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Fujifilms nye sensorteknologi

Sammenlikning av tidligere og nytt pikseloppsett.

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Fujifilm har hatt flere forsøk på alternative sensorteknologier, og har i stor grad lyktes med det også, særlig modellene F30 og F31fd har blitt lovprist verden over. Deres Super CCD-sensorer har gjort innrykk både i kompaktkameraer (HR-sensorer) og speilreflekskameraer (SR-sensorer), og nå lanserer Fujifilm en kombinasjon av disse teknologiene, som er ytterligere forbedret, i sin nye 12 megapiksel Super CCD EXR-sensor. Det spesielle med Super CCD sammenliknet med "vanlige" bildebrikker fra for eksempel Canon og Sony, er at pikslene ikke er plassert i et ordinært rutenett med rader og kolonner, i stedet er de organisert diagonalt, og minner mer om sølvhalid-oppbygningen fra filmeraen. Dette gir høyere horisontal og vertikal pikseloppløsning, på bekostning av diagonal oppløsning. SR II-brikken, som har vært brukt i speilreflekskameraet Fuji S5 Pro, hadde dessuten et ekstra sett med sensorerelementer, som fanget opp de ekstreme høylysene, og gav dermed forbedret dynamisk omfang. Den nye teknologien tar med seg begge disse elementene, og Fuji har satt seg som mål å lage en fleksibel bildebrikke, som i større grad enn tidligere tilpasser seg motivet som avbildes.

Tidligere har pikslene på sensoren vært organisert tilnærmet som en vanlig Bayer-sensor, med en blå, en rød og to grønne piksler, og binning (sammenslåing av piksler for bedre lysfølsomhet) har måttet gjøres på kryss av en annen farge. Dette har skapt problemer med feil fargegjengivelse og redusert skarphet i forsøk på å kompensere for dette. Den nye sensoren har i stedet to og to sensorer av samme farge inntil hverandre, slik vi ser i bildet over.

Dette gjør binning av piksler enklere og mer nøyaktig, og "Pixel Fusion" som Fujifilm kaller det skal øke signal-til-støy-forholdet betydelig ved eksponeringer i dårlig lys, men resultatet vil naturligvis bare ha 6 megapiksler.

"Pixel fusion" kombinerer to og to pixler til én større pixel for bedre egenskaper i dårlig lys.

Den nye teknologien åpner også for å hente ut data i to omganger, og kombinere de to bildene til ett optimalt bilde automatisk, med "Dual Capture". Det gjør den ved å først hente ut data fra halvparten av pikslene mens den andre halvparten fremdeles eksponeres. Dermed får man i følge Fujifilm langt større dynamisk omfang i bildene. Dette kan minne litt om den eksisterende Super CCD SR II-teknologien, men der brukes to forskjellige sensorelementer, der det ene er større og mer lysfølsomt, mens det andre er mindre og mindre følsomt for lys, slik at det ikke går i metning like fort. På den nye Super CCD EXR-sensoren er alle pikslene like store og like følsomme, og kan som tidligere nevnt også brukes til å øke lysfølsomheten. Med "Dual Capture" vil bildet du får beholde alle 12 megapikslene.

Dual Capture-teknologien laster ut bildedata to ganger på én eksponering, og kombinerer bildene til ett bilde med bedre dynamisk omfang.

Det siste punktet Fujifilm poengterer i pressemeldingen, er at sensoren også kan fungere som en "vanlig" 12 megapiksel-sensor også, selv om den er optimalisert for å kunne brukes til "Pixel Fusion" og "Dual Capture".

Fujifilm mener at dette er fremtidens sensor, og vi kan langt på vei være enige i at teknologien tilsynelatende virker bra. Undertegnede mener dog at fremtiden eliminerer Bayer-filtrerte sensorer fullstendig i sensorteknologi laget av bl.a. Foveon, men samtidig er det tilsynelatende ingenting i den nye teknologien til Fujifilm som er til hinder for at fremtidige versjoner kan ha full RGB-sampling på samme piksel. Uansett er det alltid positivt med dem som jobber for bedre bildekvalitet, og en av Fujifilm sine ansatte påstår i et intervju til DPreview at denne bildebrikken, som er i ferd med å bli implementert i et nytt kamera i disse dager, skal gi bildekvalitet på høy ISO bedre enn F31fd. Vi gleder oss!

Pressemelding (engelsk)

Pressemelding:

Revolutionary sensor blazes the way to a new era of high image quality

Announcement Date: 22 September 2008
"Super CCD EXR"
A 'three-in-one' sensor for high resolution, high sensitivity and wide dynamic range
Made by photographic specialists for photographic specialists

PHOTOKINA 2008, COLOGNE, GERMANY, September 23, 2008: FUJIFILM Corporation, on the anniversary of 10 years of FinePix cameras, has developed "Super CCD EXR," a revolutionary new sensor developed in the rigorous pursuit of high image quality.

There is strong demand in the digital camera market to increase the number of pixels on a sensor, which, all too often, is used as a convenient yardstick for image quality. While introducing excellent 12-megapixel cameras such as the FinePix F50fd and the FinePix F100fd, Fujifilm has had great success in increasing pixel density while at the same time controlling noise and optimising sensitivity. Fujifilm's campaign to improve overall image quality, while at the same time increasing sensor resolution, has been coordinated under the program of 'Real Photo Technology.'

