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optical and digital zoom

Discussion in 'Photography Forums' started by scratchyjase, Sep 24, 2005.

  1. scratchyjase

    scratchyjase
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    well i was in jessops yesterday and i thought that digital zoom was useless. But I was talking to an assistant in there and she said if a digi camera is 6mp or above digital zoom is as good as optical zoom, is this right?

    this would be important to me as i would buy a camer 3x optical zoom x 4x digital zoom = 12x zoom.

    this would save me buying a much bigger camera which has a 10x optical zoom.

    I hope this is clear enough.
     
  2. stevegreen

    stevegreen
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    I use a little A95 and rarely usae the digital zoom on it to be honest. i find the quality is rather questionable unless using a tripod or some other stabilisation.

    I think it better to go for as high an optical zoom as possible and this can then be supplemented by a digital zoom if needed.

    I can't see that a digital zoom is going to be as good as an optical zoom though.

    Others may well put me right.
     
  3. RobertP

    RobertP
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    Get a picture... crop the size to a quarter of what it was (ie throw 3 quarters away) and then zoom in your view until it is as big as the original. Homemade digital zoom.

    Buy a camera for its optical zoom and ignore digital zoom. The only way digital zoom is better than the crop above is that it applies less jpeg compression and so retains a little more detail - but it is only a little.
     
  4. barongreenback

    barongreenback
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    Hmm...that doesn't sound quite right. In fact, you may get better image quality by cropping and enlarging your shot in photoshop or another image editing package. I guess it all depends on the quality of the camera in the first place and also what size of photos you are intending to print.
     
  5. Nick_UK

    Nick_UK
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    Up to a point. A few years ago 1M pixel cameras were the "bee's knees". Then came higher resolution cameras. If you have a 6M camera and 3 x digital zoom it, you still have 2M useful pixels, which is enough for a lot of applications. However, if you want to retain all 6M pixels, then you must go for optical zoom. Don't forget that even 6M pixels is only about 30% of the resolution that you can get from 35mm film.

    P.S. Never use digital zoom on the camera. You can achieve the same effect in the editing stage by cropping and enlarging. Always turn digital zoom off, on the camera itself.
     
  6. Ikki

    Ikki
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    When the lens is at it's telephoto end, the image that covers the sensor can't be made any larger or magnified by optical means. All digital zoom does is effectively crops the image on the ccd and blows the cropped area up to full size by processing the information (I guess by some form of interpolation).

    As the image information hitting the ccd through the lens stays the same no matter how much digital zoom is applied, the image quality will gradually reduce as the magnification is increased. You can do the same in any image processing software such as Elements and probably get better results. I think that it is just a sales gimmick, there is no substitute for optical magnification or zoom.
     
  7. Pink Fairy

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    A good example of the sales staff in Jessops these days :thumbsdow
     
  8. RobertP

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    Nearly true but not quite.

    Try it yourself - I did with my Oly C5050. There is more detail in a digital zoom capture than in a photoshop enlargement. The camera compresses the data in the whole scene for a full shot and does so less on a digital zoom - so less image data is discarded. The difference however is not that much.
     
  9. JayCee

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    Is that still generally true?
    I thought digital was catching up with 35mm.
    So all these mega-expensive Canon/Nikon Pro DSLRs are still no match for a 35mm SLR with a good quality lens?
     
  10. Ikki

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  11. longleyc

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    2o Mega pixels is about equivalent to 35 mm film resolution.
    In the future with larger CCD`s and better circuitry, digital will surpass film as it will offer a better or equal dynamic range too.

    There are a few manufacturers of Digital Backs which offer very high numbers in terms of pixels. I wouldnt concern yourself with these. You can never afford such equipment :)

    Now, I tried Digital Zoom experiments in the past. Lets say, its not awful. In some cases its quite a decent compromise, given the circumstances. I think it depends on the algorythm used to "fill in the blanks" as it were.
    Theres no reason to say that in camera processing isnt any worse than Photoshop algorythm for increasing resolution by interpolation. Its one and the same. Some software methods employ fractal processing for interpolation. The results are good.

    In essence, the optical is obviously better than digital interpolation. The question is: Is it that bad? Depends on the camera, but not much in it. Is a 180 mph Ferrari better than a 170 mph BMW? On paper yes, in practise no.

    As regards to digital zoom vs cropping and enlarging. You wont notice much difference. Im a very experienced PhotoChop user, I cant tweek it to better digital zoom in any noticable way. With digital zoom you at least get all the pixels (interpolated). By cropping and enlarging you are first throwing optical pixels away then interpolating. Whats the difference? None. Plus you best spend some time Sharpening to bring back the detail too.
    The only drawback might be the cameras interpolation algorythm. That might be different from camer to camera. (Sony tends to digital zoom well).

    Panasonic have solved this problem in a way. The new FZ30 has 8-megapixel high resolution CCD. This further extends the powerful 12x optical zoom when less than 8-Megapixel resolution is selected. The zoom ratio can be extended to 15.3x optical for 5-Megapixel and 19.1x (688mm) optical for the 3-Megapixel image recording.
    Zoom range can be extended in total to 76.4x (equivalent to 35 mm to 2674 mm on a 35mm film camera) when combined with 4x digital zoom, even if the shooting range is as short as 2m.
     

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