If we're talking about a true CRT monitor, then the input signal is basically driving the display directly. So there is no delay (other than the time required for the electrons to travel through the entire circuitry, which is negligible).
Late-era CRT televisions would have digital post-processing filters and such, which means the signal would get decoded and digitized first, then processed, then turned back into steering signals for the CRT. The latency depends on how fast this processing logic is.
I do not know of any CRT monitors that have such post-processing, but who knows...

In the case of LCD, you always have some digital processing logic. And if you feed it with a VGA signal, it will digitize this first, which may have additional delay compared to using DVI-D/HDMI/DisplayPort.
The actual latency will differ from one monitor to the next, and I believe I've seen latencys of over 30 ms on some models.
On TVs the processing is actually so long, that they have introduced special 'Game mode' settings which bypass the processing to reduce the latency.

So TL;DR: Yes, there's nothing faster than a CRT. LCDs suffer from latency, some more than others. This means they are not very suitable for a reaction test, unless you know what latency the LCD introduces, and this latency is within the margin of error of the total reaction time (which it probably isn't with 30+ ms).
Also, don't forget that there can also be delay on the computer-side, if you are using double-buffering or even triple-buffering.

I don't know any specific numbers but I'm guessing it's on the order of 10-100ms. The "response time" in an LCD's specifications is only the best-case scenario, usually measured while switching between two shades of gray.
CRT phosphors have some light->dark "response time" too (afterglow), but dark->light is always instant. There's also some time delay between activating the first pixel and the last pixel on the screen. At 120Hz, for example, this is about 8ms (slightly less than 8.33ms, since the vblank interval takes some time too).

Here are some tests to determine the response time and input lag in an LCD:
http://www.lagom.nl/lcd-test/response_time.php

Input lag depends entirely on the LCD.

It can be anywhere from less than 5ms to over 100ms. There's really few ways to figure out as LCD manufacturers do not list input lag. Just Google model numbers and hope someone has made an accurate measurement.

That said, if it's critical I'd look for a LCD with known low latency over hunting down old CRT monitors.

Honestly I don't think it will matter much. Humans are so slow to react that the monitor shouldn't affect it much.
I would doubt that most monitors would exceed 2 frames (33mS) behind.

I'll have a tester try it on the CRT today and will see if there is any difference.

Reaction time is a factor in this so please pay attention...

That popped into my head as soon as I read the title. 😜

Well, using the CRT made little difference.One candidate did worse on the CRT, another one slightly better (around 30 or so ms on average). Either way, it's not a massive amount by any means.

smeezekitty wrote:

Honestly I don't think it will matter much. Humans are so slow to react that the monitor shouldn't affect it much.
I would doubt that most monitors would exceed 2 frames (33mS) behind.

Monitor lag is added on top of human reaction time. You can't react to something before you see it.

His results if he had a 33ms (which is a noticeable amount of lag btw) monitor would be wrongly skewed by 33ms.

I don't really see how the monitor type matters though, all you need to do is know the difference and subtract it and you have your reaction time.

A few years ago I noticed a difference when playing the NES game "Super Mario Brothers 2". At the end of each level, you play a slot machine to earn extra lives. I would always watch for the cherries appearing, figure out the rhythm and then hit the A button accordingly. I'm better at it with an old CRT television than with an LCD.

philscomputerlab wrote:

A bit of a random question, but here it goes.

Been working on a reaction tester project, that measures how long it takes between the screen going green and the user pressing space. We used LCD monitors, and I am basically wondering if using a CRT monitor would yield faster results. If so, how many milliseconds faster would results be when using a CRT monitor?

I will actually test this, but wondering if anyone has experience in this regard.

I wonder how long will it take Phil to actually realize that there is currently no alternative to CRT. Probably the same amount of time just like with using Matrox G550 instead of G400:)

When it comes to reaction times, the fastest LCDs today are indistinguishable from CRTs.

ZellSF wrote:

When it comes to reaction times, the fastest LCDs today are indistinguishable from CRTs.

