Today I have a comparison test to present regarding the Hoya HMC Circular Polarizing filter. Circular polarizers have a characteristic two-part design of a static inner mounting element and a rotating outer one. By rotating the filter, the light is polarized at different angles. I first began using this filter four years ago, but did not completely understand how to make use of the expected photographic results. This filter offers a decent tradeoff. It can produce more contrast in images and reduce glare and reflections but cost the lens about one and a third stops in light. Additionally, due to the thickness of the filter, vignetting can occur at wider focal lengths.
Here are two images of a rose that can help illustrate the differences between a non-polarized (left) and polarized image (right). Both images were taken at 70mm, f/22 and ISO 100 with no exposure compensation. Due to the light absorption of the filter, the shutter speed decreased from 1/40s to 1/15s. The first observation to note is the apparent darkness of the right image despite neutral exposure compensation. The result shows darker colors across the image. The whites of the petals in the bottom left now hold more texture and appear to be a truer white. Similarly, the dark pink petals on the right are more accurately exposed. Inside the flower, the yellow is richer and less glaring. This apparent darkening cannot be achieved with a negative exposure compensation. While the colors are toned down, the contrast is increased. Overall, the image has a crisp effect in the petal outlines and in the color transitions.
These photographs convince me that it is a useful and necessary filter for the field, whether it be landscape images or flower portraits. Let me know what you think of this comparison.