Color in CCD

First of all, why can’t a CCD detect colors? What happens inside a CDD is rather simple: when a photon hits the CCD’s substrate, it “generates” electrons. More precisely, the photon transmits its energy to an electron in the valence band, making it pass to the conduction band. At least, this happens if the photon has sufficient energy. So, there is a threshold of energy above which each incoming photon can generate electrons. Energy is strictly correlated to the wavelength and so to the “color” of the photon. So electrons are generated regardless of the color of the incident light. For this reason, CCD is said to be “panchromatic”, although it is usually improperly referred to as “monochromatic”.

So, how come we obtain colored pictures from an inherently panchromatic sensor? The trick consists of covering the photosensitive area with a color filter array (CFA), so that each pixel is covered with a colored glass according to a certain pattern. The most used pattern is the “Bayer CFA pattern”, which consists of a 2×2 matrix repeated both horizontally and vertically:

GR

BG

where R=red, G=green, B=blue. The repeated pattern yields:

GRGRGR…

BGBGBG…

GRGRGR…

BGBGBG…

We are getting to the gist. As an example let us consider a pixel covered with a blue filter. It has only the information of the intensity of the blue light hitting it. However, it is surrounded by 4 green pixels and 4 red pixels. Hence, although the blue pixel under consideration has no information about neither green nor red light hitting it, it can be guessed by interpolation, exploiting the neighboring pixels.

This is done off-chip: the sensor just outputs the sequence GRGR… and BGBG… alternately. This output is known as “sequential RGB” (sRGB).

Note that by covering all the pixels with a color filter array (CFA), letting just a fraction of the electromagnetic spectrum pass through, we reduce the light received by each pixel by about 1/3. That’s why in low-light applications (e.g. astronomy) panchromatic sensors are used, resulting in black and white images.

The off-chip interpolation is not trivial at all for many reasons.

First of all, it is inherently inaccurate, because it can only be a (sound) guess. And it is even more so where edges or fine details are present, that is where color in the original image changes abruptly compared to the filter pattern. Moreover, interpolation cannot be a simple linear average. Indeed, each of the colored pixels is affected by glass transmission (different for different colors) and by the quantum efficiency (again, different for different colors). Besides, humans’ eyes do not see colors as a sensor does. So a further correction is needed.

Zeroing in on Flash

The proper position of the flash is directly over the lens. This will ensure that any shadows from the flash will occur behind the head and body and not to one side. Of course, when shooting square format like Hasselblad, the flash can be fixed in that one position. For shooting with a rectangular format like Bronica ETR or Canon DSLR, the flash must be mounted on a swinging bar so that the flash can be positioned over the lens in either a horizontal or vertical shot.

I have determined through many tests that the ideal distance of the flash head above the lens is twelve inches. There are many advantages to using this distance. First, the unavoidable reflections on the forehead, nose, cheeks and chin are conducive to making the subject look good. The forehead reflection is positioned higher on the forehead, almost into the hair line and much diminished in strength. This leaves the flat portion of the forehead reflection free and retaining the natural color of the skin.

The shape of the nose is determined by the fall off of light along the sides and the position of the reflection on the bridge of the nose. When the flash is positioned closer to the lens, the bridge or indentation receives no highlight but rather the bony lower part of the nose is emphasized. The tip of the nose also benefits from the twelve inch distance of the flash head by appearing smaller and less intense.

Cheek reflections are considered acceptable when they are centered on the upper portion of the cheek. With a lower positioned flash head, the reflection highlight the unattractive line of muscle from the cheek to the nose. The twelve inch flash position also enhances the cheek bones. Chin reflections lower down on the point of the chin are unattractive and make the chin look wet. Alternatively, the twelve inch flash position just places a small crescent shaped highlight under the lip. An added benefit also occurs in the form of a more defined chin line and the placement of some double chins in shadow.

Those terrible eye glass reflections are greatly minimized with the twelve inch flash. The flash highlight now appears near the top of the eye glass, completely avoiding the area of the iris and pupil. The eyes are the most important feature of the face and ugly flash reflections can wipe out the eyes completely. An added benefit is a slight darkening at the bottom of the picture, enhancing the composition with a natural fade out.

Remember that since most natural light comes from a position over the horizon the most natural flash lighting will do the same for the face. Don’t let convenience prevent you from capturing your flash subjects in the most attractive light.

