Wednesday, July 15, 2015

Photography basics from - We don't always use a camera...but when we do, we prefer Pentax.


 Hi Photographer friends,

There are a lot of new photographers just starting out. They need to learn the basics of photography and start using the various settings of their camera, and forget about the "Auto-everything" mode. It may sound silly to experienced photographers, but everyone has to start somewhere. So, here we go, this is for beginners.

New to Digital Photography? Not sure how to use your new DSLR? Drop the "Auto-everything" mode and learn the basics.
Photography Basics

Here are some basic photography techniques we should touch upon. Keep in mind that this  will not make you an expert in photography by itself. Like all other skills we learn, practice is what makes us excel in any of our undertakings. There are many books on photo techniques on the market that you can get to further learn the craft and art of photography. For years, Kodak has regularly published photography books targeted to the beginners all the way on up to the professional photographers.

Photography, is about light. It’s about light reaching a media, film or digital sensor, and turning the results into an image that we can see, on a computer screen for example, or printed on paper.

Other than the actual lighting conditions of a scene, there are three major entities that directly affect how the light reaches the recording media. The Aperture (lens opening), the shutter speed (the speed at which the shutter opens and closes) and the media sensitivity also known as ISO number (the amount of light recorded on the media for a given exposure). Too much light reaching the media, and the image will be washed out. Too little light reaching the media, and the image will be too dark.

This is to say that the balance between these three settings must be just right. Technically speaking, a large aperture will let a lot of light in, and therefore the shutter speed and/or the recording media will need to be adjusted accordingly. Let’s assume for a moment that the sensitivity is set at ISO 200 and cannot be changed. We now have to balance the aperture and shutter speed to get the correct amount of light in. Again, assuming that an aperture of f/4 at a shutter speed of 1/125th of a second would be adequate, the same results could be achieved with an aperture of f/5.6 at a shutter speed of 1/60th of a second. In other words, increasing the aperture by one f/stop and decrease the shutter speed by one step, the same amount of light would reach the film or sensor. The difference between the two is the composition (depth of field or clarity of moving subjects). Since we are dealing with digital single lens reflex (DSLR) cameras, from now on lets use the word “sensor” for media.

Aperture Scale Explained

The aperture, being the lens diaghphram opening, lets more or less light pass through the lens. The f/number (aperture opening) is proportional to the ratio between the lens focal length and aperture diameter, which is proportional to the square root of the aperture area. Big lingo, but what does it mean for you? Well, lenses are usually marked with the f/numbers ranging from the largest aperture to the smallest aperture. For example, a typical lens could have an aperture range of f/2.8 to f/16. The lens would be marked as follow: f/16, f/11, f/8, f/5.6, f/4, f/2.8. In this example, the largest aperture would be f/2.8 while the smallest would be f/16. Have you noticed something a little surprising here? The larger the number is, the smaller the aperture is. You need to remember that. Furthermore, each (f- stop) number to the right lets twice the amount of light in as the (f-stop) number to its left and each (f-stop) number to the left lets half the light in as the (f-stop) number to its right. For example, f/4 lets twice as much light in as f/5.6 but only one half the light of f/2.8, and so on. One unit of increment in aperture is called a stop.

An f/stop number to the right lets twice as much light in than the number to its left.
f/16      /              f/11        /           f/8         /          f/5.6         /           f/4          /         f/2.8
An f/stop number to the left lets half as much light in than the number to its right.

The f-number is a geometric progression based on changes in the size of the lens aperture, as it is opened and closed. As the scale rises, each number is multiplied by a factor of 1.4. The standard numbers for Calibration are f/1.0, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8,

f/11, f/16, f/22, f/32, etc. Each change results in a doubling or halving of the amount of light transmitted by the lens to the film or sensor plane.

Shutter Speed Scale Explained

In photography, shutter speed is the length of time the shutter takes to open and close. The total exposure is proportional to the duration of light reaching the image sensor. Similarly to the aperture, a standardized 2:1 scale was adopted for shutter speed so that opening one aperture f-stop and reducing the shutter speed by one step resulted in the identical exposure. The agreed standards for shutter speeds are typically 1 sec, 1/2 sec, 1/4 sec, 1/8 sec, 1/15 sec, 1/30 sec, 1/60 sec, 1/125 sec, 1/250 sec, 1/500 sec, 1/1000 sec, and so on. A shutter speed of 1/125 sec lets twice as much light in as a shutter speed of 1/250 sec, but half the light of a shutter speed of 1/60 sec. For example, combining aperture and shutter speed, a shutter speed of 1/125 sec with an aperture of f/16 is equivalent to a shutter speed of 1/250 sec and an aperture of f/8. Alternatively, a shutter speed of 1/125 sec with an aperture of f/16 is also equivalent to a shutter speed of 1/60 sec with an aperture of f/22. Remember that one unit of increment in shutter speed is called a step.

