【转贴】HP LP2475w 测试报告！

gz0921

HP LP2475W
Simon Baker, 9 September 2008

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It's not often that you see this in the 24" sector, but HP have broken from the current trend of producing cheaper TN Film based displays, and have introduced a rare IPS based model into the market. At the time of writing, there are really only two IPS based screens in the 24" sector, one being available predominantly in the US, the NEC LCD2490WUXi, and one being available predominantly in the UK, the Hazro HZ24W (now updated to the HZ24Wi). IPS based screens are proving popular amongst enthusiasts out there, and have long been the choice of photography professionals and those looking for a screen for colour critical work.
HP have kindly sent us their new LP2475W screen, using the latest H-IPS panel from LG.Display, the LM240WU4. On a quick note, HP list this screen as being S-IPS based on their website, but close inspection of the pixel structure reveals the pixel orientation to be vertical, and characteristic of the latest H-IPS generation. Ultimately they are IPS matrices, just with different naming schemes depending on structure and generation. Being one of the few IPS 24" screens in the market, the LP2475W is obviously picking up a fair amount of attention. Let's take a look at the listed specs first:

Size	24"WS	Colour Depth	16.7M (8-bit), 92% NTSC colour gamut
Resolution	1920 x 1200	Viewing Angles	178 / 178
Response Time	6ms G2G (12ms ISO)	Panel Technology	H-IPS
Contrast Ratio	1000:1	Interfaces	DVI-I (x2), HDMI, DisplayPort, Component, S-Video and Composite Video. 6 port USB hub
Brightness	400 cd/m2	Colour	Black bezel with silver stand
Special Features	Tilt, height, pivot and rotate ergonomic adjustment. Full range of aspect ratio control options, 92% colour gamut, PiP and PoP support, integrated USB hub

要点翻译：使用的是LGD的H-IPS面板，但是不带A-TW Pol。

gz0921

接口图


Colour Accuracy, Black Depth and Contrast
The HP LP2475W utilises an 8-bit H-IPS panel, capable of producing a true 16.7 million colours. The screen uses enhanced W-CCFL backlighting and so it's colour gamut covers 92% of the NTSC colour space.

Default settings of the screen were as follows:

Monitor OSD Option	Default Setting
Brightness	90
Contrast	80
RGB	n/a
Colour Temperature Mode	6500k

HP LP2475W - Default Settings (Default 6500k Colour Mode)

	Default Settings
luminance (cd/m2)	357
Black Point (cd/m2)	0.45
Contrast Ratio	793:1

The screens default settings were considerably over-bright, and you could immediately feel this when you started to work with it. Our colorimeter revealed the default luminance to be a pretty high 357 cd/m2, not far off the specified maximum brightness of 400 cd/m2 even! You could tell that you would need to adjust the brightness of the screen straight away. Considering the OSD brightness control was defaulted at 90%, this should be easy enough to adjust later on anyway. With this high luminance value, we recorded the default black depth at 0.45 cd/m2, giving a static contrast ratio of 793:1. This was a little out from the specified 1000:1, which is perhaps a little hopeful for an IPS matrix, but very close to 800:1 which is a decent performance for an IPS screen.
As you can see from the measurements on the left of the image above, the default gamma was actually very good, being only 2% out, and rounded to 2.2 overall; this being the default for computer monitors and for the Windows operating system and sRGB colour space. Despite the default preset colour mode of ''6500k' being selected, the recorded colour temperature was actually only 5553k, quite a way out from the desired value (by 15%), that being the colour temperature of daylight.

In a new test, I wanted to see how much variance there was in the screens contrast as we adjusted the monitor setting for brightness. In theory, brightness and contrast are two independent parameters, and good contrast is a requirement regardless of the brightness adjustment. Unfortunately, such is not the case in practice. We recorded the screens luminance and black depth at various OSD brightness settings, and calculated the contrast ratio from there. All other monitor and graphics card settings were left at default. It should be noted that we used the BasICColor calibration software here to record these, and so luminance at default settings varies a little from the LaCie Blue Eye Pro report.

OSD Brightness	Luminance (cd/m2)	Black Point (cd/m2)	Contrast Ratio ( x:1)
100	356	0.45	790
90	355	0.45	789
80	315	0.40	788
70	282	0.36	783
60	255	0.33	774
50	231	0.29	797
40	207	0.27	765
30	181	0.23	786
20	155	0.20	777
10	129	0.16	807
0	103	0.13	793

As you can see from the above results, the control of the screens luminance via the OSD menu was very good. The default 90% OSD setting gave a luminance value of around 355 cd/m2 as we have discussed already. As you lower the brightness control in the menu, the voltage sent to the CCFL backlighting is reduced, and therefore the backlight intensity is reduced as well. The luminance ranges down to 103 cd/m2 when brightness is set to 0%. Even if proper calibration is not possible, you can get a comfortable luminance of the screen at around 10% brightness setting, which is re-assuring.
While brightness is reduced, the black depth improves quite nicely as well, reaching a very impressive 0.13 cd/m2 at 0% brightness. This is very respectable for an IPS matrix, and the best black depth we have recorded on such technology so far in our reviews. During these brightness changes, the contrast remains pretty static and within the range of 774:1 to 807:1. Very good performance in this regard, showing that with proper backlight adjustments you can achieve not only comfortable settings for every day use, but retain a decent contrast and black point throughout the range.

