I read a review of circular polarizing filters in www.lenstip.com and one of the tests is to judge the homogeneity of the filters.
Quote from the test explanation page:
Homogeneity is a qualitative parameter consisting of the bubble content in the glass and streakiness of the glass. While you can always reclaim an element with air bubbles in it, it’s harder to show streakiness to the sales clerk. This aberration occurs when the surface is uneven or the components of glass (foils) are badly mixed. Light refracts and, as a result , the resolution of images decreases. Precise measurements require so-called shading method, but in the case of filters there’s no need to for this much precision (using shading method you can detect convection of warm air over a hand!)
While I understand what streaks and bubbles would do, I fail to see what does it matter if I can't see it myself. When/where does it matter?
Am I simply not seeing it with my unexperienced eyes, or is it that the effect of streaks in a filter are not visible at computer screen resolution? I don't see it even when pixel peeping.
What part is lens quality playing here? My low-quality kit-lens might just do such a poor job that streaks in filter foils disappear in the overall mush?
In case I did, after all, not really understand the effect: What faults in image quality exactly should I be looking for to actually see the effect of poor filter homogeneity?
My polarizing filter is a Hoya Pro1 Digital MC PL-C which performed very well in other parts of the test but vignetting (which I don't see either) and homogeneity part.