Samsung LN46C630 review: input lag, deinterlacing and upscaling using the piLagTesterPRO

This  "120hz" 1080p TV sold for around $900 in 2011.  It has very bad input lag. 

Overview/Image quality

I tested a TV that had damage to the panel so I couldn't do my standard image quality tests. 

It advertises itself as supporting 120hz, but this is really a motion smoothing option, and the TV can't accept a 120hz input signal - the fastest input it can sync to is 60 hz. But as we will see there is some truth to the 120hz designation, see below. It also supports 24hz mode for movies, properly displaying at 24hz with no dropped frames. 

It has all the standard inputs, including 4 HDMI, VGA, and 2 yPbPr.

Input Lag

This display has a game mode. I couldn't find any evidence that game mode was any faster in terms of input lag, but it did make one difference: it turns on the backlight flicker. This probably makes motion look a little smoother, though the set has "motion smoothing" features which might do the same outside game mode (motion smoothing is off in game mode). 

I used a piLagTesterPRO to measure input lag. This device sends a frame of video over HDMI and measures how long it takes to display it. 

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.

This TV has two unusual features: it redraws the screen every 8ms (instead of 16ms), which is the sense with which it's a 120hz screen. That helps lag a little bit and supposedly improves motion smoothness if you fill in the implied motion between frames intelligently (I didn't test this). The other thing that's odd is it draws from the bottom of the screen up. Thus the first pixels painted on each frame are the bottom row:

		bottom		top
Resolution		1st (average)	full response	1st response	full response	scan out	response time
480i		72.6	82.6	80.7	90.7	8.1	10.0
480p		72.4	82.4	80.3	90.3	7.9
720p		71.3	81.3	78.5	88.5	7.2
1080p		54.5	64.5	62.3	72.3	7.8
960p60		54.0	64.0	62.3	72.3	8.3

This seems like a REALLY dumb choice; since the HDMI signal is sent from top to bottom this means the TV can't possibly start processing the next frame until the entire thing is sent to the TV, implying an extra 16ms of lag. And indeed this TV has lots of lag. To be fair, given the motion smoothing algorithms that it's using to fake 120hz, it may have to wait until the entire frame is delivered before it can start processing anyway. Whether it's a bad design or a moot point, the TV has awful lag, even in game mode. 

It was fastest in native (1080p) mode, where it started drawing pixels 54ms after the frame was sent to the TV. It was noticeably slower in 720and 480p, taking about 18ms longer to start drawing. For a modern display to take that long to upscale is scandalous. I'm not sure it's exactly that, because the set also supports 960p and that's just as fast as 1080p. Whatever is going on, if you use this for gaming it had better not be retro gaming!

The only bright point is that deinterlacing (480i) is no slower than 480p. Not sure why that is; usually it means that bob deinterlacing is being used, but I couldn't tell because of the screen damage. There's so much delay in the TV that maybe there's plenty of time to deinterlace properly. Who knows. 

Response time was around 10ms. This was in game mode. Outside of game mode response time as a bit slower; around 13ms. So game mode does two things: smooth motion by flickering the backlight (many TVs do this and don't call it game mode) and speed up response time a little. I guess every little bit helps but with a TV this slow it doesn't add up to a very good package. 

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. For this set, since it draws from bottom to top, Min lag is the first response at the bottom of the screen; real lag is the full response at the top. For most sets it's the reverse, but think of it this way: min lag is when the screen starts drawing, real lag is when it finishes. Numbers in red denote average values that can vary by up to 8ms between power cycles. 

This list is sorted by real lag in the display's native mode. Thus, if the display supports higher than 60hz refresh rates it can get a boost in this table, and TVs that struggle outside of native resolution are not penalized. 

