Understanding Red-Eye in photos and how it can be prevented

Red-eye is a phenomenon that happens only when taking photos using a flash. When taking photos in day light or when in high ambient light scenarios people’s eyes look normal. When taking pictures in low ambient light scenarios using a flash the result many times is redness in the people’s eyes.The reason for the color red is simple – when flash light from the camera hits the eyes it penetrates and is reflected back from the retina. The color of the reflected light is red because the light is actually reflected from the red blood in the retina.In some scenarios the red-eye is evident while in others it is mild or doesn’t seem to appear at all. One of the main factors for that is the state of the pupils. If the pupils are dilated (for example the pupils dilate in darkness or when drinking alcohol) more light is reflected back from the retina and the eyes in the photo appear redder.Common way to reduce red-eyeThe most commonly used method to reduce red-eye is activating the camera’s built-in red-eye reduction feature. The red-eye reduction feature is very simple yet effective. When turned on the camera shoots a series of pre-flash strobes followed by one more strobe when actually taking the photo. The pre-flash strobes cause the pupils to reduce in size and by the time the photo is taken the pupils are small enough for the eye redness to substantially reduce. The red-eye reduction feature does what it is supposed to do: reduce the red-eye effect but almost never is it completely prevented. There are many limitations to this feature for example pupils reaction time to light can vary. In addition this feature can have a side-effect that results in photos having people’s eyes closed. The reason is that the pre-flash strobes blind the people and cause them to close their eyes.Other ways to prevent red-eyeUnderstanding what causes red-eye helps being more creative in preventing it. Following are some ways to prevent red-eye other than using the built-in camera red-eye reduction feature:Increasing the light where photos are taken (for example by turning on the lights in a room before taking photos of people) causes people’s pupils to reduce in size and eye redness to reduce.Point the flash away from the eyes. Since red-eye is caused by flash light reflected from the retina the best way to prevent red-eye would be to eliminate such reflection as much as possible. In most cameras the angle between the flash and the lenses is narrow (this is especially true for built-in flash and pocket cameras) causing most of the flash to bounce back from the retina to the lenses. Increasing the angle (for example by using an external flash) reduces the reflected light. You can also use a bounce flash – by having the flash light bounce off a bright surface (a white wall or a professional reflector) most of the direct reflection from the retina can be eliminated.Red-eye can also be removed after photos were already taken by using photo processing software on your PC. Most digital cameras include a CD with PC software that embeds this feature. Although this method doesn’t eliminate the red-eye from the source it can result in a practically red-eye free photo. Some software are better than others some are manual while others automatically identify the red-eyes and process that area to revert to normal eye colors.

Digital Noise - What Is It? What Causes It? And How Can I Get Rid Of It?

Digital noise in photos taken with digital cameras is random pixels scattered all over the photo. It is a similar effect as “grain” in film photography and it degrades the photo quality. Digital noise usually occurs when you take low light photos (such as night photos or indoor dark scenes) or you use very slow shutter speeds or very high sensitivity modes.When taking pictures with a digital camera an electronic sensor (also known as a CCD) built from many tiny pixels is used to measure the light for each pixel. The result is a matrix of pixels that represent the photo.As with any other electronic sensor the CCD is not perfect and includes some noise (also know as white noise to hint on its randomness attribute). In most lighting the light is significantly stronger than the noise. However in extreme scenes where the light is very low or when a high amplification is needed noise levels can become significant and result in pixels in the photos that include more noise data than real photo light data. Those pixels usually appear as random dots or stains on the photo (for example white dots scattered randomly on the photo).Understanding digital noise in various scenes:low light (night photos or dark scenes): when the scene is dark the amount of light measured by each pixel of the CCD is low. When the light intensity is very low it can become too close to the level of noise naturally found in the CCD. In such cases some pixels can appear as noise because the noise level measured for them is significantly close or higher than the actual light intensity.slow shutter speeds: when the shutter is kept open for a long time more noise will be introduced to the photo. A slow shutter speed translates to the CCD integrating more light per pixel. The effect can be easily understood as the CCD “accumulating” light in each pixel and measuring the total light over the shutter period of time. However at the same time the CCD is also “accumulating” noise. For that reason in slow shutter speed photos some pixels will appear as noise because for these pixels the amount of noise integrated is significantly close to or higher than the actual light measured.high sensitivity modes: high sensitivity in digital photography is implemented by mechanisms that result in amplification. The CCD amplifies the measurements it takes. However there is no way to just amplify the actual photo light that falls on the CCD pixels instead the noise and the actual light are both amplified. The result is that the CCD becomes sensitive not only to light but also to its own noise. When too much amplification is applied some pixels will appear as noise.While it is impossible to completely prevent digital noise there are a few options that allow you to significantly decrease it. When taking photos in low light scenarios such as night photos there are two main parameters to play with: sensitivity and shutter speed. Raising sensitivity creates more internal noise in the CCD while slowing down the shutter allows for more noise to integrate on the CCD. The amount of noise generated by both parameters is different. It is recommended that you set your camera to manual mode and play with a few different sensitivity/shutter speed pairs to find out the one that generates the least noise. Some cameras include a built-in feature called “noise reduction”. Noise reduction is implemented by sophisticated software that can identify the noise pixels and remove them. For example the software can identify the noise pixels based on their randomness and usually extreme intensity gap between them and their neighboring pixels. Removing the noise can be implemented by interpolating a replacement pixel value based on its neighboring pixels.If you do not have a built-in noise reduction feature or it does not work properly you can use a PC based software that removes digital noise. Many photo processing software include a combination of automatic and manual digital noise removal. Some software packages can also use a few photos of the same object to “average” them and thus remove the noise (relying on the fact that digital noise is random and the noise pixels will be different in each photo taken). To conclude digital noise should be understood by any amateur or professional photographer. However for most photographers digital noise is not a practical problem even in low light scenarios usually digital noise is minimal and can be significantly reduced by simply turning on your camera’s noise reduction feature. For professional photographers who shoot in more extreme conditions digital noise can present a real problem and can be dealt with using a combination of optimizing the camera settings and removing noise with professional software.

