lightroom 6 übernimmt rauschreduzierung im export nicht

I've examined the DNG file and the differences you are seeing are due to the way the Develop and Library previews are created. The Library module creates a JPEG preview file containing an image pyramid (1:16 through 1:1 View Sizes) using Bicubic interpolation. The Develop module renders its preview real-time using the simpler and faster nearest neighbor interpolation. This simpler interpolation is less accurate and will make the image appear sharper and lower in noise. Normally applying sufficient Luminance Noise Reduction reduces the differences between the Develop module and Library module previews. In the case of this image file even the maximum 100 Luminance NR setting is not sufficient to lower noise in the more accurate Library preview.

Two things you can do that should help. After making your Sharpening and NR adjustments at 1:1 Zoom View evaluate the image in both the Library and Develop modules using the pyramid Zoom View settings 1:8, 1:4, 1:3, 1:2 and NOT Fit or Fill modes. The Fit and Fill Zoom settings use a 2nd Interpolation to resize the pyramid preview to the current window size. This can cause the image to appear less sharp. For images to be viewed on screen resize them to the maximum target screen size such as 2400x3600. This should reduce the differences observed in other picture viewers that use the simpler nearest neighbor resizing algorithm.