EBU Tech 3297-E 35 mm High Resolution Test Film for the assessment of telecines and scanners May 2004 EBU UER european broadcasting union Geneva EBU Technical Documents can be downloaded from www.ebu.ch EBU – 35 mm High Resolution Test Film for the assessment of telecines and scanners Tech 3297 May 2004 Key words: Film, telecine, scanner, resolution Details of where to obtain samples of the test film are given at the end of this document. The EBU High-Resolution 35 mm Test Film The EBU has been investigating the performance of modern telecines and scanners with a view to recommending design parameters for future machines. In the course of measuring the resolution of machines it became evident that a test film was required that contained sufficient high frequency detail to challenge the resolution capabilities of current telecines and scanners. As no such film was known to be available, a group of experts designed a high-resolution target and a limited run was produced on a 35 mm monochrome film stock with a 125 mm polyester base. Figure 1 is an illustration of a frame of the test film. Please note that no meaningful measurements can be made from this figure, as its printed resolution is too poor. Test Film Resolution The test film is not intended for use in standard definition television. Note that just 10 line-pairs1 per millimetre (lp/mm) distributed across the 24.92 mm width of a frame of super 35 mm film scanned at standard 625-line television rate would equate to: 10´24.92mm = 4.79MHz 52ms This is very close to the 5.5 MHz upper limit of PAL System I television. So-called 4k scanners have 4096 elements distributed across 24.92 mm – the width of a frame of super 35 mm film. Simple arithmetic equates this to 82 lp/mm. Even ignoring Nyquist criteria, it would be impossible for a 4k scanner to cope with this resolution as the scanning elements would have to line up precisely with the film image, which would not happen in practice. In order to resolve 100 lp/mm across a frame of super 35 mm film, a scanner would need to be capable of 6k (6144 scanning elements) resolution. Image Calibrations The test film is designed around the SMPTE style 'C' aperture (24·92 mm x 18·67 mm). Ruler markings are included, as are calibrations for EBU recommended scanning areas for both 4:3 and 16:9 aspect ratios. The centre resolution patches are 10, 20, 30, 40, 50, 60, 70, 80, 90, & 100 lp/mm. This is effectively a calibrated frequency sweep. An important requirement of the test film is to highlight shortcomings in anti-aliasing filtering. A block of test patches with 35, 40 & 45 lp/mm is included to investigate responses around the 41.1 lp/mm Nyquist limit for 2k scanning. A similar facility is available for 4k scanning by using the 70, 80 & 90 lp/mm sections of the main sweep. Lower frequencies are placed in the corners of the target. This is because practical lenses are not at their best at these extremities. Measurements were made on the initial batch of test film. The results are shown in Table 1, referring to the numbered cells in Figure 2. 1 A line pair corresponds to a black element followed by a white (or clear) element on the surface of the film. 2 EBU – 35 mm High Resolution Test Film for the assessment of telecines and scanners Tech 3297 May 2004 Table 1 Box No Resolution Amplitude % Box No Resolution Amplitude % Box No Resolution Amplitude % lp/mm lp/mm lp/mm 1 10 80 21 50 85 41 60 50 2 25 75 22 60 65 42 60 70 3 60 40 23 70 50 43 60 75 4 60 65 24 80 50 44 25 95 5 60 40 25 90 50 45 10 100 6 25 80 26 100 40 46 10 85 7 10 95 27 35 90 47 25 80 8 10 90 28 40 90 48 60 40 9 25 85 29 45 85 49 60 70 10 60 50 30 10 100 50 60 50 11 60 75 31 20 95 51 25 90 12 60 50 32 30 95 52 10 90 13 25 90 33 50 80 14 10 100 34 70 50 15 25 85 35 90 40 16 60 55 36 100 30 17 10 100 37 60 70 18 20 95 38 25 95 19 30 95 39 10 100 20 40 95 40 25 85 Note that resolution measurements are listed with respect to peak-peak level at 10 lp/mm. Compared to this, the black/white reference boxes in the centre of frame have a pk-pk value of 110%. It is probable that flare in various parts of the production chain is responsible for this. In addition, the manufacturer’s data sheet shows a maximum of 90% for all frequencies used in this test film. However, the pk-pk values for each line pair patch are still valid as they were measured individually. The following photographs, taken from the top of a microscope, show the 10 and 100 line pair patches on the test film respectively. Test Film Samples The EBU has a limited number of film samples that can be made available to EBU members and their associates. These will be distributed on a first-come first-served basis. Please contact [email protected]. Film samples or longer lengths, together with the conditions of purchase, may be obtained from: R.H. Testfilms 27 Carpenters Wood Drive, Chorleywood, Hertfordshire, WD3 5RN, United Kingdom email: [email protected] 3 EBU – 35 mm High Resolution Test Film for the assessment of telecines and scanners Tech 3297 May 2004 Figure 1: High Resolution Test Film Target 4 EBU – 35 mm High Resolution Test Film for the assessment of telecines and scanners Tech 3297 May 2004 Figure 2: Annotated Test Film Target 5.