A quote for the day: Sam Abell

As I have practiced it, photography produces pleasure by simplicity. I see something special and show it to the camera. A picture is produced. The moment is held until someone sees it. Then it is theirs.
                                                                                                        Sam Abell 

A quote for the day: Robert Frank

Black and white are the colors of photography. To me they symbolize the alternatives of hope and despair to which mankind is forever subjected.
                                                                                                    Robert Frank 

New photos added to my flickr

I've added a new set of photos to my flickr photostream:
http://www.flickr.com/photos/63191587@N07/

A quote for the day: Henri Cartier-Bresson

Your first 10,000 photographs are your worst. 

                                                                      Henri Cartier-Bresson

Thought for the day: Robert Capa

'If your pictures aren't good enough, you are not close enough.'
                                              Robert Capa (Endre Friedman)
                                              1913-1954

Internet sources for the 'Gamma Corrections' exercise

The quote below is from an article publicised on the Siggraph.org website. Although it is a bit technical, I find this explanation helpful so I am including the quote here for future reference: “Since we know the relationship between the voltage sent to the monitor and the intensity which it produces, we can correct the signal before it gets to the monitor. The signal is adjusted so that it is essentially the complement of the curve shown above. Note that the task of gamma correction is accomplished by raising the input value to the 1/2.5 power. This is referred to as a gamma correction of 2.5; because we are correcting the input for a monitor whose gamma is 2.5” (extract from http://www.siggraph.org/education/materials/HyperGraph/color/gamma_correction/gamma_intro.html)

Some of the internet sources that I’ve used for this exercise

Would you care for another Gamma, dear?

My lessons from this exercise:

1) In an ideal world….There wouldn’t be a need for a gamma correction if all components of an imaging system (cameras, printers, monitors, computers, scanners etc) had linear characteristics.

2) Why is it important? I think that a gamma correction is important for displaying an image accurately. Most displays, films, and many digital cameras have nonlinear (what is sometimes called ‘signal-to-light-intensity’) characteristics. So, a gamma correction is used to adjust an image to make it ready for reproduction or display. It is about choosing which part of the original image’s dynamic range will be reproduced.

3) So, how does it work? It’s interesting to note

Making noise or keeping quiet: what do you think Gamma?

Using my loupe tool, I compared the noise of the 3 mages used in this exercise. The original image seems to be of sufficient quality and there does not appear to be a significant increase in noise in the adjusted images. However, there is a loss of shadow detail in image 3 when compared to image 2.  

It's all about gamma corrections! Thoughts on completing an OCA exercise

This exercise looked at the way a digital camera records and modifies an image, in particular the sensor linear capture. The exercise was hugely useful to me as it really made me look at gamma corrections and why they are needed. 

Picture 1: Linear image

The curve of the image was adjusted to simulate a linear image. The Picture demonstrates how this image would have appeared before the camera processor’s corrections. The curve is positioned to the right and the majority of the tone values are assigned to highlights. The levels available to represent shadows are limited.  

Picture 2: Original image with corrections applied by camera’s processor

This is the original image as recorded by my camera, i.e. showing the camera processor’s adjustments. It appears lighter than the image above. A wider range of highlights, mid tones and shadows is represented in the image.    

Picture 3: Gamma correction

The final image shows my attempt to apply a gamma correction to the curve of the linear image. I tried to make the image look as close as possible to the original and the final result appears to be slightly lighter and possibly less contrasty than the original picture. The whites of the building walls seem brighter and the warm tint of the setting sun reflected on the buildings and windows is less present in the image. The curve shows the values shifting to the top left corner and the darker tones seem to be particularly affected by the adjustments. Due to the increased contrast there seem to be less detail visible in the shadow area.