This series of images illustrates what happens when the diffuser is moved between the light source and the “negative”. Between the light source and the negative, I put a diffusor and moved it from close to the light to close to the negative while the distance between the light and the negative remained a constant 25 cm. The practical side of this setup is, that I can change the looks of the negatives by simply moving a diffuser…
The leftmost image still shows the matrix of white and yellow LEDs from the backlight. Moving the diffusor towards the negative increasingly reduced the grittiness of the resulting image - without sharpness per se. The shots at left might look sharper but it’s looks only and nothing that cannot be compensated for with Lightroom’s sliders.
Here’s a photo that shows the whole rig: