Monday 29 August 2011

Non-Destructive Image Editing

Part I – The Evolution of Non-Destructive Imaging


Define ‘Non Destructive Imaging’

In general, NDI refers to imaging processes where the source image may be adjusted in
a way that leaves the original data intact.


List four challenges introduced by digital photography :-
  1. The creation of a vast number of photos
  2. The need to apply identical adjustments to many photos in one operation
  3. The need to interpret a single source image in multiple ways (black andwhite, and color, for instance)
  4. The desire to take advantage of rapidly evolving imaging technology to reinterpret images with more capable software in the future
What is meant by a ‘Derivative File’ ?

You might have an exact duplicate of the photo file—a copy—or you might have
a version of the photo file that has had some adjustments incorporated—which we will call a
derivative file, since it’s derived from the original.
 

What are two problems with using ‘Save As …’ to create derivative files ?
  1. might be hard to sort out later.
  2. in terms of storage.
What is ‘Self Referenced Non Destructive Imaging’ ?


In Photoshop 3, layers were introduced and it became possible to save multiple versions 
of the same image within a single file. This helped with the management difficulties associ-
ated with derivative file workflow but did nothing to address the storage needs. In Photoshop 4adjustment layers were introduced, and it became possible to wrap up the source image with a set of instructions (or many sets of instructions) for rendering the photo. Let’s call this 
self-referenced NDI.


List two advantages of Self Referenced NDI over the use of Derivative Files :-
  1. Using self-referencing files offers some significant advantages over derivative file workflow. Since the instructions to adjust the image take up much less space than creating an additional file, it’s much more economical in terms of storage.
  2. Using adjustment layers also offers you the ability to create a separate interpretation of the file—a black-and-white version, for instance—while still making use of some of the work done for other versions, such as retouching.
 
Define ‘Parametric Image Editing’ :-

In video editing, referenced file editing is again
necessary because file sizes are too large and processors are too slow to work with the full-
resolution assets.
We’re going to call the editing of images by creating instructions or parameters parametric image
editing (PIE). For the purposes of this paper, we’ll call the software that does this PIE software.
 

What is the difference between a Live Rendering and a Fixed Rendering ?
Nearly all digital cameras produce a mosaiced image as a raw file. Although this may look like a regular photo once it’s displayed in software, in reality it is a checkerboard of red, green, and blue values that are transformed into an RGB image when the file is processed by a Raw File
Converter. When we look at one of these raw photos on our computer screen, we either see a 
live rendering of the mosaiced data, or we see a fixed rendering in the form of a JPEG preview that has been made by the camera and placed inside the raw file.

List three advantages of NDI :-



  1. Multiple photo manipulation: Digital cameras have the ability to produce large numbers of similar files in a way that scanning photos never would have. Parametric image editing (PIE)the process of editing images by creating instructions or parameters for adjustment—makes it easy to apply settings made for one photo to many others very quickly.
  2. Unlimited undo: Since all image adjustments are saved simply as processing instructions, it’s easy to change those instructions to create a different interpretation of an image. In order to save the additional variations, all the user needs to do is to save the instructions that are used to create the variations.
  3. Space savings: Now that computers are fast enough to create renderings from the images as needed—let’s call this just-in-time rendering—the user can build a library of images that consists largely of the source images and the rendering instructions. Since instructions are a lot smaller than pixels to store, the storage requirements are greatly reduced.


