17 March 2016 – Learn Your Camera

Tonight was all about learning camera basics – ‘Table top photography and a chance to discover your camera settings.’

One of the club members provided the evenings ‘learn-in’ which included some test setups for us to photograph, to illustrate how a change in aperture and shutter speed would affect the images we produce.

“Eyes are only as good as they need to be”, every animal has the eyesight it needs for survival.  A hawk, for example, can locate a mouse on the ground whilst in flight and it needs to do this to find its next meal to survive.

We looked at this photograph and was asked what could we see:

 

Some of us could see the profile of a young girl looking away and some could see the profile of an old hag sideways on.  The young girl’s ear being the old hag’s eye.

What we were actually seeing though was some light areas, some dark areas and some in between ‘grey’ areas.  All that information was being sent back to our brains to process/interpret.  The brain processed this information and, based on our previous experiences,  converted them into what we then perceived the image was.

Producing an image using a camera goes through a similar process to the eye, put simply:

Eye sees => data goes through the visual cortex => brain collects and processes the data
= image created

Camera sees => data uploaded to computer => software (e.g. Photoshop) processes the data
= image created

However, the final image actually relies upon both of these processes; we look through the viewfinder to find the image we want to capture, which is processed by our brain, we then use the camera to capture this, process it using software and reproduce it for another person, who then goes through their ‘eye sees’ process and personal interpretation.

A lot of processing which raises the question, ‘Do each of us process/interpret the image we see in the same way?’.  Using the example of the young girl/old hag picture above this is proved not to be the case, so everyone will have their own opinion about an image.

Next we went through the 3 settings which affect exposure; ISO, aperture and shutter speed.

ISO – ‘International Organisation of Standardisation’ (or ASA – ‘American Standards Association’ now replaced by ANSI ‘American National Standards Institute’) is film sensitivity or nowadays with DSLRs it relates to camera sensor sensitivity.

The most common ISO to use is 100.  It is used in situations where there is good light. The sensor or film is not that sensitive.  It produces a ‘noise-free’ image.

A high ISO means the film or sensor is more sensitive to light.  If you increase the ISO (over 400) you will start to see noise and grain in the image but in certain circumstances such as inside churches at weddings (400+) or at concerts (1600+) using a higher ISO is unavoidable.

The eye naturally adjusts its sensitivity.  When there is a change in light a chemical is released.  If you go from a light to very dark surroundings your eyes can take some time to adjust and that is this chemical reaction taking place, after a while though you can see in the dark.

For the test shots, grain was not an issue and we were inside without a great amount of light, so we set the ISO high, this gave us more range of aperture and shutter speeds to work with.

Aperture – A hole or opening.  In camera terms it is a variable-sized hole that controls the amount of light that enters a camera.

The numbering system for aperture at first glance seems counterintuitive: f2.8 being a big hole which lets a lot of light in and f22 being a small hole which lets less light in.  However, if you look at these as fractions of light then it starts to make more sense; f2.8 lets 1/2.8 of light in and f22 lets 1/22 of light in.

So to the first of the test shots to see the effect aperture has on an image (we used aperture priority mode for simplicity):

  

You can see by focussing on the red brick at f2.8 (left hand side) that most of the other bricks are out of focus, this is called shallow depth of field.  By focussing on the red brick at f20 (right hand side) most of the other bricks are in focus.  Knowing what your camera/lens can capture at different f numbers is key, for example, if you want a whole flower to be in focus.

To measure this more specifically, you can use a point on some graph paper or next to a ruler, focus on the point at say f2.8, see what area is in focus, then do the same at other f-numbers to see how much more you can get in focus as this f-number changes.

From your eye’s perspective, if you look directly at a word on a page about half an arm’s length in front of you it is difficult to clearly see the words two lines above or below.   Also noting that the eye has a ‘blind spot’.

After determining our dominant eye, the eye we would normally look through a camera with, we tested our visual ‘blind spot’ .  Your ‘blind spot’ is caused by the optic disc, approx. 1.5mm in diameter, at the back of the eye where the optic nerve exits and the blood vessels enter the eye.  This is a very tiny gap in your vision where you are essentially blind, however, you do not see the ‘blind spot’ as your brain fills in the gaps.

This is important to know when composing a photograph.  You need to look around the whole of the frame including the corners to check that you know what is in the frame and what will be visible by the camera which doesn’t have a blind spot.

Shutter Speed – The amount of time the aperture is kept open to allow light in on to the sensor.  The faster the shutter the speed (e.g. 500 = 1/500 of a second) the less light let in on to the sensor.  The longer the shutter speed (e.g. 5 = 1/5 of a second) the more light let in on to the sensor.  This also controls whether a moving subject is ‘frozen’ or whether there is motion blur.

The two photographs below show the effect of different shutter speeds; the left hand side shows 1/800 of a second and the right hand side shows 1/25 of a second.

    

Note: If you wanted to take a photograph of a building or landscape which had people walking about but you did not want to capture them, you could set your camera on a tripod and use a long exposure.  This would capture the stationary aspects of the image and ignore the moving elements.  This is something I am keen to try…

There is a photograph that was taken by Louis Daguerre in 1838 called ‘Boulevard du Temple’ which illustrates this technique.  Daguerre would have taken this picture using the daguerreotype, one of the first photographic processes which needed very long exposures to form an image on the surface of a silver plate. It is likely the Paris streets were busy at the time and, as the image would have taken 10-15 minutes to form, the man – and possibly his shoe shine boy – were the only ones who stood still long enough to show up.

Next week is a model night using studio lights… so, until next week…

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s