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E for Exposure
The reasons why?
Optimum exposure is vital for the opportunity to enhance and enlarge your vision, style and intent. By understanding the parameters that control exposure we can use this knowledge to our expressive advantage.
The medium of photography requires creativity and control if you are to use it to its and your highest potential. Controlling exposure in the camera and at the printing stage are interlinked you cannot achieve the highest print quality without first having a well exposed digital negative to print from.
Optimum exposure means recording of sufficient highlight detail to make a black and white print glow with luminosity.
The word “Exposure” can also mean:
Expose to record detail in the highlights
Recording File Format – JPEG Vs Raw
Think about the potential end use of the pictures you take, how and where will the pictures be used? If your pictures will only be seen on your website and blog or any other internet based platform with a small amount of post-processing the JPG format may suit your needs. The critical part is the amount of post processing if you are doing in colour, a small amount is fine for colour for JPG files.
The Exposure Triangle
In the exposure triangle, everything is configured around the ISO rating.
Each point on the exposure triangle is linked, if you change one, one or both of the other two controls will also change to maintain correct exposure when in Program, Aperture and Shutter Priority mode.
For example, with a fixed ISO, if you allow one-stop more light in the lens by opening the aperture by one-stop (double the original amount) in Aperture Priority Mode, the exposure meter will correspondingly give a new shutter speed that is half the original time with a fixed ISO.
For example, before 1/125 s, f8.0 after opening up the lens aperture with a one stop increase becomes 1/250 s, f8.0.
If the camera is in Manual metering mode, then you live and die by your choices, which is a great way to learn particularly with a film camera.
See the related article on Depth of Field
The same exposure but with a different picture intent of expression
1/125s, f8 = 1/15s, f22 = 1/1000, f2.8
These three exposures for a fixed ISO allow the same amount of light to reach the sensor.
It should be noted that the types of pictures you can make with these three different settings have vast implications how the image looks regarding depth of field and subject freezing or motion blur.
Optimum Digital exposure – expose for the highlights
Using a digital camera, you MUST expose the digital negative to retain printable highlight detail. This cannot be emphasised enough.
When making an exposure, you are not trying to record colour or texture in the specular highlights. A specular highlight may be the sun reflected from a bright object such as a pond, usually it will be so bright that even our eyes cannot register its brightness. Another example would be reflections off of highly polished surfaces.
If you have to make a choice about recording the highlights or the shadows in every single case go for the preservation of the highlights. The counter-argument to the above statement may be that you are creating body of work where the shadows are of the upmost importance.
Expose for the highlights and process for the shadows. Shadow detail can always be brought back in the post-processing.
You will be amazed at the amount of information that is lurking in the shadows. The Histogram on the back of the camera will tell you straight away if the exposure was good or not giving you the opportunity to reshoot the picture.
Never judge an exposure by its brightness on the LCD on the back of the camera it is fraught with danger. Some cameras have light sensors attached to the LCD to adjust the brightness of the LCD depending on the ambient lighting. So only use the Histogram to assess exposure in the camera.
7 Things you should know about Histograms
1 A Histogram is a graphical representation of the range of contrast within the picture file.
Below – a normal histogram
2 The height and shape of the Histogram graph are not important.
3 The Contrast range is demonstrated by the overall width of the Histogram, the wider the base of the Histogram the more contrast and potential greater difficulty in post-processing.
Below – a very low contrast histogram.
4 The perfect technical exposure is when there is a tiny gap at both ends of the Histogram, i.e., there are no clipped pixels at either end (a line going up the left or right-hand side) of the histogram.
Below – a histogram with excessive contrast.
5 Shooting to the right, means giving maximum exposure without burning out the highlights – the Blinkies are not flashing.
6 The highlight side of the Histogram on the right is far more important than the shadows on the left.
7 Chimping is the process of taking a shot and referring to the Histogram to check exposure. Those using cameras with electronic viewfinders will have a Histogram in the EVF making chimping a less frequent occurrence.
Highlight over-exposure warning tell you when pixels are clipped that means they are at 100% brightness (ensure this feature is turned on in your camera – tip – RTFM). Retake the shot and underexpose using the compensation dial, repeat the process until the Blinkies stop.
Embedding Skill Exercise
Take a series of shots exposing for the highlights, check the Histogram before taking the shot. Do not deliberately under-expose for effect, as this will introduce noise.