What is resolution
Resolution is a term that is talked about a lot in imaging, but its meaning can vary depending on the context. This article seeks to clarify the meaning of resolution in the context of microscopy, specifically for image analysis.
See also
Introduction
The Wiktionary lists 14 separate definitions for "resolution". In microscopy resolution is mostly related to the ability of the optical system to separate fine features clearly. In photography, resolution is used to measure the number of pixels in a camera sensor. In Imaging, resolution is something in between. It is formally defined as "the ability to separate the constituent parts of a whole".
In imaging, resolution is mostly defined by the following 4 factors:
- Optical resolution - how finely the optics separate points of light from their neighbors
- Sampling resolution - how finely the pixels on the camera sensor are separated
- Signal-to-noise ratio - how much light are we collecting compared to the noise generated by the system
- The bit depth of the imaging sensor - the degrees of separation between the minimum and maximum value recorded by the imaging device
Conclusions
We discussed a lot of factors that affect what image analysts call resolution, but in the end, the consideration of what is useful resolution is fairly simple. We just need to ask ourselves the question:
When looking at the image at the pixel level, can I reliably identify the links connecting objects or the gaps separating them?
If we can answer that question in the positive then we can say that we have enough resolution in the image. If not, then considering the factors above should help in formulating a strategy to try and improve the resolution of our images. Of course, in the end, some compromises will most likely be required, but we should then be in a better position to judge the limitations of the analysis capabilities.