Panasonic TH-42PX75U Plasma TV review: input lag and upscaling tested using the piLagTesterPRO

This 720p Plasma TV from 2008 is very unique and quite nice in many ways. It used to retail for around $1300. If you can find one it's a great choice for retro gaming. 

Overview/Image quality

This is a plasma TV, which generally means at least the following: nearly infinite viewing angles, and jaw dropping weight. That's true in this case as well. This 42" model weights 75lbs. 

At native resolution (720p) this TV crops 20 pixels off the top/bottom and 30 off the sides. 480p/i crops 20 pixels off all sides. Both modes have aliasing, too, though it's not too bad. There's really no excuse for aliasing on a TV this big: you know the panel was designed specifically to be a tv. Why not hit 720p exactly? And as for 480p/i, they could have at least offered a zoomed out mode with black borders and 1:1 pixel mapping. But no such luck. There are zoom/stretch options to crop even more, but none that crop less.

While the native resolution supposedly is 1366 x 768 it does accept a 1080p/i signal and downsamples it.

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

One thing that's a little odd is that there seems to be some kind of defect on the inside of the glass, which I have now seen in two Panasonic plasma TVs from this era. It's kind of like a sputtering of very dilute yellow paint - I assume this defect develops with age. So be sure to check your second hand set before spending money on it.

Measuring Input Lag

This display does not have a game mode; not even a game 'color' preset. I tested all quality settings; none changed the lag. 

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. I measure at the top and bottom of the screen, but as it turns out these produce the same results: the entire frame updates at the same moment, top to bottom. I've seen at least one other plasma display that drew the screen faster than the refresh rate but this is the only model that does the entire thing simultaneously. 

Full Input Lag 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.

Normally I have an entire table of results here, but they'd all be exactly the same. This TV updates every pixel simultaneously, top, bottom, and middle.  It starts to update those elements 28ms after a frame is sent to the set, and finishes around 6ms later, at about 34ms. So instead of a table, let's look at exactly what happens to the brightness over time:

This TV, unlike a LCD, flashes all pixels briefly a couple times and then goes dark between frames. This means the viewing experience is a bit more like watching a CRT. This is good for reducing motion blur, although the display is not without motion artifacts. It's a little unclear where the fair point to measure input lag is, since the display starts to flicker very dimly for ~5ms before abruptly jumping to half and then full brightness. I kept my regular 5% threshold which makes the input lag appear extra low and conversely the response time somewhat longer. The full response (or realistic lag) may be the fairest way to compare this set to others.

Interestingly, even upscaling to 1080p doesn't slow the panel down relative to its "native" resolution. All resolutions have the same timing. That's true even for interlaced content. Hold on, how can that be? Fair question. The set adaptively switches between bob and weave deinterlacing depending on much motion there is. Truly impressive stuff. This algorithm is as fast as possible, but blocky, on high-motion stimuli, and sharp and crisp for static stimuli. The tradeoff is that for high motion stimuli it is fairly blocky looking compared to what good traditional deinterlacer would produce (such as on Sony sets).  Given the choice for action games I think I like using my OSSC to deinterlace with 25% alternating scanlines, as this cuts the blockiness some, but the built in deinterlacing is great and would be ideal for RPG style games. 

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 first response at the top of the screen, real lag is the full response at the bottom. The min lag value is really unfair to this set, so I've written it out in green. I'm sorting here by native real lag.

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
Dell U2410 (game)	2010	1080p	4.0	26.2	62.2	28.3	26.5	26.5	6.00	16.20
TCL 40S325	2021	1080p	6.5	27.3	60.6	29.0	27.9	27.7	6.00	14.83
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
Panasonic TH-42PX75U	2008	720p	28.0	34.0	34.0	34.0	34.0	34.0	6.00	0.00
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
Vizio VX20L HDTV	2007	720p	28.0	62.0	95.0	62.0	62.0	62.0	18.00	16.00
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
SANYO DP50749	2010	720p	67.0	75.0	103.0	94.0	79.0	75.0	7.00	1.00
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

What's truly amazing here is how well this performs on a 480i signal. Its real lag is half that of any other TV set I've measured other than it's bigger brother. It even compares favorably to a CRT. A CRT takes 16ms to draw from the top to the bottom of the screen. Some people consider counting this refresh time as unfair, but keep in mind that consoles update the screen between frames not during them so the game state is definitely 16ms stale at the bottom of the screen when refreshing at 60hz.  From this perspective, this TV is only 16ms slower than a CRT. I don't consider 16ms of extra lag to be an issue. The only remaining reason to choose a CRT over this set is that CRTs have no aliasing issues. That's not a small thing, but if you can't have both in your home, this seems like a winner. If you can find it.

It's also one of the lowest lag TVs for 720p, though at least at that resolution there are modern sets that can beat it by a tiny margin.

Conclusion

This is an old set, long since discontinued. But in a big metro area it's not hard to find one for sale or even given away for free (that's my source). 

If you have the space for it, it's always better to have a CRT for the retro gaming, along with a nice 1080p or higher flat screen for modern gaming. But if you can't fit all of those in your space, this is a great choice. Good retro; good modern (if you don't mind the 720p resolution limit). 

Make sure to get a remote. It's not really possible to operate without one. 

 

Other models  

I tested the TH-42PX75U and the TH-58PE75U. Panasonic's model numbers are hard to follow, so I can't be sure, but the motherboards of the TH-50PX75U, TH-42PX77U, TH-42PC77U, and TH-42PX75U look identical so I'd suspect they would perform similarly. Other reports online suggest that maybe all Panasonic plasma's had the same excellent lag as this one, but I chose not to report data I didn't collect.