====== Canon PowerShot S120 ====== {{.:canon_s120:canon-s120.jpg?direct&200|Canon PowerShot S120}} ===== Exif Tags ===== Using the **exiv2** command linee tool (should be packaged into every GNU/Linux distribution), you can view all the [[wp>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 [[http://www.exiv2.org/metadata.html|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! ^ Camera Settings ^^ ^ Exif.CanonCs.AFPoint | Auto-Focus frame setting. Exiv2 library is incomplete or misleading, here it is the true meaning of values:\\ ''(0)'' => **None** (Manual Focus)\\ ''(16390)'' => **Face AiAF**\\ ''Manual AF point selection'' => **1-point** | ^ 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%** | ^ ISO Speed ^^ ^ Exif.CanonCs.ISOSpeed | ISO speed mode. Version 0.24 of Exiv2 library is missing some values, see issue [[http://dev.exiv2.org/issues/1217 |#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.ISOSpeedRatings'', sometimes it has decimals. This value seems to be always 200 when ISO speed is in auto mode. | ^ Aperture ^^ ^ Exif.Photo.FNumber | [[wp>F-number]]: the ratio of the lens's focal length to the diameter of the entrance pupil. | ^ Exif.Photo.ApertureValue | The lens aperture in [[wp>APEX_system|APEX]] value. Practically it is always the same value as ''Exif.Photo.FNumber''. | ^ Exif.CanonSi.TargetAperture | Its value is always close to the ''Exif.Photo.FNumber'', sometimes it differs for few decimal points. | ^ Exif.CanonSi.ApertureValue | Sometimes it differs for few decimal points from ''Exif.CanonSi.TargetAperture''. | ^ Exposure ^^ ^ Exif.Photo.ExposureTime | The exposure time in seconds or fractions. | ^ Exif.Photo.ShutterSpeedValue | The shutter speed in the [[wp>APEX_system|APEX]] units. It differs slightly from ''Exif.Photo.ExposureTime''. | ^ Exif.CanonSi.TargetShutterSpeed | Always equal to ''Exif.Photo.ShutterSpeedValue''. | ^ Exif.CanonSi.ShutterSpeedValue | It differs sligthly from ''Exif.Photo.ExposureTime'' and ''Exif.CanonSi.TargetShutterSpeed''. | ^ Ligth Value ^^ ^ Exif.CanonSi.MeasuredEV | May be it is the calculated light value for a proper exposure. See [[http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Canon.html#ShotInfo|here]]. | ^ Exif.CanonSi.MeasuredEV2 | Unused? Seems to be always -6.0 | ===== i-Contrast ===== **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 [[https://www.dpreview.com/forums/thread/2679932|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: * **Dynamic Range Correction**: to avoid washed-out highlights * **Shadow Correct**: to preserve image in shadows In playback mode you can instead apply **i-Contrast** in four variant: **Auto**, **Low**, **Medium** and **High**. Whatever it means! ===== Image Stabilization (IS) ===== 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: * **Continous**: (Intelligent IS) applied automatically * **Shoot Only**: applied only at shoot time * **Off**: disabled 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. ==== Dynamic IS ==== 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**: * **Option 1**: enable software stabilization, labeled as "//Enhanced stabilization//". * **Option 2**: disable software stabilization (use only lens stabilization), labeled as "//Reduces camera shake//". 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 1920x1080 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. ===== Manual Focus ===== * Manual Focus (**MF**) is available in **P**, **Tv**, **Av** and **M** modes. * Press **[Left/MF]** on the //control dial// and choose **[MF]**. * Press **[Up]** or **[Down]** on the //control dial// (or rotate it) to adjust the focus. * Press **[Right]** on the //control dial// to change zoom magnification. * If **Peaking** option is **On**, edges in focus area are colored in red. See [MENU], camera tab, **MF Peaking Settings...**. * Press **[MENU]** if you want to enable **Focus-BKT**: in that case three images will be shoot, with slightly different focus settings. * Press **[FUNC./SET]** button to accept the focus. * If the **Safety MF** option is **On** (see the [MENU], camera tab): * Move the **focusing frame** (orange rectangle) tapping the touch screen. * Press **halfway the shutter button** to **refine the focus**. Warning! The instruction manual talks about //fine-tune//, but it is not clear how much can be this fine tuning. Some users reported that a manual set of one meter, was corrected by fine-tune to infinite, beacuse no objects to be focused were in the one meter range. ===== Safety Shift ===== **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//. ===== Neutral Density Filter ===== 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**. ====== Python Script Download ====== Here it is a Python script to decode Exif metadata from photos taken by the Canon PowerShow S120: **{{.:canon_s120:canon-metadata.txt|canon-metadata}}**. ====== Web References ====== * **[[https://www.exiv2.org/tags-canon.html|Exiv2 - Canon MakerNote Tags]]** * **[[https://www.dpreview.com/forums/post/35260903|Wow.... focus distance reported in EXIF???]]** * **[[https://photo.stackexchange.com/questions/105977/what-is-focus-distance-lower-upper-and-how-is-it-different-from-depth-of-field|What is “focus distance lower/upper” and how is it different from depth of field?]]** * **[[https://www.dpreview.com/forums/post/51962463|Distance in EXIF]]**