NoRedEye is a program used to correct the 'red eye' problem that is frequently encountered in digital photographs taken using a flash. The program uses the latest advances from the field of image processing, to automatically detect the presence of red eyes and correct them, so making the whole process transparent to you and helps to reduce your workload.

In case the program mis-detects the presence of red eyes, or you are not completely satisified with the result of the automatic correction, you can select to perform the process manually. Even in this case, NoRedEye makes things much simpler for you - just select the area containing the red eye and let NoRedEye do the rest.

What causes the 'red eye' effect?

The red eye effect normally occurs when taking photographs using a camera flash in low light conditions. Light from the flash travels towards a person, enters his or her eyes through the pupil, bounces off the retina and is reflected back into the camera. This reflected light looks red in colour because of the blood vessels present in the retina.

This problem occurs in photographs taken with both digital and traditional cameras. The main factors which increase the probability of getting red eyes, include:

• In most compact cameras, especially digital ones, the camera flash is situated very near to the lens. Since light travels in straight lines, the light emitted by the flash should in theory be reflected back towards the flash. But in practice, the light from the flash gets reflected in a cone, part of which intersects the lens.
• When taking photographs in low light conditions, the pupils of a person tend to be larger than in broad daylight, so allowing more light from the flash to enter the eye and be reflected back.
• Persons with light coloured eyes, tend to be more prone to the red eye effect, because they have less light-absorbing pigment in their eyes.

Many modern digital cameras come equipped with in-built features to reduce the red-eye effect, such as a dimmer flash. This is a small flash that goes off a few seconds before the main flash to make the person's pupil constrict in size. But this is not 100% effective. For example, if a person happens not to be looking at the flash when the dimmer flash goes off, his or her eyes would not react and the pupil sizes are not reduced. But even if he or she are looking at the dimmer flash, other factors, such as the closeness of the subject to the camera, mean that the red eye effect is never totally eliminated (perhaps only reduced slightly).

The last line of defense against this problem is digital image correction, like that performed by NoRedEye.

Using NoRedEye

In most cases, using NoRedEye is very simple, requiring little user interaction, thanks to its automatic red eye detection and correction.


Automatic Red Eye correction

To run in automatic mode:

1. Simply start NoRedEye.
2. Ensure that Auto Red-Eye is enabled, by activating the following button in the toolbar (this is enabled by default).
   
   
   
3. Then load an image from disk by selecting 'File', 'Open' from the menu; or by pressing CTRL+O, or by simply using drag-and-drop from 'File Explorer' or any other windows application.
4. The image will be displayed on screen and automatic red eye detection and correction will occur.

That's it! As simple as that.


Running in manual mode

In some cases, you might wish to have more control over the process, or the results of the automatic correction are incorrect due to misdetections (for example, when the eyes are very small).

1. If auto red-eye has already run, just undo the last operation by clicking on the 'Undo' button in the toolbar:
   
   
   
2. Then manually select a rectangular area in the image that encloses the eye. You do this by pressing down the left mouse button on the image where you want the top-left corner of the area to be. Keeping the left mouse button pressed, move the mouse across the image until you reach the bottom-right corner of the rectangular area. As you move the mouse, a box will be drawn on screen as shown below:
   
   
   
3. Then release the mouse button and the program will correct the red eye for you.
   
   
   
4. If you wish to fix another eye, repeat the same process. If you want to undo the last asction and re-select the area, press the 'Undo' button and repeat the selection. The program keeps track of all the actions performed on an image, so you can use the 'Undo' or 'Redo' buttons repeatedly to remove or re-apply the changes you made.

As you can see, even in manual mode, NoRedEye does most of the work. You only have to indicate where the red eyes are located, and let the program do the rest.


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