No Flash - Low Light Photography

by snapshot2 Moderator - 1/5/09 2:22 PM

In Reply to: (NT) Camera Tips and Information by snapshot2 Moderator

Low Light Photography and Why it is a Pain With A Small Camera.
Shooting Without Flash.

The biggest remaining shortfall for small digital cameras is low light performance.
The larger DSLR (digital single lens reflex) cameras perform much better due to their large CCD or CMOS image sensors.

A camera (of any type) must have a certain amount of light to get a perfectly exposed image.
During the day time, that is not a problem because there is an abundance of light.
The camera uses 3 methods to reduce the amount of light.
1. Shutter speed - the faster the shutter speed, the less light that enters the camera.
2. Aperture setting - This works like the iris of the eye. It closes the diameter of the eye to reduce the amount of light entering the camera
3. ISO setting - This is similar to changing 35mm film to a faster or slower film.

When the sun goes down, the camera must use those same settings to see that the camera gets enough light to take a perfectly exposed image.

You can open the aperture larger and larger to let in more light.
Aperture is measured in f-stop settings.
How far it can open is determined by the lens rating.
A common small camera lens is rated at about f/2.8 to f/8.0
The smaller the number, the more light is let into the camera.

You can raise the ISO setting. Modern small digital cameras are usually rated from in steps of 100, 200, 400, 800, 1600.
The higher the number, the more light is let into the camera.

You can slow down the shutter speed and that lets in more light.
Shutter speeds are usually rated from several seconds to about 1/2000th of a second.
To shoot at 1/2000th of a second you need lots and lots of light.

In low light (or inside a house) you have to use all of the settings to get enough light.

1. Your aperture is usually maxed out first. It will be set to f/2.8
its brightest setting.
2. You will still not have enough light so the camera raises the ISO setting to a high number.
3. If you still need more light the camera will reduce the shutter speed.

And that is where you start to get into trouble.
If the shutter speed is set slower than 1/60th of a second, most people can not hold the camera steady enough to prevent blurring due to camera shake (movement). And at slower shutter speeds you will find that people movement (action) will start to show up as motion blurring.

So with a camera that has manual controls, like the Canon G9, you can set the shutter speed manually at 1/60th of a second and the camera will automatically raise the ISO setting higher to get enough light.
And that is where you get into trouble.
Due to the small size of the image sensor, the higher you set the ISO, the more noise you will get. When you get to ISO 200 you start to see noise. ISO 400 is usually very noticeable and by the time you get to ISO 1600, the noise is so bad that it ruins the image.

Here is what noise looks like:
http://www.dpreview.com/reviews/canong9/page7.asp

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In low light, you can end up with a slow shutter speed and lots of noise.
Not a good combination for a good picture.

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Since low light can mean many different settings, you can play with the camera and see exactly what problems your low light is causing.

Set the Canon G9 mode switch to Aperture Priority, labeled as Av on your mode dial on top of the camera.
Look at your User Manual and see how to set the aperture.
Set it to f/2.8
Now set your ISO setting to 100. (read your user manual).
Point the camera at someone and press the shutter switch half way down.
Look at the LCD and see what shutter speed the camera has chosen.
If it is slower than 1/60th of a second, you probably need to use a tripod to support the camera to keep from getting camera-shake blurring. Then you will get a properly exposed image with no noise.
Anyway, take the picture.

Just for kicks, try a shot using Shutter Priority:

Set the G9 camera to Shutter Priority.
I believe it is marked as Tv on the mode dial on top of the camera.
Then set the shutter speed to 1/60th of a second. See you User Manual to find out how to set it.

Set the ISO to "Auto"

Now point the camera a someone and press the shutter button half-way down.
You should see on the LCD display, the ISO setting and Aperture setting the camera has chosen.
Most likely the Aperture will be set to f/2.8 (the brightest setting).
If the ISO is set above 400, you will get noise in your picture.
If it is 1600, you will likely get a very poor picture.
Anyway, take the picture.

So, if your particular low light is too low, you will be stuck with the decision to hand hold the camera at 1/60th second and get a noisy picture, or to put the camera on a tripod and get a good picture.

One final tip:
Do not use any optical zoom during the tests above.
Most lenses will lose some light when zoomed.
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Solution.....add more light.
Photographic flood lights are very helpful, and not too expensive.
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