What is spatial frequency tuning?
Spatial frequency (SF) and orientation tuning are intrinsic properties of neurons in primary visual cortex (area V1). To investigate the neural mechanisms mediating selectivity in the awake animal, we measured the temporal dynamics of SF and orientation tuning.
How do you measure spatial frequency?
For the spatial variation where L is measured in distance units, the spatial frequency of the variation is 1/L. Generally, a sinusoidal curve f(x) = A sin(ωx + θ) is similar to the above pure sine but may differ in phase θ, period L = 2π/ω (i.e. angular frequency ω), or / and amplitude A.
What is spatial frequency analysis?
Spatial frequency analysis is a way in which one can predict the response of a linear spatial filter to any spatial pattern or complex waveform. Sinusoidal (sine-wave) gratings are used to determine the spatial filtering characteristics under study.
What is spatial frequency grating?
The unit employed to express spatial frequency is the number of cycles that fall within one degree of visual angle (each cycle is one dark and one light bar). A grating of high spatial frequency — many cycles within each degree of visual angle — contains narrow bars.
What MTF 50?
Introduction. MTF50 (MTF stands for Modulation Transfer Function, also known as SFR – Spatial Frequency Response) is the common parameter used for measuring image sharpness – the most important image quality factor.
How do you calculate MTF?
The MTF, or Modulation Transfer Function, is defined as the ratio of the image contrast to the target contrast, expressed as a function of spatial frequency. That is, MTF(u) = C'(u) / C(u). C is the contrast in the target, C’ is the corresponding contrast in the image.
How do you convert Snellen to cycles per degree?
These other notations can (with care) be converted to a Snellen fraction for comparison….LogMAR/Snellen Conversion.
| Snellen equivalent | LogMAR | Cycles per degree (cpd) |
|---|---|---|
| Snellen equivalent 6/360 (20/1200) | LogMAR 1.8 | Cycles per degree (cpd) 0.50 |
| Snellen equivalent 6/480 (20/1600) | LogMAR 1.9 | Cycles per degree (cpd) 0.28 |
Why is spatial frequency important?
The spatial frequency (SF) scales of facial information are generally used to categorizing faces. The image with high spatial frequencies (HSF) represents the fine-scale details of the original image, while the low spatial frequencies (LSF) retain the large-scale global shape of visual formation.
Is higher 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.
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 MTF and 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 the dynamic property of spatial frequency tuning?
Spatial Frequency-Tuning Dynamics. The nonseparable residual of V1 STRFs showed an interesting dynamic property: preferred SF tended to shift from lower frequencies at short latencies to higher frequencies at longer latencies.
What is spatial frequency and orientation tuning in primary visual cortex?
Spatial frequency (SF) and orientation tuning are intrinsic properties of neurons in primary visual cortex (area V1). To investigate the neural mechanisms mediating selectivity in the awake animal, we measured the temporal dynamics of SF and orientation tuning.
How separable is SF-Orientation tuning?
SF-orientation tuning in our sample is more than 70% linearly separable (marginal analysis), with a mean separability index of 0.90 (SVD analysis). For most cells we could not determine whether the nonseparable SF-orientation residuals were meaningful or were merely caused by measurement noise.