Spatial frequency

Question 1

Dark adaptation

Answer 1

Rods take over vision in the dark;

• Pupil dilation
• Cone to rod transition
• Bleaching of pigment in receptors becomes undone
• Less receptor signal, less negative feedback from horizontal

Question 2

Spatial frequency

Answer 2

Every image/contour can be decomposed into spatial frequencies.

Sharp edges contain low and high frequencies

Small spots of light (impulse function) also contains low and high

Question 3

High spatial frequencies

Answer 3

Shows mainly the details, sharp but not the global shape

Question 4

Low spatial frequencies

Answer 4

Shows mainly the global shape

vague and unsharp

Question 5

Spatial freq. sensitivity

Answer 5

Depends on contrast and brightness.

Thats why detailed tasks are best done in well lit room

Changes throughout life (bad as baby, best around teens and decreases later in life)

Man is most comparable to monkey

Question 6

Receptive field size

Answer 6

Strongest response yielded depends on the receptive field size.

Combined input of center component and surrounds gives the characteristic SF tuning

Question 7

Midget and Parasol

Answer 7

Midget (X) have small RF, so tuned to high spatial freq.

Parasol (Y) have large RF, so tuned to low spatial freq.

Question 8

Proximity

Answer 8

When further back, the contrast changes which makes the low freq. dominant; global picture

Close up triggers the high frequency, more detailed.

Seenin hybrid / mosaic pictures.