What is MTF in imaging?

The modulation transfer function (MTF) is the spatial frequency response of an imaging system or a component. It is the contrast at a given spatial frequency relative to low frequencies.

What is an OTF image processing?

The Optical Transfer Function (OTF) is a complex-valued function describing the response of an imaging system as a function of spatial frequency. Modulation Transfer Function (MTF) = magnitude of the complex OTF. Phase Transfer Function (PTF) = phase of the complex OTF.

How is contrast created in transmission electron microscopy?

The contrast between two adjacent areas in a TEM image can be defined as the difference in the electron densities in image plane. Due to the scattering of the incident beam by the sample, the amplitude and phase of the electron wave change, which results in amplitude contrast and phase contrast, correspondingly.

What is CTF in cryo em?

CTF correction is a procedure that aims to restore the distorted high-resolution information in cryo-tomograms. The CTF is determined and corrected on each individual projection comprising a tilt series before the tomogram is reconstructed (Fernández et al., 2006).

What is a good MTF value?

Generally, contrast will typically be higher than resolution in MTF charts, so anything higher than 0.9 indicates excellent contrast, between 0.7 and 0.9 is generally very good, between 0.5 and 0.7 is average and anything below 0.5 is soft / bad.

How does MTF affect image quality?

To define the MTF, the lens reproduces lines (grids) with different distances (spatial frequency in line pairs/mm). The loss of contrast due to the optical reproduction is shown in the MTF-graph for each spatial frequency. The more line pairs/mm that can be distinguished, the better the resolution of the lens.

What is coherent transfer function?

The transfer function itself is merely the scaled version of pupil function for coherent light, and pupil autocorrelation for incoherent light. In effect, the system impulse response acts as a smoothing spatial filter, softening edges, reducing amplitude, and suppressing high frequency distributions.

What is the use of PSF in aliasing?

A high-resolution representation of the PSF where aliasing errors are minimized is used to obtain improved restorations. The SNR is the parameter which ultimately limits the restoration quality and determines the need for an accurate PSF model.

What is contrast in electron microscope?

Diffraction contrast means the intensity change in an electron microscope image that is formed when the diffraction condition is changed with areas of the specimen. In the bright-field image (formed by the transmitted wave), the area where diffraction takes place loses its image intensity, thus getting dark.

What is phase contrast and electron microscopy?

In TEM, “Zernike phase contrast” means contrast which is obtained by converting the phase change of electron waves scattered by a specimen into the amplitude change. The conversion is performed by using a phase plate or a combined effect of the spherical aberration of the electron lens and defocus.

What is CTF formula?

The contrast transfer function (CTF) mathematically describes how aberrations in a transmission electron microscope (TEM) modify the image of a sample. This contrast transfer function (CTF) sets the resolution of high-resolution transmission electron microscopy (HRTEM), also known as phase contrast TEM.

What is FSC in cryo-EM?

Fourier Shell Correlation (FSC) is a measure of reliability of the three-dimensional (3D) structures of biological macromolecules obtained by “single particle analysis”.

Is a higher or lower MTF better?

In general, the higher and flatter the lines the better. Higher lines indicate better contrast (10 lines/mm) or resolution (30 lines/mm) while a flatter (left to right) line shows that the optical performance is close to the same at the edge of the image compared to the center.

How do you read a MTF chart?

What is the relation between MTF and resolution?

The MTF of a lens, as the name implies, is a measurement of its ability to transfer contrast at a particular resolution from the object to the image. In other words, MTF is a way to incorporate resolution and contrast into a single specification.

What is MTF PSF?

A point spread function (PSF) or modulation transfer function (MTF) is a measure of how well focused a satellite imaging sensor is. Every type of camera system has a slight amount of defocus.

What is line spread function?

line spread func·tion (LSF), a measure of the ability of a system to form sharp images; in radiology, determined by measuring the spatial density distribution on film of the x-ray image of a narrow slit in a dense metal, such as uranium; from this can be calculated the modulation transfer function.

What is contrast of image?

The difference in brightness between light and dark areas of an image. Contrast determines the number of shades in the image. A low-contrast image (left) retains detail but tends to lack dimension and looks soft. An image with normal contrast (center) retains detail and dimension, and looks crisp.

What is contrast in EM?

What is phase contrast used for?

Phase-contrast microscopy is a technique used for gaining contrast in a translucent specimen without staining the specimen. One major advantage is that phase-contrast microscopy can be used with high-resolution objectives, but it requires a specialized condenser and more expensive objectives.