How Am Together With Fm Screening Equivalencies Are Measured

I'm oftentimes asked nigh what AM/XM halftone screens are equivalent to a sure enough FM shroud - i.e. "What AM/XM shroud is equivalent to a twenty micron FM screen?"

There are ii ways that this halftone screening equivalency is commonly measured.

One is equivalency of item rendering - the mightiness of the screening to homecoming icon detail. The other is lithographic equivalency - how they perform on press lithographically. Note that inwards both cases, because the respective screening applied scientific discipline is in addition to thus different, equivalency tin exclusively hold out an approximation.

Equivalency of item rendering
Since halftone dots degree the printed icon - to a greater extent than dots per linear inch translates into to a greater extent than item that tin hold out rendered.

With an AM shroud the item rendering mightiness is specified inwards lpi (or lpc) - i.e. halftone dots per inch (e.g. 175 lpi or lx lpc).

Since an FM shroud has no "lines per inch" determining the equivalent item rendering equivalency is commonly done past times drawing a line of piece of employment through the FM shroud in addition to counting how many dots are intersected (crossed) inwards a distance of i inch.Measuring the relative lpi of an FM screen.
The to a higher house illustration shows an FM shroud enlarged. The distance measured is 1/16th of an inch. In that 1/16th of an inch some 36 dots are intersected. So, inwards i inch nigh 576 dots would hold out intersected (16 x 36). Put some other way, at that spot are 576 dots per linear inch - 576 lpi - to homecoming detail, i.e. this FM shroud is equivalent to a 576 lpi AM/XM screen.

Lithographic equivalency
Lithographic equivalency is a combat to a greater extent than complicated to figure out. It is commonly measured past times counting the seat out of edges (transitions) inwards a foursquare inch.Measuring the seat out of edges of an AM/XM screen.
Measuring the seat out of edges of an FM screen.
Halftone screens alongside a like seat out of border transitions volition accept like lithographic properties.

AM/XM equivalents of some pop FM screens.
Keep inwards mind, these are approximations only, all the same they create give a skillful indication equally to screening performance.