I think you might be confused about the use of tweeners. I apologise in advance if I am mistaken. The tweener is for animation. It is an interpretation of a change in some property of an object between keyframes. The name comes from the fact that you dont have to figure out all the motion in between keyframes, the program does it for you. In "between" = "Tweener". The program "tweens" the animation between the keyframes, calculating position, velocity, etc. Prior to computer animation programs, animators had to manually draw all frames, the computer tweens between Keyframes. Think of straight lines and bezier curves. Say for instance you have an object that moves between point A and B. With linear, the speed would be the same throughout, which wouldnt be realistic if the object is supposed to accelerate from a stand still. A curve tweener will allow you to show the object building up speed and then slowing back down to a stop. Carrara can do this with Ease in and Ease out on a linear tweener, but using a bezier curve often gives better results. For that particuliar example, the velocity curve would work well too. That example was for motion, but the concept applies to all animatable properties. Now, regarding image shaprness, as GK said, the object accuracy and the antialiasing options are what you want to explore along with the filter sharpness in the render room. The filter sharpness and the AA settings work hand in hand. If you set the filter sharpness high you will most likely need higher antialiasing. AA settings that work great with a filter sharpness of 75% often arent good enough when the filter sharpness is 100%. Resulting in noisy animations/images. The best thing to do is take a black sphere in an empty scene, set the background to white and experiment with all the settings. One last thing, if you are using texture maps, take a look at the filtering options in the image properties. That will have an impact on final image sharpness as well, if you are using texture maps. Hope that helps. Sorry for the long winded explanation. Donnie