The phenomenon of red eye occurs when the flash is incident on the eyes and gets reflected back by a dilated pupil.
The eye’s pupil dilates and shrinks as per the need for an optimum eye sight. In case there is low light, the pupil dilates to let in more light, while it shrinks if there is excess light.
When, in a low light condition, a flash is fired, the pupil doesn’t get enough time to shrink and the light illuminates the retina, which is captured by the camera. This causes the red eye effect. The following photo of Nikhila exhibits the issue.
The above shot was taken at a low light condition with flash being fired directly at her.
In the following shot, also in a low light condition, the flash was fired with the Red Eye Reduction mode enabled.
What this mode does is, in Nikon cameras, it lets out a strong light from a bulb at the subject so that their pupils shrink, and then the photo is taken; while in Canon cameras, the flash strobes and then the actual shot is taken, giving similar results.
Red Eye is not an issue if there is already a sustained light incident on your subject, as evident from the following shot of Milind Soman.
So, while shooting in a low light condition, if you are forced to use flash, it is useful to have a red eye reduction mode switched on, or have some sort of light on your subject’s face.
The Red Eye phenomenon has a medical aspect to it too. In case, in any of your photos, you notice that a person is exhibiting red eye in just one of the eyes, do recommend a visit to the doctors to that person, for it may be a case of leukocoria.
Let me know about your brushes with red eye in the comments.
Rear Curtain is a term used to describe flash setting when the flash is fired at the end of the exposure. In general, the flash is fired at the beginning. In a fast shutter speed, it doesnt really matter, but in the slower ones, having a rear curtain flash has very interesting effects. It shows movement, and then freezes at the end moment. On the flip side, is the front curtain, which also shows movement, but in a different form. I suggest all to try these out. A full detail post can be found here.
Flash photography, is simply put using the flash during taking the photo. We all know what a flash does, add light to the scene, thats the nutshell. Good use of flash allows the proper amount of light and also not washing off the colors in a photo. Most common use is during the night time photographs we take. These basic things, we are all aware off, and knowingly or not, we use them every other day.
But what do we do, when our subject is backlit, most commonly by sunlight? We take a photo without flash, and we end up having silhouette photos. I, personally, love the silhouette shots, but sometimes, you would like that the subject’s features, expressions too be captured. This is when the flash becomes indispensable. This technique of using the flash is known as “Fill Flash”.
Now, in a DSLR, you will have options of how strong you want the flash to be. With use and experience, you shall be able to judge the amount of light your scene needs and other than practice and trial and error, there is no short cut to it.
When you go through the options within the flash menu, generally, you ll come across the following options.
1. Normal Flash: This one is the standard issue flash setting. The shutter and the flash are synced and they normally fire simultaneously.
2. Slow sync Flash: This option comes up if you want to depict both motion and also freeze your subject. On the point and shoots, the party mode gives you this option. Here, the flash fires with combination of a slow shutter speed. The slow shutter speed gives the option to depict motion, while the flash freezes the subject in sharply.
Slow sync has two options, which come up in the Manual mode in the DSLR…
a. Front Curtain: Here, the flash is fired at the beginning of the exposure. Practically speaking, suppose you take the picture of a car moving from left to right using this method, then, the photo will have the car being sharp on the left side of your shot and then the trail of light leading it as the car exits from right. Here I show it with a coin toss! Notice how the falling coin is also captured in the shot.
b. Rear curtain: Similarly, here the flash is fired just before closing the shutter. It also does the same job, just from a different perspective. Same car, same direction, same shot, but this time, the car will be sharp in the right side of the photo with a trail of lights in the back. Similar coin toss, but here, you can see it spinning and in the moment the flash was fired, the coin’s motion has been frozen.
Flash photography can be used very creatively from making weird blurred backgrounds to eliminating shadow to freezing motion and so on…Go on take the shots and have fun creating stunning effects in the photos right in the camera.