Force the colors of the projector with Epson Cinema Filter

    In the post “ Epson Home Projectors - Putting All the Dots Over i (Part 2) ”, we outlined the Epson Cinema Filter, an optical filter installed in some Epson home projectors. In this post, we will consider it in more detail, and at the end of the article we will even conduct a small experiment!

    Many people know that projectors allow you to select the image output mode. Epson home projectors have four classic modes: Dynamic , Living Room , Cinema , and Neutral . The first two are designed for illuminated or partially lit rooms, the last two are the least bright and designed for darkened rooms:


    In addition to the fact that excess brightness in a dark room is undesirable in itself, it is in these modes that the best color rendering quality is achieved. What is the difference between the two?

    "Neutrality"


    Epson's traditional approach is that the Neutral mode seeks to provide the most accurate color reproduction. In other words, this mode seeks to match the sRGB color space.which is the main standard for Blu-ray discs, HDTV, web graphics, etc. That is, colors are measurable, and we can say that within the framework of a standard there is only one correct red color, like green, blue, white, etc. It is customary to describe and distinguish all colors, first of all, according to some of their characteristics, which are directly perceived by a person and intuitively clear - by hue (red or green) and by saturation (white - reddish pink - red - very red). There is still brightness (bright red - dark red - I see nothing). In this article we will talk primarily about color saturation. Saturation distinguishes black and white cinema from color. Each color is strictly defined and it is assumed that it will be unchanged all the way from the Hollywood studio to your Blu-ray player or video card, and then to the projector screen. In general, if the author intended to show 100% red, then 100% red should be displayed on the screen, and if 50% red, then 50% red. The more expensive the image output device, the more accurately it must comply with the standard.

    Right?

    "Filmmaking"


    The logic of the “Cinema” mode for  Epson home projectors is also clear: “Let's please the viewer with more saturated colors! Even if the viewer is not happy, he can always return to the “correct” mode. In any case, it’s better to have a choice than not to have one. ”There is a problem: as a rule, the projector is initially limited by the color space for which it was created (sRGB). We can show 60% red instead of 50% red, but more than 100% saturation will not work. About this is done on projectors that are not equipped with Epson Cinema Filter. Of course, in some cases, this approach will allow, after coloring the picture, add sensations.
    Nevertheless, I would like more. Since painting the picture, I would like to get, say, not 100%, but 120% red, green and blue, go beyond the sRGB color space, where the DCI digital cinema space lies .


    In other words, we include regular content created under sRGB, and we get something close to DCI. Is this correct in terms of the sRGB standard? “Not really.” Does it create a “wow effect”? - Of course!

    Epson cinema filter


    It is for this purpose that some Epson home theater projectors, such as, for example, the Epson EH-TW7200 and  Epson EH-TW9200 , use the Epson Cinema Filter. In general, this is a light filter mounted on a special retractable “door”, which allows you to use it, or remove it from the path of light.


    The light route turns out to be very ornate: a lamp, an Epson Cinema Filter, an auto iris to improve the black level in dark scenes, then the light is divided by filters into red / green / blue, then each stream enters a separate LCD matrix (see 3LCD ).


    The conclusion is simple: Epson Cinema Filter changes something in the spectrum of white light before white is divided into three primary colors and before color correction using LCD matrices is applied. Here are pictures taken from one of the foreign sites that tested the Epson EH-TW9200 projector . According to them, the color space in the "Neutral" and "Cinema" modes look like this:


    According to this scheme, in the "Neutral" mode, the projector gives a color space that is most consistent with the sRGB standard. When you use the "Cinema" mode, you get a color space that is pretty close to DCI. The conclusion is this: Epson Cinema Filter is activated in the "Cinema" mode and gives an expanded color space (increases the color saturation), especially between green and red, where we generally get colors on the verge of distinguishability by the human eye.
    It would be necessary to bring some photos to illustrate the effect, but to show colors with more saturation than your display can display (provided that you do not have a display to work in the expanded color space, of course), it will not work. Therefore, let's do this: take a ruler in Photoshop and in the above diagrams we compare the distance from white to the edges of the triangle. It turns out that the red color in the "Neutral" mode is 88% of the red in the "Cinema" mode, green is 71%, blue is 91%, etc. Reducing the saturation of individual colors in Photoshop, we get this result:


    Or you can show the difference "before and after" in this figure:


    The difference should be noticeable to you in all colors except blue and magenta and roughly correspond to the effect that Epson Cinema Filter really gives.

