While acquiring images or subsequent to acquisition, the background correction be able to be applied. The difference between these is that a priori correction uses additional correction images obtained at the time of image capture at the same time as in a posteriori correction the correction images are not available and therefore an ideal illumination model is assumed. The a priori methods are therefore the preferred option. In digitizing images, the camera noise, background illumination intensity and colour temperature are the sources of image degradation to consider. The camera noise include random noise that is due to uncorrelated fluctuations above and below; fixed pattern noise that us characterized by pixel intensities that are consistently above random noise fluctuations and it is due to faulty CCD or pixel differences in charge leakage rate; and banding noise that may arise during the process of reading the data from the digital sensor or by interference with other electronic equipment.

The background illumination intensity provided by the microscope light source optics is commonly not homogeneous throughout the view field. The colour temperature of the light source also affects image quality. Light sources have a characteristic radiation spectrum. With most filament light bulbs this spectrum varies depends the temperature of the filament. Therefore, images taken at different times may exhibit backgrounds with slightly different hues. This makes difficult to standardise procedures such as colour segmentation, colour separation, hue quantification, etc. Some brightfield light microscopes have a button which sets a fixed voltage to the bulb to deliver fixed colour temperatures. If this is used, then the intensity of the light can controlled with neutral density filters in the light path. The camera and brightfield light microscope settings includes make sure has an infrared filter; switch on all your equipment and leave it warm up for some time (the warming time depends on room temperature, how sensitive the equipment is to temperature and how long it takes to stabilize.

You can find out this by taking a time series of background shots over a period of time and see whether the light distribution drifts over time. You are likely to observe a plateau where the results become more stable. You may want to do image capture during the plateau period.); switch off the camera auto gain; put the specimen on the stage, focus the objects, adjust the light/neutral density filters and condenser, set an appropriate camera exposure time; if the camera has a white balance function, you can apply it now on the illuminated bright field: take out the specimen and apply the white balance; reposition the specimen and check again that the image histogram is not saturated and that the grey scale values span most of the grey scale space; and from now on, the settings of the camera and the brightfield light microscope should not be adjusted anymore. Capturing the bright field, open the light path, remove the specimen, and capture shot and saving it as bright field (to compensate the background illumination) is done when you capture the bright field. Brightfield light microscopes, often referred to as metallurgical microscopes, are used to examine opaque specimens which will not transmit light.  Reflected Light is also called Incident Light or Episcopic Illumination.

The illumination is reflected off of a beam splitter - a half mirror where half the light is reflected and half passes through.  The reflected light travels through the objective lens, which in this arrangement acts as both a condenser and an objective, and strikes the specimen.  It is then reflected off the specimen back up through the objective lens, the half mirror, the head, the eyepieces, and finally to the eye.  The way in which the specimen scatters light will determine how well it can be imaged in this way.  Natural color is usually obscured.  Highly reflective specimens such as polished metals, ceramics, and microchips are well suited for Brightfield Light Microscope.  Objectives on a reflected light microscope are usually corrected for use with specimens without a cover-slip.  For some specimens a combination of transmitted and reflected light is ideal.  Inverted brightfield light microscopes have the advantage of accepting larger specimens, and these specimens have to be flat on only one side.