that skin doesn't shift from frame to frame.

Mini assignment

In this assignment you will shoot a panorama on a tripod, of a wide landscape with a nearby object in its foreground.

1. Holding the camera vertically, fixing the exposure, white balance and focus, and leaving about a third of overlap in each frame, shoot a five-frame panorama.
2. Shoot the same panorama once more with automatic exposure and compare the two stitches.
3. Line up a nearby post or railing with a distant object and rotate the camera; look for the rotation point first around the screw, then by sliding the camera forward, and find the position where parallax disappears.
4. Stitch with two different projections and compare how the straight lines and the horizon change; if there are people in the frame, check by enlarging that the faces appear single and unbroken and that skin doesn't shift from frame to frame.

Check yourself

• Can you explain why you need to fix exposure, white balance and focus for a panorama?
• Can you say why parallax error is pronounced only in a close foreground, and how it is removed?
• In a group panorama, did you make sure people didn't fall on the boundary between two frames and that skin looked consistent?

Glossary

Mini quiz

1. What is the benefit of holding the camera vertically in a horizontal landscape panorama?

• A) Shooting faster
• B) Shooting fewer frames
• C) Being able to leave the exposure on automatic
• D) Increasing the panorama's height and resolution and leaving cropping room

2. Why are panorama frames shot with manual exposure?

• A) Because automatic exposure would meter each frame separately and create bands in the combined image
• B) Because manual exposure is sharper
• C) Because it increases the overlap
• D) Because it decides the projection

3. If in a panorama with a close foreground the railing looks broken where the frames join, what is the cause of the problem?

• A) White balance
• B) Too much overlap
• C) The camera being rotated around some other point instead of the entrance pupil
• D) The projection being spherical

4. In a group panorama, a person's face looks warm on one side and cool on the other along the line where frames join. What is the most likely cause and fix?

• A) Parallax; sliding the camera forward
• B) White balance changing between frames; fixing the white balance and keeping the person away from frame boundaries
• C) Too little overlap; shooting more frames
• D) Too much exposure; closing down the aperture

Answers

1. D — The long side of vertical frames forms the panorama's height; cropping room remains at the top and bottom.
2. A — Automatic exposure changes from frame to frame; the combined image carries inconsistent bright bands.
3. C — A wrong rotation point shifts near and far objects relative to each other; the foreground doesn't join up.
4. B — White balance that isn't fixed gives frames different colors; it stands out most on skin.

Summary card

• Hold the camera vertically; leave about a third of overlap.
• Fix the exposure, white balance and focus.
• Level the tripod; don't let the horizon wave.
• In a close foreground, rotate around the entrance pupil; remove parallax.
• Choose the projection by the scene's lines; keep people away from frame boundaries, check skin by enlarging.

Bridge to the next lesson

When the valley panorama was finished, your friend bent down to a small ladybird sitting on a leaf at the edge of the bridge. When they shot very close with a macro lens, only the insect's eyes came out sharp, while the back of its wings and its legs stayed blurred. When they closed down the aperture, the sharpness deepened a little but the photo softened, and the insect still wouldn't come out sharp from front to back. How does an insect become sharp from end to end? The next lesson tells about focus stacking, which extends depth by combining frames focused on different points.