I wanted to add a section to explain some of the mystery surrounding anamorphic lenses and other methods of dealing with various wider aspect ratios. This was partly inspired by recent PMs and questions regarding the Panasonic AE3000/4000 which has a lens memory feature (so I can link to this post to save me retyping continuously
) and also to try to explain the types of lenses and resources for finding information and suppliers.
As per my previous post, I hope it is OK for me to add this to the FAQs, I'm sure if a mod feels it isn't relevant then I won't be too offended if it gets removed.
Anamorphic lenses:
There are basically two types of lenses; Vertical Compression and Horizontal Expansion, from now on referred to as VC or HE. Both lenses require the use of some kind of Image Processing provided by a
scaler (it may be in the PJ, BluRay/DVD player or an external video processor) to vertically 'stretch' the image so that the black bars are no longer on the 16:9 panel of the PJ and the image then looks 'tall and thin'. This is effectively like upscaling the image from approx 1920 x 810 (ignoring the black bars) to 1920 x 1080, so the better the scaler, then the less chance of artifacts.
The choice of one of two types of lens is required to correct the proportions of the now stretched image. The point of either method is that the whole of the projector's 16:9 panel is used to create the image, rather than the top and bottom being 'wasted' projecting black bars on aspect ratios wider than 1.78:1 (16:9). Both types of lens will give a brighter 2.35:1 image than when zooming (see below) as the pixel density is greater and it is using the whole panel of the PJ.
VC Lenses:
VC lenses tend to be used with a
Constant
Image
Width (CIW) screen setup (where the 'black bars' are projected onto a 16:9 screen which may or may not have masks that cover the bars when watching a wider AR film such as 2.35:1). They work by squashing the image back down to correct the image distortion created above by the PJ/Player/VP. The wider AR image will remain the same width but will have less height than the 'native' 16:9 image, requiring top and bottom masking to get the best out of the image.
Watching 16:9 content requires the VC lens to be moved out of the way and the IP setting changed to 16:9 (exact naming may differ between PJs and VPs). The resulting 16:9 image will then fill the 16:9 screen exactly (after any masking has been removed of course).
VC lenses seem to be less common, but they still available (see links added lower down this post). This type of lens can cause an image distortion known as ‘barrel distortion’ where the image is bigger in the centre of the screen. Good edge masking can help to hide this slight overspill.
HE Lenses:
HE lenses tend to be used with a
Constant
Image
Height (CIH) screen setup. The HE lens stretches the tall and thin image created by the image processing to make a picture 33% wider, but the same height and in the correct proportions. This will require the use of a 2.35:1 screen to get the best out of the setup and in this mode will fill the screen exactly. This type of lens can cause an image distortion known as ‘pin cushion’ distortion where the middle of the image is les high than the sides, so can be used with a curved screen and /or good edge masking to absorb slight overspill.
Watching 16:9 content with a HE lens can be done two ways: Either slide the lens out of the way (motorised or manual) and change the IP setting to 16:9 for 'pure' viewing with the least processing and no lens distortions.
Alternatively, the lens can be left in place and the IP's 4:3 mode used (again names may vary between PJs and VPs) for an instant AR change. This method squashes the 16:9 image so that it is not using the whole panel width, which distorts the image, which in turn is corrected by the lens. This means that some horizontal resolution is lost in this mode, but many users say that losing horizontal resolution is less significant and has the convenience of leaving the lens in place for all viewing. Viewing 16:9 on a 2.35:1 screen will require side masking as it will not fill the whole width of the screen.
HE lenses are easier to find, with variations on how they achieve the HE end result, such as using prisms or cylinder lenses.
For both types of lens:
Pros: Uses full panel 2.35:1 content, brighter image, increased pixel density allowing closer viewing distances.
Cons: Cost of a good enough lens for full HD PJ, throw distance issues can result in excessive barrel/pincushion distortion, slight loss of ANSI contrast due to reflections from the glass back into the PJ. May require an external VP at additional cost.
I should add for completeness that there is a third screen arrangement called
Constant
Image
Area (CIA). This is an arrangement that may (but not exclusively) be based on a screen of around 2.05:1. It would use 4 way masking: For 2.35:1 (and higher ARs such as 2.55:1) content use the top and bottom masking, for 16:9 content the side masks come into play. The two main ARs would effectively have the same area, which means that the images would have similar impact: With CIH setups the complaint is that 16:9 can appear too small and for CIW that 2.35:1 content is smaller than 16:9. CIA can be achieved by a combination of zooming, using a scaler and/or a lens.
Non lens alternatives:
16:9 screen setup 'Standard':
The simplest method for watching different AR content is to have a 16:9 screen, with the projector adjusted to fill the screen for 16:9 content. Wider AR content will add top and bottom black bars, which will still be 'projected' by the projector: Depending on the black level of the projector in question they may be quite visible especially against a white screen. Reflections from light coloured walls/ceiling in the viewing room will also tend to raise the black level of these bars. This setup is exactly the way that widescreen TVs work, so it is a more familiar situation for many new PJ owners. Adding top and bottom masking will help frame the image for wider AR content and many commercial and DIY methods exist.
