jump to navigation

#21-Getting Rid of Red Eye

December 02, 2002

LTA Overview

Red eye is a commonly encountered problem with photographs that employ flash. In the somewhat darkened space, the subject’s pupils are dilated and when the camera flash occurs, light reflects off of the individual’s retinas and is seen as a redness in the eyes.

Credits

Richard H. Falk
Academic Technology – Faculty and Instructional Support Services
Virginia Commonwealth University
rhfalk@vcu.edu

Some cameras use a preflash in an attempt to make pupils constrict before the true flash and picture are made. This often does not work well.

What follows is a technique to “fix” the red eye problem using Photoshop after the fact. And it works well for anyone who may have a copy of Photoshop on their computer or have access to a computer with this application program.

Kaitlin1Notice the red eyes in the image above. We can start the fix by duplicating the image into a separate layer. layer > duplicate layer

Let’s call the duplicate layer something like false color.

The image below shows what the layers window looks like after the duplicate layer operation.

Layers2Now we need to remove the red eye. We can do this by removing the red channel from the duplicate layer. To do this, select the “false color” layer only as is seen above.

Then switch the window to “channels” and select the green channel with a select > all. Copy it to the clipboard with an edit > copy command.

Now paste the clipboard contents into the red channel with an edit > paste command.

If you now select the RGB channel, you will see an image that looks like:

Kaitlin3A very greenish image but the pupils are black as one would desire them to be.What one has to do now is combine the useful parts of the two layers. And to do this we’ll use a layer mask.

Go back to the layers view in the Photoshop window and make sure that the false color layer is selected.

Then add a mask by selecting layer > add layer mask > hide all.

The original image should pop back into view, red eye and all.

The next step is to select the parts of false color that needs to be overwritten in the original image. Painting onto the layer mask does this.

Any area of the layer mask that is black will select the original, correctly colored image. White parts of the mask will select the new, red eye removed false color image. Any gray shade in-between will blend the two layers.

So, with the false color layer selected, go back to channels and select the mask channel. It will be named something like false color Mask. Select the paintbrush tool and select a brush with a graduated, gray edge. The size of the brush depends on how large the pupil’s in the image happen to be. You might want to zoom in on the eyes.

Now select white as a color and paint into the pupils. They will become black. Don’t paint into the iris of the eye. If you do this by accident, change your color to black and paint over your errors. This lets you fix an image and retain the flash specular highlights.

A final step would be to issue the command, layers > flatten. This yields an image as follows:

Kaitlin4

Comments»

No comments yet — be the first.

Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: