 Charisse Baldoria |
Black Circle around the Picture I got 2 rolls of film where some of the pics have a black circle surrounding the images. It may have started when I began using a linear polarizer (I've just started to do photography), but am not 100% sure if that's the cause--don't know if there's something wrong with the polarizer, the camera, or the way I use them. The lens I used for these was a 28-70mm zoom. I use a Canon F-1. This problem occurred in all the ff. cases: when I used both fast and slower shutter speeds, in color and BW, in a horizontal and vertical pic, with or without tripod, indoors and outdoors. Help!
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John A. Lind |
Charisse, Without seeing the photographs to be certain, your description sound much like "vignetting" caused by stacking the polarizer mounting ring. Vignetting is caused by the lens looking through something smaller in diameter than its angle of view. The edges of the film frame are blocked, particularly the corners. This problem is independent of shutter speed used. Vignetting is not always that obvious in the viewfinder; it usually doesn't look as dramatic as it does on film, or in the resulting print. It can be easy to miss seeing if you're not specifically looking for it. Vignetting typically this occurs when too many filters are stacked, sometimes with a lens hood. Also, the wider angle the lens, the greater risk of occurrance. Were you usually at the shorter focal lengths on the zoom in these photographs? Nearly all polarizers are deeper than other types of filters because there is a ring that screws onto the front of the lens and a rotating one holding the filter on top of that. Because of this, always consider a polarizer as if it's two filters stacked. If stacked on top of a lens hood or another filter, it's as if there are three filters stacked and the vignetting risk increases, especially with a wide angle lens. -- John
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Charisse Baldoria |
Ooooh. Thanks for the enlightenment! Yeah, I guess I was shooting at shorter focal lengths then (and in BW, with a filter). So is the type of polarizer I have a bad, cheap kind? Is there no way to shoot with a polarizer and 28mm? Even when I used a 28mm, a skylight, and a polarizer, that's already what's happened. So taking off the skylight might help?
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John A. Lind |
This is a problem common with polarizers, cheap and expensive, because of their depth. There are "thin" polarizers with very thin rings on them made for super-wide angle lenses (about 21mm and shorter; expensive too). Few users need them. Using filters on wide angle lenses requires care to avoid vignetting. Some lenses, because of exactly how the front of the lens is designed, are more prone to it than others. The 28mm end of your zoom isn't so extreme that a standard thickness polarizer alone should cause a problem. If the problem is vignetting, taking the skylight off before using the polarizer will probably solve the problem. Using a skylight with B/W film doesn't really do anything. A skylight acts much like a UV with slight warming. The warming part slightly affects color film but it's undetectable with B/W. A polarizer will also knock down UV content in the light. Using the two together is unnecessary for handling UV content. A little more about UV: If you use a lens hood that screws onto the lens, put filters on first and the lens hood last. Because of how nearly all screw-on lens hoods are designed, it minimizes vignetting risks. [Lens hoods can also vignette if one is used that is narrower than the widest angle of your zoom.] -- John
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