Your statement makes me wonder why do some eBay shoppers often buy CRT monitors and end up paying much more when you can just simple go to a local store buy an LCD one and pay much less. If only it was that simple...Anyway, If you're talking about TN ( poor's man technology ) then you can keep it =) When LCD monitors will catch up with CRT monitors in every aspect including gamma only then I personally will consider using it with my retro systems. On a good note the IPS technology is moving in the right direction, just need to improve the response time.

Dreamer_of_the_past wrote:

ZellSF wrote:

When it comes to reaction times, the fastest LCDs today are indistinguishable from CRTs.

Your statement makes me wonder why do some eBay shoppers often buy CRT monitors and end up paying much more when you can just simple go to a local store buy an LCD one and pay much less. If only it was that simple...Anyway, If you're talking about TN ( poor's man technology ) then you can keep it =)

I'm not. Plenty of IPS monitors with unnoticable amounts of input lag, probably a few VA ones too.

And tbh, while there are some areas where CRTs are better still (and a few where they're much worse), I've seen a lot of people go with CRTs for nostalgia reasons. There's as many people who buy CRTs because the fondly remember defects of the technology (scanlines...) as there are people buying them for better black levels.

ZellSF wrote:

Dreamer_of_the_past wrote:

ZellSF wrote:

When it comes to reaction times, the fastest LCDs today are indistinguishable from CRTs.

Your statement makes me wonder why do some eBay shoppers often buy CRT monitors and end up paying much more when you can just simple go to a local store buy an LCD one and pay much less. If only it was that simple...Anyway, If you're talking about TN ( poor's man technology ) then you can keep it =)

I'm not. Plenty of IPS monitors with unnoticeable amounts of input lag, probably a few VA ones too.

And tbh, while there are some areas where CRTs are better still (and a few where they're much worse), I've seen a lot of people go with CRTs for nostalgia reasons. There's as many people who buy CRTs because the fondly remember defects of the technology (scanlines...) as there are people buying them for better black levels.

Perhaps you should try to play Quake I, II or III on it. Scan lines don't bother me since all you have to do is to pick the right distance. Black bars related to the 16:9 aspect ratio bother me a lot more on modern widescreen TVs\monitors. Got myself a nice 27" Sony Trinitron KV27FV310 a few days ago and just love it. I am ready to throw away my LCD TV. I love the 4:3 aspect ratio. To me 16:9 is a technological leap back.

Dreamer_of_the_past wrote:

Perhaps you should try to play Quake I, II or III on it.

I have (I and III anyway). Maybe you should, your experience with LCDs seems severely outdated if you think the best of today's LCDs hinder the playability of the Quake games.

No problem playing quake on an LCD

Boring anecdotal evidence maybe, but I've seen many people on the internet complain how v-sync introduces terrible lag in games (Skyrim, specifically). I thought they were all exaggerating until I played it on my sister's LCD screen, holy shit it was downright unplayable. I'm still not sure how vsync could cause that, or why it would be noticable on an LCD specifically.

jwt27 wrote:

Boring anecdotal evidence maybe, but I've seen many people on the internet complain how v-sync introduces terrible lag in games (Skyrim, specifically). I thought they were all exaggerating until I played it on my sister's LCD screen, holy shit it was downright unplayable. I'm still not sure how vsync could cause that, or why it would be noticable on an LCD specifically.

The input lag hit associated with vsync gets worse the higher the framerate (vsync does not lock it to 60, it only presents 60). So CRTs didn't usually have so bad vsync lag because the computers of the time didn't really run games much faster than the screen's refresh rate.

Also, tearing is more noticable at higher framerates, people turn vsync on to get rid of tearing. So less CRT users back in the day turned vsync on, because they weren't reaching those framerates. So they wouldn't have vsync problems in the first place.

So that's why you don't remember this problem from the CRT days, or don't get them on your period accurate CRT computer.

This is a problem that modern LCDs are solving with FreeSync and G-Sync. So if that's the sort of tradeoffs that bother you, go LCD.

If you want to try do deal with it on another setup... Frame limiting, triple buffering and adaptive vsync are things you should look into. They're all tradeoffs mind you.

I did play Quake3 on a Voodoo3 without vsync, it felt a bit laggy when enabled but nowhere near unplayable. With my current machine I'm basically hitting the vsync limit all the time, even in Skyrim, but never noticed any lag like that.