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| =Optical Low-pass Filter (OLPF)=
| | Moved to https://wiki.apertus.org/index.php/Research_Pending/OLPF |
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| An [https://en.wikipedia.org/wiki/Anti-aliasing_filter#Optical_applications optical low-pass filter] is used to reduce/eliminate moire and aliasing artifacts which would otherwise be visible when filming some types of subject matter (detailed repeating patterns like meshes, grills, brick walls). Although post-production workarounds exist, they aren't usually as effective and remnants of moire will often remain.
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| [[File:Moire_fence_example.jpg | 400px]]
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| For a filter to be effective and also not excessively blur the image, it needs to be designed for a specific sensor pixel size. The Cmosis CMV12000 and CMV2000 have the same pixel size (5.5µm), but the Kodak On-Semi KAC12040 is 4.7µm. A different filter might be needed for the latter.
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| Filters of different thickness and refractive indexes placed between the back of the lens and sensor will shift the back focus to some degree. Any combination of OLPF and IR/UV filters needs to be carefully designed to avoid this. A buyer might request a camera without an OLPF, but still with an IR/UV filter. How can this be accommodated? Some filter manufacturers sell combined OLPF/UV glass of varying thickness which might be a solution.
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| Design considerations:
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| * IR/UV filters might also introduce a color bias which would need to be corrected as part of the camera calibration process
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| * Should the filter be removable by the end-user?
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| * Should it be hot-swappable on location (no special tools required)?
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| * Should it be fitted 'as standard' or as an optional extra?
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| Typical cost for a Super35/APS-C sized filter seems to be around $200/€187 - Red sell one for their cameras at this price.
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| A [https://twitter.com/apertususer/status/848584997388812289 Twitter poll] was run to get user feedback. Question; "How important is an Optical Low-Pass Filter (OLPF/AA-filter) for you?". Results on 2017-04-06;
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| * 42% 'not important'
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| * 32% 'quite important'
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| * 26% 'essential'
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| So a combined 58% of users opted for either quite important or essential.
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| List of possible manufacturers: <br>
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| http://www.optics-online.com/lpf.asp <br>
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| http://www.made-in-china.com/manufacturers/olpf.html <br>
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| http://www.made-in-china.com/showroom/eddiet1716/product-detaileqjxuOYMYJfA/China-Optical-Low-Pass-Filter-OLPF-.html <br>
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| http://www.made-in-china.com/showroom/refet88/product-detailRMtJbgsUhDky/China-OLPF-Crystal-Filter.html <br>
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| http://www.made-in-china.com/showroom/jiujonshane/product-detailBMKmSRtdEbcU/China-Olpf-Optical-Low-Pass-Filter-.html <br>
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| Research is being conducted in the Labs here - https://lab.apertus.org/T127
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