Why is it so hard to do a panorama at night?

Shooting a panorama at night is a difficult task, and as such I have yet to shoot a night panorama of Burning Man that is as sharp as my daytime ones.

In general night photography is harder. When you are trying to combine dozens of shots into one image, if you goof up just one of them, you run the risk of having an image with a big blurry section. And indeed, this is often what happens. It's hard to check right there, even on a digital camera, if a shot is perfectly sharp. Especially if you are shooting a lot.

Let's examine the issues:

F-Stop and illumination

Turns out to get the very sharpest image from a lens, and to put a wide range of things in focus, both close and far, you must stop down your lens, typically to F/8. I will do daytime shots at F/8 or F/11. However, on a fast lens, shooting at F/8 means an exposure 16 times longer than at F/2. And that's only if you were shooting something equally bright -- of course things in the night are much dimmer than they are in the day.

So a night photo often requires an exposure of 1 or 2 seconds, where your day shot might use 1/500th of a second. You can even handhold 1/500th but 2 seconds requires not just a tripod, but a sturdy one.

There is an answer, namely a camera that can do high ISO. High ISO means more noise in your picture, and until recently it meant a lot of noise in your picture. The newest cameras are able to do much better, but if you plan to boost gamma (as you tend to want) you can't do too much ISO boosting.

Stable platform

As noted, you need a good tripod. But even that's not enough. Most ad-hoc structures actually move a bit in 2 seconds, especially if people are on them or the wind is blowing. This is especially true for Burning Man structures. Scaffold towers are completely useless. Even the 11 story steel Babylon tower in 2008 was no good! Only rarely have I found a solid tower able to do really sharp long exposures.

Even your tripod may not be up to it. If you put a long lens on the camera, then it becomes less stable. Anything, even pressing the shutter, will introduce vibrations that will blur the photo. That's why for night shots you use a remote shutter release cable.

Worse, even the movement of the mirror inside the camera will make enough wobble to blur the shot. For the best shots you must use "mirror lock" mode where you move the mirror up, wait and then shoot. It makes each shot take several times as long.

Sadly, multi-row panorama heads need to put the camera on a long moment arm. That's just asking for trouble and vibration. For night panoramas, it is better to stick to single-row pano heads, or to just use the regular tripod and work to avoid the paralax problems that come with this.

Moving people

To make it worse, people, cars and things affected by the wind are moving in your shot. In a 1 second exposure they will be blurry, you have no choice. This is where you may decide to bump the ISO and get more noise, to avoid having too much blur from this.

Wide range of lighting

In the sunlight, everything is lit by the same source. There are shadows and there are things directly lit but it's all in a modest range. At night, you are shooting everything from the light bulbs themselves to things illuminated by them, or by the moon. It's like trying to have the sun and something lit by the sun in the same shot.

You can't easily stop the bulbs from being overexposed if you are going to see anything else. But you can't do it too much or you will lose their colour. (Many cameras try to figure out the colour of overexposed lights.)

One trick is to bump the gamma of an image with a curves adjustment. This brightens the shadows, so you can see things like dim objects lit by lights or the moon, and doesn't brighten the very bright things that much. However, this really brings out any noise in the image so it can't be done with high ISO.

Another new trick is called high dynamic range or HDR photography. This involves shooting several shots at different exposures. A fast one for the lights, long ones for the backgrounds. This can do interesting things, but of course means there will be even more motion between shots. If you shoot a moving car the lights might get caught OK in a fast exposure but the body will be a long blur if it's even still in the shot.

After doing HDR you must compress it all back into the normal range a screen or piece of paper can see, which is still far less than the real world.

Stitching it

After you get it, you have to stitch it all together. Sometimes the black zones are your friend -- you can have blending mistakes and there is nothing to see. Other times they are your enemy, in that you can't find anything to mark how to overlap the photos. That's OK in a single row but a problem in a multi row shot.