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I bought a B+W 77mm KR-6 to go with my AE700!

Discussion in 'Projectors, Screens & Video Processors' started by Sigismund, Jun 18, 2005.

  1. Sigismund

    Sigismund
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    After reading all the filter tweak threads on AVSForum I decided to go for a B+W 77mm KR-6 (81EF). It’s taken me a while to really get to grips with adjusting the contrast, brightness and especially colour settings, but it has definitely been worth the effort.

    I just realised that some people may be unaware of the purpose of adding a colour filter to the Panasonic AE700 – I believe the theory goes something like this – generally speaking the Normal setting gives reasonably accurate (D65) colour settings, but contrast levels are quite low… much lower than Panasonic’s quoted “2000: 1”, so people began to tinker with the Cinema 1 setting and adjusting the colour temperature. This improves things nicely, but still leaves the Panny streets behind say the Sony HS50. A quick look at any AE700 review reveals, however, that using Video mode sees an abundance of blue and a deficit of red in the image – so, boosting the red contrast with a filter and then tweaking the green and blue using the individually adjustments and we should end up with a win/win situation – ie. greater contrast across the board.

    In my case I needed to boost the blue and green contrast, increase red brightness slightly, take down blue brightness slightly and really turn down the green brightness – result? A really smooth image with a much improved contrast level. In summary – I'm amazed at the difference this filter has made :)
     
  2. Peter Parker

    Peter Parker
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    That sounds about right - when boosting the green and/or blue contrast settings, your increasing the image brightness but don't increasing the black level, so the contrast ratio is increased.

    Of course the filter will dim the image equaly across the board from black to white but this won't effect the contrast ratio, just improve the black level - so you win on two counts!

    With my HT1000, I measured almost a 900:1 CR increase with an fl-day filter, which is quite an improvement. It was 1300+ out of the box, and around 1250:1 @ D65 (so out of the box was pretty close). Adding the fl-day allowed quite an increase of green and blue to get it back to D65 but the increase in CR was amazing. In contrast, the Optoma H77/78 have a better balanced colour wheel so less improvement can be found, but a further 300:1 is easily attained.

    Finding a perfect filter is the real trick - if you max out the RGBs and can see the colour balance via Colorfacts or similar, you can then place a filter over the lens and see if it flattens the colour balance out. Idealy you need a swatch of filters so you can go through them one by one, and a little uindertsanding of what colours are cut by what filter can help - yesllow will cut blue, red will cut green etc:

    http://www.aeimages.com/learn/color-correction.html

    By measuring the colour temp you have with unbalanced colours, you can kind of use the Mider system to calculate which filter or combination of filters will bring teh CT down to 6500k. That's not the same as D65, and the cut in green and blue may not be accurate (more green then blue when you wwant more blue than green), but it might it be usefull guide.

    Adding filters does reduce lumens and give a dimmer image (so a brighter pj can be an advantage), but I found that even with a very dim 4ft lamberts on a double filtered HT1000 and 2200:1 CR, the picture was very watchable and seemed much brighter than it was. The aim for cinema levels is 12ft lamberts, but I think that the more contrast you have, the less of an issue it is - hence why CRTs with lower lumens than digitals are more than watchable.

    Gary.
     

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