An angular resolution calculator can help you determine a lens’s angular resolution, or its ability to detect minute features of an object.

Angular Resolution Definition

Angular resolution is a fundamental determinant of image resolution since it represents the capacity of any image-forming instrument, such as an optical or radio telescope, a microscope, a camera, or an eye, to differentiate microscopic details of an object. It employs optics when dealing with light waves, antenna theory when dealing with radio waves, and acoustics when dealing with sound waves. When a camera has high resolution because of its excellent picture quality, it really has a poor angular resolution. Because the angular distance or difference in angle, at which it can still resolve individual objects, is low.

The word spatial resolution, which is closely related to angular resolution in imaging tools, refers to the precision of a measurement with regard to space. The Rayleigh criteria illustrate that diffraction limits the minimum angular spread that a forming image system can resolve to the ratio of the wavelength of the waves to the aperture width. In high-resolution imaging systems, we use big apertures. For example, high-resolution imaging systems are astronomical telescopes, long-distance telephoto camera lenses and radio telescopes.

What does angular resolution measure?

Angular resolution is nothing but the ability of an optical instrument to separate some two objects located at a small angular distance. So, to make it easier to explain, with this physical quantity, we can:

  • solve some two points that are close to each other,
  • we can also distinguish two objects very distant.

The lower the angular resolution is, the more different details you can see. Also, it is necessary when we are designing a microscope, telescope or camera. Even we humans have the angular resolution in our eyes!

How to calculate an angular resolution?

Two different spots resolve when the diffraction maximum of one picture coincides with the initial minimum diffraction of a second image as stated by the Rayleigh criteria. The two points are resolved if the distance between them is more significant, and they are not resolved if the distance is smaller.

Angular resolution formula

The requirement for angular resolution is Rayleigh’s criterion. Lord Rayleigh, a notable scientist, provided an empirical formula for angular resolution:

θ = 1.22 * λ / d


  • θ is the angular resolution (that are in radians),
  • λ is the wavelength of the light,
  • d is the diameter of the lens aperture.

The formula above is developed for diffraction gratings but it may also be useful in other situations. Two light sources resolve when the major diffraction maximum of one picture coincides with the initial minimum of the other according to Lord Rayleigh.

How to calculate the wavelenght?

The electromagnetic spectrum is most typically linked with wavelength, which is the distance between one frequency wave peak and the next. The information you are provided affects how you calculate wavelength. You can use the fundamental wavelength formula if you know the wave’s speed and frequency. Also, you can use the energy equation to estimate the wavelength of light given the specific energy of a photon. As long as you have the right equation, calculating wavelength is simple.

Calculating Wavelength Given Speed and Frequency

The wavelength formula, when wavelenght is given in speed and frequency is as follows:


Also very important, when we want to measure wavelengt, use the proper measurement units. Both metric and imperial units can be helpful to express speed. Miles per hour (mph), kilometres per hour (kph), meters per second (m/s), and so on are all examples of speed. The units of wavelength are nearly invariably metric: nanometers, meters, millimetres, and so on. Hertz (Hz) is a frequency unit that stands for “per second.” 

Always use the same units throughout the equation. The majority of computations are in metric units. For example, if the frequency is in kilohertz (kHz) or the wave speed is in kilometres per second (km/s), multiply by 1000 to get Hertz and m/s (10 kHz = 10,000 Hz).

The next step is to enter the known data. Calculate the wavelength of the light waves that were employed to focus the picture. This number is represented by W in the angular resolution formula. Assume you’re dealing with a yellow light source. The wavelength of yellow light is approximately 577 nm. This phone number may be looked up. Next, you’ll need to figure out what frequency the light you’re utilizing is. To get a more specific answer, you should also know the speed of light. So, if we want to compute a wave’s wavelength, we must feed the wave’s speed and frequency into the equation. We will have the result of the wavelength by dividing speed by frequency.

If you have a wavelength, you may rearrange this equation and solve for speed or frequency. Use the formula to compute speed given a frequency and wavelength:


Use the formula to compute frequency given a speed and wavelength:

v=\lambda \cdot f

Calculating a Photon’s Wavelength Based on Its Energy

Using the following energy equation, calculate the wavelength:


where E represent energy of the system in Joules, h is Planck’s constant: 6.626 x 10-34 Joule seconds (J s), c is speed of light in vacumm 3.0 x 108 meters per second (m/s) and lambda is the wavelength in meters (m).

To solve for wavelength, restructure the equation using algebra. When both sides of the equation are multiplied by wavelength and then divided by energy, the result is:

\lambda = \frac{hc}{E}

As a result, the final objective is to include known variables and solve the issue. You may solve the wavelength by introducing energy variables after you’ve adjusted the equation. The other two variables are always the same since they are constants. Multiply the constants together and divide by the energy to solve.

Catching Mistakes

When we finish the task, we need to see if we have made a mistake. To make sure that you have correct answer go and do these steps below:

  • Multiply the wavelength by the frequency to check your answer. Multiplying the wavelength by the frequency should give you the wave speed you started with if you obtained the proper value for the wavelength. Check your math if it doesn’t. If you’re using a calculator, double-check that the numbers are entered accurately.
  • To eliminate calculator rounding problems, use scientific notation. When working with light speed, wavelength calculations can entail very big numbers. Rounding issues on your calculator may result as a result of this. Write your numbers in scientific notation and double-check the significant digits to avoid this.
  • When a wave reaches a different medium, it should not change frequency. A wave that crosses the boundary from one medium to another appears in many word puzzles. Calculating a new frequency for the wave is a typical blunder here. The wave’s frequency remains constant when it passes the border, but the wavelength and wave speed change.

What is the angular resolution of the human eye?

The diameter of an eye pupil (our natural lens) varies throughout the day and night, on bright days, it is roughly 2 mm, and at night it is approximately 8 mm. Let’s pretend we’re trying to resolve points that are green in color; the wavelength of green light is 550 nm. So, the angular resolution during the day is 0.02°, according to the Angular Resolution Calculator.

This finding may be similar to the Hubble space telescope, which has a 2.4 m diameter mirror (it collects light just like the eye pupil). Angular resolution is 0.000016°, so it is 125 times greater than our eye!