    Experiment


    After removing the optical filter from the projector, the first idea was, of course, to install it on a  budget office projector (Epson EB-W10) and look at the result. Installation is carried out by leaning the filter on the projector lens:


    The projector is used in the "Photo" mode. Measurements showed that the color space of this projector initially does not reach sRGB in all colors. Mostly I'm talking about green and blue colors. Blue is not saturated enough, and green is slightly biased towards yellow. For a budget projector, this is a good result:


    Having activated “Epson Cinema Filter” by leaning against the lens, we get the following picture:


    Red, green and blue colors improve in saturation, the color gamut of the projector is wider than sRGB. A side effect - white is colored in purple, but we can easily adjust it through the projector menu, this also improves the situation with yellow and blue, which are becoming more correct. As a result, all 6 colors with a saturation of 25%, 50%, 75% and 100% + white look like this:


    Based on the fact that the color gamut is equal to the area of ​​the triangle, we can state the following: leaning the Epson Cinema Filter against the lens, you can increase the color gamut by 28%!

    If you are suddenly confused that some colors have turned, then for projectors that Epson Cinema Filter is installed on normally, this is not a problem, because inside the color space displayed by the projector, even the user can turn the colors to the right place, not to mention the engineers who are responsible for initial adjustment of the image.

    Now you need to illustrate the effect of the filter with some screenshots. Unfortunately, it still fails to show the effect of color transformation with maximum saturation. However, nothing prevents showing the effect of the filter on colors with a saturation of less than 100%. Here is a picture with a profile of an unprecedented animal with a rainbow mane:


    Here are the screen shots that we will mirror:


    Of course, there is a difference in brightness, because we lose some of the brightness when using a filter. In this regard, the colors in the right image are darker, but also more saturated. This picture is good because each color is uniform and does not contain transitions - you can evaluate it in Photoshop using a pipette, and here is the result for some colors (before - after):


    The effect is obvious.

    As for the brightness drop, in our experiment it is quite significant (more than 2 times) and is easily explained by the fact that we applied the filter to the exact and dim mode of the image, which has already undergone color correction. Initially, as we said above, Epson Cinema Filter is installed immediately after the lamp and until the moment when color correction occurs. In general, color correction in the Neutral mode is applied to light with other characteristics and is significantly different from color correction in the Cinema mode. One of the independent websites that reviewed the Epson EH-TW9200 shared the following data: the luminous flux in the “Cinema” and “Natural” modes were 871 and 928 Lm, respectively. If this data is correct, then the difference is not so great.

    Conclusion


    Now you know what is behind the term “Epson Cinema Filter”. In the post, we saw for ourselves that this is a completely useful part of the projector, which adds to the lucky owner of top Epson home projectors “mathematically sound fun” - the color becomes almost a third! (Approximately by this figure the color space of the projector expands).

    If you have a favorite movie or animation where there are rich colors, then you can see them in a color space pretty close to DCI, just by running on the appropriate Epson projector. Epson Cinema Filter is one of the functions of top-end projectors, along with “frame interpolation” and sharpening improvement algorithms. These “gadgets” and “enhancements” are aimed not so much at displaying your content exactly in the form in which it was conceived, but at some embellishment of the original. The desire of the user to go for such embellishment may be due to the fact that the era of Blu-ray and HD is nearing completion, but it will be many years before the new color standards firmly enter our lives.

    In the meantime, fortunately, there is an "Epson Cinema Filter", which, you can turn it on, or you can not turn it on =)

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