There are different mechanisms and features in projectors that allow for adjustments when need be; one of these features is the Dynamic iris.
Naturally what would come to mind when you hear the term Dynamic iris is the colored part of the Eye, which is also called the Iris. However, the mechanisms that are used in these two cases are different.
Dynamic iris is used in projectors to adjust the light coming from a projector depending on the brightness of an image. It is used to give bright images enough light that is needed, and also reduces the light for dark images. Simply put, it makes bright images as bright as they can be, and dark images as dark as they can be.
How does Dynamic iris work?
The Dynamic iris works mainly by influencing the light output of a projector, in a bid to improve image contrast. The contrast ratio of an image is the difference between its lowest black and its brightest white. It is often seen in projector descriptions as the ratio of 1 and a very high number.
Two concepts of contrast ratio are the ANSI contrast or the On/Off contrast. The On/Off contrast is the difference in the lowest blacks and brightest whites that an image can show in any two frames, while the ANSI contrast is the difference that an image can show in the same frame.
The object which performs the mechanism of Dynamic iris differs in projectors. Some projectors use a wheel-like instrument with an aperture that rotates to control the light output of the projector. Other projectors use objects like moving blades or leaf shutters. These apparatus increase and decrease the size of the iris, and affect the image’s contrast ratio.
When is Dynamic iris used? Use cases
One major reason why Dynamic iris is used is to improve the contrast of an image. It sometimes adds depth to an image, making the dark areas look darker and the bright areas brighter. This mechanism makes the image look more like 3D than 2D.
In reality, the contrast ratio does not change. The minimum and maximum contrast for the projector remains constant. What happens is that the projector adjusts the light output scene by scene depending on the blacks and whites on the images.
It is an easy way to improve the contrast and brightness of an image. Since not all projectors use the D-ILA technology which has a high contrast on its own, Dynamic iris will be of great help to projectors which do not have such technology.
Blacks and whites are improved, this makes images look better and more defined rather than washed off.
This process is a bit noisy. Although the sound is not extremely loud, it can still be heard. Also, the continuous changing of the image brightness can be annoying.
Dynamic iris adjustment is noticeable. If the iris does not close or open quickly, you may see the whole process as it plays out.
For images that need both the blacks and whites enhanced, there may be a contradiction. If the iris allows more light the white becomes enhanced and the black may get washed away. In the same way, if the iris restricts light, the blacks become enhanced, and the white gets diminished.
The image brightness ends up becoming very unnatural when Dynamic iris is used, compared to the original brightness and contrast. The native contrast is far better compared to the contrast obtained through the use of Dynamic iris.
Comparing Dynamic iris Vs Auto iris
Auto iris is very similar to Dynamic iris; they are often used interchangeably and may be said to mean the same thing. The Auto iris mechanism is motorized, and it can automatically adjust the iris opening according to light change throughout the day.
It is common to projectors and cameras, and like the Dynamic iris, it also affects image brightness. Auto iris is used in an area where the brightness changes from time to time. Its effect is mostly on the brightness level and less on the contrast ratio.
Auto iris differs more in cameras where it is in two types, the DC-irises whose control is in the camera and the video irises whose control is in the lens itself.
Although the mechanism of Dynamic iris varies in different projector brands, and even between models of brands, the same principle is used.
Some projectors like the BenQ models have upgraded to a Dual Dynamic iris. The first one is the major dynamic iris, and the other serves as the step-aperture iris. These two work together to give an impressive image contrast.
Sony projectors also have a good Dynamic iris feature. Unlike most Dynamic iris projectors, the Sony brand has proven to be the best. The contrast adjustment happens without being noticed and without any sound. There are other projectors that will also work well for this purpose.