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What are the differences between CRT and CCD technology?
Now there's a question! Although there are fundamental differences in the technology, both methods of film scanning can achieve great results. It is worthwhile splitting the CCD camp into Line Array and Area Array technology. Cintel has embraced all three technologies at some point and it is important to look at the scanning application to determine which technology is best suited.
CRT (Cathode Ray Tube) film scanners; Cintel: MKIII, URSA, Rascal, C-Reality/DSX, Millennium2 and dataMill, Film and Data Technologies: Nova.
CCD (Charge Coupled Device) film scanners; Line Array - BTS/Philips: FDL/Quadra, Thomson: Spirit/Shadow, Grass Valley: Spirit 2K and Spirit 4K, Imagica: ImagerXE, Filmlight: Northlight, Cintel: ADS-1/2, Klone. Area Array - Cintel: diTTo, Sony: Vialta, ARRI: Arriscan, Imagica: HSX.
Let's look at the methods of scanning in a little more detail:
CRT Scanning - The Good:
- Resolution independent detection devices - no limit to the resolution scanned.
- LIVE still image - the image on the monitor is Live and exactly what will be recorded.
- Continuous motion servo - real time (and faster than real time) scanning possible.
- Pin Register and Wet Gate capability.
- Resolution Independent Scan Effects.
- Higher resolutions can be achieved by decreasing spot size.
- A deeper, more 'filmic' look to the pictures.
The not-so-Good:
- Seen as expensive as the CRT can require replacement every 2 or 3 years.
- Can require complex circuitry to mask ageing effects.
- Sometimes requires expert alignment.
Line Array CCD - The Good
- Continuous motion servo - real time scanning achievable.
- Relatively cheap illumination, easy to change.
- Diffuse illumination - can help reduce dust, scratches and film grain.
- Flexible vertical scan.
The not-so-Good
- Fixed horizontal resolution - the native CCD resolution is the maximum that can be scanned.
- No LIVE still - the image on the monitor is not 'real', it is a frozen image from a framestore.
- Registration can be difficult.
- A flatter, more 'video' look to the pictures.
Area Array CCD (or CMOS) - The Good
- Promotes Pin Registration - perfect stability achievable.
- LIVE still frame - the picture viewed is the 'real' picture.
- Relatively cheap illumination, easy to change.
- Diffuse illumination - helps reduce dust, scratches and film grain.
- Longer exposure time.
- No registration issues.
The Not So Good
- No Continuous motion - Real-time very difficult to achieve.
- Fixed Resolution.
- CMOS can suffer from Noise issues. So is CCD more "digital" than CRT? Absolutely not. As far as today's machines are concerned, they both have an 'analogue' light source (the light bulb or the CRT) and 'analogue' detection (the CCD or the APD) to actually scan the 'analogue' film. After this point all machines have an Analogue to Digital converter and are 100% digital from then on.
Hopefully that has explained how the technology basically works and some of the differences. So which to chose? It really depends upon your requirements and your application:
Real Time SD or HD video? - choose CRT or Line Array CCD
A deeper, 'filmic' look? - choose CRT
A flatter, cleaner, 'video' look? - choose Line Array CCD
A pin registered high resolution data scan? - choose Area Array CCD.
The flexibility of Video or Data scanning, Continuous or Pin Registered - choose CRT.
Many people would argue that if you are looking to scan film in a 'creative' environment looking at, and grading, the images real time in a 'telecine' workflow on a video monitor then it is difficult to beat the filmic look from a CRT. Most people would argue that to achieve the best quality pin registered Data scan, Area Array CCD is the best technology. All the latest Data Scanners use this method of scanning.
If more flexibility is required - real time SD and HD video, continuous motion fast 2K scanning and Pin Registered data scanning then the only technology to use is CRT.
So what are the differences between CRT and CCD technology? Pretty fundamental but they both achieve similar results. Choose which makes the most sense for your application.
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