Samsung 2494 PC Monitor Review: Input lag and refresh rate overclocking tested using the PiLagTesterPRO
SAMSUNG 2494SW review: input lag, upscaling and "overclocking" using the piLagTesterPRO
This 1080p computer monitor from 2011 has good upscaling, and low lag, and decent response time. It's a TN display so viewing angles are only good directly in the sweet spot. Paired with an OSSC it would be a great retro gamer choice. It's one of the rare displays I've tested that supports "overclocking": it has unadvertised support for higher than 60hz refresh rates and actually draws those higher refresh rates properly.
Image quality
Good upscaling is critical for retro gaming. Ideally, all pixels should appear equally sharp and bright (no aliasing), and angled lines should appear smooth, with no jagged, irregular steps. Also important is that the display shows most or all of the pixels it is sent. Often, this is not the case, with some number of pixels cropped from the bottom or top edges. Shockingly, these tests are relevant for modern gaming as well, because even at their native resolution many TVs have aliasing and cropping.
I attempted to adjust the set to minimize cropping and aliasing. The monitor has a PC/AV toggle in the settings screen; the only difference seems to be that it crops a lot of content off the edges when set to AV mode. So I used PC mode for all the below tests, which has zero cropping
Note that interlaced content is not supported, neither 480i or 1080i.
| resolution | appearance |
| 480p | somewhat soft but no aliasing |
| 720p | sharp but with pixel rearrangement that causes 45 degree lines to look a bit jagged |
| 1080p | Perfect |
| 12800x960 | mild aliasing, A- |
| 1600x900 | minimal aliasing and jaggedness, B- |
This LCD supports 960p. This is
particularly interesting to retro gamers since that mode is used by the OSSC upscaler
to display 480i/p with zero added artifacts. The OSSC can use this mode to
display 480i with alternating scan lines and bob deinterlacing, which does a
very good job of matching the visual experience of 480i on a CRT. On this
display 960p is sharper than 480p but has a little aliasing. I think 480p would
be closer to emulating a CRT's appearance.
The display has 1 DVI and 1 VGA. I only tested DVI
Input Lag
I used a piLagTesterPRO to measure input lag. This device sends a frame of video over HDMI (via a passive adapter to the DVI plug) and measures how long it takes to display it. This display does not have a game mode. I toggled all the display quality settings and did not see a consistent effect on lag, however the tests reported are with every "enhancement" set to off.
This display does not support 24hz, though it does work at 48hz. Perhaps that means smooth movie watching? I don't know how movie playback apps would handle having a refresh rate 2x the desired one.
Input Lag Test Results
I report two kinds of values. 1st response measures how long it takes for the TV to start responding (I use a 5% change in display brightness). This overly optimistic value doesn't tell how long it takes to see anything useful, but matches what other reviewers call input lag. full response is a more realistic measure of lag, and requires the display to reach 80% of full brightness. This combines both input lag and response time, and is closer to what you would actually experience in a game.
The recommended resolution and refresh rate for this display is 1920x1080x60p. At that resolution (and lower) the results are all the same.
Interestingly, the display supports refresh rates above the recommended 60hz. This is with proper sync: that is to say the monitor doesn't drop frames, but actually increases the redraw rate to keep up with the rate that data is sent to it. As you might expect the limit is somewhat dependent on the total number of pixels needed to be processed per second; a higher refresh rate is possible with a lower resolution. Above that limit the monitor struggles to keep up, either losing sync after a period of time, or filling the display with static (see photo!).
The high refresh rates do translate into noticeable reductions in lag. 1080p at 72hz is stable and is 2.4ms faster than 60hz. 1600x900 at 80hz is another 1.6ms faster than that, and while the picture looks fine the monitor can't sustain the demands for more than a couple minutes and eventually loses sync. This is impressive: many computer monitors (including much newer) will accept a high refresh rate but just buffer it internally and drop frames, displaying as best it can the result at 60hz.
One issue is the response time is quite variable depending on the transition the LCD has to make. Black to white is fast and fairly clean, whereas other transitions can happen in a 2-step process where the LCD gets close to the desired brightness, pauses for about a frame, and then steps the rest of the way. Here I quote the time to complete the first of the two steps, but to ding it some, I picked the slowest transition I measured. Hence my value of 8ms is slower than the official 5ms the spec sheets quote. I'm sure this two-step process causes some motion artifacts when viewed on a high speed camera, and probably results in moving stimuli looking more muddy to the human eye than they would otherwise. I'm not going to be too hard on the display, however, as this is a common issue.
Results compared to other displays
To allow quick comparison between many displays I've summarized the results across all the displays I've personally tested with the piLagTester Pro. Min lag is the time to the first response, measured where the screen starts drawing (typically, the top); real lag is the time to the full response, measured where drawing finishes (usually the screen bottom), i.e. input lag + scan out + response time. Numbers in red denote average values that can vary by up to 8ms between power cycles.
This list is sorted by real lag for each display's native resolution and max
refresh rate (usually 1080p60 but some sets are 720p60, and other monitors
support > 60hz). Here I'm using the display's results for 1080p72 since
that mode is visually flawless despite not being officially supported.
Helped out by the higher refresh rates and good response time, this monitor is nearly the fastest I've tested and only 5 of the displays tested are even remotely close to it. Very impressive indeed. It would be a fine choice for PC gamers or retro gamers with a OSSC. It continues the trend that pretty much any PC monitor completely dominates top tier TVs.
Conclusion
TN LCD computer monitors, even when not designed for gaming, seem to perform pretty well, and this one especially. If you don't mind the limited viewing angles it's a great choice, boosted by its unofficially support for "overclocking" the refresh rate.