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Krisana Polyotha

Photography 3.2 (formally 3.1)

Today, it is about aperture & lenses: controlling depth of field and field of view.

Aperture controls depth of field (DoF):

Depth of field is amount of stuffs that is in focus, at the front and behind the subject you’re focusing on.

Screen Shot 2019-10-24 at 21.48.01

Portrait should be focusing on the subject, therefore, the background should be blurred. Small DoF for this. To allow that 3D perspective (i.e. picture on the right).

Contrast to that, in a landscape. You should have a big DoF. Especially, when you want the viewer to see everything in frame (i.e. picture on the left).


As you can see, larger the aperture, smaller the F number (and vice versa). Another way to learn this is smaller F number, create small DoF (less things are in focus). Equally, Large F number, create large DoF (more things are in focus).

Screen Shot 2019-10-24 at 21.12.50

Portrait mode will automate the camera to have small DoF = small F number.

Landscape mode will automate the camera to have large DoF = large F number.

However, as a photographer is better to use AV or A (aperture priority mode), to allow you to have more control and enable to exaggerate what you want. This is where you pick the F number, and camera picks shutter speed for you. This is very useful when your main priority is the DoF (portrait or landscape).

Screen Shot 2019-10-24 at 21.18.20

In addition, your camera isn’t focus on the middle of your DoF. It should be focusing on a subject that’s 1/3 at the front and 2/3 behind of your DoF.

Screen Shot 2019-10-24 at 21.28.39

Hopefully, the diagram above is allowing you to understand on how to control the outcome of your photograph a bit more. For AV mode, if you want the photo to be brighter the camera will choose a longer shutter speeds. Whereas, for darker photo the camera will choose a faster shutter speeds.

Therefore, large F number can result in slow shutter speeds. It would be good, if you can use a tripod for this to avoid camera shake or use something to lean on (if you forgot or too lazy to bring one). On another hand, small F number can result in faster shutter speeds.

Quick tip: don’t look through the view finder to work out DoF. It’s better to take a picture and look at it after!

In addition, understand the limitation of your camera. Even if you have an expensive brand new camera. When the camera is flashing the F number or shutter speed on your screen depending what camera you have, it’s warning you the photo you about to take might be too dark or too bright. A simple way to solve this problem, it’s to adjust the F number or change your ISO.


Focal length: the distance between the centre of the lens and the sensor. Also, Choice of lens will affect depth of field and field of view and perspective.




Standard / prime / fixed lenses: same as human eye. Let in more light than zoom lenses often down to f/2.8 (very small depth of field). Therefore, as it has wider aperture which means I can achieve a very shallow depth of field (only a small selected area in focus). Usually a 50mm. They tend to be expensive because it is designed to do one job and enable to do it perfectly.

Wide angle lenses: get a wider view (good for landscape or taking picture in tight area). Can be a 10mm or anything < 50mm.


Telephoto lenses: are like telescope, it let you zoom right in. Good for sport as well. Larger the focal length the larger the magnification. Can be a 400mm or anything > 50mm. It will compress the distance between object making things look flatter (more flattering for portraits).


Macro lens: let you focus on small things and still look pretty big. Also excellent for portrait.

Fisheye lens: give you an aesthetic of 180 degree view.

Zoom lens: different focal lengths, larger minimum aperture, less light. You can adjust the lens from 24mm to 105mm or 70mm to 300mm (depending on the brand and the model). Weirdly, it is cheaper than fixed lens because when you zoom in and out it create problems but it is very handy when you’re able to stand on a stable ground. However, when you’re in a car or dealing with an earthquake, then you increase it to 300mm (zooming into your focal subject) the image can be very shaky!


Affect of zoom:

  1. aperture change
  2. foreshortening
  3. shutter speed
  4. motion shake

To avoid shaky picture set your shutter speed no more slower than 1/focal length. For example, 50mm use 1/50 or 500mm use 1/500. In addition, stabiliser nowadays are very good it can help you get that sharp picture.

Shout out to Chris Bray (he has a really good YouTube channel)


This entry was posted in Photo.

2 comments on “Photography 3.2 (formally 3.1)

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