# The simplified Formula of Depth of Field

The common photographer knows that the Depth of Field varies with the aperture, focal length and subject distance. But which one is the dominant parameter ? And how much is the influence of each parameter ? This article uses the equation of the DoF, and demonstrates that when the DoF is short, it varies proportionally with the aperture, and with the square of the focal length and distance to subject.

So here comes the only formula you need to know when you deal with short DoF but not macro photography :

```
- A is the aperture number
- c is the circle of confusion
- f is the focal length
- s is the subject distance
- H is the hyperfocal distance
- DoF is the depth of field```

In the rest of the article you can read where this simplified formula comes from, what it means in practice, and how accurate it is compared to the exact formula of DoF.

# Depth of Field and Subject Magnification

The focal length and the distance to subject have an influence on the Depth of Field, and this influence is simple to understand if it is explained with the notion of subject magnification. The subject magnification is a function of the focal length and the distance to subject. It is the parameter that influences the most the DoF, much more than the aperture. This articles explains what is the subject magnification and in which way it impacts the DoF.

# Depth of Field and Aperture – A simple relationship ?

It is common knowledge among photographers that the Depth of Field increases when the aperture decreases, but by how much ? Unfortunately there is no simple relationship between the DoF and the aperture, but this article provides a accurate and simple answer to the question.

# Flash Technique – The 1st and 2nd curtain explained

A DSLR camera provides the option to fire the flash on the 1st or 2nd/rear curtain, which can produces different photographs in the same conditions.  This article explains what it means, and how to use it.

The series of pictures below shows a tennis ball falling down, captured with different settings of flash and ambient light. It put in evidence the influence of setting the flash on the 1st or 2nd curtain.

The rest of the article also explains what are 1st and 2nd curtains, and provides recommendation on which setting is better.

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## Depth of Field and Hyperfocal Distance

The Depth of Field (DoF) increases with the distance to the subject, and even becomes infinite beyond a certain distance, which is called the hyperfocal distance. This article tells you everything you need to know about it…

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## Depth of Fied and Circle of Confusion

The definition of Depth of Field (DoF) from Wikipedia says that it is “the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image“. It relies on the notion of “acceptable sharpness” which is based on a criteria called the ”Circle of Confusion” (CoC). This article explains the essential about the criteria of sharpness and DoF.

A photograph is exactly sharp only on the focus plane, and more or less blur around it. The transition between little blur and definitely blur is gradual, so where do we determine the limit of acceptable sharpness that defines the Depth of Field (DoF)?

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## Introduction to Depth of Field

This article is the first of a series dedicated to the concept of Depth of Field (DoF). It is a technically complex topic that scares many photographers including the experienced ones, and caries many popular misconceptions. The aim of these articles is to explain ‘how to control the DoF in your photographs’ in an understandable, but accurate way.

The articles will explain among other things that :
– DoF is not 1/3 in the front and 2/3 behind the focus point.
– Aperture is not the dominant parameter to control DoF.
– It is possible to make a group shot of 120 people with an aperture of f1.2 and have everyone in focus.
– A blurred background is not the same thing as a shallow DoF.
– It is possible to estimate the DoF at a glance in just a couple of seconds.