How to Use High ISO Speed Noise Removal on a Canon EOS 70D
As ISO increases, making the image sensor more reactive to light, you increase the risk of noise, which looks like bits of sand and is similar in appearance to film grain, a defect that often mars pictures taken with high-ISO film.
The High ISO noise-reduction filter on the Canon EOS 70D, found on Shooting Menu 4 and spotlighted in the figure below, attempts to do just what its name implies: eradicate the kind of noise that's caused by using a very high ISO setting. You can select from these settings:
Low: Applies a little noise removal
Standard: Applies a more pronounced amount of noise removal; this setting is the default.
High: Goes after noise in a more dramatic way.
MultiShot: Tries to achieve a better result than High by capturing four frames in a quick burst and then merging them together into a single JPEG shot.
Off: Turns off the filter.
This filter is applied after you take the shot, slowing your capture rate. In fact, using the High or MultiShot setting reduces the maximum frame rate (shots per second).
It's also important to know that High ISO noise-reduction filters work primarily by applying a slight blur to the image. Don't expect this process to eliminate noise entirely, and expect some resulting image softness. You may be able to get better results by using the blur tools or noise-removal filters found in many photo editors because then you can blur just the parts of the image where noise is most noticeable — usually in areas of flat color or little detail, such as skies.
So what about this mysteriously named MultiShot setting? Canon promises that this setting delivers a better result than the High setting by capturing a burst of four images and merging them into a single JPEG frame. It can work very well, but you need to understand these caveats:
Flash is not possible.
The feature is off limits when any of the following are enabled: Long Exposure Noise Reduction, Auto Exposure Bracketing, White Balance Bracketing, Dust Delete Data, Multiple Exposure, or HDR Mode. You also can't use the feature in B (Bulb) mode.
The merged images may not align properly, resulting in ghosting or blurring, if there's any camera shake during the exposures. So for best results, use a tripod. In addition, any moving objects may also appear blurry, so this feature works best with still life and landscape shots.
The setting automatically reverts to Standard if you turn off the camera, switch to a fully automatic exposure mode or Movie mode, or set the exposure mode to Bulb.
Direct printing of shots taken with this setting isn't possible.
Your end result is a JPEG photo, even if the Image Quality setting is set to Raw or Raw+JPEG. So if you're a Raw fan, don't use this setting.
If you opt for the MultiShot setting, you see a little multi-box symbol in the Shooting Settings screen, as shown in the figure below. The same symbol appears in the LCD panel.