Why aren't my night shots sharp even when I shot at ISO 100 on a tripod?

Question

I recently purchased a tripod because I really want to do some night photography. I have tried practicing with street lamps, moon shots etc with my Canon 550D and 70-200 f/4L and most of them are shot at ISO 100 and at max ISO 400. Although there is improvement over handheld but when I zoom into a region (or crop the moon) I can see noticeable noise.

So, my question is, what are the things to consider in night shots to get sharp, noise free images? What are the additional steps I can take to get better night images?

Answer 1

Some of the following suggestions will depend on your camera (I have a Nikon so I'm not sure about Canons).

1. Rather than press the shutter button directly, try using a remote shutter release or alternatively there may be a timer function which delays the shutter - this will allow (at least some) vibrations to settle down.

2. Look in your camera manual to see if you can use mirror lockup - this may also help.

3. Can you attach a weight (even your camera bag) to your tripod to improve its stability - some tripods have a little hook off the center column for exactly this reason.

4. If you wish to use a higher ISO, you could use noise reduction software, such as Noiseware, which has a free version: http://www.imagenomic.com/nwsa.aspx Or other software to try includes Noise Ninja.

Answer 2

the long exposure times needed will cause things to move during the exposure if there's only the slightest breeze or tremor (if you're shooting indoors on a wooden floor, you stepping away from the camera after setting the exposure timer can be enough). That causes perceived unsharpness, but in reality it's motion blur.

Noise you'll always have with digital when using long exposures, it's a side effect of the sensor generating stray photons when heating up. When there's a lot of light coming in, those get swamped out and you never see them, when there's hardly any light at all coming in they become apparent.

Using slide film alleviates that to a large degree. Films like Velvia 100 are quite capable at exposures of up to several minutes with a minimum of problems (they do start to get some colour degeneration at very long exposures, but no noise).

Answer 3

I have a 500D and recently took some tack-sharp night shots with the 24-104mm f/4L lens - should be of similar quality as your 70-200. Here's what I did.

• Got myself a new tripod (well I got one for Christmas). I used to have a cheap tripod, and there's a huge difference. Especially in windy conditions, the cheap tripod cannot take sharp pictures. Also if you have a center column in the tripod, don't extend it unless you have to. Extend the legs instead.
• For focusing, I switch to live view. The focusing in live view is more precise. Also, you can zoom in 10x in live view and make the focusing manually. Then switch off live view, and change the lens to manual focus, so you don't accidentally move the focus point when taking the shot.
• Turn off image stabilization on the lens (some lenses will introduce movement when trying to counteract it, some lenses can work with IS on tripod, but if unsure, turn it off)
• Turn on mirror lock-up. That means you have to press the shutter twice, first time locks up the mirror, second time takes the picture.
• For most of the pictures I simply used the camera's build in timer function, allowing the camera to stabilize itself after pressing the shutter button. But a cable release is better.

A note on mirror lock up. When hand holding the camera, your hands will absorb the vibration caused by the mirror movement. But placing the camera on a rigid tripod, the vibration will bounce back into the camera. The amount of vibration is very small though, so for longer exposures, enabling mirror lock up will not have a profound effect.

Also for very long exposures, using a cable release, or build in timer may not be necessary, as maybe you will get vibration for the first 1-2 seconds of e.g. a 20 second exposure. But if you want the sharpest possible pictures, you should.

The pictures however are not noise-free. The body has a cheap sensor that does not perform well in regards to noise. When shooting long exposures, the sensor will heat up, and a heated sensor generate more noise. That is also the reason why you should only use live-view for focusing.

Also note that if the subject is illuminated by tungsten light, there will be very little image information in the blue channel, or in other words, the blue channel will be very noisy. When adjusting the white balance, you will amplify the blue channel quite a lot, therefore also amplify the noise. Most of the tack sharp night shots I took got converted to BW which produced significantly less noisy pictures, as I could skip white balance correction and take image from the red and green channels.

Answer 4

If you are using really looong shutter speeds you will get movement of the astronomical subject you are taking, this may look like blur if it is only a minute or so. The only way you can get around that is with a motorised equatorial mount used for telescopes.

Clearly this will not apply with terrestrial structures such as lamp-posts

Answer 5

I' m pretty sure your shots are blurry at night because there is not enough light (initially) for the camera to focus. If you are taking photos of street lamps or the moon, it's only a specific part of the photo that provides some kind of light. To get your image in focus, I would recommend experimenting with your focus metering options on your camera.

Answer 6

A few things to try, YMMV:

• Set the parameter for long exposure noise reduction. It will take twice as long per exposure (a 10 sec exposure will take approximately another 10 sec to process) but the results can be quite good.

• Use live view and zoom in fully to set your focus manually.

• Take an exposure of the same length with the lens cap on before your real exposure, then try dark frame subtraction techniques in post processing.

+1 to Trican's list as well.

Answer 7

I apologise if any of these items have been covered but I think the following are the most likely explanations:

1. Tripod is simply not sturdy - this could be because the camera is too heavy for the tripod and the head is not supporting the weight properly, or because the wind is moving it.

2. You are moving the camera when you press the shutter button - this is tough to avoid with long exposure shots so you should use a remote lead or if you don't have one of these you can set the camera timer.

3. Enable mirror lockup and use live view on the camera. Sometimes the mirror slap on an SLR can cause slight blur in the shot when the camera is still.

4. Disable stabilisation on the lens itself (if present) as having this functionality enabled when the camera is stable can actually introduce blur into your otherwise still shots.

If the above are all taken care of then your shots should be incredibly sharp. Of course this only applies if your subject is stationary. If your subject is not completely still you will have blur or motion in your shots and this cannot be avoided without using flash, higher ISO, higher shutter speeds, panning or a combination of all of these techniques. Also don't forget when taking photos of the moon that the moon orbits the earth and the earth is spinning on its axis so long exposure shots of the moon or stars will always end up with visible movement. This can be fixed by using an equatorial mounted telescope but without some extra equipment your options are going to be limited.

In order to reduce noise you will generally need to use the lowest ISO possible. You will want to limit your exposure times, the longer they are the more noise you should expect. Some cameras are just better at handling noise than others, full frame is generally considered to be better for noise. Low light photography is generally where the more expensive cameras tend to be demonstrably better.

Answer 8

You have not given any details on the tripod you bought, but with tele lens rigidity and weight of the tripod becomes quite important. As a rule of thumb, head and legs and extra weights should weigh at least as much as the equipment you have above the head; even more in windy conditions.

In his article, Thom Hogan suggests two simple ways to test if the tripod gives enough support for your system:

• set your camera to take a shot with 1/2s shutter speed, watch the end of lens while the shutter opens and closes; or
• pull down on the end of lens slightly and release.

In either case, the end of lens should not move.

Answer 9

My problem solved - silly schoolboy error: The lens focus goes way past infinity. There's an 'L' shaped marker on the focus ring between '10m' and the infinity symbol. Infinity is where the vertical of this 'L' mark is, not where the infinity symbol is - easy to see in the light, but not when you're trying to photograph the Milky Way at 8,000ft on a freezing October night.

Experiment with your camera focus during the day, using live view and the digital zoom (magnification) on a distant horizon if you want to calibrate the infinity point.