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Avoiding moire while filming a CRT

falter

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I'm trying to do some video of various machines in action and with my Samsung Galaxy Note 20 Ultra I've been able to eliminate the wave or band effect by setting the frames per second to 1/30 or 1/60. But no matter what I try, I cannot get rid of moire. I'm filming a composite monitor (Apple II color), and nothing in the way of angle changes or such seem to work. Is it just impossible with a cell cam? I've looked around and on youtube and I see people filming with DSLRs with minimal moire. But on mine it's horrific.
 
You need to play with the distance. Also, cameras with a low-pass filter are better on that. Sadly, removing the low-pass filter is a trend for years now.
 
Don't auto-focus; do it manually and defocus just a bit from maximum sharpness until the guilty hi-frequency detail is filtered out. Also: slower shutter speeds seem to reduce moire patterns for some reason, but then you're limiting the frame rate as well. Either way, I wouldn't get my hopes up about taking CRT videos with a cell phone.

In particular, Samsung seems to have trouble getting the frame rate right. NTSC is 59.94 Hz, and for Apple II video you need something closer to 59.92. With the two Samsung Galaxy models I've tried, if you pick 60 fps (and set the shutter to 1/60) the real framerate goes way off... like 59.3 or something. With that much of a difference you don't get the typical "dark band" effect, but you do get very obvious rolling tearlines whenever there's lots of on-screen movement. (If you want to verify the actual framerate of what you just shot, try VLC for Android.)
 
I've looked around and on youtube and I see people filming with DSLRs with minimal moire. But on mine it's horrific.

So you have the same issue with your DSLR? The same rule applies; defocusing just a bit will usually solve the problem. (Useful tips here.) You can also try fooling with the focal length or cranking down the aperture, although the latter is going to have knock-on effects.
 
I actually don't have a DSLR - well, I do but it's ancient. I'm trying to mollify my wife by not adding to the number of expensive hobbies I have. Interestingly, I found my phone handled filming my IBM 5154 better than it did the composite Apple II monitor. With composite it *really* goes wonky. I've attached a shot below, one with composite, the other without.

I suppose at some point I'll have to make a decision and maybe give up on using my cell. I purchased a cheap usb composite video capture device - that might suffice for now. I just find with those the colors and sharpness are a bit off.
 

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My StarTech SVID232 arrived tonight. It was $50 or so. Using OBS studio.. it seems like it works fairly well.. once I get the sharpness dialed in. A question though - would there be any difference in quality if I were using something more fancy/expensive? Composite will come out the same way regardless right? Most of my machines are either composite/monochrome video or no video at all. My PC are RGB but I rarely have the desire to film those.
 
How 'ancient' is your ancient DSLR? Some have both official and unofficial firmware upgrades for extra capabilities.

Mine's a 9 year old Canon EOS, and I recently came across a wonderful little 3rd-party add-on for it called Magic Lantern (lets you fine-tune a whole bunch of settings much more flexibly - frame rates, shutter speeds, apertures, exposures, white balance, focusing, recording bitrates, you name it). Managed to get some good results with that thing installed... no bars, no tearing, mostly faithful colors.
 
Also if possible, do a live feed of the camera's video output to a full-resolution monitor when setting up the shot, because you can't always trust the camera's own LCD preview screen to be 100% accurate. With my camcorders, I've seen it show moiré patterns that were not in the actual video it recorded, and not show moiré patterns that were in the video it recorded.
 
Mine's a 9 year old Canon EOS, and I recently came across a wonderful little 3rd-party add-on for it called Magic Lantern (lets you fine-tune a whole bunch of settings much more flexibly - frame rates, shutter speeds, apertures, exposures, white balance, focusing, recording bitrates, you name it). Managed to get some good results with that thing installed... no bars, no tearing, mostly faithful colors.
Speaking of shutter speeds... can it be set to 1/70 shutter speed to record a VGA monitor without flicker? I've been looking for some way to do that for years, but virtually all video cameras only offer shutter speeds in multiples (or fractions) of the frame rate.
 
I wonder if the difference between the IBM 5154 and the apple II color is how glossy or matte the tube is? I know my Apple monitor is quite shiny. I don’t have a 5154, but a clone, but looking at photos online they seem to be slightly matte finish. Do you have a 5153? They are pretty shiny so maybe that would be a good comparison to the Apple monitor.
 
Speaking of shutter speeds... can it be set to 1/70 shutter speed to record a VGA monitor without flicker? I've been looking for some way to do that for years, but virtually all video cameras only offer shutter speeds in multiples (or fractions) of the frame rate.

That may be achievable; the video frame rate is set through dividing the camera's clock frequency by two timers in succession, and Magic Lantern's "FPS Override" lets you adjust those two timer values in either direction. Then you can tweak the shutter speed by some offset from the FPS value.

Problem is, I can't test 1/70 due to a bug in the specific ML build for my camera... it works fine if you slow down the timers, but not if you try to speed them up, so I can't get from 59.94 to 70.
 