Pros: Simple, cheap and no scaling of image.
Cons: Requires top and bottom masking to remove black bars.
CIH using the ‘Zoom method’:
The requires a 2.35:1 screen and the projector needs to be arranged such that for 2.35:1 content there is enough zoom range on the projector to zoom the top and bottom black bars off the top and bottom of the screen. A projector with good ‘fill ratio’ for the pixels helps as you will be effectively increasing the size of the pixels by 33%. This requires dark walls behind the screen or material/masking to soak up the black bars which as still projected by the projector so need good black level performance to help ‘hide’ the off screen bars for best effect. I personally have a dark brown screen wall and found that with my original AE1000 the bars still showed against the wall. Subsequent upgrades to AE2000, AE3000 and HD350 have made the bars progressively less visible (virtually not noticeable since the AE3000 upgrade).
For watching 16:9 content the projector is zoomed back to fit the ‘taller’ image on the 2.35:1 screen: Note this leaves side bars on a 2.35:1 screen, but these are unlit by the projector (unlike the top and bottom bars of 2.35:1 content) so they tend to be very dark, provided the room décor is also dark enough to quell reflections. Side masking can still be worthwhile with this arrangement however.
To be able to use this method, the projector needs to have a zoom range of greater than 1 to 1.33 and ideally more than this to allow flexibility in positioning. It helps if the projector has a remote controlled zoom, focus and shift as the image will often tend to move up or down as the zoom is adjusted.
The Panasonic AE3000 and recently announced AE4000 allow the zoom, shift and focus settings required for ‘zooming’, other projectors may be announced later that also allow this feature, so I’ll add them at the bottom of this post. It is important to note that neither of these projectors do anything more than zoom, shift and focus: The black bars are still present and the full panel is not used for wider ARs than 16:9 so the increased pixel density of using a VC or HE lens does not apply. A 2.35:1 screen is also required to use this feature (exactly the same as the above details for manual/remote ‘zoom method’.
Pros: Cheap, no extra glass to distort the image, no scaling required so image is 1:1 pixel mapped. Lens memory convienience.
Cons: Pixel density reduced, not using the full panel for 2.35:1 content so may be less bright than using a lens, more adjustments required (especially with manual zoom PJs).
Video processor ‘Shrink method’:
This is my current setup and a relatively unknown method: It generally requires a separate video processor with the ability to shrink the image within a window. A worthwhile option for users that tend to watch mostly 2.35:1 content: I find a high percentage of BluRays I watch tend to be this format, though older film, TV production and sports viewers may not find this to be the case. However, this method reduces the resolution of the image, so is not really recommended for watching an entire BluRay, but it is perfect for a quick one button press to fit 16:9 menus/trailers on to a 2.35:1 screen without having to adjust the zoom, shift and focus. In practice watching a DVD using this method means that the 720 x 576 image is upscaled less than for full HD, which doesn’t seem to hurt the image quality (provided the viewing distance is far enough back not to allow the pixels to be visible, such as greater than 0.7 x screen width in the case of my HD350). Effectively, watching 2.35:1 content is the same as the zoom method and most of the time I leave the PJ adjusted and zoomed for 2.35:1 content, with the VP set to 1:1 pixel mapped mode.
When watching 16:9 it is a 16:9 ‘window’ within the 2.35:1 section of the screen: If this image was sent to a widescreen TV, you would see black bars on all four sides; I’ll try to post some pictures later to explain more clearly: The 16:9 resolution for this method is roughly 1440 x 810 when using a full HD projector, which is plenty to view the menus and trailers even on BluRay (some users even watch entire BluRay films in this setting, but I prefer to rezoom for these relatively rare occasions for best quality). On Lumagen HDP/HDQ (and presumably the Radiance models) this feature is in a sub menu called ‘Shrink’ and can be assigned to the ’16:9’ button on the remote. On some projectors (including the AE3000) selecting the ‘S16:9’ mode has the same effect, I’m not aware of other projectors that have this option, but I’ll add any that I find out about.
Pros: Convenient one button 'instant' AR change, no lens to effect the image in 2.35:1 mode.
Cons: Lowers resolution for 16:9 content, cost of external VP if not available in PJ. Pixel density reduced, not using the full panel for 2.35:1 content so may be less bright than using a lens.
Some useful links:
AVSForum 2.35:1 sub forum
AVSForum 2.35:1 FAQ thread for much more in depth reading than my post.
Lens suppliers:
http://www.panamorph.com
http://www.prismasonic.com
http://www.schneideroptics.com
CAVX Aussiemorph Mk3 AVForums powerbuy
ISCO home cinema
I'll return to this thread to edit and add further details and links.
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