Outdoor Group Portraits

I want you to picture yourself and your family outside on a nice afternoon. It’s Thanksgiving, a great day for a family portrait. Unless it is a cloudy day, some nice shade will produce a flattering lighting ratio for your portrait. This means that the brightest part of the picture and the darkest part are not too far apart in value for the film or hard drive card to capture. Then choose a uniform background for you portrait. A stand of dark evergreens, a barn wall, a distant lawn, or a high hedge are all excellent backgrounds. The back of the house and patio, the driveway with the parked cars, or partially sunlit woods are too busy a background for your picture.

Next find something for people to sit on: a log, a small table from the patio, a picnic bench or a patio chair. The object is to have everyone’s head at a different level. Small children are, of course already low to the ground. Seat some people at chair height, others on the ground. Sitting like an Indian is not a viable pose. Try sitting the person down on the ground with their knees together, ankles crossed and to the side. Standing and leaning against something also provides a different height for your composition. Try to place the heads so that they do not line up either vertically or horizontally. Rather than presenting a square shoulder to the camera, a slight turn to the body is preferable. Eye glasses can be held in the hands or tilted down. Be creative in you grouping – two, threes and fours in a close grouping look better than one group of seventeen evenly spaced. Remember to overlap shoulders so that heads are closer together. One shoulder is all that is necessary to see.

Arms should never hang straight down. Instead, place some hands in pockets, around shoulders or holding hands. Diagonals in the composition increase the dynamic qualities of your portrait. Pay attention to the legs and feet. Natural looking positions include crossed ankles, placing the feet forty-five degrees apart (standing), and crossed knees. After the positioning everyone, stand back and squint at the effect with blurred eyes. Turn any straight on bodies and relocate any misplaced color or glaring whites for a more pleasing effect.

A broad, low light source is ideal for a flattering look to your portrait. An open sky overhead will result in dark eye shadowing. Reflecting light into the shadow areas or using fill flash will correct this situation. Take advantage of the light from a white building or a setting sun. A natural solution is to place your group under some overhanging branches.

Light Exposure

One of the first technical specifications you may encounter when you look at camera information is the aperture. (‘ap-&(r)-‘chur) The word aperture comes from the middle English aperture and Latin apertus. Apertus is the past participle of aperire, which means to open. And this is exactly what an aperture is.

Aperture refers to the size of the diameter (distance from one side of the opening to the other) of the iris when it is open at its largest point. Aperture is measured in the units F-stop. Try to remember that the smaller the F-stop, the larger the maximum lens opening on the camera. The sensitivity of the camera to light is controlled in part by the aperture.

If you are purchasing a new camera, you should look for product with an aperture range from F2.8 to F8, while advanced photographers may need a range closer to F1.8 to F16. A large aperture means that you have more leeway with lighting conditions when you are shooting. If you have a larger possible aperture, you will be more prepared for low-light conditions. To give you some perspective, the mid-range Z650 digital camera by Kodak offers both wide and telephoto options for aperture, which range from F2.8 to F8 and F3.7 to F8 respectively.

Aperture is related in part to shutter speed. Shutter speed on cameras can range from as short as one eight-thousandths of a second up to a full thirty seconds. This time refers to how long light is allowed in through the camera lens when you hit the shutter (picture capture) button. Today’s digital cameras generally offer both an automatic and manual shutter speed mode. For example, the new Kodak EasyShare Z650 has an automatic shutter speed range between 1/8th and 1/1700th seconds. The manual mode of the Kodak Z650 goes from eight to 1/1000th seconds.

It doesn’t hurt to pay attention to shutter speed when you’re picking out a new digital camera for yourself because there are some interesting techniques you can practice with a variable shutter speed. One example is using your camera to capture an object in motion. If you follow the object and have adjusted your shutter speed correctly, you can succeed in showing the object in perfect focus and yet a blurry moving background.

An interesting aspect to keep in mind as you look around for a digital camera is that aperture and shutter speed are related terms. These two aspects of a camera work together to control the amount of light that reaches your CCD, CMOS or other digital sensor. By shopping for a camera that offers you maximum aperture size and range of shutter speed, you will be giving yourself more options to shoot different kinds of photos.

