I get this question all the time. "I have film positives or negatives, and I want to get the best quality scans, but drum scanning is so expensive. Is it worth it?" Things to consider:
1. What does quality mean to you? If it means sharper scans, drum scanning is thee best. Imacon scans run second, dedicated film scanners run third, and flatbed scanners are dead last. Within each category, there are different levels of involvement and cost, but that is the simple breakdown.
2. If a large file size is what you are looking for, then you need to consider why that might be? The only reasons to have a denser file size are a. Post processing capabilities (photoshop more before tone degradation appears) b. To make bigger prints. Again, the ordering scale is just as above in (1.). Drum, Imacon, Film Scanner, Flat Bed from sharpest to blurred.
3. How large a print are you making from the scan? If you want a big 20x30 - 40x50 digital print, then you would benefit in having a drum scan as the sharper image blown up will yield little quality loss. So, even though you may get a 500mb file from a drum and 500mb file from an Imacon, if you are making a large print, the drums scan will look better due to its sharper quality. However, if you are willing to make sharpness less of a priority, you can get away with an Imacon file (and most people do). If you are making 20x30 or smaller, then drum scanning is really over kill, unless you are going to post process the file heavily in photoshop. You can also sharpen the file (if you do it correctly) to get close to what you can yield off the drum scanner with an Imacon file. Again, you can save a lot of money and do an Imacon scan, not as sharp, but great file size which you can then sharpen in photoshop to look really great. So great, most people wouldn't be able to tell the difference.
4. Do you just want to archive you negatives because you fear they may or are getting damaged? If this is your concern, you should just get a dedicated film scanner, Nikon 4000, 5000, 8000, or 9000 will do a great job at archiving your images to print up to 16x24. Again, not as sharp as the Imacon and surely not as sharp as a drum scan, but really a professional, and affordable solution. You can also get these scans done at many service labs for fairly reasonable prices and fast turnaround times. (see: Rayko or Dickerman Prints).
5. What if I just want to see what is on my contact sheet, or put stuff on the web from my film shots? A consumer level flat bed scanner will do just fine for just figuring out what you may want to scan and print later on, or simply to put on the low resolution living environment of the web (72 ppi).
BOTTOM LINE: A great digital print comes from a great digital file. The more you can do for your image in its translation from film to digital, the better it will be. This means knowing what you actually need. Print Size and Sharpness vs. Cost and Post Processing abilities is all it really comes down to.
Below are examples of an Imacon scan vs. Heidelberg Drum Scan I did at Rayko.
yellow light detail zoom: (Imacon on the top, Drum on the Bottom)
full image (zoomed out): Imacon on the left, Drum on the right (has subtle tone transitions).
Fence and Road Detail (Imacon on top, Drum on bottom)