Luminance histogram and RGB histograms in digital camera

One of the nice features in digital camera that cannot be found in traditional camera is the ability to display histogram.

Histogram shows the distribution of brightness in an image horizontally, and the amount of brightness vertically. A typical histogram looks like mountain as below. It is a handy tool to evaluate the exposure.

If you see the peaks are gathered on the left, the image is dark; and if you see the peaks are gathered on the right, the image is bright.

In normal situation, we would like the peaks to be in the middle, so that there is no under-exposure (too dark) or over-exposure (too bright). However, there are situations when dark is OK (e.g. shooting the Earth Hour scene) and there are situations when bright is OK too. Anyhow, you can make use of histogram to assist you in adjusting the exposure value of your picture.

Canon PowerShot S95 camera is able to show histogram in Shooting Modes and Playbank Modes. Histogram is not available in Auto modes (you won't need it, as the camera is taking care of the exposure adjustment for you), and is available for P, Tv, Av, M modes.

Canon PowerShot S95 has two customizable shooting displays, and the default setting for each of the shooting modes is different. You can use the Custom Display setting to turn histogram on or off for either one or both of the shooting displays. You can switch between the custom displays using the DISP. button.

Histogram can also be shown in Playback screen of Canon PowerShot S95. You need to switch to the Detailed Information Display playback screen in order to see the histogram of the picture. You can rotate among the available playback screens by pressing the DISP. button. You can set the default playback mode with the Review Info option.
Canon PowerShot S95 is able to display the RGB histograms of the picture in Detailed Information Display screen. You can toggle RGB histograms on and off by pressing the "Up" button when you are in Detailed Information Display.

The RGB histograms show individual graph for each of the Red, Green and Blue colour captured by the camera in the picture. This will be good piece of information to judge the colour and white balance of the picture.

Shooting modes of Canon PowerShot S95 - from fully automatic to fully manual (part 2 of 2)

In the 1st part of this article, I wrote about the shooting modes of Canon PowerShot S95 digital camera when you dial its mode dial clockwise from Auto (inclusive). Now I would like to share about what I learnt about the shooting modes of this camera when you dial anticlockwise from Auto.

P-mode (Program mode)

P-mode is very close to Auto mode as opposed to Manual mode, in the sense that the camera will automatically adjust the aperture and shutter speed for you. One of the major reason for using P-mode (and above) is the ability to save the picture in RAW format for post processing.

In P-mode, you can decide on the image brightness/darkness by controling the ISO level. You can also make correction to the white balance.

Normally, we like to keep the ISO level as low as possible to produce better quality photographs. That's why we want to take control over ISO level adjustment rather than using Auto-ISO.

ISO level controls the light sensitivity of the camera's image sensor. If the ISO level is too low, you might get camera shake (blur) in the photos. If the ISO level is too high, you will get a lot of digital noise (grains).

Canon PowerShot S95 supports ISO levels from 80 until 3200.

P-mode is handy when quick adjustment is needed to shoot the precious moment that won't wait.


TV-mode (Time Value, Shutter Priority mode)

TV-mode allows us to control the shutter speed, which determine how long the camera's image sensor is exposed to light.

You can use longer shutter speed to capture trailing motion effect, and shorter shutter speed to freeze the moving objects.

Canon PowerShot S95 supports shutter speed as fast as 1/1600 second and as slow as 15 seconds. You need TV-mode to set for slower shutter speed less than 1 second.


AV-mode (Apperture Value, Apperture Prioirty mode)

The aperture controls the depth of field of the photo.

Wider aperture enable you to produce photos of shallower depth of field, with clear focus object and blur out its background. Smaller aperture creates deeper image, with more sharpness across the whole picture.

AV-mode is best when shooting macro (close up) photography with wide aperture. It is also suitable to shoot for landscapes and sceneries with small aperture.

Canon PowerShot S95 supports apperture value from f/2.0 to f/8.0. The smaller the f-number, the larger will be the aperture. One of the selling point of S95 is its f/2.0 capability.


