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Selection of monitor

Hello!
I just want to ask a question about the benefits of Display ++ LCD monitor on presenting stimuli with PsyhoPy. In our lab we are studying on spatial frequency and color. We think to buy EIZO CG248-4K but we can’t decide. We will study with LMS values and have to make RGB conversion but would using Display ++ LCD or EIZO make a big difference on displaying color values?

Hello,

In short, they are both good choices. Those monitors have lots of similarities in terms of peak luminance, 10-bit RGB input/output, and excellent colour accuracy. There is a trade-off in terms of vertical refresh rate and resolution. The EIZO is 4K and the Display++ is FHD. The D++ has a higher refresh rate than the EIZO which makes it good for motion experiments. I never ran a ColorEdge at less than 4K resolution, so I’m not sure if using a lower resolution than native will give you higher refresh rates. The Display++ has a few I/O features but I haven’t heard much about them.

A question I have after thinking about this. Does vanilla PsychoPy supports 10-bit RGB output?

Thanks A lot! Actually what I really want to know is what is the difference between using psychopy (or psychtoolbox) + a good monitor like Eizo versus using display ++? Is using an ordinary open gl graphics card with psychopy enough to carry out vision experiments? Or are there advantages to using specialized hardware such as BITS# or Display ++ (which has BITS integrated in it) from CRSLTD.

Hello Gizem,

High end displays give you a brighter picture, a larger color gamut, and more contrast. If your experiment doesn’t need to use CRTs, always settle for a high-end LED/LCD display if you can get them.

Between the two displays, you get more color, higher contrast, and better response times on the Display++. Display++ outputs 10-bit color but claims to get 16-bit output through “temporal dithering” (not sure how that works), where you are constrained to 10-bits out with the Eizo. If you don’t take advantage of the aforementioned features of the D++, they are pretty much the same for displaying static stimuli, but the Eizo gives you a much higher resolution.

GL cards are generally a good idea for vision research and Quadro K2200s can easily drive a 4K Eizo.

Colour calibration can be performed on either monitor. The real advantage of the Display++ is the additional bits of contrast resolution (most flat panels are limited to 8 bits, so 256 greyscale levels, and having a Bits# can’t help you fix that). If you’re going to measure detection thresholds or increments then you should buy the Display++

Note also the very different sizes that you should think about in your lab set up. The Display++ is massive which also means moderately big pixels. If you need high spatial frequencies you’ll need to mount your Display++ a long way away!

The last concern about the Eizo is that you don’t know if it’s doing any post-processing to your image before displaying it. This is a big issue in flat screen TVs but can also be a problem with a monitor. If EIZO have decided the image looks nicer “sharpened” then it changes what you wanted to present. This can also take time so some monitors end up having a lag to display stimuli. Display++ is designed for presenting stimuli exactly as you wanted them and very quickly.

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Display++ has integrated hardware gamma correction tables, spatial uniformity correction and a CIE XYZ colour management system. The contrast ratio is typically 1400:1 - we use an IPS panel which is natively 10-bit RGB and runs at 120Hz (5 ms G2G response time). When the temporal dithering feature is enabled, the system supports up to 16-bit RGB resolution over a 64 frame video cycle. This takes about 500 ms to run with a 120Hz input (full details are provided in the documentation). Each Display++ unit is calibrated in the CRS factory using a reference spectroradiometer and provided with a comprehensive report (SPD files generated during calibration are available on request). The delivered “ready-to-run” state is linear light output with CIE XYZ values reproduced across the full scale range within 1 DE. The peak output is calibrated to 120 cd.m^-2 but this can be changed to other values just by editing a number in the device configuration file. This is with the LED backlight set to strobing mode - higher peak values are possible if the backlight is running in DC mode. Display++ features an integrated calibrated luminance sensor; the light output through the whole system is measured continually and the LED backlight adjusted to keep the peak value held constant. The principle is to compensate for short and long term drift and deal with fluctuations in temperature. If anyone wants to see a factory calibration report, just let me know.

Steve Elliott @ CRS

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Thanks a lot! I guess my professor got in contact with Steve,
Bests,
Gizem