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3:00 · Narrated · Captions included
Watch, then move the focus yourself.
Captions are included in the picture. You can also read the transcript below.
Recorded from the MVLscope exhibit. Ideal lens model and synthetic specimen; schematic distances and illustrative ray motion.
Read the transcript
Follow the Light — narration
What actually changes when you turn a microscope’s focus knob? Let’s follow the light and find out. This is an ideal lens model, with a made-up specimen and enlarged distances so we can see what is happening.
Start with the specimen reference. It contains a ring, bars, and a square frame at three different depths. Choose a point on the ring. The gold marker identifies that same location in the sensor image. Notice where it appears: on the opposite side. The lens forms an inverted image.
Light passes through the specimen, and the lens redirects it towards the sensor. The gold lines show paths from just our chosen location. Every other location contributes too. Together, they form the complete image. Selecting a different point changes what we follow; it does not change focus.
Now choose Find focus, then Set up this discovery. Watch the square frame as I slowly move the focus slider. The specimen moves, while the lens and sensor stay still. When this layer reaches the focus plane, its image becomes clearer.
Look at the ray crossing. At geometric focus, the rays meet at the sensor. Away from focus, they spread across it, producing blur. Diffraction still limits detail, even at focus. Now focus on the ring. The ring sharpens, while the distant frame softens. Those layers have not disappeared.
Open Depth or detail, and set up the comparison. Both pictures now use the same specimen and focus. Only the aperture differs. Numerical aperture, or N A, describes the cone of light collected by the objective. Here, we compare a smaller cone with a larger one.
Look first at the focused ring. The larger aperture separates its two tiny dots more clearly. Now look at the far frame. The smaller aperture preserves its open centre better. But it softens the ring’s fine detail through diffraction. A smaller opening is not automatically better: depth and detail compete.
Try it yourself. Bring the frame into focus. What happens to the ring? Then compare the two aperture pictures again. Remember: select a point to follow its path, move focus to choose a depth, and compare apertures to explore the trade-off. Follow the Light, inside M V L scope.
Ready to try it? Choose a point, move focus and compare the apertures yourself.
Open the interactive exhibit →