Wednesday 3 August 2011

Ex 4 - Colour Theory



Exercise 4 – Colour Theory 2

1.     Start Photoshop and open the document you created in Exercise 3.
·       What is the keyboard shortcut for opening an existing Document ?  command “O”   
2.     Change the Blending Mode of the layer Group to ‘Pass Through’.
3.     Make the background layer the working layer by selecting it in the Layers palette.
4.     Use the Rectangular Marquee tool to select the top half of the image.
5.     Use the Paint bucket tool to fill this area with Black.
·       What is the keyboard shortcut for this tool ?             command “B”    
6.     Change the Blending Mode of the ‘Red Circle’ layer to ‘Lighten’.
7.     Do the same for the Blue and Green Circle layers.
8.     Select the Move tool.
·       What is the keyboard shortcut for this tool ?             “V”      
9.     Turn on the ‘Auto-select’ option and set it to ‘Layer’ (Not ‘Group’).
10.  Drag the three circles so they all overlap each other.
11.  This simulates the     RGB                 Colour System.
12.  Rename the group of circle layers to indicate this.
13.  Add a text layer (using white text) saying ‘<name> Colour System’.
14.  Select the group of circles in the layers palette.
15.  Duplicate the group using ‘Layer -> Duplicate Group …’.
16.  Use the Move tool with ‘Auto-Select’ set to ‘Group’ to drag the new group to the bottom half of the page.
17.  Change the Blending Mode of the this group to ‘Difference’.
18.  This simulates the     CMYK               Colour System.
19.  Add a text layer saying ‘<name> Colour System’.
20.  Save the document as ‘Ex 4 – Primary_Colours.psd’


Ex 3 - Primary Colours


Exercise 3 – Colour Theory 1


1.     Start Photoshop and create a new document with the following properties :-
·       Name : ‘Ex 3 – Primary Colours’
·       Size : A4 @ 300dpi
·       Colour Mode : RGB / 8 bpc
·       Background Colour : White
2.     What is the keyboard shortcut for creating a new Document ?  Command “N”
3.     What is the size of the image in :-
§  Megapixels -            10.8        Megabytes  1.1
4.     Set the foreground colour to Red (ie R 255, G 0, B 0).
5.     Select the Ellipse Tool (not the Marquee tool). What is the keyboard shortcut :-    “M”      
6.     Draw a circle with the Ellipse tool approximately 6cm in diameter (about 1/3rd of the page width) – display the rulers and use Preferences to set the units to cm .
·       Which key forces the ellipse to be a circle ?           shift       
7.     Change the layer name to ‘Red Circle’.
8.     Duplicate the layer and
·       change the colour to green and
·       change the name to ‘Green Circle’.
         Note: To change the colour click on the colour button on the option bar immediately after duplicating the layer, or double click on the layer in the Layers palette.
9.     Duplicate this layer and
·       change the colour to blue and
·       change the name to ‘Blue Circle’.
10.  Select the Move tool. What is the keyboard shortcut ?   “V”        
11.  Turn on the ‘Auto-select’ option.
12.  Spread the three circles across the top of the page with a small space above them (they may overlap a bit – that’s OK).
13.  Fit the image to the screen (ie so the whole page is visible).
·       What is the keyboard shortcut for this ?       Command ”0”
14.  Go to Full Screen Mode – ‘View -> Screen Mode ->Full Screen Mode’.
·       What is the keyboard shortcut ?    "F"
15.  Stare at the centre of the middle circle for 20 seconds, then look at the white area below. You will see an after image.
·       What colour are the after images for each circle ?
Circle
After Image Colour
Red
blue
Green
yellow
Blue
red

16.  Select all three layers in the layers palette.
17.  Group the three layers together by selecting ‘Layer -> Group’.
·       What is the keyboard shortcut ?     command “G”
18.  Select the group in the layers palette containing the three circles.
19.  Change the ‘Blending Mode’ for the group from ‘Pass Through’ to ‘Difference’. (We will be looking at Blending Modes later, so don’t worry if you don’t understand them now).
20.  Stare at the centre of the middle circle for 20 seconds, then look at the white area below. You will see an after image.
·       What colour are the after images for each circle ?
Circle
After Image Colour
Cyan
magenta
Magenta
yellow
Yellow
cyan

21.  Save the document as ‘Ex 3 – Colour Theory.psd’
22.  What is the size of the .psd file on disk ?      more then twice the size      How does this compare to the image size you recorded in step 3 above.



Monday 1 August 2011