I have a series of images obtained from a microscope as followsI need to create a series of filters that would isolate the centre section    on the yellow droplet.(This is highlighted by the bright yellow circle area), and remove all the noise and other pictures.I tried using just RGB  channel threshold but its not working. Also ambient light may also change so I am not getting a consistent output. Can anyone provide a MWE for the workflow of the filter required in MATLAB to achieve this?
Appropriate filter steps for resolving a droplet pixel
image processing;matlab
First simple thresholding is usually not a good idea. However, if you want to do that, I suggest to also consider other color spaces. In your case, HSV might be a better choice; You can convert your image into HSV-image then you can define a range on Hue channel to select yellow.Also, take a look at this article; it is about implementing Adaptive Thresholding.