Document feeder types from ADF to RADF DADF and SPDF made simple
Four acronyms describe four different document feeder mechanisms on office MFPs. ADF, RADF, DADF, and SPDF. Dealers throw them around in conversation as if everyone knows what they mean. Most office buyers do not, and the dealer counts on the gap to push higher segment options when a lower one would do. The differences between the four matter most when scanning two sided originals at speed, and they map almost directly onto the segment classification.
Stripping the acronyms reveals four levels of mechanical sophistication. Each one solves a specific paper handling problem the previous one created.
ADF the baseline
ADF stands for Automatic Document Feeder. The simplest version. A tray on top of the platen holds a stack of original pages. A pickup roller takes the top sheet, pulls it through a path that crosses a fixed scan glass beneath the unit, and deposits the scanned page on an output catch. The mechanism handles single sided originals only. To scan the back of a page, the user has to flip the stack manually, run it through again, and merge the two passes in software, or do nothing and only capture one side.
Most Segment 1 desktop MFPs ship with basic ADF. Capacity ranges from 35 to 50 sheets. Speed runs 25 to 40 originals per minute single sided, since ADF performance tracks scanner speed rather than print speed. The Canon i-SENSYS MF754Cdw, the Brother MFC-L8900CDW, and the HP LaserJet Pro MFP M283fdw all carry single sided ADFs of this type. Buying decisions in this segment hinge on whether the office ever needs to scan two sided originals. If the answer is yes more than once a week, ADF on its own becomes a daily friction point.
RADF the older two sided approach
Reverse ADF, abbreviated RADF, was the standard two sided document feeder through about 2018. Across most older Canon iR-ADV C5240, Ricoh MP C3504, and Konica Minolta bizhub C284 units, RADF is what shipped. The acronym describes the mechanism. After a sheet passes the scan glass, the feeder reverses it through an internal switchback path, runs the page back across the same scan glass with the back side now facing the sensor, then flips it again to deposit the page right side up on the output tray.
The trade off is speed. A RADF reading both sides of a page essentially scans the page three times mechanically. Forward through the scan glass for the front. Backward through a reverse loop. Forward through the scan glass again for the back. The throughput on duplex originals drops to roughly half the simplex rate. A 60 originals per minute single sided rating becomes 28 to 32 originals per minute double sided on a typical RADF. The full mechanical breakdown of the chassis around this feeder is at A guided tour of every part inside a modern office copier.
RADF still ships on some Segment 2 and lower Segment 3 machines in 2026, particularly on Brother and on some HP LaserJet workgroup models. The cost advantage to the manufacturer over a more sophisticated feeder is real but small, on the order of 80 to 150 euros per unit. Buyers comparing two units at the same price point should check the spec sheet for which feeder type is fitted before assuming they are equivalent.
DADF a transitional design
Duplex ADF, abbreviated DADF, sits between RADF and the modern single pass approach. The name covers any document feeder capable of scanning both sides without manual paper flipping. In practice, DADF on an older machine usually means the same reverse switchback mechanism RADF uses. DADF on a newer machine often means the single pass duplex mechanism described in the next section. The acronym is ambiguous and dealers use it loosely.
Pinning down what a specific DADF actually does usually requires reading the spec sheet line that lists duplex scan speed. If the duplex rate is half or less of the simplex rate, the feeder is a switchback type. If the duplex rate matches or nearly matches the simplex rate, the feeder is a single pass duplex type. The asymmetric rate signal is what cuts through the marketing label uncertainty when comparing models.
The buying implication. The acronym DADF on a brochure tells you only that two sided scanning is possible, not how fast. Asking the dealer specifically about duplex throughput in originals per minute, and comparing that number to the simplex throughput, is what reveals whether the unit carries an older switchback design or a newer single pass design. The everyday distinction between machines marketed at different segment levels often comes down to exactly this feeder choice, which the dealer segment classification captures explicitly. A reader being pitched in segment numbers without a clear feeder spec can pick up the segment mapping at What the industry copier segments from one through six actually mean for you to triangulate.
SPDF the modern single pass design
Single Pass Duplex Feeder, abbreviated SPDF, solved the speed problem on RADF by adding a second scan head. The mechanism uses two scan elements arranged in line above and below the paper path. A single sheet passes through once. Both scan heads read simultaneously, one captures the front, the other captures the back. No switchback. No second pass. The duplex throughput equals the simplex throughput, and on machines optimized for SPDF, the duplex rate sometimes exceeds simplex because the feeder runs at a higher continuous speed when both sides scan together.