Display	Year made (TV?)	Native Res	native min lag	native real lag	480i real lag	480p real lag	720p real lag	1080p real lag	native response time	native scan out
Dell E198FPb	2008	1024p	2.7	20.4		39.0	35.0		5.00	12.70
Vizio VO370M	2010	1080p	2.5	23.6	83.0	49.0	47.0	24.3	5.47	15.67
AOC/Envision G19LWK	2010	900p	3.1	31.2	39.5	38.7	38.4	37.8	15.50	12.60
Dell E2211H	2014	1080p	3.0	33.6	34.7	34.5	34.1	33.8	15.00	15.57
Panasonic TH-58PE75U	2008	720p	28.0	34.0	34.0	34.0	34.0	34.0	6.00	0.00
Dell 1907FPc	2008	1024p	3.0	34.0		35.9	34.8		15.00	16.00
Corprit D157 (hdmi)	2021	1080p	3.1	34.5	34.9	34.8	34.6	33.9	16.25	15.13
Samsung S27C230	2014	1080p	2.9	36.1		36.6	36.1	37.0	18.25	14.97
Vizio E470VL (vga)	2011	1080p	22.0	39.0		39.0	39.0	39.0	9.00	8.00
Dell U2410 (sRGB)	2010	1080p	20.5	42.8	62.4	45.0	43.1	43.1	6.13	16.13
ACER AT3265	2012	1080p	19.5	43.8	62.7	45.3	43.8	43.8	8.00	16.27
RCA L40FHD41	2010	1080p	20.3	46.6	65.0	48.0	47.0	46.0	9.68	16.63
Sony 40VL130 (game)	2008	1080p	22.8	47.3	66.3	49.0	47.3	47.3	9.08	15.43
Polaroid FLM-373B	2007	720p	28.0	49.0	82.0	49.0	49.0	49.0	7.00	14.00
Philips 42PFL3603D/F7	2009	1080p	29.0	50.0	84.0	50.0	50.0	50.0	5.00	16.00
Emprex HD 3202	2007	720p	27.0	50.5	126.0	51.0	50.0		8.50	15.00
LG 42LC2D	2006	720p	28.3	50.6	54.6	50.8	50.4		6.30	15.95
GPX TDE3245W	2016	720p	28.0	51.0	102.0	51.0	51.0	51.0	8.00	15.00
Sony KDL-46EX400	2010	1080p	28.0	52.0	87.0	52.0	52.0	52.0	8.00	16.00
Toshiba 40L2200U	2014	1080p	30.0	56.0	74.0	56.0	56.0	56.0	10.00	16.00
Vizio VO22L FHDTV10A	2008	720p	28.0	61.0	94.0	61.0	61.0	61.0	18.00	15.00
Sharp LC-C3234U	2009	720p	33.0	64.6	83.6	66.6	64.6		15.00	16.60
Toshiba 46L5200U	2013	1080p	55.0	71.0	89.0	76.0	71.0	74.0	8.00	8.00
Sony 40S20L1	2007	720p	48.4	72.0	90.1	72.9	73.4		9.60	14.00
Samsung LN46C630	2012	1080p	54.5	72.1	90.7	90.3	88.5	72.3	10.00	7.63
Samsung HP-T4254	2011	1080p	69.7	75.7	94.1	76.0	75.7		5.00	1.00
LG 47LW6500-UA	2012	1080p	66.6	80.7	149.7	149.0	81.7	80.9	2.27	11.83
Vizio E470VL (hdmi)	2011	1080p	69.0	86.0	128.0	95.0	95.0	86.0	9.00	8.00

Note that sorting by real lag really helps this TV because it has the 8ms scan out.  Nonetheless, it's still near the bottom of the TVs I've tested.  Although I haven't looked at many smart TVs from the early/mid 2010s, they all have been poor performers. Dumb TVs may be a smarter choice for gaming...

Conclusion

This tv has bad lag. It's probably a fine choice for Movies, TV, Netflix, etc. 

If you do decide to get this for some reason, make sure it has a remote. In a fit of marketing buzzword compliance, it uses capacitive buttons on the set itself, making it nearly impossible to find the buttons and/or press them one at a time. 

Other models (to avoid)

I only tested input lag on the LN46C630, but I would expect that the LN40C630, LN55C630, and LN60C630 would perform the same, based on similarity of the model numbers and specs, just with different sized pixels.  Honestly, I'd just avoid all Samsung TVs from this era based on how poor this one behaved.