M-mode (Manual mode)

This is the fully manual mode for the professionals. In Manual mode, you take full control to adjust the aperture (rotate the front dial) and shutter speed (rotate the control dial). You can also decide on the ISO level.

As opposed to the P-Mode, the exposure reading is displayed on the LCD screen, and change accordingly when you adjust your aperture and shutter speed.


C-mode (Custom mode)

This is a place for you to instantly get back your favourite settings. You can make the adjustments and settings to the camera, then save them by using the "Save Settings" menu options. When you come to C-mode, you'll get back the settings and adjustments.

Shooting modes of Canon PowerShot S95 - from fully automatic to fully manual (part 1 of 2)

Canon PowerShot S95 is my first high end digital camera. Before this, I use a Kodak EasyShare LS743 point-and-shoot digital camera which doesn't have so much features (it is my 1st digital camera purchased in 2004 and is 7 years old now).

So, what I'm going to write down here is something new I just learnt in order to know how to use my PowerShot S95. If you are also a rookie photographer like me, probably this information might be useful to you too.

You can find the Canon PowerShot S95 camera's shooting mode dial on its top right. This is the dial to control among fully automatic, semi-automatic, and fully manual modes of photographing. It is also the place to switch between photographing and video-graphing.

AUTO mode

This is the fully automatic point-and-shoot mode to let the camera decide and adjust itself on almost everything to get a good quality picture (in the camera's A.I. points of view), and you cannot take control most of the settings in this mode. In Auto mode, your main concern is the focus (or focuses) of the image. Canon PowerShot S95 supports 9-point face detection AiAF, and also 1-point AF at the center.

This is a good mode to start with, before you familiar with the camera features and functions. You can straightaway start shooting photos with this mode right after you get it, even without reading its manual or knowing its controls and settings.

It seems that you can only save the photo in JPEG and cannot save it in RAW mode. Photo saved in RAW mode allows you to do post processing using Canon Digital Photo Professional software provided in the CD that bundled in the box with the camera.

Photo saved in JPEG image is 8-bit image and RAW mode is 14-bit image. This means more colour information is saved in RAW mode.

Low light (Candle) mode

This is a point-and-shoot mode used to take photos in dim environment. The camera will automatically use a wider aperture and higher ISO level for the picture. (Normally, we should use ISO level as low as possible to reduce noise in the picture)

It is ideal to capture dark situations, especially when you don't want to use the flash light. Example will be birthday cake with lighted candles in a dark indoor.

Scene (SCN) mode

This is a point-and-shoot mode to tell the camera to optimize itself specific to the subject you want to shoot. Sometimes, the camera Auto mode has no idea what type of subject you are photographing, and you can get better pictures using SCN mode instead of Auto.

The modes available for Canon PowerShot S95 are: portrait (shooting people), landscape (shooting scenery), kids & pets (capture the moment while they are moving around), beach (people in bright surrounding), underwater (aquatic life, with higher ISO shot), foliage (trees and leaves), snow (people in white snowy background), and fireworks (higher ISO shot).

Besides that, you can also make special effect to your photos in SCN mode. The effects available for Canon PowerShot S95 are: Super Vivid, Poster Effect, Sepia, Black/White, Color Accent, Color Swap, High Dynamic Range, Miniature, Fish-eye, and Nostalgic.

In addition, you can produce panoramic (long) photos using software, by merging the continuous shot of Stitch Assist pictures.

Video mode

One of the nice features of Canon PowerShot S95 is its capability to shoot 720p HD video.
There are 3 picture quality options for video shooting in this camera:

• 1280x720, 24 frames/second (fps). You'll probably need a Class 4 or higher SDHC Card to get a smoother movie with this setting.
• 640x480, 30 fps
• 320x240, 30 fps

Special effects available for Canon PowerShot S95 video shooting are Miniature Effect, Color Accent, and Color Swap.

... continue reading on Part 2