Dionoid Posted January 1, 2021 Share Posted January 1, 2021 (edited) Hi, I'm experimenting with flickering sprites on an Atari 2600 + real CRT. I always assumed that -when it comes to flickering objects- it's better to display the object as often as possible to get the least amount of perceived flickering; so e.g. displaying a sprite 2 out of 3 frames (67% visible) is better than displaying it 1 out of 2 frames (50% visible). However, in my perception, a constant flicker-frequency of 30Hz (i.e. showing a sprite every other frame) looks less flickering/annoying compared to showing it 2 out of 3 frames. And showing it 3 out of 4 frames is even worse. Is this just me? Here is a ROM showing 4 sprites. Anyone wants to test this ROM on a real CRT and give me feedback on which of the bottom 3 sprites shows the least flickering? (Note: the top sprite is just for reference, and is not flickering). flicker_test.bin flicker_test_moving.bin [Edit: when moving the object horizontally, the effect is even more noticable] Edited January 5, 2021 by Dionoid 6 1 Quote Link to comment Share on other sites More sharing options...
RevEng Posted January 1, 2021 Share Posted January 1, 2021 It's a very counter-intuitive result, but indeed I perceive the flicker getting worse for each square that's lower on the screen. (save the first, of course) Tested on real hardware with a CRT. Nice discovery! ? 1 Quote Link to comment Share on other sites More sharing options...
Thomas Jentzsch Posted January 1, 2021 Share Posted January 1, 2021 (edited) Interesting and unexpected finding. I have experimented with variable luma boosts (e.g. 0, 0, 4) for 3/4, but that didn't improve the flicker. The flicker frequency is effectively lower for 2/3 (20Hz) and 3/4 (15Hz) than for 1/2 (30Hz). That seems to be the reason. BTW#1: It might look better if every sprite is displayed at 30Hz, even if it is not flickering. That avoids switching between flicker on and off. BTW#2: I found that the best boost for $0a at 30Hz on my PAL TV is +4. Edited January 1, 2021 by Thomas Jentzsch 1 Quote Link to comment Share on other sites More sharing options...
+ZeroPage Homebrew Posted January 2, 2021 Share Posted January 2, 2021 12 hours ago, Dionoid said: Here is a ROM showing 4 sprites. Anyone wants to test this ROM on a real CRT and give me feedback on which of the bottom 3 sprites shows the least flickering? (Note: the top sprite is just for reference, and is not flickering). Thanks for making this! This will also be extremely useful for testing purposes on digital hardware for how well flicker translates through capture devices and then displayed on various streaming and video hosting services. - James Quote Link to comment Share on other sites More sharing options...
+Andrew Davie Posted January 2, 2021 Share Posted January 2, 2021 In order of preference. 1 2 4 3 #3 (2 out of 3) has a weird-ass strobing on the verticals that hurts my eyes. I suspect it's related (like photosensitive epilepsy) to individuals' response to flicker frequency as to what's preferable. Another effect I noticed is that the one I am looking at always looks MUCH (i.e., 2x) brighter than all the others. 1 1 Quote Link to comment Share on other sites More sharing options...
Mr SQL Posted January 2, 2021 Share Posted January 2, 2021 This is pretty cool it's good to see other programmers being open minded with variable Hz flicker tests, great tests @Dionoid Quote Link to comment Share on other sites More sharing options...
Just Jeff Posted January 3, 2021 Share Posted January 3, 2021 Part of your flicker on #2, has to do with your scanline count/frame rate of 266/59.1. That pulse that happens every second or so will go away if you get that to 262/60. I think I can see that on the others as well though its not as distinguishable. 1 Quote Link to comment Share on other sites More sharing options...
Dionoid Posted January 5, 2021 Author Share Posted January 5, 2021 On 1/3/2021 at 4:23 PM, Just Jeff said: Part of your flicker on #2, has to do with your scanline count/frame rate of 266/59.1. That pulse that happens every second or so will go away if you get that to 262/60. I think I can see that on the others as well though its not as distinguishable. I missed that the frequency wasn't at 60Hz; I fixed that and updated the ROMs. However I don't see why that would give a pulse on a CRT every second? 1 Quote Link to comment Share on other sites More sharing options...
+ZeroPage Homebrew Posted January 5, 2021 Share Posted January 5, 2021 23 minutes ago, Dionoid said: I missed that the frequency wasn't at 60Hz; I fixed that and updated the ROMs. However I don't see why that would give a pulse on a CRT every second? I'm guessing it has to do with the same issue if you try to film a CRT at the wrong shutter speed, you need all of the frequencies lined up perfectly. - James 3 Quote Link to comment Share on other sites More sharing options...
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