The difference between achromatic, semi-apochromatic and apochromatic

Achromatic or flat field achromatic objectives can at least correct the position color difference (red and blue), spherical difference (yellow and green light), sinusoidal difference and eliminate paraxial point comet. However, Less than optimal image effect can be obtained in green and white light microphotography.

Semi-apochromatic or flat field semi-apochromatic objective can correct the spherical and chromatic aberration of red and blue light, and it is far better than the achromatic objective in terms of imaging quality, and the selection of semi-apochromatic objective in color microphotography is the Best choice in terms of imaging quality and economy.

Apochromatic or flat field apochromatic objective lens can not only correct the color difference of red, green and blue light, but also create images on the same focal plane to eliminate the effect of "residual color difference "(also known as secondary chromatography), and can correct the spherical difference of red and blue light. It has a larger numerical aperture, higher resolution, better image quality, and higher effective magnification. The apochromatic objective has high performance and is suitable for research microscopy and photomicrography. Its depth of field is smaller than other objectives, so it is more expensive than other objectives.