Stranica 69 [69]
OCR
Display mode Select the option to show the RGB Histogram, if this is available. The histogram is a useful guideline to assess the exposure of an image. It is a simple graphical representation of data collected. Digital images are made up of millions of tiny square pixels. In every 8 bit digital image each pixel is assigned a brightness value between 0 and 255. The camera scans each pixel and adds up how many pixels there are at each brightness level. Then it translates that into a frequency graph called a histogram. On the horizontal axis 0 at the left of the histogram represents pure black and 255 at the right is pure white. The vertical axis shows the number of pixels recorded at that brightness value or frequency. The more pixels at a specific brightness value, the higher the line. It should be noted however, that the on-camera histogram shows the histogram of the incamera conversion to J] PEG (see Chapter 3) and not that pertaining to the RAW data, and as most cameras apply a fairly strong S-curve to the RAW data so that the J PEGs have a more film-like response, the result is that the on-camera histogram often suggests that the highlights in the image are saturated when, in fact, they are still comfortably in the range.” Summary General camera Settings: RAW (check RAW file will be saved by and exported from the Image-recording format camera) Image quality (bit depth) 16 bit (or highest available) Colour space SRGB White balance Set custom white balance if required Camera mode Manual mode (M) Picture style (if available) Neutral Set camera to timer (2 s or 10 s), to avoid camera shake Self-timer mode ; during long captures or use a remote release shutter Display mode Check the RGB Histogram box vi. Exposure settings The settings for the following parameters determine the exposure of the image and will depend on the type of object being imaged and the type of imaging being carried out. Exposure is determined by three camera settings: ISO speed, aperture (F-stop), and shutter speed (the “exposure triangle"). Below are some general guidelines on setting these parameters, for more information the reader is referred to designated texts or websites on photographic techniques and concepts.” Version No. 1.0 61 Date : 14/10/2013