The results were plotted on the above graph, showing the contrast stability of the screen. You can adjust the brightness setting to anywhere within the 0 - 100% range without really impacting contrast ratio. As you reduce the brightness setting, luminance is adjusted nicely, and black depth improves as one would hope.

gz0921

要点：
1、色域广泛，覆盖sRGB达到100%
2、亮度调节范围广泛，最低量度可以降到100尼特左右，适合长时间观看。
3、黑色亮度很低，这是IPS面板显示器的一大进步，这是LP2475w最令LZ看中的优点。
4、对比度稳定在整个亮度范围内保持稳定

gz0921

Testing with the colorimeter revealed the graph on the right hand side above, showing DeltaE (dE 94) values across 16 shades. As a reminder, the lower these bars down the Y-axis, the better, in terms of colour accuracy. For reference, LaCie describe the DeltaE readings as:

If DeltaE >3, the color displayed is significantly different from the theoretical one, meaning that the difference will be perceptible to the viewer.
If DeltaE <2, LaCie considers the calibration a success; there remains a slight difference, but it is barely undetectable.
• If DeltaE < 1, the color fidelity is excellent.

As you can see from the graph, the default results were not that great. DeltaE on average was 4.5, meaning the colours displayed were considerably out from the requested colours overall. Maximum dE even ranged up to 11.1, so you are definitely going to need to calibrate this screen if you intend to do any colour critical work. This is quite a common situation in todays market, especially where extended gamut backlighting is used. In contrast, the IPS based Hazro HZ26Wi we recently tested showed much better colour accuracy out of the box, showing that perhaps the HP was not particularly well configured in the factory. This of course need not matter if you have access to a hardware colorimeter device, but for those without, it might be a consideration to take into account.

The graph on the left hand side (recreated here as well) shows the CIE diagram which represents the colour space which the monitor is capable of displaying. The LP2475W uses enhanced  wide colour CCFL (W-CCFL) backlighting which offers a colour space (gamut) covering 92% of the reference NTSC space. On the above diagram, the black triangle represents the monitors colour gamut, and it stretches considerably beyond the reference triangle of the sRGB colour space. The sRGB colour space covers about 72% of the NTSC colour space for those interested.

HP LP2475W - Default Settings (Custom Colour Mode)

	Default Settings
luminance (cd/m2)	394
Black Point (cd/m2)	0.45
Contrast Ratio	875:1

We tested the screen again after simply switching to the "custom colour" mode in the OSD. This allows access to the RGB controls for calibration and moves the screen away from the preset 6500k mode. To the naked eye, the image looked a little more blue, and a little less yellow, and testing with the colorimeter actually revealed a slight positive change on the most part. Luminance was actually increased to 394 cd/m2 resulting in an even better contrast ratio of 875:1, but being a little less comfortable for prolonged use. Colour temperature was actually nearer to the desired 6500k than it was using the 6500k preset mode (!!) and gamma still remained very accurate at 2.2 (1% out now). Colour accuracy was also improved a little, with maximum dE reduced from 11.1 down to 9.5, and average dE was now 4.3 instead of 4.5. Not a massive change overall, but even if it's just for the sake of a better colour temperature, it's worth switching to the 'custom colour' mode from the off-set.

HP LP2475W - Default Settings (sRGB Simulation Mode)

	Default Settings
luminance (cd/m2)	232
Black Point (cd/m2)	0.45
Contrast Ratio	875:1

The LP2475W offers a supposed sRGB simulation mode via the OSD menu as well, so we wanted to test how this performed, again with everything else left at default. The screen immediately looked darker and slightly more 'murky' to the eye, and the colorimeter revealed luminance was reduced down to 232 cd/m2 now. Colour temperarture moved further away from the desired 6500k (being 16% out now) and colour accuracy didn't really change. The main thing this mode is supposed to do is simulate the sRGB colour space, which is important for those not wanting to work with extended colour spaces. Strangely, this mode did nothing for the screens gamut, and the CIE diagram on the left shows the colour space remains considerably larger than the sRGB reference triangle! I am left to assume that all this mode really does is darken the image! Very odd...

