Drum Scanning
What is it?
Drum scanning is the ultimate pursuit of quality in the realm of film photography. It is the last scan you will ever need, since there is nothing that will give you the kind of resolution, detail, sharpness and dynamic range that drum scanning can give you.
Image taken in Germany with a Hasselblad 501C, 80mm 2.8 Zeiss CF lens, and Fujichrome Astia 100 reversal film.
PMT vs CCD/CMOS
CCD and CMOS scanners are basically all consumer, prosumer, and many high end scanners, that are not drum scanners. The difference here is essentially that it uses the same technology that digital camera's use (a chip) that is used to record an image through a lens (often one that is highly inferior to the one you shot the image with). Essentially, with a CCD or CMOS scanner, you are taking a picture of your image with a digital camera.
How a drum scanner differs is that it uses PMT's (Photo Multiplier Tubes). These are basically vacuum tubes (one for each RGB color) that capture the image line by line. It's a technology that was derived from nuclear physics and is not very common in use.
Why compromise on quality when you can get the best scans that are out there? National Geographic, Vogue, pretty much every big publishing house used to have drum scanners which cost up to $65K or more when new and could scan at up to 12,000 dpi. For these publications, for advertising agencies, for anyone that wanted to have the ultimate quality and/or print big, there was no compromise.
As you can see - the image on the left scanned with a prosumer CCD scanner is a lot less sharp with much less dynamic range than the one on the right scanned with a drum scanner. The left image was actually slightly sharpened in post, while the right one had absolutely no sharpening done to it. This is again due to the fact that a CCD scanner is basically taking a picture of your image through a lens and sensor, not unlike taking a digital camera. Why the drum scanner scan is so much sharper and clearer is the least-optics on the signal path, better mechanics and that it uses PMT's.
PMT's are ultra sensitive to light and therefore outperform CCD and CMOS sensors in their dynamic range. The stated D-Max on most CCD and CMOS scanners is highly inflated. Many of the consumer and prosumer manufacturers do this to show that their specs are higher than drum scanners, when in reality those specs are not very accurate.
In this slide of a shoemaker in Kobe, Japan you can easily differentiate between the two images. The one on the right (Drum scan) is more accurate in terms of both color reproduction and shadow detail. You can really see the creases and lines on the shirt and the image is overall sharper on the drum scan vs. the CCD on the left.
Wet-mounting
Wet-mounting is the act of sandwiching the film on the drum between a sheet of mylar and the drum surface. Having the film in this fluid creates an optical effect that increases dynamic range, color vividness, renders fine details more refined, hides many of the defects (scratches, etc...) and reduces film grain. You can't emulate, simulate or fake this optical effect in digital post processing - it's pure physics.
Unlike flatbed or prosumer scanners the scanning surfaces on the drum create almost no side-reflections from neighbouring areas. This drum design gives the best possible flatness to the film.
A wet mounting station holds the drum in place, while the roller on top helps to press the mylar sheet onto the film, getting rid of most of the bubbles.
I use the highest grade mylar and oil based fluid. These fluids are completely neutral to the negatives and positives and do no harm to the film. In fact, the mounting fluid evaporates fairly quickly after dismounting the mylar sheet. Wet mounting is a lot of time-consuming handwork but the results are well worth it.
Resolution and Color Rendition
Drum scanning is slower but a lot more precise reading the film point-by-point when compared to a CCD or CMOS scanner that scans an image much like taking it with a digital camera. The drumscan therefore has the upper hand in optical density, resolution and color rendition.
Taken with a Hasselblad 501C with 80mm CF T* and Fujichrome Velvia. The depth and clarity one can achieve is unparalled.
The scanner I use is a Danish made Scanview Scanmate 5000 which offers up to 5000 DPI in optical scanning resolution. The larger formats make digital look like it's years behind in resolution.
Operation
Drum scanning is a lot of hard work due to wet mounting compared to regular consumer or prosumer CCD-scanning. Drum scanners are high-end, high-precision mechanical devices that need a lot of care, regular maintenance and most of all - a skillful operator. It takes a long time to learn the skills and nuances needed to be able to wet mount and scan well.
The drum in operation here is spinning at up to 1600RPM in the drum scanner. The xenon light bulb illuminates through the drum onto the film. The image is fed through the PMT's and transformed into a digital signal through A/D converters.
Drum scanners need a lot of care, regular maintenance, and often big investments to replace expensive high-end electronic or mechanical parts to keep them performing to the very best of their ability. However, they are overall very bulletproof and built to last many years, even decades of use with proper maintenance.
Value
For those seeking a fast and cheap solution, this may not be something you would be interested in. Drum scans are not as cheap as a local lab's CCD scan, but they are truly the best and purest path to the ultimate quality possible. It's better to scan less but scan the best images you have in the best quality possible for reproduction and exhibition.
View of the Cliff House in San Francisco taken with a Leica M3 and Voigtlander 15mm lens.
The costs of running a drum scanner is never as cheap as a CCD or CMOS. The costs may add up - from the chemicals, tape, and mylar needed for wet mounting - to the maintenance and power usage. However, the value is worth it when you compare the quality and only want to ever have to scan an image once. It may be a time consuming process but drum scanners were actually built for volume scanning, so even though the actual mounting of the drum may take a while, scanning many images at once is easier than with many CCD or CMOS scanners that allow you to preview only one image or strip at a time.
View of a house in Virginia City, Nevada on the way to Reno. Taken with a Hasselblad 501C, 80mm Zeiss CF lens, and Fujichrome Astia reversal film.
My goal is to make the highest quality scan of your negatives and slides with a 16 bit tiff output. The high resolution and detail is something that will be future proof for many years to come. In fact, for larger negatives the resolution is still years ahead of digital. Analog photography is something that is pure and it is my goal to keep this art form alive by helping people digitize their images.