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Neutral Density Filters

Discussion in 'Projectors, Screens & Video Processors' started by ZippyCat, Nov 24, 2004.

  1. ZippyCat

    ZippyCat
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    Can anybody suggest a suitable Neutral Density Filter for my newly acquired Toshiba MT200. I’ve been looking at the Jessops website, however I’m a little worried the filters they sell will not fit. What do they look like? For example, they sell a ‘HOYA NEUTRAL DENSITY X4 49mm’ for £12.49, is 49mm the overall diameter of the filter, or is it 49mm + a trim? I’m currently at work, so I can’t off the top of my head give details to the size of my lens. BTW, I don’t want to use tape to secure the filter in place, I would rather it fits securely by itself.

    Thanks :)
     
  2. MikeK

    MikeK
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    If the MT200 lens is threaded to take a filter - then that's the filter size you should buy - the 49mm refers to the size of the screw thread (that's an example BTW - I don't know what size the MT200 lens thread is, or even if it's actually threaded at all)

    The MT200 is not a massively bright projector in the first place - are you sure you want to put a 4x ND filter on it?
     
  3. ZippyCat

    ZippyCat
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    Thanks for the response MikeK. :smashin:

    The reason why I require an ND filter is due to its current location (bedroom), where the image is only 4ft wide resulting in excessive brightness, and hence the requirement for the filter. The lens is not threaded, but I presume you mean the internal diameter of the lens barrel would need to be 49mm for a 49mm ND filter to fit. In other words, if I measure the internal diameter of the MT200 lens, would I require an ND filter with the same measurements? In addition, what does the ‘X4’ or ‘X8’ stand for? Strength / Intensity of the filter?

    Thanks again.
     
  4. MikeK

    MikeK
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    If the lens isn't threaded, then you'll need some other method to secure the filter - very fine slivers of blutac should be OK.

    Yes, the measurement is the internal diameter of the lens barrel thread - these filters are really primarily designed to be fitted to camera lenses, practically all of which (SLR type anyway) are threaded. Note that it's a 49mm thread in this example - the diameter of the actual barrel itself will probably be 1-2mm less - it's a thread thing :)
    The x4, x8 etc is the strength of the filter - AFAIK, x2 allows only half the light through the lens, x4 a quarter and x8 one eighth

    I take it your PJ is running in Eco-mode, with the brightness/contrast turned down appropriately!

    BTW, what do you think of the MT200?
     
  5. ZippyCat

    ZippyCat
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    Once again thanx, you’ve been a great help! :)

    The barrel itself measures 56mm, so if I understand you correctly, a 58mm filter would be ideal.

    The projector is running in ‘Eco’ mode with the brightness turned right down. The black level on screen matches that of the black level surrounding the picture (the supposed “non-reflective” part of the DLP chip that surrounds the mirrors), so no further tweaking will reduce the level without some form of physical intervention.

    (Apologies for the following adaptation from one of my previous posts)

    So far I’m really impressed with the MT200, having to continually remind myself of just how little I paid. Colours leap of the screen with virtually no perceivable screen door effect or pixelation (2x screen width viewing distance). It’s an attractive package to mount on your ceiling (photos on the internet don’t do it justice), much better looking than the H30 or SP4805.

    The only slight niggle I have is the scaler, but you must appreciate this has be manufactured for a price point. Occasionally it struggles to de-interlace fast moving objects or transitions correctly, whereby a ‘striped like’ appearance can be seen (I’m running an interlaced component signal). These however are infrequent, and you would really need to be on the look out to spot them. I would imagine a suitable progressive signal from a more adequate scaler would alleviate this problem.

    Rainbows will occasionally appear just like any other 6 segment 4x model, but are viewer dependant (demo time!). ‘Dithering’ is present, but can’t be seen from normal viewing distances.

    Sure you can bet better images, but you would have to pay twice as much to get any significant improvement. :smashin:
     
  6. MikeK

    MikeK
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    The barrel itself measures 56mm, so if I understand you correctly, a 58mm filter would be ideal.

    Actually I meant the diameter of the threaded barrel on a camera lens would measure a bit less than 49mm due to the threading.

    I suspect you'd have more joy with a 55mm filter, rather than 58mm.
     
  7. ZippyCat

    ZippyCat
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    Thanx!

    I almost ordered the 58mm filter last night :rolleyes: , I’m glad I waited.
     

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