Colors not changing intensity

Coding
1

I am running a script that presents red, green, and blue colors with intensities that range from 0-256 for each color, incrementing by 25 steps. The purpose of this is to calibrate the screen. However, before doing that, I ran this script to see whether intensity changes are visible to the naked eye (from my understanding, they should be; at least to detect a difference from 25 to 200). The problem is that intensity does not seem to change on the screen, despite the loop working (confirmed/reproducible via on-screen messages between each intensity change). I was wondering if anyone might have suggestions for fixing this.

Here is the reproducible script (press ‘q’ to quit whenever):

from psychopy import visual, core, event
import csv

# Create a window for calibration
win = visual.Window(size=(1920, 1080), fullscr=True, units="pix", color=[0,0,0])

# Define color channels and steps
channels = ['red', 'green', 'blue']
steps = list(range(0, 256, 25)) # Set the steps

# To store the records
records = []

# Function to check for 'q' key press
def check_quit_key():
    keys = event.getKeys()
    if 'q' in keys:
        # Save the records before quitting
        with open('color_calibration_records.csv', 'w', newline='') as file:
            writer = csv.writer(file)
            writer.writerow(["Color", "Intensity"])  # Header
            writer.writerows(records)  # Data rows
        win.close()
        core.quit()

# Create a rectangle to cover the entire screen
rect = visual.Rect(win, width=1920, height=1080)

# Calibrate each color channel
for channel in channels:
    for step in steps:
        if channel == 'red':
            color = [step, 0, 0]
        elif channel == 'green':
            color = [0, step, 0]
        elif channel == 'blue':
            color = [0, 0, step]
        
        # Show the color
        rect.fillColor = color
        rect.draw()
        win.flip()
        core.wait(3)  # Show color for 3 seconds
        check_quit_key()  # Check if 'q' was pressed

        # Record the value
        records.append([channel, step])

        # Display the "Just shown" message on a black screen
        rect.fillColor = [0, 0, 0]
        rect.draw()
        message = f"Just shown: {channel.upper()} {step}"
        text = visual.TextStim(win, text=message, height=50, color='white')
        text.draw()
        win.flip()
        core.wait(1)  # Display the message for 1 second
        win.flip()

# Save the records to a CSV
with open('color_calibration_records.csv', 'w', newline='') as file:
    writer = csv.writer(file)
    writer.writerow(["Color", "Intensity"])  # Header
    writer.writerows(records)  # Data rows

# Close the window
win.close()

I am using Psyvhopy coder version 2023.1.2 on a Windows computer (running Windows 11) with a BenQ Zowie XL2540K 8-bit 240Hz display.

2

The problem here is that you haven’t specified a color space, so PsychoPy’s using its default color space, which is RGB between -1 and 1.

With 1 being the maximum, [25, 0, 0] is maximum red, medium blue and medium green, which is why the color isn’t changing.

If color space isn’t specified for a stimulus it uses the color space of the window, so you can leave the Rect as is and just add colorSpace = "rgb255" to where you create the window (visual.Window(...))

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