setup ring = vignetting?

[thebox]

Hello guys,

Please let me know if someone could clarify my mind.

I'm not findingany Hoya Circular Polarizer with 55mm diameter here in Brazil... but I found one with 58mm diameter. My camera is a Fuji S5000. The camera's diameter is 55mm with a adapter ring included. I already have a Skylight filter mounted on it.

My question is: Do you think that I couldhave some vignette if I mount a setup ring 55-58mm for using the circular polarizer 58mm? In another words,I would havean adapter ring 55mm + Skylight filter 55mm + setup ring 55-58mm + Circular Polarizer 58mm.

Thanks in advance!

Marcos

[KCan]

thebox wrote:

My question is: Do you think that I couldhave some vignette if I mount a setup ring 55-58mm for using the circular polarizer 58mm? In another words,I would havean adapter ring 55mm + Skylight filter 55mm + setup ring 55-58mm + Circular Polarizer 58mm.

Probably. Why don't you just forget the Skylight filter? just mount the step up ring + the polarizer.

[shene]

thebox wrote:

My question is: Do you think that I couldhave some vignette if I mount a setup ring 55-58mm for using the circular polarizer 58mm? In another words,I would havean adapter ring 55mm + Skylight filter 55mm + setup ring 55-58mm + Circular Polarizer 58mm.

The answer depends on three factors: (1) the thickness of the 55-58 step-up ring, (2)the total thickness of the filters, and (3) the tolerance of the lens filter thread. Some lenses have filter thread very close to the front glass. This makes the use offilters very difficult. For example,the Minolta A1 has a 49mm filter thread; however, even avery high quality Heliopen 49mm thin polarizer can cause vignetting. Since I don't have a Fuji, I cannot answer this portion for sure. Second, not all step-rings are created equal. Some are thicker than the others. A thick step-ring will push a filter further into the angle of view of the lens,and vignetting may be possible. Third, stacking two filters together has the same effect of a thick step-ring plus a filter, and, hence, vignetting is also possible. So,you might want to (1) buy a thin step-up ring, and (2) use the polarizer only without the skylight.It is in general not a good practice to stackmultiple filters together unless it is absolutely necessary.

CK

http://www.cs.mtu.edu/~shene/DigiCam

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