The diffraction is a physical phenomenon which appears when light goes along some edge. It is well demonstrated on a slit or pinhole.
We as photographers see this effect when ever we close the aperture. Then the aperture acts similar to the pinhole in this article on Wikipedia.
Diffraction in Photography
The light comes into the lens and passes the aperture on its way to the film or sensor. It is either blocked by the aperture or passes through the hole that the aperture forms. That part of the light that passes the edge of the aperture very closely is affected by the diffraction. The smaller the aperture is the larger is the portion of the light that is affected.
Calibrating your Display
When you view pictures on some screen from the internet or elsewhere it is as well important as for editing pictures, that your display is sort of calibrated.
Doing so you ensure that the image is displayed on your screen in the same manner as it was seen by the autor/photographer/editor and vice-versa.
This article describes some basic but easy calibration method to make sure that brightness and contrast are at its best.
Have a look at the grey wedge above. Every shade of grey, although here are just 16 of them, should be clearly distinguished from its siblings to the right and left. Especially the differences between 01 and 02 or 15 and 16 may be difficult to see.
Lightbrush, Painting with Light
Lightbrush is some very unique illumination technique. Instead of using flashlight or available light we work with very long exposure times in total darkness and bring the light exactly there where we want it to be. We use a torch (flashlight for the Americans) or pocket lamp to illuminate the motif for several seconds. We can move the light cone along the motif or illuminate it from different angles. We can set light spots here and there to highlight only certain parts of the scene. Etcetera etcetera. All the individual illuminations will add to the sum of the total image.
Some parts of the image will get brighter than others. It gets brighter where you rest the light cone for a longer time or move it slowly. The light gets brighter as closer you get with your torch.
Give it a try and be patient. With time you will develop a good understanding for the light and a feeling of how to move the torch along the scene in order to get the image you want.
Which Canon Bodies Complement Each Other?
Sometimes you ask yourself whether to keep an older body as spare body when you buy a new one, or you intent do by a second body. Naturally the same body is the perfect match. However, you may want to look for a budget (used) body as spare one.
It is advantageous when both have the same look and feel with respect to the menu structure, the buttons etc. Canon is quite good at that. However, Canon does badly when it comes to the compatibility of Batteries. The same mount is important too, so that you can use all lenses on both bodies. And have a look at the remote control curt (it is the plug that is different) and the memory cards.
Converting Colour to Black and White
You may just take all colour from your colour images. That is called desaturation. That means that each pixel gets converted into a grey pixel with the same luminosity that the colour pixel had before.
That is more or less what classic black and white photographers used to do. They just used some b&w film in their camera. However, that was often way to boring even for b&w photographers. That is why they used colour filters like red and green, which are called B&W filters although they are coloured.