I wonder if the difference between the IBM 5154 and the apple II color is how glossy or matte the tube is? I know my Apple monitor is quite shiny. I don’t have a 5154, but a clone, but looking at photos online they seem to be slightly matte finish. Do you have a 5153? They are pretty shiny so maybe that would be a good comparison to the Apple monitor.

My hunch is that it's more about the differences in dot pitch and beam focus, since that's what tends to generate those high-frequency sampling errors which result in moire patterns.

BTW: the DaVinci Resolve video editing software lets you remove moire patterns to some degree (tutorial), even in the free version. Haven't tried it myself but I've seen a few promising attempts with CRT footage so may be worth a shot.
 
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It’s been a long time but I remember those Apple monitors having a visible-to-the-human-eye dot pitch graininess. Dirty little secret about Apple II color is it usually looks better on objectively worse monitors because the artifacts are less obvious.
 
The actual composite monitor I'm using is the Applecolor IIe (I think that's the name). Has the front panel that opens downwards out front (which is usually missing). It looks fantastic in person-- very nice and sharp, especially with text, but yeah, my Galaxy hates it. And yes, you can definitely see the 'grain', so to speak. I've tried different angles, turning the phone sideways.. anything I could think of. Adjusting the framerate down to 1/30 seemed to help a bit.. but still looking at it after the moire is pretty awful. I also tried my Commodore 1701.. but it actually bugs out with the Mindset.. it'll be good for a minute and then suddenly the video will go dark or out of sync. It works great with other machines so not sure what that's about.

I ordered a cable for my Taxan 420 monitor, which is really what belongs with this Mindset anyway, but I could only find it in Britain and have to wait. I'm hoping it works, and that that monitor has fewer issues than filming with my composite. I seem to be cursed with RGB monitors. My original 5154 works, but brightness is just a bit dim. I got a Tandy CM2 - but Fedex bounced it and the PCB got broken inside. Then I got that monitor with my Computerland machine... it has that weird issue with a moving dark spot up top. I got a 5153 that was in good working order, but Fedex absolutely destroyed it. Pulverized it. Then I got the other 5153, it works except only for a minute or so before brightness cranks way up and it starts flaking out. I have a Zenith ZVM-135, but don't have the 25 pin connector it uses. Composite works though. And then lastly I have this Taxan, which comes up white with nothing connected but I don't have a proper cable to try it with anything. I tried jumpering it to the Mindset but got nothing. Heh. Someone just doesn't want me to have a good RGB.

My ancient DSLR is a Lumix which is more than 10 years old. I need to probably do something about that. The video capture device I got seems acceptable, but when I'm filming a computer I like to actually show the computer.. just showing the screen output - well, you might as well just use an emulator for that.

I do have a 5153.. however it has this issue where all of a sudden the brightness goes to full, retrace, etc... I think the controls might be dodgy.. if I work them a bit beforehand it'll stay normal longer. But I'll give it a try just for testing purposes.

Many thanks for the great suggestions so far! Such a vexing issue.
 
As much as I love the old-school feel of a CRT I'm really starting to feel like we're hitting the far end of the bathtub curve for most of these 80's RGB displays. If you find one with electronics that aren't crumbling then the case is.

(My Commodore 1084s are suffering pretty badly from both. Annoyingly my 1702 seems to be working like brand new.)
 
Yeah.. sadly I think that's where we're at. Honestly I kind of cringe a little every time I turn a real vintage CRT on. I'm always expecting something to explode inside. I just hate LCD with vintage gear.. it doesn't feel authentic. But I'm too intimidated by the risk of shock to recap things. My CM-2 could probably be easily fixed by repairing the board and damaged traces. But to get to that I have to disconnect the anode cap, and even though it's been sitting 2 years I still don't feel like I could trust my discharge skills to be sure it was safe.
 
For composite monochrome work (which is where most of my interest is these days) I’ve been thinking of intentionally messing with a composite to VGA adapter so it outputs red or amber instead of white. Then I can at least pretend I’m using a gas plasma or electroluminescent display.
 
So last night I made a splitter cable, so that I could split the composite video signal coming from my Mindset to both the IIe composite monitor, as well as the Startech USB video capture. Didn't seem to lose any signal quality. I then did some captures, and compared them to 8bitguy's captures for his Mindset video, and I think they look same or even slightly better. I think this is the best way forward as it allows me to flip back and forth, showing the machine itself, rather than just a video feed which could have come from an emulator.

I could not stop the moire effect no matter what I tried, as suggested above with my Note 20. I think it's just a limitation of Samsung cell phone cameras, and perhaps I should just be grateful it has the quality it does to start with. I'm looking at maybe picking up a used Lumix G7 or something. Not really up to speed on DSLRs but I don't want to spend $1k right now, or my wife will spend half that much to have me buried in a shallow grave outside town. I did manage to reduce the moire when I had the insight that maybe the 5154's low brightness was a factor. I lowered the brightness on the IIe monitor and the moire quite noticeably diminished. Anyway, I think that's as good as I can get it for now.
 
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