• Photography for Everyone!

    Back to Basics

      Yesterday, a very dear friend suggested, that, I should explain all the photography jargon that I write below my photographs on my Facebook page. I believe she was right. This way I could help everybody understand what all those numbers mean and would enable me to better connect with my audience. So, in this post, I shall try to explain how to read the recipe and draw conclusions after reading the same; in the easiest manner possible.

      First, let us start with "Shutter Speed". It is the easiest to understand, technically.

      To define, it is the time for which the shutter remains open. What it means is that , it is the time for which the light is allowed to fall on the sensor to capture the image. It is expressed from, as a fraction of a second to multiple seconds. Fastest being 1/8000 sec. for my DSLR (Canon 60D) and the slowest being 30 seconds in Manual mode. DSLRs have a special mode called Bulb mode wherein the shutter will remain open for as long as you keep the shutter button (image clicking button) pressed. It will close only after you let the button go. 

     1/8000 sec. implies the shutter remains open only for 8000th part of 1 second. Pretty quick huh! Whether to use fast or slow shutter speed is decided based on two criteria. Firstly, if you want to freeze a fast moving subject in a shot without getting a blur, you will use fast shutter speed (also called short exposure). If you intentionally want to get a blur you will use a slow shutter speed (also called long exposure). However with slow shutter speeds, there is a high probability that the image will be completely blurred due to the unsteadiness of the hands. So, in such cases, a tripod is used to support the camera to avoid unwanted blur.

    Note: To view large images, click on them.

    1/400 sec.
    In this image I used 1/400 sec. shutter speed to freeze a still shot of the sparrow who was continuously moving.

    3.2 sec.
    In this image, as you can see, I have used a slow shutter speed to get the trailing light lines that give character to the image.

     The second criterion that decides the shutter speed is the availability of light and whether you want a dark or light image. If less light is available and you do not want to use a flash, then a slow shutter speed is employed. Likewise, if you are out on a bright sunny day, then fast shutter speed is employed to obtain desired brightness of image. In essence, you exhibit control over how dark or how or how light (characterized by a white layer) the image is, in the end.

    1/20 sec. 
    As you may see I have used a slow shutter speed in this image. If I had used a shutter speed of 1/60 sec. all I would have got is a very dark (under exposed) image or maybe just a black picture. Using a slow shutter speed , I was able to obtain a bright image even though I did not employ a flash.

    1/1000 sec.
    In this image, I have employed a fast shutter speed to obtain a darker image. Had I used a slower speed like 1/20 sec., I would have got a washed out/over exposed (white looking or probably plain white) image.

     Moving on to the second bit of information, the "F number"; known by many other names like relative aperture, F-stop, Focal ratio of F-ratio. It is commonly denoted as F/1.8, F/6.3, F/22 and so on. Technically, it is the ratio of the lens focal length to the diameter of entrance pupil. Simply put, it is the size of the hole through which the light will pass and fall upon the sensor to create the image. Rule of thumb for easy understanding of F no. is that, 'smaller the number, larger the hole and vice versa.' So, if I have a lens that has F no. from F/1.8 to F/22, then F/1.8 is the largest hole diameter (also called minimum aperture) and F/22 will be the smallest hole diameter (also called maximum aperture).

     Apart from shutter speed, if you want to obtain a bright or a dark image in the available light, you will increase or decrease the size of the hole to allow or limit the amount of light falling on the sensor. Hence, if I use F/1.8; being the largest hole size, it will allow the most amount of light to fall on the sensor, producing a bright image even in a dark environment. Similarly, if I use F/22; being the smallest hole size, it will produce a dark image even in bright and will lit environment. To obtain clear understanding, let us observe the following examples.

    1/40 sec.
    For this image, I used F/2.8. Hence, I was able to obtain a bright image inspite of an overcast evening. This enable me to use a faster shutter speed of 1/40 sec. thereby avoiding camera shake (unwanted blur). If I would have set aperture at F/4, then I would have used a slow shutter speed of 1/10 sec. or even slower to obtain an image as bright as this.

    1/15 sec.
    In this image, I set the aperture at F/25. This made the passage for light very small. Hence, I was able to achieve a dark image, even though the room was well lit and very bright. This produced an image in which only the brightest parts of the object are visible and the rest has turned black.

      Now, coming to the last ingredient; "ISO". ISO is an international standard of measuring and quantifying the sensitivity of the sensor towards light. In film days, a similar standard was employed for the roll of film. Film has a single ISO number as it is a characteristic of film obtained on account of its manufacturing process. Sensors can alter their sensitivity towards light using various electronics and hence this setting is available on digital cameras.

      Low ISO number like, ISO-100 indicates low sensitivity towards light than a high ISO number like, ISO-800. However, high ISO number also produces a grainy (spotty) image. Hence, it is advised to use the lowest ISO setting on the camera to obtain the best image quality. Sometimes, though, it is necessary to use high ISO so that a bright picture can be obtained in a dark environment without the use of flash. This is the last step to fall back on and is used only if the image is dark despite using the lowest F no. and the lowest possible shutter speed that would allow you to obtain a clear image, free of any unwanted blur; without using a tripod. Let us understand better, the use of high ISO in the following picture.

    1/250 sec.
    As you may see, in this image, I have employed the lowest F number allowed by my lens and the lowest possible shutter speed to obtain a steady shot. This setting coupled with an ISO-100 setting produced a completely black image. Hence, I set the ISO to 3200 which gave me a very clear picture even in the dark room. But, this was at the cost of some sharpness. When the image is viewed at full resolution, it may be observed that the image has grainy pattern.

      With this, I conclude the article on understanding the three basic variable of photography. There is a lot more to it than just these three things. However, as they say, "A step at a time."


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