Using the exiv2 command linee tool (should be packaged into every GNU/Linux distribution), you can view all the Exif metadata contained in each photo, including unknown values:
exiv2 print -p a -u IMG_1858.JPG
There are several proprietary Canon tags stored for each photo, as far I know, there is not a comprensive guide to that tags. An useful resource can be the Metadata reference tables, an index of the names of all tags recognized by Exiv2 library.
Here are some of the more interesting ones. Notice that Exiv2 library v.0.24 is rather incomplete and sometimes misleading in reporting Canon MakerNote tags!
|Exif.CanonCs.AFPoint|| Auto-Focus frame setting. Exiv2 library is incomplete or misleading, here it is the true meaning of values:
|Exif.CanonSi.SubjectDistance||Subject distance, as per manual focus or Auto-Focus. The number seems to be the distance in cm, where infinity is reported as 6553.|
|Exif.CanonSi.0x0014||According to Exiftool source code, this should be FocusDistanceLower, where the SubjectDistance is actually the FocusDistanceUpper. It is supposed that the camera knowns not the actual subject distance, but just two distances where the focus point is in between.|
|Exif.Canon.0x0027|| This multi-byte tag contains, among others, Dynamic Range Correction and Shadow Correct settings. Byte 4 (counting from zero) is a bitwise representation, under investigation.
Byte 16 is the Dynamic Range Correction:
0 ⇒ Off
1 ⇒ Auto
200 ⇒ 200%
400 ⇒ 400%
|Exif.CanonCs.ISOSpeed||ISO speed mode. Version 0.24 of Exiv2 library is missing some values, see issue #1217.|
|Exif.Photo.ISOSpeedRatings||The actual ISO speed used for the shot.|
|Exif.CanonSi.ISOSpeed|| Manual selection of ISO speed? This value is equal or very close to
|Exif.Photo.FNumber||F-number: the ratio of the lens's focal length to the diameter of the entrance pupil.|
|Exif.Photo.ApertureValue|| The lens aperture in APEX value. Practically it is always the same value as
|Exif.CanonSi.TargetAperture|| Its value is always close to the
|Exif.CanonSi.ApertureValue|| Sometimes it differs for few decimal points from
|Exif.Photo.ExposureTime||The exposure time in seconds or fractions.|
|Exif.Photo.ShutterSpeedValue|| The shutter speed in the APEX units. It differs slightly from
|Exif.CanonSi.TargetShutterSpeed|| Always equal to
|Exif.CanonSi.ShutterSpeedValue|| It differs sligthly from
|Exif.CanonSi.MeasuredEV||May be it is the calculated light value for a proper exposure. See here.|
|Exif.CanonSi.MeasuredEV2||Unused? Seems to be always -6.0|
i-Contrast is a post-processing filter applied by the S120 after the shoot. It can be applied at shoot time (supposedly on the RAW image) using two different pre-sets (see below), or it can be applied on the JPEG image in play mode using four modes.
Applying i-Contrast in play mode is rather pointless, just use your preferred photo editing software to get better control on the exposure. Using i-Contrast at shot time can perhaps get better results if it actually operate on the RAW image: adjusting the exposure before JPEG compression can lead to better results than post-processing on the JPEG image. But actually we don't know how i-Contrast operates at shot time, so - if you have any concerns about a bad exposition - just shot in RAW mode and do post-processing in your preferred software.
One user in this forum post says: I've heard i-Contrast can be used later on. So, the best is to take photos iContrast off, and applying later if necessary. Then you will have more time to check if it is better. The bottomline is, that the iContrast function is only a post processing, and does nothing at the exposure. Therefore you can get even better result from the RAW with PS.. In fact, if you shoot in RAW (or RAW+JPEG) the i-Contrast settings are unavailable.
Anyway, in P mode you can activate i-Contrast in two modes:
In playback mode you can instead apply i-Contrast in four variant: Auto, Low, Medium and High. Whatever it means!
The Canon S120 features lens stabilization, it means that it has motors, gyroscopes and/or accelerometers attached to the lenses, which try to counteract the camera movement. You can choose one of this IS settings from the menu:
If you choose Continous you can see the effect on the LCD display: set the maximum zoom and try to tap slightly and repeatedly on the camera: the image on the screen is more steady than if you set the IS to off.
For movies recording, beside lens stabilization, it is possible to enable also the image stabilization via software. The video actually records a smaller portion of the screen: the exceeding part which is cut-off, is used when required to compensate for camera shaking.
You can enable or disable the software image stabilization for videos from IS Settings menu, Dynamic IS:
The resulting video - when software IS is active - is scaled (enlarged) by the camera software, so that the resulting size is the same as per video without software IS. This means, for example, that a Full HD video will be 1920×1080 pixel regardless of the software IS setting, but our test revealed that the actual area of the video is reduced by 12% in both width and height.
Safety Shift is an option that interferes with manual settings in Tv and Av modes.
Pressing the shutter button halfway will show the aperture value or the shutter speed selected automatically to obtain a standard exposure, if such exposure cannot be obtained, the value is displayed in orange color. But if Safety Shift is enabled, the manually selected value (aperture or speed) will be corrected and displayed on the screen. To enable this option, press the [MENU] button and search the [Safety Shift] into the camera tab.
In photography, a neutral-density filter is a filter that reduces the intensity of all colors of light equally. The purpose of a neutral-density filter is to reduce the amount of light entering the lens, allowing combinations of aperture and exposure time that would otherwise produce overexposed pictures.
For example you can use it to allow an high aperture value and get a lower depth of field.
Here it is a Python script to decode Exif metadata from photos taken by the Canon PowerShow S120: canon-metadata.