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Over the Edge: An overview of Soft-Edge Blending Technology

Visual media is everywhere. In our every day lives, we are surrounded by motion graphics, movies and video clips, and we access them through different kinds of displays such as television, smart phones, digital signage devices, and so on. Video has proven to be one of the most efficient ways to convey a message to an audience.

The demand for visual media is of course increasing in Houses of Worship. Undeniably churches are using more and more visual media to capture worshipers’ attention and help to convey the pastor’s message. Screens are getting larger and projections on multiple surfaces are becoming more common. There is a captivating effect created by having multiple displays that can be separated and then merged together to form one connected image. There is a practical amount of science that goes on behind the scenes to make this effect possible.

You may have already heard the term “Soft Edge Blending” before. Soft Edge Blending is essentially a term used for creating a large screen image using multiple video projectors with seamless overlapping areas. Creating a seamless image across a wide surface can be a key element in Houses of Worship who wish to display different elements on multiple screens, with the flexibility of merging all the images into one large, panoramic display.
Soft Edge Blending used to be a technology affordable only by mega churches with experienced technicians. This is not the case anymore. New solutions have been developed that can be used by all types of churches, regardless of their budget or the technical skills of their volunteers.

This article aims to clarify some of the key components you should consider if you are interested in incorporating Soft Edge Blending into your worship services.

Knowing Your Video Projectors
To make an image as seamless as possible, the first element you need to consider is the configuration of your projection. You will also have to know which video projectors you plan to use.

First of all, to ensure optimum results, it is recommended that front projection be used rather than rear projection for Soft Edge Blending. You can still achieve excellent results with rear projection, as long as you account for the proper space behind your screen, and as long as you do not use projectors with short-throw lenses. Short-throw lenses can cause hot spots in a rear projection installation. Another point of note: you should use digital connections between projectors and Mixers/Seamless Switchers as opposed to analog connections, wherever possible.

The quality of your projectors will have a direct impact on the end result of the Soft Edge. Among the main criteria to consider here is that all the video projectors you use must be identical in terms of color setting (lamp life-time), black adjustment, resolution, etc. Horizontal and vertical lens shift is required, since lenses with this functionality provide a far more precise result for adjustments.

Once you have chosen the right video projectors, you need to follow a few guidelines in order to position them properly. The video projectors must be physically aligned to provide an image on the screen within one pixel precision, with no distortion. They need to be perfectly horizontal and perpendicular to the screen in both the horizontal and the vertical axes. This alignment must also include an overlap between the projectors of from 10 to 25 percent of the total screen width. To help you properly align the projectors together, you can use the “Grid” test pattern that is available in the menu of many video projectors.

Any image shape distortion is due to misalignment, screen position or shape (not exactly vertical) or optical distortion (maximum lens shift).
Warning: You must not use the projector’s Keystone function to correct image parallelism problems. Using Keystone correction will make it impossible to properly adjust the Soft Edge Curve. In other words, by using the Keystone on the projectors, it will be impossible to have a clean Soft Edge projection.

Making Adjustments
Now that your video projectors are perfectly positioned, you can begin to adjust the settings that will create your seamless blend.

The principle of Soft Edge Blending lies in projecting an image on a wide screen thanks to two or more video projectors displaying the same content. Overlapping or covering areas are created on the screen where two adjacent projectors meet.

Basically, each overlap zone receives the light of two video projectors and receives the content projected twice. The art of Soft Edge Blending is to harmonize, or blend the overlapping area with the rest of the image.
You can use different test patterns provided by your mixer/seamless Switcher to make all the necessary adjustments outside and inside the overlapping area. These adjustments must be done on a blank projection screen (no sources) and will be easier to perform in the darkest environment possible.

The light coming from the adjacent video projectors is combined in the overlapping area, which results in a brighter space. To deal with Black level, the solution consists of raising the luminance in the left and right areas of the projection, outside the overlapping zone, to match the luminance of the overlapping area.

Finally, since the overlapping zone receives the same image from the video projectors twice, adjustments have to be done inside the overlapping area.
Making a perfect blend entails gradually decreasing the light provided by the video projector on the left side of the overlapping zone, while gradually increasing the light provided by the video projector on the right side, at the same time.

With the help of these different adjustments, the overlapping areas are less visible, and you are ready to achieve a projection this is as seamless as possible.

Content for projection
To develop an effective presentation, you are encouraged to use various types of sources: computer, camera, VCR, DVD, Blu-Ray… Many options are possible and they will help you create an attractive presentation that compellingly conveys your message.

Here are a few tips to obtain the best possible results.

To ensure a successful Edge Blend it is fundamentally important that the image used as the background be at the same resolution and aspect ratio as the blended projection. In other words, the image needs to fit with the size of your screen.

If your image is too large, part of it will not appear on the screen. If too small, the image will not cover the entire surface of the screen, which will not produce a satisfying result.

To help you calculate the correct screen/picture ratio, some companies offer free software to facilitate the calculation of key parameters. In some cases, by entering basic information, such as your projector matrix size and your image size, you can automatically obtain all the essential variables (Projector image size, distance between projectors, etc.) to make your Soft Edge. It is also recommended to use a Hi-Res DVI computer source for this background.

As for the other elements you will display, you should avoid using grey and white images. The Soft Edge Blended presentation will be much more impressive with contrasted images and saturated colors. Now that you know some of the basics of Soft Edge Blending technology, you can start to envision how this can be an effective tool in your video arsenal. Soft Edge Blending presentations will offer you the opportunity to change the overall look of a space in a few minutes. With the flexibility of displaying multiple sources of video, with the option of merging the image into one, the impact of your services and presentations is increased exponentially. With such visual media, you can offer your congregation a truly affective worship experience that will show the unique character of your church.

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