Progressive Scan (p)

After each exposure, the full frame is captured/output from the sensor. This scanning method provides the highest resolution per frame and is comparable to the way images are captured on film. It delivers good material for keying or masking in postproduction. The only problem is fast motion or fast panning, which easily results in jittering/juddering images. Shooting with higher frame rates eliminates this effect.

Progressive material is denoted with the letter “p”, attached to the image format:

• 720p meaning progressive HD material with 1280 x 720 resolution
• 24p for progressive Material at 24 frames per second
• 1080/24p for progressive HD material with 1920x1080 resolution at 24 fps.

Interlaced scan (i)

After each exposure, odd (1,3,5…) or even (2,4,6…) lines of the full frame are alternately captured/output from the sensor, as so called fields. Two sequentially output fields make up one frame. Fields are output at twice the frequency of frames from progressive capture. This principle bases on the afterglow of CRT phosphors and the characteristics of human vision, which results in two fields being perceived as a continuous image once the frequency is high enough. Due to the higher frequency of the fields, this scanning method provides a smooth motion representation. Fast horizontal movement or quick pans, however, cause jagged vertical edges in the image, as the two fields composing a frame are captured one after another. This reduces the quality of keying or masking in postproduction. Interlaced material usually has to be de-interlaced (combining fields to frames), before it can be worked on using today’s post processes. Interlaced material is denoted with the letter “i”, attached to the image format:

• 1080i meaning interlaced HD material with 1920x1080 resolution
• 25i for interlaced material at 25 frames, i.e. 50 fields per second
• 1080/25i as a combination of the above.

Some people prefer relating to fields- rather than frames per second, e.g. 50i or 60i. As current cameras also offer progressive capture of 50 or 60 fps, the declaration of fields per second can be rather confusing.

Progressive segmented frame (PsF)

This is not a scanning method used for capturing, but a transmission method. Basically, a progressively captured frame is segmented into two fields, which are then transmitted similar to an interlaced signal. This enables devices that usually work with interlaced material to also work with progressive material. The notable difference to an interlaced scan signal is that both fields originate from the same frame and have not been captured sequentially. Therefore, transmitting progressive scan material using PsF means no loss in image quality. Motion representation and resolution is exactly the same as in progressive scan material. PsF material is denoted with the letters “psf” (or PsF), attached to the image format:

• 1080/25psf for progressive HD material with 1920x1080 resolution at 25 fps, transmitted as PsF.