Using Depth of Field For Storytelling
“To make your video look like film use shallow depth of field. Deficiency Syndrome but with a little education and therapy, we can move on. . Next time you lens your camera and choose your aperture, take some time to think about depth. Which podcast specifically shows the relationship between. Depth of field is determined by three factors – aperture size, distance from the lens, and the Deep is when the included range is a couple of yards to infinity. What is depth of field? Understanding depth of field is one of the first big hurdles in photography. Knowing how your aperture, focal length and.
These ideas are illustrated in the figure below: We can make two important observations based on these diagrams: As the object moves farther from the lens, the image moves closer to the lens and decreases in size.
As a result, the angular size of the bent light cone increases. Even though the first and second object shifts are the same size, the second image shift is smaller than the first image shift. In other words, the image position is less sensitive to the object position when the object is farther from the lens.
The answer to this question is not very straightforward because we have two competing forces. Depending on the relative strengths of the angular and sensitivity effects, the DOF might decrease or increase! To proceed any further, we will need to quantitatively determine the depth of field for different object distances.
For a lens with a given focal length, the general procedure would be as follows: Choose a central object position. Determine the corresponding image position. Assume that the camera sensor is located at this position. Choose another object position, locate its corresponding image, and determine the size of the circle of confusion it produces. Repeat step 4 many times to find the object positions at the extreme edges of the approximate focus range.
This will determine the depth of field at this central object position. Repeat steps many times for different central object positions. It is possible to do this graphically by drawing bazillions of ray diagrams. However, it is much easier to calculate the depth of field numerically using equations that describe a simple model of a lens. The Thin Lens Equation The thin lens equation is the key to numerically determining the depth of field. For a point-sized object that is radiating light towards a lens, the equation relates the object-to-lens distance dothe image-to-lens distance called diand the lens focal length called f in the following way: Strictly speaking, this equation only applies to idealized lenses that have zero thickness.
Of course, such lenses do not exist in real life. However, camera lenses are carefully designed so that they function almost exactly like perfect thin lenses. Note that the thin lens equation contains all of the information we learned from the ray diagrams I drew above. Specifically, we can use the thin lens equation to discover the angular and sensitivity effects.
To do this, we can solve the equation for the image distance and then plot di vs do for a particular focal length, say 50 mm: We can easily see that as the object position increases, the image position decreases towards the focal point.
The Relationship Between Aperture and Depth of Field
From this we can infer the angular effect. Additionally, we can see that the curve becomes flatter at larger object positions. From this we can infer the sensitivity effect.
A Model for Depth of Field Before we can numerically calculate the depth of field, we will need to determine the diameter of the circle of confusion C as a function of object position, focal length, aperture radius Aand sensor position S.
The following diagram illustrates how these quantities are related, and also includes the object height ho and image height hi: Next, we can find the angles using A and hi: When we combine these three equations, the image height actually cancels out: As the final algebraic step, we can find the image distance using the thin lens equation. When we combine everything together, we can get a big ugly equation for C. When photographing peoples faces I make sure their eyes and face are in focus.
Its ok if the hair goes out a bit. This clearly separates the two.
Depth of field explained | TechRadar
When the eye is just out of focus it becomes distracting. There are a few exceptions but for the most part I find these rules to help keep my shots from becoming distracting.
- Understanding Depth of Field for Beginners
- How Do Object Distance and Focal Length Affect Depth of Field?
- Focusing Basics
The first shot of the showerhead is the clear one. While the handle is out of focus, it is consistently out all the way down. And the sprayer head is completely in focus. But notice in the seconded shot, half the showerhead is in focus and the other half is out.
You can tell it looks sloppy when compared with the first shot. The same goes for the book text. Notice the first shot the text is readable and you can tell its a page from a book. While the second shot does have the text in focus, you can barely tell what the rest of the image is. Which brings us to our next point.
A great example of good shot clarity can be seen in this shot from Inception: In situations like this shooting with deep DOF keeps the layout of environment clear to the audience.
Just like left, right, top, and bottom of the frame can be used to isolate the scene; DOF can be used to control how deep a scene is. This gives the cinematographer the option to limit space. Take for example a parking lot. While in reality it may be a large space, using shallow depth of field one can create a very small, intimate scene with a character.
Check out this shot from Dear Frankie: