Let’s get right to it – the three major factors that determine the quality of any photo you take with a DSLR (or any camera with manual settings).
Your aperture determines how blurry the background of your photo will be.
Higher Values: The higher this value is (eg: F32), the more in-focus background objects will appear. Higher aperture values will darken your photos as the lens allows less light reaching the sensor to reduce blur. To compensate of loss of light, lower your Shutter Speed and/or increase your ISO.
Lower Values: As values get lower in number (eg: F1.4), background objects will appear blurrier, giving your photos a “bokeh” effect. Lower aperture values will also brighten your photos. If your photos appear too bright, you may want to keep your ISO setting at the lowest value and your Shutter Speed higher.
Your shutter speed determines how blurry your photo will be when challenged with movement.
Higher Values: The higher the Shutter Speed, the less blurry your photos will be. As your Shutter Speed reaches higher values (eg: 1/1000), the shutter on your camera will open and close faster, causing less and less light to reach the sensor. This will make your photos darker since light has less of a chance to reach the sensor in time. You can compensate for this by increase ISO or lowering your Aperture.
Lower Values: The lower the Shutter Speed, the blurrier your photos will come out – if there is movement. Lower Shutter Speeds (eg: 1/2) keep the shutter on your camera open for a longer period of time, allowing more light to reach the sensor. However, if your hands are shaking or the subject you’re photographing is moving, lower Shutter Speeds will blur your photo as the sensor is exposed to light longer. If too much light is entering your sensor, increase your Aperture and keep your ISO at its lowest setting.
This is basically “fake light.”
Higher Values: Higher ISO values (eg: 25,600) will make your camera sensor more sensitive to light, but will increase the grain or “noise” in the photo. Higher ISO values are best used in low-light conditions such as indoor events or astrophotography, where shakiness and movement needs to be suppressed with higher shutter speeds or the use of a tripod.
Lower Values: Lower ISO values (eg: 50 or 100) will make your camera sensor less sensitive to light and will decrease the amount of grain or noise in the photo. Lower ISO values are best used in daylight conditions as you want to minimize the amount of light in your photos.