Microscope optical resolution calculator
Explore how objective numerical aperture and detected wavelength affect the smallest detail a microscope can theoretically distinguish.
Generic drawing; the broad band shows magnification and the narrow band shows immersion (grey for dry in this illustration).
Theoretical lateral resolution
0.52 µm
Estimated minimum separation of two point-like details under ideal conditions. A smaller number means finer detail.
d = 0.61 × 0.550 µm ÷ 0.65 NA
40× magnification enlarges the image; it does not change this optical limit by itself.
Choose your setup
The ring colour is a common guide; always read the engraved magnification and NA.
Even illumination around a specimen
340–900 nm
For fluorescence, use the light emitted by the specimen. The LED excites the fluorophore; its excitation wavelength is usually different from the emission wavelength the microscope detects.
*White light is a mixture; the 550 nm setting is a representative calculation. Coloured choices are examples, not specific fluorophore or filter specifications. UV and near-IR estimates need suitable optics and detection.
CoolLED pE-800 example: its illumination covers 365–740 nm; pE-800fura covers 340–635 nm with dedicated 340/380 nm excitation. These are excitation ranges. Enter the fluorophore’s detected emission wavelength above. See CoolLED’s range.
How this compares with a 10× / 0.25 NA example
Bar length represents the minimum separable distance; shorter is finer. Both use your selected wavelength.
About this estimate: Uses the Rayleigh criterion, d = 0.61λ/NA, with wavelength converted from nm to µm. For transmitted light it assumes a condenser NA matched to the objective. Technique changes contrast and visibility, but no universal numerical correction is applied for phase contrast, DIC, darkfield, polarised light, or interference. This tool does not model confocal, super-resolution, or interferometric measurement sensitivity. Actual performance may differ because of the specimen, optical alignment, clean optics, condenser adjustment, illumination, immersion medium, and image sampling. Routine microscope servicing and proper setup can help maintain performance, but cannot improve the fundamental resolution limit of an objective.
Educational guide from Auckland Scientific. Nikon objective colour guide · Resolution reference: Nikon MicroscopyU.
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Interactive tool, software, graphics and original content. All rights reserved.
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Interactive tool, software, graphics and original content. All rights reserved.
Unauthorised copying, reproduction, republication, modification or redistribution is prohibited.