Technical info:
Break in:
The C7 was broken in for a total of 200 hours, with multiple power and compensation cycles throughout. Cinema mode was chosen to track the C7’s break in since it is one of the more accurately measuring modes, while the ISF Expert modes would be reserved for calibration and other testing. Fresh out of the box with just a normal warm up time, after turning the power save feature off the C7’s Cinema mode measured extremely well. The previous 6 series’ familiar greenish emphasis in the mid tones was significantly reduced, and color tracking at different brightness levels and saturation points was excellent and greatly improved over the 6 series. Even the skin tone simulations measured with the correct tint and saturation, a feat that eluded the 6 series. Initial picture impressions were somewhat surprising; unlike the previous 6 series OLEDs which tended to have overly rich color and dark shadow detail, the C7’s color was polite, with slightly pale skin tones, and most content did not seem to be lacking in dark textures.
After 97 hours, the C7 was remeasured under identical conditions and settings. As the break in process progressed, the gamma shifted lower which tends to slightly reduce the depth perspective and wash out the image. There was also a tiny bit more green in the white balance.
Finally, at 200 hours the C7 was measured again, with the same settings and under the same conditions. Between 97 and 200 hours, the gamma lowered only a tiny bit more, but the green emphasis in the white balance increased to the point where it would become more visibly intrusive.
The resulting pre calibration picture was good, but watching Blu Ray movies within the initial 150 hour period showed a mixture of both enjoyable and annoying characteristics. First, the motion had the unnatural Soap Opera Effect along with fleeting jagged edges and general weirdness around the borders of moving objects. Blacks looked superb, but depth and dimensionality of the image was not as great as hoped; and whites often seemed compressed. Dark picture content just above black was easy to see and very well delineated. Skin tones, while generally natural and inoffensive, sometimes had a jaundice tinge. The image had excellent pop and a great photo realistic quality.
Windows and fields:
Some other surprising departures from previous LG OLED models included differences with various size and style measurement windows. Previously, there had been no significant change in the way different standard window sizes and styles measured. With the C7, shadow detail measured a tiny bit stronger with small windows than with medium to large windows, and significantly stronger than with APL style windows. This is shown as an increase in gamma at the low end with larger and APL windows. Measurements attached for 2, 10, and 25% size conventional windows and 10% size/25% APL windows.
Thankfully, the white balance was very consistent with all sizes even up to full fields. Peak light output when calibrated to 50 fL was basically unchanged with 50% windows and an extremely impressive 43.1 fL with full fields. The dynamic brightness pattern on the AVS 709 disc looked similar to past OLEDs with only a slight darkening of 10-30% as the APL changed. These results suggest that, while shadow detail may now suffer from small dynamic shifts, ABL (undesirable brightness limiting with full white screens) is pretty much a thing of the past.
Color:
A second departure from previous models concerns color reproduction and behavior of the color gamut selection and color filter functions. The C7’s color reproduction seemed too relaxed at times, lacking in richness, despite measurements suggesting nearly perfect color accuracy with color gamut at the default Auto setting. While measurements are generally the preferred way of setting and testing color, LG provides a color filter function to aid in color calibration in the absence of a suitable meter. Surprisingly, the C7’s color had to be increased to 72 with a tint of G2 for the result to be correct with the color filter function, with the image looking surprisingly decent but at odds with the measurements. Changing the color gamut selection to wide “fixed” that problem, indicating perfect color alignment at default color and tint settings with the color filter. Reference screencaps looked impressive in Wide, but the measurements showed colors were oversaturated. The same experiment was done on the 6 series, which did not show the same color gamut differences with the color filter function. The 6’s color gamut selection behaves as expected, with colors ranging from merely rich in Normal color gamut to over the top in Wide.
As with the C, E, and G6, the C7’s CMS behavior is somewhat less than desirable. While an improvement over the CMS behavior of the B6 and earlier OLEDs, the C7’s CMS tends to have sharp adjustment transitions which can lead to artifacts on some content. In addition, in between color shades such as skin tones tend not to be touched at all by the C7’s CMS. CMS behavior was tested with color gamut set to both Wide and Auto with slightly modified but ultimately similar results. It is therefore advisable to keep CMS calibration to a minimum.
HDR:
HDR was significantly improved over the 6 series, in more ways than just higher peak light output. The grayscale and gamma can now be calibrated nicely over the entire range, though a modified “code value” adjustment remains as the multipoint control. By running very closely spaced measurement runs, it was possible to determine exactly which brightness level the different code values adjusted. The lower three and uppermost three controls had a wide coverage area (like Q factor in the audio world), while the middle 14 controls adjusted a fairly narrow range. The stimulus level each code value adjusted, with contrast and brightness at default, will be listed in an attached document. I was able to use the levels editor of CalMAN to make a special set of measurements that lined up with these levels, which facilitated calibration.
Uniformity and misc:
There was an inconsistent change in light output when switching the screen shift function off in the OLED panel settings menu. The screen shift caused resolution patterns to garble slightly as the screen shifted. Turning it off caused a puzzling loss of peak light output, going from 50 fL to 42 fL, though cycling the picture modes or power seemed to bring the light output back up.
After break in, dark uniformity was the best I’ve seen on an OLED. Full fields were examined coming out of black in 1% increments. There was no vignetting (though I believe I caught glimpses of it earlier in the break in process), and banding was only slightly visible on a 3% field, though it did not look like it would be visible at all on any real image. With bright 50%-100% fields, uniformity was good, though the right side looked slightly warmer than the left. Measurements of the C7’s near black behavior showed excellent shadow detail with gamma near ideal from .5% to 5%. This is dramatically better than the 6 series, and proof of the C7’s superior shadow detail and near black performance.
Input lag with any picture mode except game and any combination of motion settings was 88 ms. Game mode measured an impressive 21 ms. Relabeling the input to PC was not tested.
Even with sharpness set to 0 and all enhancements switched off, there was some edge enhancement on sharpness patterns with 1080P or lower resolutions. 4K/UHD sharpness and resolution patterns looked superb, with full resolution and no artifacts.
