So now that we've introduced bright field microscopes in this video we're going to talk about light microscopes that increase contrast and so recall from our previous lesson videos that one of the drawbacks of bright field light microscopy is visualizing unstained transparent organisms and that's due to really really poor contrast that's associated with that. Now sometimes staining cells with dyes can help to increase contrast and in those cases the bright field light microscope can be used. However sometimes these staining dyes can also kill cells or distort the features of those cells and that may be something that the scientist is not interested in doing. And so in those cases bright field light microscopy is not going to be the best solution. But thankfully there are other special types of light microscopes that can help to improve contrast when visualizing unstained cells. And so some of these microscopes include dark field microscopes instead of break field microscopes, phase contrast microscopes and D. I. C. Microscopes or differential interference contrast microscopes. And so as we move forward in our course we're going to talk a little bit about each of these three different types of light microscopes that increase contrast and so notice down below we have our map of the lesson or our outline of the lesson on light microscopy. And as we mentioned we're going to be following this map by following the left most branches first. And so we've already talked about the bright field microscopes and our previous lesson videos. So that part is done with. Now we are moving on to the light microscopes that increase contrast which once again includes dark field microscopes, phase contrast microscopes and differential interference contrast microscopes or D. I. C. Microscopes. And so that's what we're going to be focusing on as we move forward. And then later after we finish those we'll move on to the light microscopes that detect fluorescence which are the ones that are over here. But for now, this year concludes our brief introduction to light microscopes that increase contrast. And once again we'll talk about the dark field microscope first and then we'll move on to the phase contrast and D. I. C. Microscopes. So I'll see you all in our next video.

in this video, we're going to talk briefly about dark field microscopy. And so dark field microscopy is basically the opposite of bright field microscopy because instead of observing a dark specimen against a light or bright background, dark field microscopy observes a bright specimen against a dark background. And so the dark field is referring to the dark background that's present. Now. Dark field microscopy microscopes use a special mechanism that will direct the light at a at a certain angle so that only light scattered by the specimen is observed. And so notice down below, we're showing you some images of dark field microscopy where again, the field is referring to the background and so notice that all of these images shows organisms that are brighter against a dark background. And that's really the main idea here with the dark field microscopy is the dark background. And so here we're showing you valve box arias algae against a dark background than we have assorted dia tom algae against the dark background. Shigella dysentery. a bacteria against the dark background and micro story um Canis fungus against a dark background. And so dark field microscopy really can help to improve the contrast and so notice that the contrast in all of these images is really, really good. And so it's very easy to distinguish the specimen from its background. And so this year concludes our brief introduction to dark field microscopy, and we'll be able to apply some of these concepts as we move forward. So I'll see you all in our next video.

in this video, we're going to continue to talk about light microscopes that increase contrast by focusing briefly on phase contrast microscopy. And so phase contrast microscopes are microscopes that will make cells and their debt structures appear darker than the grayish background that they tend to create. And so in many phase contrast microscope images, you'll find that the background is going to be a grayish color and the cells and they're dead structures will appear darker. However, there are some variations in these phase contrast microscopes that do not necessarily create grey backgrounds and so that is not necessarily what defines the phase contrast microscopes. Instead, what defines these phase contrast microscope is the complex special optic devices that they use that once again are very complex and beyond the scope of this course. And so really, um what you can know about these special optic devices is that they increase the differences and how different substances and surroundings refract light differently. And so ultimately different substances and surroundings will refract light differently from each other naturally. However, those differences may be small sometimes, but these special optic devices can increase those differences to make the difference is much larger between the two and ultimately that can help to increase contrast. And so these phase contrast microscopes can be excellent for enhancing the contrast of internal details an unstained living cells. And so that's one of the advantages of the phase contrast microscope is that there's usually no staining procedure that's required and you're able to visualize living cells. Also, phase contrast microscopes can help to reveal cell structures that may not otherwise be able to be visualized using a normal bright field microscope. And so these phase contrast microscopes do have advantages. So down below, in our example, we're showing you some example images of from a phase contrast microscope. And so with these phase contrast microscopy images noticed that many in many cases the backgrounds are going to be grayish and the cells and the cell structures will tend to appear darker. However, once again, there are some variations in these phase contrast microscope and they do not always create grey backgrounds. Uh and once again, what classifies all these phase contrast microscopes um Together is the complex special optic devices that they used. But down below here, what we're showing you is an image from mu core ressam Asus or reason moses mold here. We're showing you an image from claudio philosopher of banteay, anna fungus. Here we're showing you an image of florida's Austria's fungus spores And here we're showing you an image of sacrifices services yeast. And so ultimately what you can take here from phase contrast microscopy is that it is one of the microscopes that's going to help increase contrast and be of an alternative use too bright field microscopes. And so this year concludes our brief introduction to phase contrast microscopy, and we'll be able to apply some of these concepts as we move forward, so I'll see you all in our next video.

in this video, we're going to talk briefly about differential interference contrast microscopes or D. I. C. Microscopes. And so D. I. C microscopes are going to create very detailed, highly contrasting three dimensional or three D. Images of live specimens. And so in terms of the special optic devices that they use, those special optic devices are similar to the special optic devices used in phase contrast microscopy. However, the main differences between the two is that the D. I. C microscopes are going to be adding contrasting colors And they're going to be creating three d. images. And so the three D. Images is really one of the biggest takeaways that you can take from these D. I. C. Microscopes. And so notice that we have this three dimensional cube shown over here. To help remind you that the differential interference contrast microscopy or D. I. C. Microscopes will create these three dimensional images. And so you can see that the images themselves do appear uh in somewhat of a third dimension. You can see, especially in this one here, how it appears to be kind of coming off of the surface. And that seems to be the case in all of these images. And so here we have an image of Clostridium algae, pina, lara, dia tom algae, paramecium called adam and pedestrian algae over here and so once again, this year is going to be one of the microscopes that helps to increase contrast, allowing for very detailed, highly contrasting three dimensional images of live specimens. So we'll be able to get some practice applying these concepts as we move forward in our course as well. So, I'll see you all in our next video.