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Samsung LE40F71BX Picture Quality

by Colin Tang
21 February 2007

As you may expect, the Samsung LE40F71BX's out-of-the box settings were optimized for showroom performance. The picture was artificial and uncomfortably bright. You could see that the color temperature was set way above the D65 standard. Red push was used to compensate for washed out flesh tones.

My first instinct was to turn off any video processing from the user menu on the Samsung LE40F71BX. Although you can change the picture with the 4 modes (dynamic, standard, custom and movie), you cannot disable DNIe (Digital Natural Image engine) from the user menu. I will elaborate on this in the next section; now on to the tests…

Torture Test

Stuck/dead pixels Passed
Backlight test Passed

Overscanning (HDMI, Component)

Failed. 2-3 percent

Blacker than black

Passed
Black level Average, red tint present
Black level retention Unstable with dynamic dimming
Primary chromaticity Poor
Scaling Below average

Video deinterlacing

Below average
2:2 pulldown detection N/A

Viewing angle

120
Motion blur N/A

Digital noise

Mild

Black Level

PLUGE
BTB black bars visible on PLUGE pattern. You may need to turn up your brightness control to see this.

Our set came good from the manufacturing point of view. We looked for problematic pixels and backlight issues with our selection of full colour screen tests and found none.

The black level on the Samsung LE40F71BX was average, especially when compared to the Sharp XD1E and Panasonic TH42PH9 (a plasma screen). The thing that bothered us was the presence of a red tint in the darker regions. Even after grayscale calibration, there was still a trace of it.

Another problem was the floating black level which we noticed when we were checking for the black level retention. The picture seemed to flicker depending on the brightness of the current image on the screen. This was caused by the dynamic dimming function in the service menu; disabling this cured the problem. Regrettably, this option is not available in the user menu. Is this feature part of DNIe processing?

Samsung’s LCD backlight control is actually labeled as `energy saving’ under the miscellaneous sub menu. With 4 level of controls, you can reduce the backlight and overall brightness of the screen. I recommend setting this to medium or high to get the most satisfying blacks.

Colour

Gamma AMLCD Gamma off
Gamma with AMLCD
Gamma OFF (notice smoother curve)

Greyscale calibration presented a problem with the gamma curve. This curve, putting it simply, controls the brightness and saturation of mid tones in a picture. In the first graph(with original settings), the curve had an unusual configuration that was undesirable. This can be fixed again by changing the gamma function in the service menu from AMLCD to OFF. It gives us the second curve, which is closer to standards.

The color manager controls the brightness and contrast of the three primary colours (red, green. blue) in the grayscale, and NOT the saturation. Don’t use this to dial down the red push. If you’re not sure, you should probably leave this alone. You can attempt to calibrate this by using a greyscale step pattern found in many calibration discs but accurate results are rarely achieved this way.

Gamut
The white triangle represents the colour range of the Samsung LE40F71. The darker triangle represents the HD 709 standard.

The CIE chart above shows the color decoding accuracy for the Samsung compared to the HD 709 standard. The green and cyan colours are significantly off and this will cause color errors. There is no way to correct this; you can dial the colour saturation control generally but attempting to correct one colour will introduce inaccuracies in the others.

Motion

There is no significant motion blurring on casual watching with this TV. Some mild motion smearing was present on our test but we are confident that this will be acceptable to the majority.

Detail and Sharpness

Before
In the top bar you can see the fine 1 pixel width black and white lines on VGA 1:1 mapping.

After
The detail is lost on HDMI input due to overscanning on DVI/HDMI.

No overscan overscan
On VGA, you can see the icons (just barely)
Overscanning on HDMI

The scaling in the F71 model was inferior to our Toshiba HD-E1 player, showing soft and blurred edges. This was also contributed by the 2-3 percent overscanning on HDMI and component inputs when testing on the Toshiba. On PC testing, there was only 1:1 pixel mapping on VGA input with the sharpest pictures. There was softening and loss of detail on other inputs (shown above using a multi-burst pattern). Samsung has released a firmware upgrade to fix this issue on HDMI inputs through their customer care services, although implementing the upgrade is not exactly straightforward. However, their response to this issue was exemplary and so we can now recommend this Samsung model for PC use without reservation.

Viewing Angles

The viewing angle on Samsung is the best we have seen in its price range. This stellar performance is due to its S-PVA panel which we will cover briefly in the Technology section.

Video Artifacts

Some jaggies and combing artifacts were noticeable on interlaced material but this is not unexpected. To its credit, there was hardly any digital noise on direct viewing. This was a problem with some recent LCD models, but is usually tolerated by sitting further away from the TV.

Moving on to real life testing…

Standard Definition

There is no digital freeview tuner included with this model, so buyers beware. With analogue signals, you get frequent combing and ghosting artifacts with a soft picture. You’re better off with an external freeview digital tuner; we used a HTPC and got fairly good results. DVD watching was better with an up-scaling player due to the TVs inferior scaling process.

High Definition

We had mixed results with HD material. While the Samsung blows you away with crisp, high resolution pictures, you get the impression that all is not exactly fine. For example, looking critically at the black level reveals poor shadow detail in dark areas on some scenes. This is especially prominent in dark shows like Batman Returns where you frequently get a good portion of the screen disappearing into a black background when you expect to see something.

Motion in fast action material was examined subjectively on football and action shows such as Tokyo Drift: Fast and Furious. Again there was the slightest hint of motion smearing but this was only present if you looked real hard.

With green foliage, we could never get realistic looking colours. On a recent FA cup game the field looked lifeless most of the time. This could be improved by dialing up the colour control, but at the expense of other saturating colours.


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