'Real Photo Technology' is underpinned by the belief that experienced photographers, many brought up using famous reversal films like FUJICHROME Velvia or PROVIA, understand that true image quality is about a combination of many factors like tone, hue, colour fidelity, dynamic range, sharpness, and resolution. It is well known that increasing the pixel count on a sensor actually makes it more difficult to achieve high sensitivity and wide dynamic range. As the photodiode gets smaller, the problems of increased noise, blooming and clipping increase.

It is widely believed that 'high resolution' and 'high sensitivity' are irreconcilable opposites, and impossible to optimise on the same sensor, particularly for compact cameras, where sensors are necessarily smaller.

High quality pictures are dependent on the subject. Excellent low light pictures need high sensitivity; high contrast pictures need wide dynamic range, while fine details, like the leaves of a tree or strands of a model's hair, depend on high resolution.

Fujifilm engineers set about the task of building a flexible sensor to match the demands of the photographer. The end-goal is to produce a sensor that works as close to that of the human eye as possible. Whatever nuance of colour or sensitivity of tone that makes the scene so special to the photographer should be the continual challenge of the sensor engineer. The EXR sensor is essentially a switchable sensor; changing its complex electronic behavior to suit the subject, changing its characteristics as the photographer demands, and producing the very best picture without making compromises.

"Super CCD EXR" is the latest new generation of Super CCD to be produced by Fujifilm. Over the years, Fujifilm has excelled in high resolution sensors through 'HR' technology (F50fd, F100fd) and high sensitivity/wide dynamic range through 'SR' sensors (S3 Pro, S5 Pro). The direction in the future will be to combine HR and SR technology together to produce one universal sensor suitable for all high quality photography.

The Technology of Super CCD EXR
Super CCD EXR offers three main changes from previous Fujifilm sensors:
1. A new arrangement of the mosaic colour filter
2. A new method of pixel binning
3. A complete revision of the electronic charge control

Diagram of Super CCD EXR
Comparison of previous and EXR color filter arrangements

1. EXR: 'Pixel Fusion Technology' for High Sensitivity and Low Noise
Boosting sensitivity by increasing gain causes the generation of random increased noise, and conventional efforts to control this noise have resulted in blurred images and loss of resolution. On the other hand, a low-noise signal can be obtained by pixel binning. However, the conventional approach to binning (along the horizontal and vertical axis) generates false colours because of the separation of pixels of the same colour. Because it is necessary to suppress this phenomenon, the result is a significant drop in sharpness.

EXR changes the colour filter arrangement. Two side-by-side, same-coloured pixels are taken together as a single pixel. With this design, the area of imaging elements is doubled, the sensitivity is twice the normal level, and 'dark noise' is extremely small. Therefore, it is possible to create a high sensitivity image with little noise, instead of increasing the gain from a single pixel and increasing the noise.

Conceptual Diagram of EXR's High Sensitivity/Low Noise Technology

Another problem with traditional pixel binning is the distance between same-coloured pixels. Since the pixels are combined vertically or horizontally, the distance between combined same-colour pixels is large, resulting in the generation of false colours. Boasting a new technology called Close Incline Pixel Coupling, the new Super CCD EXR can prevent the generation of false colours by mixing two adjoining pixels as one, and managing to achieve both low noise and excellent sharpness.

2. EXR: 'Dual Capture Technology' for Wide Dynamic Range
Super CCD EXR uses flexible and high-precision exposure control to simultaneously capture two images of the same scene: one taken at high sensitivity and the other at low sensitivity. It then merges the two images to generate a photo that has excellent depth and range.

Previously, Fujifilm used two different methods to improve dynamic range. The first was Super CCD SR. Through the adoption of a "double pixel structure" based on silver halide film, which comprises an "S pixel" with a large area and high sensitivity and an "R pixel" with a small area, a dynamic range four times that of conventional sensors was achieved. The second was based on Super CCD HR, where the gradation of shadows was gradually adjusted while raising the sensitivity of signal processing, and where highlights were softened to delineate an optimal curve. Similar to Super CCD SR, the new EXR sensor uses Dual Exposure Control to impart two differing sensitivities by controlling the light exposure time (the time in which charge accumulates).

Unlike SR, the imaging elements are the same (large) size, which means the potential for widened dynamic range is even greater, and facilitates a greater spectrum of graduated expression.

Conceptual Diagram of EXR's Wide Dynamic Range Technology

3. EXR: 'Fine Capture Technology' for High Resolution
The distinctive structure of the new Super CCD EXR fully exploits all the pixels in the layer beneath the new colour filter matrix and takes advantage of the optimised signal processing of the new RP processor to create an image with the highest possible resolution quality. Even though the sensor has been designed for 'Dual Capture' for Wide Dynamic Range and 'Pixel Fusion' for Low Noise, it actually performs as well as previous 12-megapixel Super CCD sensors due to the new filter and photodiode design.

When light is full and even, and when fine detail is required, EXR can deliver exquisite detailed expression for landscape or architectural photography, and render the finest details of clothes, hair or jewellery in portrait photography.

EXR: The Future
Fujifilm is determined to use decades of imaging know-how gained through the development of film to push the boundaries of what is possible to achieve with an imaging sensor. The market for digital cameras is only around a decade old, and Fujifilm believes that it is possible to follow the holy grail of 'absolute image quality' in the domain of electronic imaging, just as it did with conventional imaging. With EXR, Fujifilm can choose one engineering direction, rather than developing separate sensors for high sensitivity and high resolution. Fujifilm looks forward with excitement to introducing this sensor into its range of high quality cameras, and expects enthusiasts to see a quantum leap in image quality from anything they have seen before.

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