The sharpness of my picture is increase when in developping mode, how to stop that ?

Thanks again for your reply! 

There is 4 screen with the histogram (I don't know what you mean when you speak about the "history"...) at 100% and you can clearly see that there is more noise I think, but I still don't understand why...

Do you have other reason for this noise to be there ?

Thanks again for you help, I wish you all a good day 

Ulysse

To make a valid comparison, you must view the image at 100% in both Library and Develop. This also applies to the exported image.

100% view shows you an accurate representation of the image because one screen pixel is used to display one image pixel. This is why 100% is also referred to as 1:1. Any other view will be inaccurate and misleading because the image has been scaled. Different applications use different algorithms for smoothing and sharpening when scaling images (and in this context, Library and Develop can be considered as different applications), resulting in differences in sharpness or noise at the same magnification. Except at 100%, where all applications should display identically.

How about two new screenshots, this time showing entire LrC screen. Interested in seeing histogram panel, and in the case of Develop module, the History

Previews in Develop are unique to all other modules and the most visually accurate. Always view at 1:1 (100%) or greater for the proper viewing of image data. Develop module IS showing you the data properly and most accurately. 

To judge sharpening and noise it should be none at 100% in both Library and Develop modules.

Library module will display preview jpeg file and Develop module renders the original image file and applies all edits to display on screen.