Wednesday, March 05, 2008

Zooming Verses Using An Anamorphic Lens

The subject of using an anamorphic lens in HT is often a hot topic of Home Theatre forums. Naturally I am pro lens, but there are those that believe the zoom method is better.

There are Pros and Cons for both but in the end I still prefer the lens for not only it's ease of use, but more importantly, the fact that I don't waste any vertical resolution when displaying Scope films. The following is a very quick and non scientific example of both full panel using a lens verse simply zooming the image to fill the screen.

Full Image Using Lens

Cropped Image LENS

The images above use the full panel of the projector and an anamorphic lens to allow a Scope image to be projected full screen without wasting precious vertical pixels. Whilst higher quality lenses would produce an even better image, generally you can not see pixel structure as the full panel is being used.

Cropped Image ZOOM
In this photo, the lens is removed, the projector set to 16:9 and the projected image is simply zoomed to fill the screen. This means that not only has vertical resolution being wasted on the blacks bars to preserve the film's aspect ratio, but those bars have now been projected off the top and bottom of the screen. The result is enlarged pixels both horizontally as well as vertically as only 75% of the panel is now used to make the same size image!

Disclaimer: The images are just a guide and in now way should be used to determine actual image quality from your video projector. The camera used to take these images was mounted on a tri-pod, white balanced for each shot, and exposure time set to 1.3.

The Anamorphic Lens used does not have focal elements, so the zoomed image may appear sharper at the edges. Because the projector was moved back to allow the zoomed shots, the throw ratio was changed causing a slight geometry shift, and this may be seen when opening each photo in a different window. This is also due to the fact the the screen is curved for the lens, so projecting a zoomed image actually creates a"barrel" effect.


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