Buying a microscope can be confusing when looking at the microscope objective types. You will notice terms like Achromatic, Sem-Plan, Plan, Super High Contrast, PlanApo, Apochromatic, etc. But what do these terms mean?
These terms help identify the quality of the microscope objective lenses, if of course you are comparing a trusted name brand to another trusted name brand. There is no governing body that tests a manufactures claim of objective quality, many Chinese manufacturers label their objective a certain quality when in fact it does not meet the expectations. The degree of color correction, curvature of field, and aberration correction an objective has determines its quality.
Achromatic Objective Lenses- Achromatic objectives are are standard objectives found on microscopes entry level educational microscopes. Achromatic lenses have a 60-70% flat field which means the outer 40-30% of your field of view will be out of focus.
Semi-Plan Objective Lenses- Semi-Plan microscope objective lenses provide an 80% flat field of view.
Plan Achromat Objective Lenses- Plan Achromat objectives provide just about 100% flat field of view.
Now that you have a basic understanding of the three most common types of microscope objectives, you still may be confused as so manufactures have their own terms for these "grades" for example Leica uses the term "Hi Plan" instead of Semi-Plan.