Nikon MTF interpretation-transferred from CPAnet.cn

MTF Curve

MTF is the abbreviation of Modulation Transfer Function. It comprehensively reflects the contrast and resolution characteristics of the lens. It is currently the most objective and accurate method for lens evaluation. The specific interpretation method is as follows:

1. The higher the MTF Curve, the better the lens optical quality. In terms of contrast and resolution, the larger the area is, the better.

2. The longer the MTF Curve, the better. The more straight the curve, the better the edge and the middle consistency. Serious reduction of edges indicates that the contrast between edges and the resolution is low.

The closer the 3. S (radial) curve is to the M (tangent) curve, the better. The smaller the distance between the two curves reflects the smaller size of the image.

4. The low frequency (10-wire pair/mm) curve represents the contrast characteristics of the lens. The higher the curve, the larger the lens contrast.

5. High-frequency (30-wire/mm) curves represent the resolution characteristics of the lens. The higher the curve, the higher the lens resolution.

 

Comparison of official MTF curves of Nikon 18-70 and Sigma 17-70HSM lenses

101 about MTF:

I have never insisted that movie friends go to the "lens" MTF Curve, because it is easy to "get angry" and regard it as the "final test standard of the camera", ignoring the comprehensive evaluation of the camera. In fact, the MTF Curve can only be used as a reference for the imaging effect of the lens. It does not reflect distortion, glare, color reproduction, level, charm, and other effects. It is the resolution, it only reflects the results of the infinite distance of the lens and does not reflect the imaging effect of the middle distance and close distance. In particular, I don't see a few "Masters" who think they are "advanced". They use the MTF Curve as a weapon to scare beginners and show themselves "brilliant "; -- this is actually nothing remarkable. It can be clearly said, but some people are willing to make the MTF Curve very complicated and do not want to make it clear-so there will be no money for others. So when I introduced the lens, I never mentioned the MTF Curve. I would like to cite the lens score as a reference. As a friend asks today, I 'd like to give a brief introduction as much as possible: 1. Abscissa: from left to right, representing the radius from the center of the imaging plane to the edge. The left side is zero, which is the center of the lens, and the right side is the edge of the image field radius. The size of the image is determined based on the field size. The unit of size is mm; 2. The ordinate of the image: from bottom to top, from zero to 1, with no unit, representing the percentage of imaging quality reaching the physical condition. 1 is 100%. Obviously this is impossible. The curve can only be infinitely close to 1 and never equal to 1; 3. Therefore, the ideal lens imaging curve should be a horizontal line "high above", from the center of the screen to the edge, is 1. But in fact, this can only be a curve that gradually drops from the highest point to the right, indicating that the lens is the best imaging in the center, the poorer the edge. Of course, high-level lenses, imaging curves can be almost horizontal in most positions, and at a certain point on the edge, the sharp drop, the so-called "abrupt stop", this is a good shot.

4. The rest is easy to handle. You only need to remember that the coarse line is "pipe contrast" and the thin line is "pipe resolution "; the black line is "maximum aperture" and the blue line is "f8 aperture". Because the resolution and contrast are different in different directions, the solid line is used to indicate "radius direction ", use a dotted line to indicate the "circumference tangent direction" of the position. The difference between the two is 90 degrees; 5. Now that you know this, you will "graduate. A line. Just check it yourself. You can roughly know the contrast and resolution of the lens under different aperture, different positions, and different directions. You can also make quantitative horizontal comparison between different lenses. 6. Finally, I would like to remind you again that this curve is measured at the longest distance. This is not the case when we approach it, and the recent distance will be much worse. Therefore, it can only be used as a reference and cannot be used as a basis for conclusion. The overall picture quality cannot be explained. It depends on practice.

Another note: for 135 films, the effective imaging diameter is a 3-2 oblique side, about 43.2mm. That is to say, in the MTF Curve, the maximum horizontal coordinate range is 21. 6mm, which is related to imaging. Beyond this range, there is no relationship between curve descent. At the same time, when the lens is used for digital SLR (except for full frames), the imaging radius will be smaller than 135 specifications. You can convert the size by yourself; in addition, we can also see that the actual photo scene of the camera has a large scale, and the larger the side