question regarding 60fps+120hz = double image

[blurbian]

So i understand that if FPS is half of the monitors refresh rate, you get a double image.
By that logic, there should be a double image when i play a 60 FPS game (many many retro games), with my LG C9s refresh rate set to 120hz.
So that suggests it would be better to set the refreshrate of the monitor to 60hz in Windows, correct?

I'm asking because, if I compare 120hz and 60hz refresh rate, with a 60fps game / test-ufo 60fps, I dont see a difference.

[RealNC]

So i understand that if FPS is half of the monitors refresh rate, you get a double image.
By that logic, there should be a double image when i play a 60 FPS game (many many retro games), with my LG C9s refresh rate set to 120hz.
So that suggests it would be better to set the refreshrate of the monitor to 60hz in Windows, correct?

I'm asking because, if I compare 120hz and 60hz refresh rate, with a 60fps game / test-ufo 60fps, I dont see a difference.

You only get a double image when using BFI or backlight strobing.

[blurbian]

You only get a double image when using BFI or backlight strobing.

Oh, right i guess i didn't read well enough / I misremembered.
Thank you for clearing that up for me!

So ideally you would set your monitors Hz to match the games FPS, and still have BFI somehow.... yeah that's gonna be difficult, as software BFI would never work. So it would need to be build into the monitor itself, like Pulsar but sadly its incompatible with OLED.

Or a CRT could technically be run at 30 fps and naturally be impulse displayed.
But if I remember correctly from back in the day, a CRT (especially a 31khz PC monitor) running at 30hz would flicker alot. I guess because the phosphors would fade out and then go without being relit for too long causing your eyes to catch up to the absence of light much more easily.
Many retro 30FPS games out there still (Mostly N64,360,PS3).

[RealNC]

So ideally you would set your monitors Hz to match the games FPS, and still have BFI somehow.... yeah that's gonna be difficult, as software BFI would never work. So it would need to be build into the monitor itself, like Pulsar but sadly its incompatible with OLED.

For a 60FPS game, you'd need 120Hz and use normal BFI. It's the BFI rate that matters, not the display's Hz For example, on a 240Hz display, you'd can still use 240Hz for 60FPS content. You'd need to configure BFI to a 1/3 mode (meaning it should output 1 content frame, then 3 black frames.)

Or a CRT could technically be run at 30 fps and naturally be impulse displayed.
But if I remember correctly from back in the day, a CRT (especially a 31khz PC monitor) running at 30hz would flicker alot. I guess because the phosphors would fade out and then go without being relit for too long causing your eyes to catch up to the absence of light much more easily.
Many retro 30FPS games out there still (Mostly N64,360,PS3).

It depends on the timings. If the scanout rate is actually 30Hz, flicker would be less. However, I'm not sure CRT monitors would be able to do that to begin with. They probably would need accelerated scanout when trying very low refresh rates, (like "QFT" of today) with a large vertical total, because they can't handle arbitrarily low pixel clocks. So you get severe flicker because the beam wouldn't jump to the top right away and thus the screen would be black for a long time. That's my guess. All CRT monitors I ever owned could only go down to 50Hz or thereabout. Once the pixel clock got too low, they gave up. I didn't know about timings back then so I never tried to keep the pixel clock high though increasing VT.