要点：
1、gamma准确
2、未校准的颜色并不是很准确

[ 本帖最后由 gz0921 于 2008-9-10 11:22 编辑 ]

ssssuuuu

H-IPS面板不错，问题是价格。几钱？

gz0921

HP LP2475W - Calibrated Settings

Monitor OSD Option	Adjusted Setting
Brightness	17
Contrast	65
RGB	251 / 235 / 242

	Calibrated Settings
luminance (cd/m2)	118
Black Point (cd/m2)	0.17
Contrast Ratio	694:1

I calibrated the screen using the LaCie Blue Eye Pro software package and hardware colorimeter. During the process, the OSD settings were adjusted, forming a small part of the overall calibration proceedings. Brightness was adjusted down to a value of 17, contrast was reduced to 65, and RGB values were changed to 251, 235 and 242 respectively. The calibration process then automatically makes adjustments at a graphics card Look Up Table (LUT) level, before creating and activating an ICC profile. There is no hardware level LUT correction with the LP2475W, which some premium colour critical screens in this sector do offer. Immediately to the naked eye you could feel the difference, with the main obvious adjustment being the far more comfortable and sensible luminance setting. Colours also looked more even to the naked eye.
Testing with the colorimeter confirmed our initial impressions. Luminance was now a far more comfortable 118 cd/m2, gamma was corrected perfectly to 2.2 and colour temperature was now less than 0.5% out at 6503k. Since we altered the OSD brightness control during the manual calibration stages to 17%, the automated LUT adjustments didn't need to alter the luminance much. We already knew from our contrast stability tests that a brightness level of around 10% was optimum for 120 cd/m2. With this adjustment, black depth was improved quite nicely from the default 0.45 cd/m2 to a very impressive 0.17 cd/m2. This is the best result we have tested from an IPS based screen, and a static contrast raito of 694:1 is very admirable. It looks like finally IPS panels might have overcome their main traditional weakness and can now offer decent black depth. Subjectively, it was impossible to detect only the first 2 shades of grey on the scale from 0 - 255 (255 being pure white). I followed the useful tests here, where the first square you could distinguish on the LP2475W was number 3 (just).
Impressively, the calibration also improved colour accuracy no end. Average dE was now only 0.3, and maximum was  down to 0.5. This was a massive improvement, and actually the best colour accuracy results we have obtained in our reviews! This even beats the Hazro HZ30W which recently became our champion in this regard with average dE of 0.3 and maximum of 0.8.
Testing the screen with various colour gradients showed smooth transitions both horizontally and vertically, and no real sign of even slight gradation. There was certainly no banding issue here.

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Conclusion
Overall I was very impressed by the performance of the LP2475W. While default colour accuracy was pretty poor, once calibrated the screen offered the best colour results we have seen in our reviews. Black depth was excellent for an IPS matrix, and even out-did many PVA matrices we have tested! These were very positive improvements for IPS technology, and hopefully this is a sign of things to come. The screens massive range of ergonomic adjustments and interfaces was also nice to see, and the HP had a very "Dell feel" in terms of finish, functionality and features. Responsiveness was very good, but there was some slight RTC overshoot which caused some dark artefacts in practice. However, the decent pixel responsivenss, combined with pretty good input lag, could make this a good screen for gamers, as well as those wanting an excellent all round performer. If you want a 24" monitor, this is a hard one to beat in my opinion. Given the extreme lack of IPS in this sector, HP are probably on to a winner here.

Pros	Cons
Excellent colour accuracy once calibration	Poor default colour accuracy
Excellent black depth, especially for an IPS panel	Some RTC overshoot causing some slight inverse trailing
Very wide range of interface and ergonomic options	Couple of missing features such as D-sub interface and A-TW polarizer

超侧卫

价格要是跟2408一个水平就买了

Jessey

原帖由 超侧卫 于 2008-9-10 11:27 发表
价格要是跟2408一个水平就买了

是啊
但是价格{closedeyes:] {blush:]

ddr9334

东西素质蛮好～
不过国内HP的价格～～售后～～～{closedeyes:]

历时1个月差两天 送修的HP牌LCD总算送回来了
用了半年不到 给换掉了面板～{wink:]

cangel

英文的 看不懂..

punkeer

决定买它了，但不知哪里有得卖，但愿国庆前能买到手，放假在家玩晴空 :)

[ 本帖最后由 punkeer 于 2008-9-10 13:32 编辑 ]

MarkII

记得有人说过好象要7K左右吧？连2275W都快4K了。要是这样真不如选EIZO

pld1982

看上去不错

hhbird

好东西有的是······  多HP一个没什么影响

关键是价格，HP不脑baichi的话应该有个合理的定位，非要脑baichi的话，消x费x者就旁边看热闹就是了。

priest

只是个噱头，没有什么卖点

FoxDle

LP2465用了很久了。。。。。确实比DELL的东西好一些，不过和EIZO还是没可比性。

flyjacky2888

难道DELL 2408的面板是IPS面板？否则怎么放一起比？PVA和IPS面板本身区别就不小。

flyjacky2888

原帖由 MarkII 于 2008-9-10 14:09 发表
记得有人说过好象要7K左右吧？连2275W都快4K了。要是这样真不如选EIZO

好像是6XXX，2275W用的是PVA面板的据说，价格应该低于3300。