Copy, or reproduction lenses are and were made for this specific purpose: Projecting a flat surface such as a drawing, a map or, indeed, a piece of film. These lenses are also used in the darkroom on enlargers, to make darkroom prints in an enlarger, therefore the most available ones are often called enlarger lenses. Because they are designed for this specific purpose they have a set of features that are ideal for accurately digitising film, in terms of colour, focus, sharpness and distortion. Note that there are good enlarger lenses, which produce spectacularly good results, but there are also lesser lenses that produce decent but not spectacular results - though they can be an economical direction to go in under the right circumstances. There is a list of lenses and categories of lenses with their expected performance. 

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Fitting your lens to a camera

The main challenge with enlarger lenses is that they never come with a focusing mechanism (the helicoid that your turn when focusing a lens), and therefore require extra hardware to make them work for our purposes. There are two options for focusing: a screw-on focusing helicoid or (macro) bellows. In addition, you need the relevant adapters to adapt the lens to your camera system, and probably various adapters to adapt your lens to and from the helicoid or bellows. Most enlarger lenses have an M39 screw thread, but check the specific lens you get - it will be out there on the internet if you search for your lens and add ‘thread size’ behind. To find the right adapters for you make sure you consider all the mounts and threads on each component. As an example, here is how you would use an M39 enlarger lens on Sony E mount:

Sony a6300 with E-mount + Sony E-mount to M42 adapter + M42 (on both ends) Helicoid + M42 to M39 Adapter + Rodagon 50mm f/2.8 with M39 screw mount.