Photography-Exposure

March 12, 2021  •  Leave a Comment

Photography and Exposure

I have spoken to many people over the years about exposure. Some people just seem to crumble at the idea and switch their camera to auto, which defeats the idea of spending some decent money on a camera that allows you to control all the settings manually. Some over complicate it and others get over whelmed by all the numbers.

 

Keep it Simple.

There are fundamentally 3 things you can change when it comes to exposure:

  1. Aperture
  2. Shutter Speed
  3. Film speed (usually referred to as ISO)

Ignore lens choices, focal lengths, composition..... for the time being. Learn it in bite size chunks, not all at once.

Now the thing I think people struggle with is that these things are inter connected. Which means if you change one of them in a given direction you have to usually have to change another in the other direction.

 

Aperture

Lets start with Aperture. 

Quite simply the BIGGER the F number, the more stuff is in focus.

The SMALLER the F number the less stuff is in focus.

What I mean is the larger F number (e.g. F11, F16) will have a bigger range (depth of field) of focus and a smaller F number (e.g. F2.8) will have a smaller range of focus, so it will have a shallow depth of field.  So the key terminology here is Depth of Field, this links to the numbers on the lens barrel and will indicate how close and far objects will be in focus on a given aperture.

Some people do go on about how a low F number (e.g. 2.8) has a larger opening to let more light in and a higher F number (e.g F16) has a smaller opening to let light in. I believe this is where most people get confused. It is useful to know but to keep it simple...

...in my head I just think; a small F number means a smaller depth of field and a larger F number means a larger depth of field.

 

Shutter Speed

Shutter speed is how long the shutter remains open to let light in. If I am hand holding the camera I generally won't go below 125th of a sec, however there are exceptions to this. If I am inside I will sometimes go down to a 30th of a sec. 

So the choice of shutter speed depends on the conditions of shooting. If I am shooting a static object in low light and I have the camera on the tripod I can use a long shutter speed because I will not get camera shake and the subject isn't moving.

If I am shooting fireworks I will still use a long shutter speed (anywhere from 1 sec to 30 seconds) as long as the camera is on a tripod. That way you can trace the journey of the fireworks in the sky, it's essentially light painting.

If I am shooting a fast moving vehicle and I want to freeze the action I will use a faster shutter speed (like 500th of a sec plus). However I say that with a word of caution. Sometimes you can freeze it too much. If you want a bit of motion you have to experiment with slower shutter speeds.

The typical thing to do is a pan tracking shot where you move the camera in a panning motion at the same speed as the subject is passing across with a reasonably relative slow shutter speed to get the background in a blurred motion but the foreground subject sharp.

 

Film Speed (ISO)

This is essentially how quick the sensor reacts to light.  so higher ISOs react to light quicker and are used in lower light conditions.

Just be careful of noise. Modern cameras are getting much better at shooting at faster ISO speeds but I try and shoot in the lowest ISO speed I can.

 

Interconnected

So all 3 change the exposure of the picture (i.e. how bright or dark the photo is). If you adjust one you have to change another to compensate for that change.

e.g. If an even exposure (measured by a light meter) is 250th, F8, ISO 400 and I want more depth of field then I could change the aperture to F11. But doing this means I have let LESS LIGHT in (by one stop). So to counter this I could change the shutter to 125th of a sec to let MORE LIGHT in.  Or I could have kept the shutter as it was and change the film speed to 800 ISO.

 

I could ramble on about this all day, but these are my general thoughts. I am sure there are loads of people that will want to correct me on the exact terminology and science but these are just my thoughts and my ways of thinking when approaching photographic work.

Any questions please ask,

Shaun at Kamara

 


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