SPDF appears on most Segment 4 and Segment 5 office MFPs in 2026, including Canon iR-ADV C5760i, Ricoh IM C6010, Xerox AltaLink C8055, and Konica Minolta bizhub C750i. Some Segment 3 units carry SPDF as well, particularly on newer model years where manufacturers have rolled the feature down the segment ladder. The full segment ladder and where SPDF lands within it is detailed at What the industry copier segments from one through six actually mean for you.
The cost premium for SPDF over RADF is meaningful at lower segments and trivial at higher ones. On a 4,500 euro Segment 3 machine, choosing the SPDF version typically adds 200 to 400 euros to the list price. On a 12,000 euro Segment 5 machine, SPDF is standard and not separately priced. Where SPDF earns its keep is on offices scanning more than 50 duplex originals a week, since the time savings compound across months.
Capacity and what it predicts
Beyond the duplex mechanism, document feeders vary in how many sheets they hold. Three capacity bands cover most of the market. 50 sheets. 100 sheets. 200 to 300 sheets. The capacity correlates with segment, with Segment 1 typically at 50, Segment 3 at 100, and Segment 5 at 200 plus.
The capacity matters when scanning long originals. A scan job longer than the feeder capacity has to pause for the operator to reload, which interrupts batch operations. Accounting firms running tax season scans of 80 page returns hit this constantly on Segment 2 machines with 50 sheet feeders. Moving up one segment to a 100 sheet feeder removes the daily reload friction, sometimes more than justifying the segment upgrade by itself. The case for sizing equipment to actual workflow rather than to dealer margin sits at How to tell whether you need an office class copier or a production class one for the larger pattern around equipment classification.
Reliability also tracks capacity. Larger feeders carry better separation rollers, more sophisticated paper handling, and more durable pickup mechanisms. A 50 sheet feeder running 200 sheets a day will wear faster than a 200 sheet feeder running the same workload, even though both can technically handle the volume. The wear shows up as multi feed errors, paper skew, and increased jam frequency over the second and third year of operation.
Failure modes specific to feeders
Document feeders fail more often than the print engine on a typical office MFP. The mechanism handles paper at high speed with multiple rollers, separation pads, and sensors that all wear with use. Two failure patterns dominate. Pickup roller wear, where the top roller stops gripping the paper consistently and either fails to feed or feeds intermittently. Separation pad wear, where the pad stops preventing two sheets from feeding simultaneously, causing multi feeds and skip pages.
Both failure modes present as paper jams in the feeder area, often with codes in the J3xx or J4xx range on Konica Minolta machines, the SC3xx range on Ricoh, and the E602 range on Canon. Replacing rollers and separation pads is a routine service operation typically included in the maintenance kit pricing on a service contract. Office staff who notice clusters of feeder jams over a week or two are usually seeing roller wear that the next scheduled service will resolve.
The everyday distinction between a printer that has no feeder at all and an MFP with a sophisticated feeder is one of the larger contributors to the price gap between the two categories, and laid out at How a photocopier differs from a printer an MFP and a copier in everyday office life. A reader thinking about whether the feeder feature set justifies the MFP price tag for a single user desk will find the contrast useful.
How to read a brochure correctly
The four numbers that matter on the feeder spec line. Capacity in sheets. Simplex throughput in originals per minute. Duplex throughput in originals per minute. The acronym for the duplex mechanism. Comparing two machines at the same nominal segment, these four numbers usually reveal a meaningful difference somewhere.
An office buying a Segment 3 color MFP often sees two candidate machines at similar list prices. One has a 100 sheet RADF rated at 70 originals per minute simplex and 35 duplex. The other has a 100 sheet SPDF rated at 80 originals per minute simplex and 80 duplex. The second machine handles two sided originals more than twice as fast as the first, and the price difference reflects 200 to 500 euros of additional hardware. For an office that scans 200 duplex pages a week, the second machine saves around 90 minutes per week in scan operator time, which compounds to roughly 80 hours over five years.
The mistake is treating the two machines as equivalent because both list ADF or both list DADF on the brochure. Both labels can hide either feeder design. Reading the throughput numbers, particularly the ratio between simplex and duplex, is what cuts through the marketing label and reveals which machine fits a duplex heavy workflow.
ADF reads one side. RADF reads both sides slowly through a switchback. DADF means either depending on the model. SPDF reads both sides at full speed using two scan heads. The acronyms differ. The feeder behavior differs by a factor of two on duplex originals. The price difference is usually a few hundred euros at the segment where the choice exists, and pays back fast on offices doing real two sided scanning.