ISO Questions

I took several shots today in fairly bad lighting conditions. I wanted to avoid using the flash because I don't like the way the pic looks with the flash. Anyways, the pictures came out extremely grainy. The photo specs are Shutter: 1/8, Aperture 4.0 and ISO 400. Can someone tell me what went wrong here? I shot these pics without a tripod so is it that the shutter speed was too slow to do it by hand? If this is the case what about the pics that came our clear but still pixelated with a shutter speed of 1/30 and same aperture and ISO??? Any help is so greatly appreciated as I am just learning what the heck I am doing, thanks

cmdecaro

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Comment by Alan Ang on December 22, 2008 at 5:37am: The higher the ISO the picture will become more grainy. So to avoid, use low ISO (100-200) with slower shutter speed and of course a tripod is definitely a must. Try out with different shutter speed and aperture until you are satisfy with the picture. This is the way to learn.

Comment by CameraClicker on December 22, 2008 at 5:04am: The ISO setting is an amplifier control (like the Volume knob on your radio). All amplifiers increase signal amplitude and at the same time, increase noise amplitude. Due to the size of photosites (Pixels) on the sensor, some sensors have a better signal to noise ratio than others. Those with a better signal to noise ratio produce a cleaner result after amplification. Larger sensors typically have larger Pixels which have more signal and possibly less noise due to pixel spacing on the sensor.

Pixels provide signal based on the amount of light that strikes them. The noise is constant, so in low light, the signal to noise ratio is not as good and the noise is more apparent.

Picture subjects, being relatively static (1/1000 sec = 1 ms, which is eons to modern electronics), offer the opportunity to be re-sampled many times during an exposure. Some of the camera manufacturers have attempted to take advantage of this to reduce noise through software. Low light picture quality varies dramatically by camera model.

In low light try over exposing slightly with a slower shutter speed or wider aperture. Bracing the camera with a tripod, clamp or bean bag may be necessary.

Comment by Sean on December 21, 2008 at 10:28pm: Most grain comes from ISO and low light...sometimes even if you have it at 100 you will still get grain with really bad lighting because there are only so many colors in the spectrum that are really close to black...hence you get grainy dark images. If you are going to do long exposures see if your camera has a noise reduction setting for long exposures.
When you talk about the flash are you talking about the on board flash or a separate flash unit? If it is a separate unit you can get a shoe and a pc cable so it will look like it is a light source from somewhere else, or bounce it off a wall or ceiling.

Comment by Keith Willette on December 21, 2008 at 7:53pm: Long exposures can increase grain/noise if shooting diggi. Yes the shutter speed is too slow for hand held, even w/ image stablization. Anything under 1/60th of a sec can give you blurr. If using IS you could have a slightly slower shutter speed but not much slower :)