Science of Photography – Focus and Relativity

The following is a guide on the Aperture sizes based on the area of reference. A crude drawing (drawn in Paint), but works to pass on the message..!!

Aperture Focus – Visual

The above diagram displays three different areas in focus, Subject, Landscape and the Horizon. To denote the focal area for each I have given them a unique id 1-Horizon; 2-Landscape; 3-Subject. Refer the following table now.

Unique IdAperture SizeWhat’s in Focusf/stop
1SmallerEntire shot in focusf/32
2MediumMost shot in focusf/11
3LargestSubject in focus;
everything else behind is
blurred
f/4.0 or
f/1.8

The following is a GRAPH (drawn in Visme, an infographic software), visually depicting how the Amount of Light changes when Aperture Size changes and how the Depth of Field (DoF) varies and how the Focus changes. Me being a visual guy, I understand such relativity better when shown in picture.

How to read the above graph:

The larger the aperture (f/1.4, f/1.8) – Less Focus and Shallow Depth of Field
The larger the aperture (f/1.4, f/1.8) – More light can come in
The smaller the aperture (f/22, f/32) – More focus and Deep Depth of Field
The smaller the aperture (f/22, f/32) – Less light can come in

Note: The numbers representing “Amount of Light” are just indicative to show an ascending growth. They are not scientific data. Probably if I research I can replace them with actual scientific unit of measurement called Candela (for curiosity sake,Candela is the standard SI unit for measuring the intensity of a light source for photography), but I won’t. I want to keep this as simple as possible for everyone to understand.

Readers, please let me know what you think about the visuals. Do they help?

Science of Photography – Elements

1: Shutter Speed

“Amount of light let in through the shutter is directly proportional to the amount of time the shutter is opened”

For example, an exposure of 1/500 of a second lets in TWICE as light as 1/1000 of a second. The following picture (Googled) might help understand the factor.

Effects on subject with changes in Shutter speed

Usage: On your camera select the Shutter Priority mode (TV or S). Use, when your subject, or any part of your shot is moving or when there are issues with getting enough light for a correct exposure.

2: Aperture

“Controls the amount of light that is allowed through it to hit the sensor”

A large aperture enables more lightto hit the sendor for the duration of time shutter is open. Aperture is usually expressed in f/stops (f/1.8, f/5.6). For example, a SMALLER f/stop (f/2.0, f/3.5) number indicates a LARGE aperture . Conversly a LARGE f/stop (f/16, f/22) number indicates a SMALLER aperture. The following picture (Googled) might help understand the factor.

Effects on subject with changes in Aperture

Usage: To acheive a good “Depth of Field-DOF” – The amount of an image that is in FOCUS. Shallow DOF means little of the image is in focus; Deep DOF means more of the image is in focus.

On your camera select Aperture Priority mode (AV). This mode gives you the freedom to select desired aperture value such as f/16 or f/22 to get a deep depth of field, while the camera take care of the shutter speed and ISO.

3: ISO

“Measurement of your camera sensor sensitivity to light”

Higher the ISO number, the camera is more sensitive to the light and produce more digital noise.

The higher the ISO the picture will have more noise (more grainy)

Usage: Usually most of the advanced cameras will have this set to AUTO. It starts from 100 and can go to 1000’s depending upon the size of the camera sensor. In broad day light when outside ISO100 works perfectly fine. If you are inside with less light to capture a photo, increase the ISO. In summary, LOWER the ISO when shooting in brighter light, INCREASE the ISO when shooting in dim or less light.

This blog is meant to be a refresher for some and information for others who are just entering into the world of DSLR. By no means I am planning to create or recreate a book on Photography. This is the first blog on the science. More will follow soon.

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