Both bright field and dark field microscopes are optical microscopes that employ light to view a sample and magnify it, but the similarities end there. The working principle of both the microscopes is entirely different.
Optical microscopes employ visible light and a series of lenses to magnify the specimen and view it in detail. A bright-field microscope uses light rays to create a dark image against a bright background.
While on the other hand, a dark field microscope operates on the opposite principle of a bright field microscope, and the entire field of view appears dark when there is no specimen and once a specimen is placed, it appears bright over this dark background.
Bright Field Microscope Vs Dark Field Microscope
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| Parameter | Bright Field | Dark Field |
| Image Formation | Works on the principle of absorption of light. Light is focused on the specimen and it absorbs the light and the contrast image that is dark is viewed against a bright background | The entire field of view appears dark when there is no specimen and once a specimen is placed, it appears bright over this dark background |
| Type of Image | Dark image against a bright background | Bright image against a dark background |
| Types of specimens | Fixed specimens are viewed and are typically stained | All live specimens can be viewed even without staining them |
| Specimen Preparation | Is complex as the specimen needs to be stained | No need of a stain |
| Color of specimen | Appears blur or dark (depending on the stain used) | Specimen appears bright |
| Background of specimen | Background is bright | Background is dark |
| Types of condensers used | Abbe Condenser, Variable focus Condenser, Achromatic condenser. | Abbe Condenser, Paraboloid condenser, Cardioid Condenser. |
| Extent of viewing | It shows the internal as well as the morphological structure of the specimen | It shows the external structure of the specimen |
| Cost | They are inexpensive | They are comparatively expensive |
| Opaque Disc | Not present | Present |
| Utility | It is very easy to use | It is comparatively complex to use |
| Ability to study Minerals and Metals | This microscope can’t be used for the study of minerals and metals | This microscope can be used to study minerals and metals |
References
- http://www.differencebetween.net/science/differences-between-bright-and-dark-field-microscopes/
- https://www.microbehunter.com/what-are-the-differences-between-brightfield-darkfield-and-phase-contrast/
- https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-19/issue-10/106002/Real-time-brightfield-darkfield-and-phase-contrast-imaging-in-a/10.1117/1.JBO.19.10.106002.full?SSO=1
- https://public.wsu.edu/~omoto/papers/Fig1.html
- https://everythingwhat.com/what-is-the-difference-between-bright-field-and-dark-field-microscope