If you are only going to digitize 35mm film - and you have a fullframe DSLR, then consider the
Auto Bellows K and Slide Copier K as they were made for fullframe.
I will have to see if the 100mm is suitable for this setup but certainly a 50mm macro works perfectly well.
Once setup, digitizing is very quick and can take only seconds per frame as all movements/focusing are minimized and most definitely faster then scanning.
Because of film's latitude, you may need to do an over and under exposure pass and merge in post.
For true b&w film postwork is relatively easy and will be as tedious as scanning as you will have to manually remove dust and scratches as ICE does not work with these types of films.
For color slides, post work is still relatively simple except now dust and scratch removal may become a factor as ICE is usually available in scanners.
In this example, I used the fullframe Nikon D800 with my Nikon version Autobellows and slide holder to digitize a frame of Kodachrome - a very dusty embedded into the frame of film.
It only takes a few seconds to digitize but it would take far longer for me to manually clean it up in post that the Coolscan's ICE does perfectly in about 2 minutes.
For color negatives, the post work may surpass the scanning time. Not only is dust and scratch removal a factor but color inversion is far more complicated and applied on a per frame basis. There are numerous workflows - manual and third party tools, outlined everywhere online and youtube. In this example, I tried it myself on a perfectly dusty and thoroughly scratched frame of Kodak 160VC.
Manually cleaning up the dust and scratches alone would take far longer then the 2 minutes it takes the Coolscan 9000 to render perfectly. Manually doing the color inversion is not a straightforward manner and varies frame to frame. There are third party tools that can help in this task but from all that I reviewed, editing done on one frame may not necessarilly be applied across all the frames of the roll. In this example, even though I have the scan - as well as an optical enlargement for reference, I still could not match it. Needless to say I will need to practice more but I can't imagine what I would have come up with if I didn't have the reference.
BTW, I have both 50mm and 100mm f4 macro lenses and they are absolutely pin sharp. I bought my 50mm macro locally super chaep - along with a few other Pentax items, and noticed how sharp the results were and wondered just how much detail can it resolve. So I setup a 4 X 4 arrangement of 12233 resolution charts and shot it using Kodak Techpan @ISO25 under ideal conditions using the 50mm f4 macro and got these results digitizing with my Pentax K20D 14.6MP 4672 X 3104, Coolscan 4000dpi 5700 X 3780 and Nikon D800 36MP 7360 X 4912.
The 100% crops from each of the devices are to the left starting at the bottom of the full frame of 4 X 4 res charts, then K20D, Coolscan 4000dpi then D800 at top. You'll notice that even though the D800 applies more pixels then the 4000dpi scan, it looks like the Coolscan resolves a tad more. To the right, I optically magnified the center area about 4.5X and you can see actual detail not resolved by the devices I used. After this test I know that even a super cheap used SMC Pentax-M 50mm F4 macro lens will not be the limiting factor in achieving detail! BTW, I also tested my 100mm macro and it is equal to the task!