Depth of field and aperture relationship questions

Focusing Basics | Aperture and Depth of Field

depth of field and aperture relationship questions

Depth of field is determined by three factors – aperture size, distance from the lens, and the focal length of the lens. Let's look at how each one works. You aren't going to be able to learn these equations and do them in your head to map an ƒ number to a depth of field in, say, feet. This is why. Does changing the focal length change the depth of field for the same magnification .. I just hope to learn the relationship between depth of field (DOF) with the.

Knowing how to make the parts of your image you want sharp and the parts you want to be out of focus, is a great artistic tool to create great images. Getting the right depth of field for your shot can make all the difference. When should I use a shallow depth of field? Shallow DoF can also be useful in wildlife photographywhere you want the subject to stand out from its surroundings. This is also useful because many wildlife photo opportunities are low light situations, and increasing your aperture size will give you more light.

The result of this should also help give you a fast enough shutter speed to freeze the action. Notice how the bird pops out from the background.

depth of field and aperture relationship questions

When should I use deeper depth of field? The focus point was set at 8 meters, which made everything from 4 meters to infinity in focus. How can you determine depth of field?

Most cameras have a DoF preview button which will give you a preview as you look through the eye piece. This is probably the easiest and most under-utilized method. Using this button may cause your image to appear darker as you view it through the eye piece, but not to worry.

Your image will be properly exposed as long as you have the correct exposure settings. Can depth of field be adjusted to get everything in focus? Yes, using what is called the hyperfocal distance.

The relationship between aperture and depth of field

Use a DOF calculator to find your hyperfocal distance. What about depth of field in macro photography? Because most macro images are produced in low light and with a longer focal length, the depth of field is often very shallow.

It may also be necessary to increase your ISO to allow you to properly expose the image and to maximize your depth of field. Still, in many macro images your DoF may be very minute. Bokeh boh-ke comes from the Japanese word meaning blur.

Understanding Depth of Field for Beginners

To summarize controlling depth of field: Increase depth of field Narrow your aperture larger f-number Move farther from the subject Shorten focal length Widen your aperture smaller f-number Move closer to the subject Lengthen your focal length Take control of your depth of field.

Understanding how these adjustments control your it will greatly improve your photography. What questions do you have about depth of field? I am looking for an in-depth explanation of the relationship between aperture and depth of field that doesn't require a physics degree. Just geometry, and a bit of trigonometry, maybe, and also algebra. Here's what I know so far please feel free to correct me: Aperture is measured in f-stops, which is the ratio between a lens' focal length real or effective?

For any given focal length, the larger the f-number, the smaller the diameter of the iris. Not the iris diameter, but rather what's called the "front pupil diameter" which is the apparent size of the iris when seen from the front of the lens. There is also a "rear pupil diameter" too, which is the apparent size of the iris when seen from the back of the lens.

If both values are equal, then the lens is said to have a symmetric design. The pupil magnification ratio is the rear pupil diameter divided by the front pupil diameter, and if this magnification isn't equal to one, then the depth of field is going to be somewhat modified, but this is really only a significant effect for macro photography. This affects the picture's depth of field, which is the plane in which objects appear in focus. The larger the f-number, the thicker the focus plane.

Now, I've been told that the actual focus plane is always a really thin slice and everything closer or more distant from the sensor plane is, to varying degrees, out of focus.

A Simple Guide to Depth of Field

It is therefore better to think of the focus plane as a slice with a gradual? That's how it people think of depth of field. At a very high f-stop number, something called defraction kicks in, which I think is related to the ratio between light bouncing of the iris' edges and, well, what exactly?

depth of field and aperture relationship questions

The light falling on the sensor? Diffraction occurs around edges or transition zones. This is due to the wave nature of light. OK, so I wasn't completely honest when I said that no physics is required! Light can be seen as undulations of electric and magnetic fields, and at an edge, these undulations can radiate energy around the corner, while the undulations at the center of the iris all move straight forward in the original direction they were headed, as deviations away from the straight line precisely cancel each other out.

As there is no cancellation on the side of an edge, the waves can deviate from the straight line. If we assume a circular aperture, then the diffraction will be a uniform circular smear around points of light; if the aperture isn't circular — many lenses have polygonal irises — then the smear pattern will be more complex, and may generate starbursts around points of light.

Now, in practical terms, this means that in order to achieve good subject isolation, one should pick a close main subject, a small f-stop number, and a distant background. In order to achieve a large depth of field, one should pick a large f-stop number. Things get tricky with a close foreground and a distant background, unless one is able to shift the focal plane for example, with a tilt-shift lens. Also, please remember that depth of field also has a human dimension.

Now, to my questions: What is the physical explanation here? It's more of a geometric explanation. A wide aperture will have a broad cone, while a narrow aperture will have a shallow cone. The closer the focus point, the squatter will be the cone. The diameter of the cone at this point is about 61 mm. But my finger will completely cover my smartphone lens, which has a diameter of less than 2 mm.

Obviously an object will have to be much smaller in order to be completely blurred when it is close to the focus point. But entire mountain ranges can be blurred beyond recognition too, if they are distant enough. Is there a way to have a thick plane of things in acceptable focus, with a very steep fall-off after that?

For example, when photographing flowers, I sometimes want the whole flower in focus, but I want objects in the not-so-distant background to turn into pleasant colour blops.

You'll need to do a trick called "focus stacking" which takes numerous photographs at various focus distances, and then blends them together on the computer to get the focus fall-off desired.

I understand that there are some cameras that can do focus stacking for you.

  • Depth of Field, Part I: The Basics
  • Understanding Depth of Field for Beginners
  • Focusing Basics

The lens creates a cone from focal point to lens and another cone from lens to sensor. Those spots are in focus where the tip of the cone hits sensor. At other parts the tip is in front or behind sensor and will appear a bit blurred if the diameter of the part of the cone is larger than a pixel.