The lens that your camera is carrying have you ever wondered why it takes such perfect photos for you? How bout the lenses you find in microscopes and much other medical equipment? It may not matter to an average person, but testing these lenses whether they are performing according to how they should be is of great importance since they will be used as a vital part of a particular device. This particular method is called the MTF Testing companies and companies dedicated to testing various lenses are out there offering their service to companies that are into created devices that employ the use of lenses.
Many people think that the concept behind the MTF is very complicated, which is why rarely anyone knows about it. This is a method wherein it measures the lens’s optical performance. To be more specific, the MTF shows the lenses’ ability in resolving detail and then transmit its contrast. This pertains to the light colors remaining light while the dark ones also remain dark. MTF stands for Modulation Transfer Function, with the first word meaning “to change.” If you take a look at the definition of modulating from different dictionaries, you will find its meaning has something to do with change. Others point to regulating or adjusting at a certain proportion or measure. Some put up softening or toning down. If you think about what the lens can do, it cannot “lighten,” “soften” or “adjust” the details that are being transmitted, but its goal is almost impossible to achieve. Because of this, a perfect score in the MTF test has not been achieved, or there are no lenses like that.
MTF sometimes make use of the bar chart as a means of testing the lenses. These are white and black bars that are projected or printed with specific widths. They are also measured in line pairs per millimeter. Such test patterns are then transmitted to the lens, and its output will be measured.
A perfect light transmission results to an image wherein it is purely white or black at the point of its measurement. It would also appear similar to the bar chart as well. The measurements that are taken in the middle of every white and black bar will show in full brightness, wherein the difference of the chart results to a perfect score of 1.0. If you take the perfect bar chart’s horizontal slice and its brightness is graphed in every pixel, the result would have a white rectangle in every black bar in the chart.
The chart’s sharp transitions equate into the same sharp transitions that details in the image has. However, there should be no misconceptions regarding this test – there is no perfection in the optics world.
So what does this mean? The lens gets impaired by some blur, and it will be reduced in contrast. It will be difficult to show you what these blur examples are, but those working with the optics know very well what this means. However, there are sample diagrams made from photo editing software that shows you what it means.