Quick guide: choose the right video projector for indoor projection mapping

What’s video mapping?

Imagine making creative, original and never seen lighting that enhances the shapes of objects and environments and makes them appear – literally – in a new light.

That’s right, this is video mapping.

Through constantly evolving technologies, using a projector as an illuminating body, light can adhere to the shapes on which it is directed and ensure that images, videos and projected texts give life to static illuminations or dynamic and animated at the speed that we desire.

Pay attention, though. The current availability of videoprojectors on the market is linked to their most common use. They are designed and developed for the conference rooms, then designed to project onto a flat wall that is perpendicular to the position where the projector will be placed or hung. It is not always easy, therefore, to find the right product for a creative video installation.

In this article I will give you some indications to find the projector suitable for your needs.

First of all, you will need to identify the dimensions and distances of your creative video projection. The first factor to consider is the ratio between the area you need to “dress” with the projection and the position where you will install the projector.

In the world of traditional lighting we consider the distance from the wall used for the lighting fixture and its optical aperture.
In the world of video projection, however, this value is indicated as a projection ratio and is determined by the ratio between the size of the image base and the distance from the projector wall.

A projector always creates a rectangular image, of different proportions depending on the format. The main formats are 16:9 and 4:3.

We will see in the next passage how to determine the distance to which to place the video projector.


Position of the projector

Let’s talk about the distance from the wall to which the projector is to be placed. It is the producer himself who indicates it, using the optical ratio.
I want to explain this by an example: 1.8:1 optical ratio. In this case, the optical ratio is telling us that, if the projection base is – say – 3 meters, the distance to which to place the projector will be calculated as follows: 1.8 x 3 = 5.4. We will then position the projector at 5.4 meters from the wall.
The table below will show you a comparison between the optical openings of the projectors and the opening angle of the light beam.

Once you have established on which surface you have to project, you will have to get an idea of ​​how big your hypothetical projection base is, so you can calculate the distance at which to place the projector.

In the choice of your projector, therefore, you can be conditioned by the position in which to install it, which will lead you to verify that it has a certain opening of the optics.
If, however, you have some flexibility in positioning the projector, you just need to know the dimensions of the base of the surface to be projected.

In the desirable case in which you already know both the dimensions of the base and the position where you will install the projector, before choosing the purchase simply divide the distance between the projector and the wall to measure the base of the projection; you will get the famous optical ratio, indicated by the manufacturer, which will allow you to select the right projector.

Let’s take an example:
5.5 meters away / about 3 meters base = 1.833333 meters.
The optical ratio you need will be 1.8: 1.

Small note: it is always better to round by default than by excess, in making this calculation. When you round by default, in fact, you’re choosing a projector that can open slightly more than you need. I suggest you always have some extra projection area, rather than running the risk of discovering only at the time of installation that the distance does not allow you to have an image large enough for the surface you need to occupy. Trust me, you will thank me.

Go ahead to the next step, we’ll talk about the other decisive factor in the choice…

The proportion

Here we are at another key aspect when choosing the projector. All projectors have a native resolution that needs attention. The native resolution tells you the precise number of points or pixels that the projector matrix is ​​supplied with. In fact, many projectors accept incoming resolutions much higher than those that are actually able to reproduce.

Calculating the size of the points you will have on your projection is very important.

You will have noticed that in low light conditions, with economic video projectors, you can also produce very large images but, if they are to be used at close range, they will most likely be “pixellated” and unclear. The projector works by pixel, moreover, and the size of the points on the projection is something you will inevitably have to deal with to evaluate the resolution of the projector you need.
Fortunately the market situation is rapidly evolving, so have faith, in a few years even 4K projectors will be cheap enough and it will be a whole other story.

How to calculate the pixel size in advance? Again, simple split calculations: take the base size of the projected area, divide it by the number of pixels in the image to be projected, and you will have discovered how many millimeters each projected pixel will measure.

Let us repeat:
Base of the projected area / number of pixels = measurement of the single projected pixel.

You have thus determined the definition of the image.
Let’s go back to the example of the previous post, your installation with a projection base of 3 meters, and imagine having a Full HD projector (1920×1080) available.
The size of each of your projected pixels will be (convert everything in millimeters):
3000/1920 = 1.56 mm.
This is a very reasonable size for an internal installation.
WARNING: exceeding 3 mm could generate a really unpleasant visual result!

Well, you learned how to choose based on the resolution.
In the next step, we will talk about the brightness!

Projection Mapping
Choose the right video projector for your indoor projection mapping

The brightness

Another of the decisive criteria for choosing the most suitable projector, and a factor, moreover, influenced by many variables.
The light output of a micro-mapping installation will depend, among other things, on:

  • type of material you will project on
  • environmental conditions
  • the color of the object you want to enhance

You do not need to tell you that projecting on white or light colors will allow a better rendering of graphic and text content. On the other hand, if the purpose of your projection is limited, for example, to complete a traditional lighting with slow moving light, you will not have to worry about the color of the object to “dress”.

Projecting on a flat surface (mostly) or projecting on three-dimensional objects involves a very different level of difficulty.

If the surface you have is basically flat, but has some lines or shapes that the eye can follow and your image can take advantage of, it gives you the perfect opportunity to intimately interact the light with the object, creating effects of augmented reality.

The three-dimensional objects, on the other hand, have edges, and here is a first difficulty. Covering a three-dimensional object with a projection will inevitably cause the light to flood a surface greater than that of the object itself. In this case, in this case, smudges will be created.

Manage smudges you can, and in several ways:

  • Use dark surfaces as a background, because they absorb light and, therefore, smudges;
  • move the object away from the background, because the light that is wearing it does not reach the background too much;
  • playing with the angle of incidence of the projector, so that the background is compromised as little as possible;
  • compensating with light that illuminates the background, making the projection smudge vanish.

Regarding the projections on three-dimensional objects, it is always necessary to consider the projection point of view, but it is a subject that deserves a separate article.

In the last step on micro-mapping, we will talk about the different projectors on the market.


The market

You must know that the projector market is divided into two macro-categories:

  • fixed-optical projectors;
  • projectors with interchangeable optics.

The common projectors from home or office, ranging from 50 to 4,000 ansi lumens, are projectors with fixed optics and will cost from 100 to a maximum maximum of 2,000 euros.
If we climb above 4,000 ansi lumens, we find the projectors with interchangeable optics. These are devices that, thanks to a bayonet mechanism, allow the optical body to be replaced. These types of projectors have prices ranging from 5,000 euros upwards.

But, fortunately there is a “but”. Between these two macro-categories, there is a range of (rare) 6,000 / 7,000 ansi lumen projectors with fixed lens.

These machines are very powerful and being able to use them will allow you to significantly reduce costs. Not bad, eh?

I want to leave you with one last piece of advice: when, in a project, you use more than one projector, we are talking about multiprojection.
In a multi-projection it is necessary to use media servers, hardware able to keep the images to be synchronized to the different projectors.
This solution, in the case of micro-mapping that we discussed in these posts, is anti-economic: the cost of media servers, in fact, exceeds the cost of the projectors, especially if you choose to use low-end projectors and fixed optics. Consider that the cost of a plant managed by a media server comes very easily to cost 3,000 euros for each projector.

And this closes our How To on micro-mapping.
I hope the article was useful to you! If so, share it with your colleagues and if you want to make a comment or ask me for a consultation do not hesitate to contact me!

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