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Ccd sensor against later sensors?

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  • Ccd sensor against later sensors?

    Hi, I was surprised to discover the e400 has a Kodak ccd, over a cmos in the later models, yet this has relatively little acclaim.

    If the Kodak ccd in the E1 and E300 is generally held up to be the God sensor, how come the e400 slides under the radar?

    I ask because I have an E420, but now I'm interested ...

  • #2
    Re: Ccd sensor against later sensors?

    CMOS sensors were originally introduced because they were very inexpensive to make. They can be manufactured using the same silicone process as computer memory and CPUs. But CMOS started with a reputation of being cheap for a reason; noise and poor dynamic range. Early CMOS sensors were use in things like webcams. CMOS was bad because the sensitivity was low; the circuitry surrounding the photosites used up too much of the surface area of the sensor. But with gradual development, making the circuitry smaller allowing the photosites to be larger or burying the circuitry behind the photosites (so-called back-side illuminated sensors) this problem has long been overcome and CMOS sensors are now as good as and even better than CCDs for sensitivity. CMOS also consumes a lot less power - CCD sensors overheat more easily than CMOS. CCDs do have advantages; as pixels are read in rows rather than individually you don't get the rolling shutter 'wobble' effect with CCD sensors because the entire pixel array is read in one operation whereas with CMOS sensors each pixel is read individually. But with improved read-out speeds CMOS sensors are now often less prone to rolling shutter problems than they used to be.

    The Olympus E-1, E-300 and E-500 had Kodak FFT (Full Frame Transfer) CCD sensors which were, for their time, high-sensitivity sensors that worked very well with good dynamic range in good light. But these sensors performed badly in low light with the ISO sensitivity turned up, probably because of photosite light leakage or degradation before the signal could be fixed and read by the image processor. The E-400 also had a Kodak sensor but this was not an FFT type but a more commonly used Interline Transfer type. This means that a significant portion of the surface area of the sensor is masked to temporarily store the photosite charges before they are read. FFT sensors require mechanical shutters while Interline sensors can be operated without a shutter and that's how video or live view normally works when implemented on still cameras; the mechanical shutter is only used for still shots.

    The E-400, it seems, was originally going to feature Live View, but for some reason - maybe time constraints, it never did and it was only until the E-330 came out, fitted with the Panasonic-made but Olympus-designed NMOS (a variant of CMOS) LiveMOS-branded 7.5 megapixel sensor that we got live view for the first time in a DSLR.

    There is a school of thought that the Kodak CCD sensors produce different (better) colour to the LiveMOS sensors but I personally think it's highly subjective.

    Ian
    Founder/editor
    Four Thirds User (http://fourthirds-user.com)
    Digital Photography Now (http://dpnow.com)
    Olympus UK E-System User Group (http://e-group.uk.net)
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