Imaging 1

Exercise 4 – Bit Depth and Colour Modes

Corinne Brigden

§ This is a formative assessment instrument § You must be rated ‘Competent’ in this assessment item.

Imaging 1 – All Learning Outcomes.

1) Download the file ‘Img 1 – Exercise 4’ from eLearn and place it on the desktop. (Remember to delete this file from the desktop when you have completed this exercise). 2) How big is an A4 page in cm ? A= 21cm by 29.7cm 3) Open the file ‘Img 1 – Ex 4 - Granger-Rainbow.jpg’ in Photoshop :- 4) Select ‘Image -> Image Size …’ and ‘Image -> Mode’ and answer the following questions :– Image size in cm 29.63 by 20.32 Pixel Dimension (W x H) 3500 by 2400 Image size in megapixels (3500 x 2400) (take away 6 digits) 8.4 Resolution of the image (ppi) 300 Image size in megabytes 24.0 Colour Mode RGB Bit depth 8 per channel or 24 in all Hint: Use the Status line to display the image size – use the number on the left. 5) Use the ‘Image -> Mode’ menu to select the following modes / bit depths and fill in the table for each case listed. (Note: Use ‘Undo’ or the History list after each case to return to the original image state) :- Colour Mode Bit Depth per channel Total Bit depth No. of available colours Image Size (Mb) RGB 8 (8x3) 24 16.8 billion (256x256x256) 24.0 RGB 16 (16x3) 48 2.8x 10 to the power of 14 48.1 CMYK 8 (8x4) 32 (2x2 32 times) 4.3 billion 8.01 Greyscale 8 8 256 8.01 Bitmap # 1 1 2 1 Indexed Colour – 256 colours N/A N/A