In an image loaded into CellProfiler, you can quickly brighten any open image by right-clicking it, then choose ‘Image Contrast’ > ‘Normalize’ or ‘Log Normalize’. Note that this simply changes the values for display. If you really want to brighten the raw data (which we don’t usually suggest), then you can use the RescaleIntensity module. We don’t suggest changing the values except for display, since the thresholding algorithms are usually set to be automatically adjusted, so that even if the images are dim, but still have some contrast, then the segmentation procedure is not usually benefitted by this adjustment. There are lots of caveats to this, but in general, I suggest you just alter the images for display and let the Identify* modules do their work on the raw data.