ISO Value Scale Explained

Similarly to the aperture and shutter speed, the ISO linear scale, which corresponds to the older ASA scale, is 2:1. Doubling the speed of a film implies doubling the numeric value that designates the film speed. Here again, a film rated at 200 ASA or ISO 200 will absorb half of the light of a 400 ASA or ISO 400 film, but twice as much light of a 100 ASA or

ISO 100 film. In the digital world, the sensitivity defines ISO speed in terms of the amount of light needed to achieve a certain quality in the sense of a per-pixel signal-to-noise ratio. The image sensors in digital cameras can be adjusted, or can have their outputs adjusted, in sensitivity to function with metering at any given comparative ISO setting. This is usually done by simply amplifying the output of the image sensor, which unfortunately also increases the image’s noise, sometimes beyond acceptable level. Just as with photographic film, greater sensitivity comes with some loss of image quality, visible as image noise. What does that mean for you? The lower the ISO value on your digital camera, the less noise you will have and therefore, your image will appear clearer. ISO 200 is twice as sensitive to light as ISO 100 but half of ISO 400.

Combining all three elements 

You can understand that to take an accurately exposed photograph, one has to balance the aperture, the shutter speed and the sensitivity value (ISO). In the 35mm film era, the sensitivity would have remained constant for the duration of the roll of film. In digital photography, the sensitivity (ISO) can be adjusted on the fly, making this third element more important and flexible than ever before. Luckily, technology spares us from long exposure calculations. We can pick one of these three elements, and most modern digital camera will adjust the two other elements automatically. We can set the Aperture, for example, and let the camera select the appropriate shutter speed. That is known as Aperture Priority, (Av for aperture value) on your camera mode dial. If the exposure is impossible at the chosen aperture, the camera will either suggest using the flash or increasing the ISO value or do one of the two automatically if already preset in the menu options. Alternatively, you can decide to set the shutter speed and the camera will choose the appropriate aperture. That is known as Shutter Priority (Tv for Time value) on your mode dial. 

Adjustments to consider

·        Choosing a small aperture can make the scene in focus from just a few feet or even inches in front of the camera lens to infinity. It is very useful in landscape photography. This effect is proportionally accentuated when using wide angle lenses. However it may require a slower speed or a faster ISO. Tripods are commonly used in landscape photography.

·        Choosing a large aperture limits the depth of field, making your subject stand out with a blurry background and foreground (bokeh). This is very useful for portraits. This depth of field is proportionally accentuated with telephoto lenses. However, it may require a fast shutter speed or a slower ISO.

·        Using a fast shutter speed can freeze the action and is often used for sports and fast moving activities. However, it may require a wider aperture, a faster ISO or the use of a flash.

·        Using a slow shutter speed will allow taking pictures at night or will render a feeling of movement by deliberately blurring moving area of a scene such as water falls, etc. You will likely need a tripod and perhaps a wider aperture and faster ISO.

·        You can shoot with a very fast ISO and capture almost any image with little effort, but the image noise will increase. However, most modern DSLR camera sensors allow much higher ISO settings while keeping the noise to acceptable levels.

You likely understand by now why photography is indeed, all about light. Modern DSLR cameras have other tools to further refine the art of capturing images with optimum results. Built-in meters have options such as multi-segments metering, center-weighted and spot metering. Auto-focus modes in either single or continuous focus make your photos crystal clear and sharp with little effort from your part. Shake reduction allows using slower shutter speeds than most humans could ever achieve by hand-holding the camera. The White balance adjustment controls assure, most of the time anyway, that the colors in the scene you photograph will be as seen by human eyes. Instant view of the captured images allows you to retake the shot(s) if not satisfied. Your camera likely has a “Live View” mode which really helps in some situations. The use of memory cards allows you to take hundreds or even thousands of pictures, at practically no cost other than the initial cost of the memory card. Remember “practice makes perfect” or close to it anyway. Go take some pictures!

Thank you for reading,

Yvon Bourque

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