Add Effects And Spice To Life

Photo effects can sometimes be funky like backgrounds, frames, borders, texts and animations. These effects are mainly found on photo effects websites or basic photo effects applications. But the more advanced effects are bundled in packs provided with expensive photo-editing software applications. In order to add effects to photos efficiently, one must know the wide variety of options available to him in terms of photo editing. Some of these advanced yet highly effective photo effects are the halftone effect, mosaic effect, stained glass effect, watercolor effect, blurred effect, displacement effect, silhouette effect and many more. It is difficult to imagine what proper effects can do to a photo. From creating rainbows on a clear blue sky to age-progression of a young woman up to her old age, photo editing can achieve any imaginable result.

Professional graphics designers will tell you that it is best not to tinker much with a beautiful photograph. Minimalist is the new trend. The aim of the photo-editor is to add photo effects as less as possible, so that the beauty of the original photo isn’t overshadowed. It should be kept in mind that editing is for enhancing the photograph, not overshadow it. Sometimes, a simple black-and-white color tone or a sepia effect is enough to achieve the desired output.

The purpose of photo editing can be diverse. A social network enthusiast may only be interested in creating a funny tagline on his/her friend’s photo to be shared on his/her social network profile. On the other hand, a fashion photographer may be trying to apply the final touches to the model’s face he had clicked. It is interesting to note that both the users are trying to add effects to photos, but their purpose and way of doing work are radically different. While an amateur just wants to add effects to photos for fun, a professional photo-editor wants to use the advanced special effects to create a stunning portrait or landscape.

One cannot help but wonder about the websites or applications that support functionalities of adding chosen effects to photos. As end-users we only see the front end and are concerned with the functionalities. But nobody cares about the thousands of lines of code that has been written or the hard work that has been put in, just to ensure that we can add effects to photos. Whenever one wants to add effects to photos, he/she should at least consider the intricate background mechanism going on behind this simple task.

Steady Cameras

Hold the Camera with Both Hands

Some people think it is cool to operate cameras with just one hand. I believe the manufacturers are doing you a favor by freeing up a hand not so you can use it to eat a candy bar, but so you can use it to steady the camera. Two hands are always better than one. It sounds obvious and simple yet every time I go to record a public event I always see folks holding the camcorder with just one hand. Stop acting like an amateur and hold the camera with both hands. Your audience will thank you, maybe not verbally, but will appreciate your effort.

The Correct Stance

People are lazy, especially during long shoots. If you have the job as videographer you had better not be leaning your weight on just one leg. Stand with your feet approximately shoulder length apart with your body weight balanced between both legs. This stance is proven to improve stability in all physical activity and it definitely applies in this case as well.

Electronic Stabilization

Once again, the manufacturers are trying to help you out. If you are shooting without the use of a tripod then turn the electronic stabilizer on, but be sure to turn it off when you put the camera back on the tripod. This technology has improved greatly in the last few years and makes a huge difference in the final shot.

Avoid Zooming, Get Closer

The wide angle is doubtlessly the most stable setting. Zooming make the camera much more reactive to the slightest movement. While holding the camera in your hands this includes up and down as well as side to side. Many zooms are digital now and I frown upon its use. Only use optical zoom! Digital zoom only enlarges existing shots which start to pixelate and the quality plunges. If you can get closer without zooming, this will keep the angle wide and will stabilize your shot.

DPI and PPI

PPI: stands for Pixels per Inch. PPI describes the number of pixels per inch in a photo. PPI is a function of the number of pixels the camera’s sensor supports (also known as megapixels) and the size of the photo. To calculate a photo’s PPI simply multiply the page length by its width in inches. The result is the number of square inches on the page. Now divide the number of pixels the sensor supports by the number of square inches. The result is the number of pixels per square inch. All that is left to do is to find the square root of this number. Following is a table that shows the PPI for various page sizes for a 5 megapixel camera.

  • page size 4X6 – 456 PPI
  • page size 5X7 – 377 PPI
  • page size 8X10 – 250 PPI
  • page size 11X14 – 180 PPI
  • page size 16X20 – 125 PPI
  • page size 20X30 – 91 PPI

DPI: stands for Dots per Inch. DPI is really a physical characteristic of a printer. Every printer prints dots that when put next to each other comprise a photo. Each dot has a physical size. DPI is also known as the maximum resolution that a printer is capable of. Low-end printers have lower DPI while high-end printers have higher DPI. DPI is defined as the number of dots a printer can print per inch. For example if a printer supports 1200 DPI it means that the printer can print 1200 dots per inch (on both X or Y axis). When printing it is important to make sure that the DPI is higher or equal to the PPI. If the DPI is lower than the PPI the printer will not be able to fully display the high resolution of the photo. When printing a photo that has a lower PPI than DPI the printer will use multiple dots to represent one pixel. As opposed to PPI, DPI is not relative to the page size. DPI is a fixed number for a given printer.

