I have access to an olympus bx41 microscope. The table on which sits the microscope is in front of a large window and unfortunately no curtains are available. I'm starting to relate that whenever the sunlight is strong, the microscope picture appears dim.

Does sunlight interfere with compound light microscope?


1 Answer 1


I'm not sure that this is exactly biology, more physics, however the answer is sometimes, though this depends on the type of microscope and how the light is impinging on it.

This answer assumes a common upright compound microscope.

The reason I say this is that microscopes used to (and some still do, such as this one. I have no affiliation with the linked site nor is this an endorsement of the site) have mirrors for reflecting the sun so that you could see your sample.

However, what you are seeing is that your samples appear dim when there is bright light in the room. What is actually happening here is that your eyes are compensating for that level of brightness in your peripheral vision, constricting your pupil so that less light enters the eye. This is called the pupillary light reflex and happens every time your eye is subjected to light. Because of the constriction of your pupil, the central (microscope) image appears dimmer.

Having said that, bright light entering the condenser, not from the (diffused) point-source of the bulb can cause loss of image definition because the light source is not linearized and condensed fully by the condenser arrangement. This results in some images being a bit less sharp. Nikon's MicroscopyU has some detail on how this works.

  • $\begingroup$ I actually forgot to say that my eyes + phone pictures both appear dim. If it's the last case then its the condenser that i need to protect for intruding light. $\endgroup$ Jan 15 at 0:45
  • $\begingroup$ Any idea of how could this be possible? $\endgroup$ Jan 15 at 0:51
  • $\begingroup$ @FreezingSoul It would depend on the exactly how the phone is taking the images, but light leakage might pay a role in that. You would need to set the shutter speed and aperture for it to take a consistent photo of set brightness, not rely on automatic mode. It's as simple as creating a shade for the microscope - a piece of card taped to the window would work... $\endgroup$
    – bob1
    Jan 15 at 7:55
  • $\begingroup$ i forgot to mark this is as the accepted answer for which it is an accepted answer. i hope i get an illness for this mistake. $\endgroup$ Jan 20 at 6:43
  • $\begingroup$ @FreezingSoul no need to feel bad - as you might have noticed, most questions with answers don't receive an accepted answer mark. $\endgroup$
    – bob1
    Jan 21 at 20:34

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