Important parameters and their effects
"My picture looks good" many a home cineaste might say. But is it really the same as the director intended the original film to be, and is the projector really using its maximum potential? We have reviewed some key points concerning projector calibration.
1. Contrast
Almost everyone knows that a high contrast ratio is very good for high image quality. The greater the contrast, the more dynamics and spatial depth are possible. Let’s take a look at an example to illustrate this point. The photo has both bright and dark parts. The scenario has a deep spatial effect in the original version:
If the contrast is limited, the picture is dull with little depth. The natural image impression is lost.
The picture above shows an approximate contrast ratio of 100:1. If we increase the contrast ratio, the picture gains in depth, the levels of brightness become more detailed.
Nevertheless, the image impression is not comparable with the original. The differences are noticeably smaller from a contrast ratio of 1000:1.
This example clearly shows how important the contrast ratio of a video image is. There are a lot of digital projectors available with a contrast of between 500:1 and 900:1. More expensive devices have between 1000:1 and 1800:1. Regardless of the price range, projector tuning often makes it possible to significantly increase the effective contrast of projectors, for example, the colour spectrum of the projector can be better utilized by colour filtering. The black level is improved at the same time, which increases the picture depth in dark scenes in particular. A 10% to 30% increase in contrast is not uncommon with projector tuning!
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2. Brightness (gamma) Distribution
As mentioned above, as high a contrast ratio as possible is the basis for a deep space image with attractive dynamics. What is equally important but less known, is a proper distribution of brightness in the image. Only this ensures that the contrast tolerance is evenly distributed across all areas of brightness. An incorrect brightness distribution leads to alienation in the image that is not easily detected without comparisons.
Here is another example:
Our original shows a typical outside shot. There are bright clouds in the sky that appear vivid thanks to fine structures. The forest on the mountain slope is dark but also has deep structures:
The original
The brightness distribution, also called “gamma”, is generally set too high in many projectors to compensate for the poor black level of the device. As a result, the picture loses its spatial depth. Although all details are still visible the result looks washed out and dull.
The forest is “overexposed”
In other cases, the gamma is lined up too low. Details are lost in dark areas of the image here. The maximum brightness is unchanged, but lower brightness areas show too little momentum.
Contours are lost
The unbalanced use of the contrast range is also a common problem in large-screen projection. There is not enough scope in some brightness ranges to guarantee a vivid detail drawing.
Unnatural clouds
In the picture above for example, the gamma distribution for bright image areas is too compressed. The bright clouds lose their plasticity and appear flat in comparison to the original, like white patches in the sky.
Correctly calibrated, we see a uniform brightness distribution. The picture shows sufficient tracing even in very dark scenes, and appears spatially deep. At the same time, there is a clean differentiation of bright shades. There are no jumps in brightness, no image elements look unnaturally over or under emphasized.
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3. Colour Temperature
An often difficult aspect of imaging is the correct setting of the colour temperature. Cheap projectors in particular appear colourful, but they do not reconstruct the colours of the original cinema film accurately. This is evident in most cases by an over or under emphasis of individual colours.
Let us consider our example image once again.
If a projector produces too much red in the picture, the colour temperature of the picture is too warm. This can be easily seen in the clouds. They no longer have the original natural colour, but appear a little too red:
"Pink clouds"
If on the other hand, an image appears to be too cold, there is too much blue. A natural representation of daylight is almost impossible.
Colour display too cool
Colour alienation like this is possible in many forms. Since the user often does not have the opportunity of comparing to the original, these projector deficits remain mostly unnoticed. An accurate colour display is very difficult to achieve with the naked eye. Furthermore, not all projectors have the same settings. With the help of measuring instruments, the characteristics of the projector can be analysed and tuned accordingly, so that an as accurate as possible colour reproduction is achieved.
Colour analysis by measuring
If necessary, colour corrections to the optics e.g. by filters, are made in addition to colour optimisation. The user often only notices where the benefits of a correct colour display are after calibration. The image looks more natural, more believable and gives a real "film feeling".
4. Conclusion
Although, only three of the most important image features were presented here, it is clear how many different settings details need to be consistently adapted to each other to really achieve the optimum image that comes closest to the cinema original. Each image calibration by www.projektor-tuning.de uses the latest software and measuring instruments among other things to increase the contrast of the projector to a maximum, while tuning the brightness distribution at the same time, and optimising colour reproduction. Thus, imaging results can be attained that can hardly be achieved with the “naked eye”, and without the necessary expertise. Many models require real settings "tricks" to really use their full potential.
Virtually every projector offers potential for tuning, no matter what model, what type and what price range!
The result is a new home cinema feeling with the certainty that the film “arrives” on the screen just the way the director intended it.
www.Cine4Home.com
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