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This section covers Exposure, Aperture, Depth of Field, Shutter Speed, ISO, White Balance.

Food_CatherineFrawley_22.JPG
 

WHAT IS EXPOSURE?

In the simplest terms to create an exposure…

  • You need a light proof box (i.e. your camera) a lens at one end and a light sensitive film/digital card at the other

  • Light enters through the lens (Aperture) and after a certain amount of time (determined by the Shutter speed) an image will be recorded

  • The recorded image is called an Exposure

  • We all want Correct Exposure

  • On an iPhone you can tape the screen, to get the sun image and use the slider up and down to change the exposure if you are in conditions where the screen is showing you an overly bright or dark scene you can use the slider to lighten or darken the scene.

  • On a DSLR the only real way to get consistent and correct exposure is to use Manual mode, the other modes on a DSLR are

  • P Mode – is Programme this lets the camera make all the decisions for you

  • TV Mode – Time Value / Shutter Speed Priority

  • AV  Mode – Aperture Value / Priority

  • So, a correct exposure is a combination of three elements; Aperture, SS & ISO

APERTURE

·      Aperture controls the volume of light reaching the film/digital card (it works like the pupil of your eye that allows light to enter and opens and closes depending on how bright the light is)

·      The term F Stops means Focal Length and are written as Fractions therefore 1/2 is bigger than 1/16 so an F Stop of F2 is much bigger than F16

·      Traditional F Stops are F1.4 / F2.8 / F5.6 / F8 / F11 / F16 / F22 (now DSLR have all sorts of F-stop numbers in between the above too)

·      SMALLER F-stops LARGER the opening (i.e. F22)

·      LARGER the F-stop SMALLER the opening (i.e F2.8)

·      On a DSLR you can choose your F Stop (the range available will depend on the lens you have)

APERTURE Depth of Field

·      As well as controlling the amount of light, Aperture choice controls What and HOW MUCH of a scene is in focus

·      At F1.4 focusing on a persons eyes, the eyes are in focus and not much else in front or behind will be

·      At F22 focusing on a persons eyes, the eyes are in focus as is pretty much everything else in front and behind the subject

 

Examples of Depth of Field

Shutter Speed

·      Shutter Speed controls the amount of time the light coming through the lens is allowed to stay on the film/digital card

·      this can vary from 1/8000 to 30 seconds

·      shutter speed is measured in fractions of a second

·      1/500 1/250 1/125 1/60 1/30 1/15 etc

·      The above are called Full Stops from the film days

·      Newer digital cameras have stops in between

·      Slower shutter speeds will give movement or blur in the image, fast shutter speeds will capture motion, like water droplets or children running

ISO (International Standards Organisation) 

·      This is the Film Speed. If you use film or are old enough to remember buying film in the ‘olden days’ you’d pretty much always Kodak Film that was for Sunny Days it had an of 100 ISO or 200 ISO you could also buy Kodak Cloudy Days which had a set ISO of 400. Digital cameras can emulate ISOs of up to 25600 and more

·      100 / 200  / 400  / 800 / 1600 /3200 ISO these are the film standards of ISOs

·      (newer cameras have options in between)

·      The lower the number, like 100 ISO, the lower the sensitivity of the film/camera sensor is to light. The grain or noise will be less or unnoticeable

·      The higher the number, like 3200 ISO, the higher the sensitivity of the film/camera sensor is to light and the higher and more noticeable the grain/noise will be.

 

White Balance

·      Light has a colour temperature, determined by the Kelvin numeric value

·      1000-2000 K Candlelight

·      (COOL / BLUE)

·      2500-3500 K Tungsten Bulb (household variety)

·      3000-4000 K Sunrise / Sunset (clear sky)

·      4000-5000 K Electronic Flash

·      5000-6500 K Daylight with Clear Sky (sun overhead)

·      6500-8000 K Moderately Overcast Sky

·      9000-10000 K Shade or Heavily Overcast Sky

·      (WARM / ORANGE) 

I generally leave my DSLR camera on AWB (Auto White Balance) it’s the only setting that I allow the camera to make the decision for me. Generally I’ve found my Canon’s are usually spot on. But this is something that can be corrected in Lightroom, if the end result ends up being too warm or too cool

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