te4o said:
That's good news because I just ordered Heliopan ND and have to step down twice - from 82 to 72 and from 72-67 - would this work as well?
It depends what lens and what you use it for on what camera.
As an example, my EFs 15-85 takes 72mm filters, if I put 2 or more filters on that are 72mm thread, I get vignetting. I couldn't use any step-down rings on this.
But my 70-300L is a full frame lens with 67mm threads, if I mount it on my 7D, I can use step-down rings to 52mm before I see vignetting. But with the 70-300L on 68mm of extension tubes for macro, I can use step-down rings to 37mm without vignetting.
And my Samyang 35/1.4 with 77mm threads, on my 7D, can take step-down to 58mm before I see vignetting.
And as neuro said, using a 67-72 step-up to my 72mm CPL on my 70-300L, I can use the hood, but I have to put the hood on before the filter, and take the filter off before the hood (and it's annoying to adjust the CPL).
In short, with an EF lens on APS-C body, you can get away with a few step-down rings before you get vignetting.
On a 1D, you can use some rings, but not as many as on APS-C.
On a 5D or 1Ds, or using an EFs lens on APS-C, you can't use step-down rings at all (unless you get lucky with a weird-designed lens, or one end of a zoom).