Taking Great Lightning Photos

The first thing to do when preparing for lightning photography is to set the camera to manual mode. Since all the preparations are done in a dark environment the camera can not automatically set the right focus, exposure and aperture.

Set the focus to manual and focus the camera on infinity. This is the right setting since lightning photography is done from long distance. Set the exposure to anywhere between a few seconds to a few minutes. The right exposure depends on the type of lightning – some lightning last a friction of a second while others can last a few seconds – and the distance from the lightning storm. Usually you would guess what the right exposure is and after the first lightning shot you would have to review the photo and correct the exposure as needed.

Remember to turn the flash unit off. Flash is not needed in lightning photography but if left in automatic mode the camera might fire it anyway due to the dark scene. The aperture should be set to a small value since lightning are very bright and with a small aperture they will still be more than visible in the photo.

Now that the camera is set you will need to choose the right scene for the photo – this is also referred to as framing the photo. To make lightning photos more interesting try to find contrast or objects that will be interesting when lit or stroked by lightning. Such objects could be trees, city sky line, roads or antenna towers. After your first lightning shot you should review the photo and make any needed corrections to the photo frame.

You can also play with other settings of the camera to achieve different effects. For example you can take photos with different white balance settings to achieve different color temperatures.

Remember that it can take a very long time to take one good lightning photo. Since there is no advanced notice as to when lightning strikes you will need to take photos continuously as the lightning storm is active. Be patient and make sure you are comfortable. Keep yourself dry have plenty of food and coffee and prepare for a shooting session that can last hours. After doing all the preparations and framing your photo the only thing to do is wait. Some luck can always be of help in getting this one perfect lightning photo.

And last but not least make sure that you are safe. Lightning can be dangerous. Make sure that you are not too close or in the heart of the storm. Avoid having metal objects around you or tall sharp objects. Remember that lightning strikes the highest object that can conduct its electrical current to the ground.

In conclusion taking good lightning photos is not hard. It takes a lot of patience some know-how of camera settings and regardless of your photography level it also takes a lot of luck.

Cloudy Day Photography

The studio photographer’s arsenal includes a number of tools to soften and redistribute light to the best advantage of the subject. Among these tools is the Softbox which provides soft, even lighting by using a diffuser in front of the light.

In outdoor photography, cloud cover diffuses the light of the sun much like a photographer’s softbox, producing a soft even light that results in softer contrasts. While high contrast can be quite dramatic, the softer contrast allows for more detail in both the light and the dark areas of your photograph. The softer light is also more flattering for portraits or candid shots of people.

On your first few cloudy day adventures, consider taking your digital camera. In spite of the differences in the cameras, what you learn about how the lighting changes your compositions and setup will be equally useful with your film camera. And with the digital, you’ll feel free to experiment without the added cost of film on your mind.

Some difficult subjects which benefit from the diffused light include waterfalls in shadowy forested areas, sea life caught in a tide pool and wildlife hiding in the shadows, as well as close ups of flowers and people.

Diffused lighting is not as bright as direct light, indoors or out, and you will need to compensate with a slower shutter speed. Or widen the aperture and adjust the depth of field. You should count on needing your tripod for wide or long shots. The picture can be blurred by even slight camera movement with really slow shutter speeds, so use your remote if you have one.

Creative With a Compact

Many compacts lack some of the settings that a SLR might have. Or, if not, the settings are less easy to understand and select. In this way, you might find setting “aperture priority”, “shutter priority” or “manual” is near-on difficult.

In fact, you might not even understand what these terms mean! And, it doesn’t matter.

Because if you have your camera set on “Auto” or “Program” then you will already be in a position to take excellent pictures which show your creative side.

How? Because, by leaving aside the worry about which settings to choose and when, you can now focus on what makes one photographer better than another – creativity. Without the worry of setting up the camera you can now concentrate on finding the image that pleases you, composing the shot on the LCD screen and selecting the right moment to take the shot.

In fact, the pressure will now be on you to get decent shots and with you mind training on “selection, composition and timing” you will be able to show the world – and yourself – that getting a great picture is not so much dependent on the type of camera you own but more on the inspirational faculties of the owner.