It so happens that I found a very good deal on a Samsung BX2450 from an on-line store, with free next-day delivery. The Samsung BX2450 is a new-generation "green" display with an LED backlight. A quick internet search revealed that the BX2450 got high marks from almost all owners. The only negatives I found was fiddly touch sensitive buttons, and that there is a known incompatibility between the BX25450 and the ATI (now AMD) graphics driver on Windows if you connect the BX2450 up with a HDMI to HDMI cable (the BX2450 doesn't have any DVI inputs, just HDMI). Apparent if you use a DVI to HDMI cable, there isn't a problem. But, for my purposes that was fine - mostly I work on a Mac anyway, and if I do need to connect to one of my Windows boxes, using a DVI cable is fine. So I went ahead and bought the BX2450.
The rest of this post is my experiences in using and calibrating the BX2475. It's written very much from an imaging and photographic perspective. Those interested in gaming performance - response times and the like - should look elsewhere.
First impressions and construction
First impressions were positive - the BX2475 looks good, and has a stand that, while it looks a bit fragile, actually seems to support the display as well as as my (much) more expensive HP unit. The BX2450 also appears to to live up to its green credentials - the power supply is external, and about the size of an iPhone. In fact, the whole display is light in weight - it was easy to carry around, and get in position on the desk.
Initial power up was fine; the BX2450 immediately showed as a second screen under OS X, with the correct resolution, etc.
The bad news: you can't adjust the height of the display. At all. There however is a tilt function.
The second piece of bad news is that all the software is Windows only. Not a single piece of Mac software - not even a display profile.
The "just be aware of" news - the BX2450 appears to essentially be an HDMI TV, rather than a computer monitor, even if you set it to "PC" mode. Now that doesn't make a lot of difference but be aware that there are some funnies: you will see the resolution listed as 1080p, rather than 1920x1080, and the display seems to identify itself as a HDMI TV rather than anything else. So you will see an "Overscan" checkbox in the Mac Display preferences which you won't for a normal monitor. Don't try to switch that off, btw - the display will no longer show a picture(!) This identification issue probably also explains the Windows HDMI issues that others have found.
Calibrating the display
Although the default setting on the display were ok, certainly better than some other displays I've seen, the first thing I looked at was how to calibrate the display. Now I didn't buy the BX2450 to display images; that's what the wide gamut LP2475 is there for. But as a I spend a lot of time looking at images, and specifically looking at the color rendition of images, bad color bothers me. I was also interested in how accurate a display I could get from a low-cost LCD display with LED backlighting. So I got out my trusty X-Rite Eye-One calibration device, and set to work. Here's the quick summary of my experiences:
- First thing that I had forgotten was the X-Rite's Eye-One Match 3 software doesn't actually support calibrating to two monitors. Now you'll see a lot a stuff written on the internet that this is because "you can't have two calibrated displays on one display board because there's only one LUT in hardware", etc. Nonsense. Any modern OS will happily let you run two different calibrated displays from one video board. This is just a limitation of the Match 3 software. Solution: temporarily disconnect the primary monitor, and use the secondary as the primary while you calibrate. OS X will automatically keep track of which profile applies to which monitor, btw.
- Second thing that I found out was that the touch sensitive buttons on the BX2450 really are as fiddly as claimed.
- Third thing I found is that the BX2450 (or maybe the combination of the BX2450 and the Eye-One puck) doesn't like to be calibrated to a D55 (5500K) white point. While you can calibrate to that, the resulting display is truly horrible; the brighter parts of the image are ok, but the darker parts get a massive red color cast - totally unusable. So I ended up calibrating to a D65 white point.
- Fourth thing I found out was that setting any of the Red, Green or Blue controls to more than 50 is not a good idea; when you generate a profile you get nasty discontinuities in the gamma curves, indicating that the display becomes non-linear. The process I followed was firstly to set the BX2450 to what Samsung call a "Cool" color tone, which was close to D65. Then I manually adjusted to D65 as measured by the Eye-One using the RGB sliders, taking care that no color control went above 50. For reference, the settings I ended up with were Red:20 Green:20 Blue:50
- As with most displays, the default brightness was way to high; I set it to 34 on the slider, which corresponds to a 110 cd/m² setting, my preferred LCD value.
The end result of this was pretty good. It's almost impossible to give any idea of color rendition on the web, but visually comparing the BX2450 to my LP2475, the BX2450 stood up pretty well for images with relatively small color gamuts. Specifically, for sRGB images, which are what almost all JPEG files use for a color space, the calibrated BX2450 looked nearly as good as the LP2475. Interestingly, to my eyes, the difference was more a slight lack of contrast in the shadows, than any major difference in color rendition.
The BX2450's gamut
The problem for the BX2450 of course, and the reason why the LP2475 costs several times more, is gamut - how broad a spectrum of colors can be displayed. A quick look at some raw images rather than JPEGs from my Nikon and Sony cameras showed a very different story; the LP2475 was able to display better reds and greens.
Here are the gamuts of the LP2475, the Samsung BX2475, and the sRGB gamut for reference.
Bottom line - the BX2450 doesn't come anywhere near the gamut of the LP2475, especially as regards greens, but also in reds. Compared to the sRGB gamut, the BX2450 is actually pretty close, but is just a bit less capable on both the greens and reds. Which is consistent with what I found looking at actual images - sRGB images are ok, raw images that have wide color gamuts, not so ok.
Conclusion
The bottom line is the following: if your imaging needs are limited to looking at JPEG images, or web surfing, the BX2450 will serve you fine, and if you have a hardware calibration device, you can get quite acceptable color if you stick to a D65 white point. Also, the BX2450 will be a good choice for those that create websites, or artwork that will primarily be seen on the web - in that case the similarity of the BX2450's gamut to sRGB is actually an advantage.
In the role that I'm using the BX2450, and given what I paid for it, I've very happy - it does exactly what I bought it for, and does better than I had anticipated in terms of color accuracy.
However, if you're a serious photographer that deals with raw images, the BX2450 is not for you, at least as a primary monitor. Firstly, the color gamut isn't wide enough. But the real show stopper is the issues I had trying to calibrate the BX2450 to a non-D65 white point. That may not be the fault of the BX2450 - it may be that my Eye-One calibration device isn't up to dealing with LED backlights. But for whatever reason, if you're serious out photography, you need a monitor that will calibrate reliably with current calibration devices.
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