Question: Why do those red eyes appear?
Answer: When strong white light enters human eye, some of it reflects, and most of the visible reflected light is red. So, when you shoot with flash, chances are people on your photos will have red eyes. Voila - Demon eyes made easy

Question: How can I prevent this ?
Answer: Here is one simple trick that sometimes can do the magic.

The light enters our eyes through our pupils. Pupils actually act as eyes apertures - they open and close, allowing more or less light to enter. Tell your subject to look at something bright for a short period of time (be careful. Don't make them look at the sun or similar dangerous objects for our eyes). Their pupils will automatically close in order to lower the amount of light entering the eye. Now, tell them to look at you and BOOM! flash them out! Since pupils were smaller, less light from your flash entered the eye, so less chance to see a red eye (d)effect.
Some photo cameras have no-red-eye mode which works in similar way: it flashes few times, which closes subject's pupils, and then the photo is made.
This trick, while useful, is not always working.

Question: How to really prevent red eyes in a photo?
Answer: Imagine that you are standing in front of a mirror, and you have flashlight in your hand. (Or, if you want, do it for real with lights off! Ideal flashlights for this experiment are the ones which have focused light. Do not try this with lasers! While they are ideal for experiment, they are also ideal for ruining your eyes!)
Put the flashlight in front of your eyebrows, pointing exactly at reflection of your eyes at the mirror. The mirror reflects the light and the light will strongly shine in your eyes.
Now, take flashlight to your right (as far as your hand goes). Point its light at the same place in the mirror.
You will notice that the light that shines directly at your eyes is none.
This is something that we are familiar with.
Now, if your eyes were camera sensor, flashlight was your portable flash unit, and the point in the mirror you were lighting was your photo subject - it should be clear that:

In order to prevent red eyes you should have your light source moved further from your lens.
How much further depends on how big light source is, how strong it is, how far you are from the subject etc.

Have fun flashing your subjects

• Short Information


• Detailed information


• Examples

Short information

This is second article on photography filters. You can read the first one on UV photo filters.

For those of you that don't want to get too technical, here are major benefits of using polarizing filters (scroll down for examples):

• colors are more saturated


• you can get darker colors in the sky - even dark blue sky


• remove reflections from water surfaces and glass


• use it to reduce light so that you can shoot with slower shutter speeds

Detailed information on how Polarizing filters work

A physicist would say: most sources of electromagnetic radiation contain a large number of atoms or molecules that emit light. The orientation of the electric fields produced by these emitters may not be correlated, in which case the light is said to be unpolarized. Which, translated to plain English means that: almost all light is, by default, is in state that is unpolarised. Here is a illustration of unpolarised light:

When this light hits some surface, as glass or water surface - it gets reflected. Leve of reflection depends on entrance angle of the light and surface reflection qualities. Interesting part is that when the reflection occurs, very often the light is being polarized, because only one of atom generated waves is being reflected. To a naked eye - the light is the same. We can not feel any difference.

When we put a polarizing filter in front of our lens, here is what happens. Polarizes acts as filter to the polarization. It has one plane of polarization - and only light that has that plane will pass. All others are blocked. So, if we use polarizer with regular light it will pass one plane and the final image will look the same - just as we did not use any (since we cannot see the difference). However, when we use polarizing filter with polarized light, interesting thing happens. The light has one orientation of its polarization and the filter has other. When those two match - the light is passed. When they do not match - filter will block the light. Quantity of blocking depends on filter make and quality.

The filter is most effective when used at 90 angles degree from the light.

Air atoms reflect and polarize some of the light that hit them. Lets say that we are shooting some landscape. If we put on pol. filter and point the lens at 90 degree from the sun, we can benefit from darker sky. So, get the sun to your left or right shoulder and make that landscape shot with and without the filter. What happens is that the polarized light from air atoms is blocked. So, the sky itself has less light that hits the sensor and it appears darker. This is useful as usually the sky is very bright, and not so pleasant for viewers eye.

Same applies to reflected light from leaves, doors, glass, water surfaces etc

Examples

See how the filter darkens the sky, defines clouds and also makes trees little greener

Polarization filter is oned on left side. check how it removed the reflection in glass, so you can see through it

The filter has darkened the sky, and also removed reflection from sea surface so that the sea bottom is visible

I received several emails from readers who wanted me to suggest some good books for photographers. Most of them wanted to buy those as a gift.

I will make some book reviews in 2009, but since it is a christmass / new year season, I decided to help you in some quick and good way. Amazon have whole section with bestseller books in photography category. Here you can see what people usually buy, so you can choose one based on personal preferences of the person that the book is going to

Also, don't forget that National Geographic photography books are always a good choice, especially if the person is just starting or wants to learn a new field.

If you are not sure what the person will like, you can always ask them In case you prefer to make this as surprise - take a look at my article for good ideas for presents for photographers, or the one which is one year old, but still useful: winter presents for photographers