User Tools

Site Tools


Sidebar

No ai soldati italiani all'estero

Indice

Eventi

Energia

Rigacci.Org usa energia elettrica da fonti rinnovabili, grazie al gruppo di acquisto Merci Dolci.

Merci Dolci - Energia Rinnovabile

Software libero!

Petizione contro i brevetti software

Faunalia: Soluzioni GIS professionali

Debian

www.gnu.org www.kernel.org

doc:appunti:hardware:canon_s120

Canon PowerShot S120

Canon PowerShot S120

Exif Tags

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!

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 selection1-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.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 #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 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.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 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 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 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 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.

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.

doc/appunti/hardware/canon_s120.txt · Last modified: 2019/03/22 11:50 by niccolo