Many of my clients (or occasionally blog readers!) will send me a photo and ask me a question. The photos are indeed much better now than they were before “everyone” had digital cameras with fairly powerful zooms. But there are still a lot of photos that are blurry or too dark or too bright. If you want to take photos for someone else to understand a situation, especially if it is not someone intimately familiar with your industry or the item in question, you now know that you need to include a scale marker of some sort (a familiar item, if a ruler of some sort is not available) and you need to include several views from different angles and maybe even brighter or darker exposures. You also have to know how to recognize what features are important to highlight. If you have been reading this blog for a while, even if you are not a failure-analysis expert, you might be getting a better idea of how to do just that.
Taking pictures of bright, shiny bits of metal can be particularly challenging if the light exposure is automatic. Often, my assistant, who has been working with me regularly now for three years, still has to take half a dozen overview photos at different exposures to get one or two that show what he thinks I might be trying to show.
Before we close, let’s look at Figure 16, which is a much higher-magnification view of the steps along facet 4 of crystal B of Figure 13. This is a scanning electron microscope (SEM) photo, and SEM images are always grey scale. The light waves that are needed to make color do not exist inside the dark chamber of an electron microscope. Note that some people colorize SEM images, and some SEMs have features that use color to show composition. But this is not the “natural” color of the specimen being viewed.
Note that this image, originally taken at 37x, is not very high magnification for an SEM. As we saw in Part 1, we may wish to use the SEM to get a better depth of field even at these modest magnifications. But Figure 17 shows another reason to use an SEM for low-magnification images. Figure 17 is an energy dispersive spectrum (EDS) composition “scan” that tells us the types of atoms that are present in the specimen we are viewing. Here, since the photos looked like pyrite, which is known to be iron sulfide “Fool’s Gold,” it’s no surprise to find sulfur (S) and iron (Fe). There are also large amounts of carbon, which is probably associated with dirt on the surface (there was more carbon when I zoomed in and scanned a darker area), and traces of several other elements that might be either on the surface of the crystal or part of the crystal. We can’t tell from this information alone.