The difference between film and digital photography

There are many differences between film and digital photography. To most amateur photographers they do not matter much. They prefer the convenience, ease of use and lower cost of digital cameras and are not going to revert to the film age. However understanding the differences can help taking even better photos and can also help when debating with friends about the future of film.Following is a list of differences that are important to understand. The differences are listed in no particular order.The sensor: The most obvious difference between film and digital is the sensor used to take the photo. With film cameras a film sensitive to light is placed behind the lens. When a photo is taken the shutter opens for a predetermined period of time and light hits the film. The result is a photo “printed” on the film. To take a new photo the film has to be rolled and a fresh “clean” film is place behind the lens. With digital cameras a fixed electronic sensor (sometimes known as CCD) is situated behind the lens. The sensor is built from tiny light sensitive sensors each representing a pixel. When the shutter opens light hits the sensor and each pixel gets its “value”. Put together all the pixels comprise one photo. To take a new photo the photo is saved on a digital media and the CCD is electronically emptied. What does a different sensor mean? The main difference is in the Depth of Field. Since digital sensors are smaller in size than a 35mm film the depth of field will be much higher and in fact in most compact digital cameras almost infinite. The result is that blur backgrounds can not be created.The cost of a photo: Photos taken with a digital camera literally cost nothing. The photos are kept in erasable memory and thus can always be discarded at no cost. Also the photos you would like to keep can be copied to digital media such as a computer’s hard disk. With storage prices going down the cost of saving a photo on disk is practically zero. Film does cost money. With a film camera you have to pay for the roll of film, for developing the negative and for printing the photo. Every time you press the shutter button you spend money.The capacity: With ever growing storage capacities digital cameras today can hold hundreds and sometimes thousands of photos on a single media. You can always have a few more in your pocket and changing is very fast. The result is that a digital camera has practically infinite capacity. You can shoot as many photos as you want and at the end of the day just dump them on your computer’s disk. Film cameras’ capacity is very limited. A roll of 36 photos can only hold 36 photos. After a roll is used changing to a new roll can take time and is not easy to do in scenarios such as darkness or a harsh environment. For that reason many professional journalists carry a few cameras on them and instead of changing rolls they turn and use another camera just so that they do not miss a shooting opportunity.The feedback: One of the most important features of the digital camera is instant feedback. Almost all digital cameras include a small LCD screen. Once a photo is shot you can go back and watch it on that screen. The ability to see how the photo looks like results in better photos. If the photo is not good you can take another one. Being able to see the photos on the spot results in an educated decision how to fix a photo or how to better compose it. It takes a lot of the guessing away from photography. With film cameras there is no way to know how the photo on the film will look like when printed. New shooting angles: Just a few days ago I took a great photo with my digital camera that I would have never taken with my film one. I shot a cat that was resting on little rock. I held the camera in my hand and positioned it down where it almost touched the ground and I started shooting. I probably took 50 or more photos. I immediately looked at the camera’s LCD to review my photos and make sure they were focused and had the cat in them. The result was one great photo looking at the cat from the ground. I can not imagine myself just lying down on the dirty ground with a film camera looking through the viewfinder and perfecting that one shot.With digital cameras you can actually take photos without having your eye glued to the viewfinder. Overhead shots where you raise the camera over your head are much easier to do since you can still see what the camera is shooting by just looking up at its LCD screen.Correcting photos: With digital cameras photos can be corrected using photo editing software. Some correction abilities are built-in to the cameras but many more are available as software packages for your PC. With film cameras what you get is what you get. After the film is developed it is very hard to make any corrections. Usually if corrections are absolutely needed the negative or the printed photo will be scanned (i.e. converted to digital) corrected and then printed again (in a long and costly process).Changing conditions: Every roll of film is designed for best results in a specific environment. For example there are indoor and outdoor films or films with different light sensitivity. If conditions change rapidly a film camera user will have to either shoot with the wrong film, change the roll (and usually lose photos that were not used in the current roll) or use another camera with a different film in it. The results of shooting with the wrong film can be distorted colors (reddish photos for example), a grainy photo and more. With digital cameras the characteristics of the sensor can be changed instantly for each photo taken. With a click of a button the camera can be put in an indoor or outdoor mode, low light, night photography etc. Some cameras will automatically sense the scenario and set the sensor mode accordingly. The myth of quality: While it is true that film photography has its advantages the claim for superior quality is no longer true. As digital camera evolved the quality of high end digital SLR cameras is superb and in many ways even better than film. When considering quality you should also consider the quality in terms of composition and the scenario caught in the photo. With digital cameras’ high capacity, zero photo cost and instant adaptability to changing conditions photographers can produce better compositions and experiment more to get the best photo possible.Longevity: We have also paged through old photo albums of our grandparents. The photo looked a a bit yellow, scratched and just plain “old”. Storage of printed film photos or even negatives results in quality deterioration. Digital photos on the other hand never lose their quality. A digital photo will be identical today and 500 years from now. As long as we remember to refresh the digital media every now and then and to back it up our photos can literally list forever and not lose their quality.