What is a anti-aliasing filter

Discussion in 'Nikon' started by joseph_leotta, Sep 6, 2009.

  1. D3X has high quality anti-aliasing filter to extract the best resolution out of the sensor(read the press release for this camera).
    What the heck is it?
     
  2. It is a filter on top of the sensor which reduces image digital sampling errors (the dark side of being digital). If it is done too much, the image can become mussy and the camera doesn't sell. If it is done too little, things like power ties, news person sport jacket and window screens can have funky moire pattern and the company CEO write apology letter (remember Leica?). It is a Russian roulette thing for the poor engineers. That is why most of them lean toward the mussy side and kept their job :)
     
  3. Anti-aliasing filters are low-pass filters that prevent spatial frequencies higher than the Nyquist frequency from passing through. They reduce/prevent the appearance of aliasing artifacts in the images.
     
  4. Ilkka has it right. However, to expand a little bit on this Nyquist thing:
    An image sensor has pixels of a given size. Imagine (...) finer structures than this size (I keep it simple) projected onto the sensor, produced by the picture and the lens. That is, one single pixel would have to resolve severeral dots, which is not possible as it is only one single pixel. The errouneous result would be these rainbow-like colour rings referred to as "moire". This then is called aliasing. The anti-alias filter prevents aliasing. It simply "unsharpens" the real picture to a resolution smaller than the image sensor can handle. If the poor engineers exagerate this, the picture gets blurry.
    That guy named Nyquist has described this, but this is complex math (forgive th pun).
     
  5. Don't get taken in by that "hot rod" thing - it's another way for people who blame their cameras for their bad photography to obsess over technical details. Instead, ask yourself: if it were possible to make a camera peform much better just by not installing the AA filter, wouldn't either Nikon or Canon do that, to gain a competitive advantage?
    In the case of the D3X, I think what Nikon is doing is making their camera sound as special as possible because it costs too much, so they have to say something. Maybe they did use a better AA filter than the average camera gets - for the price, I should hope so.
     
  6. Many medium format digital systems allow you to take the AA filter off or install it when you need it. I suppose the problem with doing that with small format digital is that there is so little space in the mirror box to maneuver; could easily break something doing it whereas if you can just take the back off the camera, the sensor is easier to access. Anyway, the AA filter is something you need to have.
    The D3X is expensive because they make it in small numbers, not because it is made of parts that are intrinsically expensive, but the development costs have to be covered somehow. This results in high unit cost. Why do they make it in small numbers? Because they didn't expect it would sell since it has disadvantages (in speed and high ISO IQ) compared to the D3 and D700, but they made it anyway, as some high-profile pros wanted one and it has value for the image of the brand as it strengthens people's faith that it's sensible to invest in Nikon lenses. Overpriced? I think it's priced in line with the competition.
     
  7. This may seem like a strange or naive question.
    I rented a d3x, and used very good capture techniques.
    I was bothered by what seemed to me to be somewhat more intrusive AA filter impact than my d90, and way more than my Hasselblad 503CWD.
    I realize you can develop expertise overcoming this by careful sharpening routines and there is a great book on this by Fraser.
    My question is? I wonder why I should bother?
    Is it possible that the AA effects would be less noticeable if my "Nikon Step Up" were to the "full frame but lower pixel" Nikon models like the d3, d3s, or d700 instead of the d3x??? soemthing about the d3x I just didn't like the feel of. And according to the Lloyd Chambers website, the bigger photosites often produce better image quality.
    Reading the Fraser book, which is a lovely book, it seems perverse that for someone who would shoot landscapes and not have the typical patterned textile moiré issues, I have to devote large amounts of learining and processing time to "fixing" the "fix" of the strong AA filter in the d3x.
    Am I crazy (feel free to say I am crazy and ill-informed, it is not unlikely I am both !)
    Thanks in advance
     
  8. This may seem like a strange or naive question.
    I rented a d3x, and used very good capture techniques.
    I was bothered by what seemed to me to be somewhat more intrusive AA filter impact than my d90, and way more than my Hasselblad 503CWD.
    I realize you can develop expertise overcoming this by careful sharpening routines and there is a great book on this by Fraser.
    My question is? I wonder why I should bother?
    Is it possible that the AA effects would be less noticeable if my "Nikon Step Up" were to the "full frame but lower pixel" Nikon models like the d3, d3s, or d700 instead of the d3x??? soemthing about the d3x I just didn't like the feel of. And according to the Lloyd Chambers website, the bigger photosites often produce better image quality.
    Reading the Fraser book, which is a lovely book, it seems perverse that for someone who would shoot landscapes and not have the typical patterned textile moiré issues, I have to devote large amounts of learining and processing time to "fixing" the "fix" of the strong AA filter in the d3x.
    Am I crazy (feel free to say I am crazy and ill-informed, it is not unlikely I am both !)
    Thanks in advance
     

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