Very different color noise between develop module and library

[jljonathan]

I am attaching two screen shots of the exact same image. One as it looks the library, and one from the develop module. There is a marked difference in the appearance of an image when viewed in the library versus the develop module. The color noise in the library module is very bad, while in the develop module, the noise reduction is doing a pretty good job. This is strictly a view problem, because if I export from the library, the proper color noise reduction is applied and it appears as it does in the develop module. This is not the first time that I have found this problem between the two modules. Any idea why this is happening? And, is there a fix in the works? It makes it hard to view images in the library.
If I boost the color noise reduction up to 100, the library image starts to look ok, but that doesn't account for the huge difference at lower settings.

There is also a dramatic slow down in the develop module when trying to make any of these changes in noise reduction and more, and also in side-by-side when trying to scroll around in the image to compare areas. Things really crawl. There is a definite two or three second delay before things respond. I have 8gigs in this mac pro, which worked beautifully with LR 3.6

[Schewe]

Are you rendering 1:1 previews or reduced size previews? If reduced previews the Loupe View won't be very good...1:1 previews will render the noise reduction accurately.

[jljonathan]

Good call Jeff. But, this is very strange because these images were imported with a preset that includes "render 1:1 previews. When I selected the image in library, and used render 1:1 previews under library, it did the full render and fixed the color noise problem. Funny that it didn't render them on import; I'll have to check why not.

When viewed at 1:1 in the library and develop, the image is the same (color noise gone in both). But, at fit or fill, there is a slight but noticeable difference in the amount of luminance noise reduction/sharpening applied. Develop view is much smoother, where in library it seems as if the luminance reduction has been reduced or shut off. This is only in fit or fill. At 1:1 they are identical. Any ideas why?

[Schewe]

The only way to accurately judge sharpening and noise reduction is to view at 1:1. At all other sizes, screen dithering goes on. In Develop sharpening and noise reduction are sometimes applied and sometimes not based on the size and ISO. In Library Loupe, once a 1:1 preview is made, what you see is still a downsampled dither but will be of the image with sharpening and noise reduction applied.

BTW, rendering previews is a background process. Rendering 1:1 previews can take a long time to complete. I generally render standard previews so I can start selection editing quicker. If I need a 1:1 in Loupe, I just zoom to 1:1 which forces the 1:1 previews to be made. At some point, down the road I will sometimes use the command to generate 1:1 previews. Since's it's a foreground command it actually takes less time-although it does tie up the CPU while doing so.