I don't speak German but here are few points I was able to fish thanks to google translate.
This is not a full review of the 870 but rather a face-off vs 760 since they are more similar than different, with focus on 2 elements the 870 has which should produce an improvement in comparison to last year's 760:
Image sharpness -due to the new sharper lens and new electronics.
Contrast- dual iris and dimming system intended to increase the contrast while lumens improved,
and how were both compare to the older 5000 flagship model.
Four different 870 units were compared to a new 760, I tried to convey Ekki's personal impressions (highlighted) yet this "quotes" should be taken with a grain of salt, or lost in translation if you will:
1. 870 has 150 more lumens -2050 in average, calibrated it is 1900 vs 1780.visible but Subtle
4200 calibrated on flagship 5000.
2. Iris and laser dimming work together on 870 yet cannot be controlled separately becomes visible only in very dark scenes,slightly better black level
3. Native contrast of the 870 ranges between 14,000: 1 and 23,000: 1 depending on the zoom and color temperature selected,dynamic contrast 30,000: 1 to 50,000: 1 not calibrated. Differences are subtle,in very dark scenes.
4. Lens sharpness on 870-image center similar to 760 even from close distance viewing.
760 lens is actually better than its reputation
(Ekkis version of silver lining...
Image sharpness on corners- better sharpness and micro-details on 870.differences are rather subtle
5. Digital Focus Optimizer on the 870 produces unwanted side effects-can create artifacts similar to dithering, in some scenes image can also lose depth. Sony wanted to create a wow effect but should have adopted less is more approach.
Conclusion by Ekki
Brightness, black level, edge sharpness, yet the 870 does not manage to distinguish itself from his smaller brother the 760 which reaches 95% of 870,that leaves you to wonder does this worth the additional 10,000 Euros ?