Circular polarizers - stepping them down?

[Picture North Carolina]

Can circular polarizers be stepped down (i.e., 77mm to 55mm) and still work correctly?

If I remember correctly, the old film polarizers were coated in a linear fashion so stepping down wasn't a problem. But if CP's are painted in a circular pattern, it seems like using only the center of the filter might be a problem.

Bizarre question, I know, but if anybody has an answer, please help. (just trying to save a buck - step down rings are cheaper than filters. ;) )

[argyle]

You're talking about stepping up a 55mm lens diameter to a 77mm diameter. Considering that an inch is equal to 25mm (actually 25.4), you're stepping up a full 22mm (nearly an inch). Depending on the focal length of your lens, you could end up with vignetting. Being that 55mm CPL's are much less dollar-wise than their 77mm counterparts, it'd be best to just have a CPL in the smaller diameter and forego the use of step-up rings completely. Want you're wanting to do will also take the lens hood out of the equation as well. The larger CPL will work with a step ring, however.

Step rings are just something else to fool with, dig out of your bag, and then have the possibility of becoming locked it onto your CPL (and with the turning of the CPL outer ring, much more difficult to separate if they do get locked together). Others may disagree, but I prefer 'simple'...I'd definitely go with a second CPL.

[gjl711]

I have a 55 to 77 step ring and it's very convenient as there are only two lenses I have that are 55mm and it seems silly to get a duplicate set if filters for two lenses. It works well.

[Quad]

B+W make polarizing filters that are stepped down to fit smaller lenes for ultra wide angle use. So I would guess it must be no problem.

eg this 86mm filter fits 72 mm lens thread

http://www.bhphotovideo.com/c/product/10888-REG/B_W_65016519_72_mm_Kaeseman_Circular.html#specific ations

[neil_r]

It will not be a problem

[20droger]

There are two separate issues here.

First, a circular polarizer has no "center" from an optical point of view. That is, if you had a giant circular polarizer, it would make absolutely no difference where on the polarizer your lens was positioned. The filter is uniform over its entire surface. It is not "painted" from center out.

Second, there is confusion in this thread about a step-up vs. a step-down ring. The designation is always relative to the lens.

A step-down ring is used to adapt a smaller filter to a lens of a given size, i.e., a 55mm filter to a 58mm lens. This will often, even usually, cause vignetting.

A step-up ring is used to adapt a larger filter to a lens of a given size, i.e., a 62mm filter to a 58mm lens. This will never cause vignetting.

The OP, unless I'm completely misreading the post, has a 77mm circular polarizing filter he wishes to use on a 55mm lens. This is perfectly doable. Once mounted, via a 55-77mm step-up ring, the circular polarizing filter will operate correctly and will not cause vignetting.

Of course, the lens hood will no longer fit, but that's a separate issue.

[argyle]

The OP, unless I'm completely misreading the post, has a 77mm circular polarizing filter he wishes to use on a 55mm lens. This is perfectly doable. Once mounted, via a 55-77mm step-up ring, the circular polarizing filter will operate correctly and will not cause vignetting.

Of course, the lens hood will no longer fit, but that's a separate issue.

This was my interpretation of the orginal post. However, I disagree about the "not cause vignetting" statement. I stated that it *may* cause vignetting based on the focal length of the lens that he wants to share the filter with....the OP didn't specify that in the post. If its a fairly wide angle lens, you can pretty much bet that extending out the polarizer, even just a few millimeters via the step ring, can result in vignetting. With a normal or telephoto lens, I'd definitely go along with your statement.

My position, and that of others that I typically shoot with, is to carry a separate CPL for the lenses that one would typically use it on. In the case of the OP's example, a 55mm Hoya Pro 1 CPL can be had for about $37, while the step ring would cost about $12. The difference in price is rather negligible considering the cost of camera gear, and you wouldn't have to fuss with a step ring and the loss of use of the lens hood. YMMV.

[Picture North Carolina]

I apologize for the misunderstanding. Yes, I am mounting a 77 on a 55 mm lens. It is a fixed - 90mm. It is a Tamron SP 90mm f/2.8 Di Macro being used for landscape.

I had considered the problem with the lens hood, but anybody who is familiar with this lens could verify that is not a problem because on this lens the front element is recessed back approximately 2 to 3 miles.

It is the only 55mm lens I have and it is not used that often, so that is why I was attempting to adapt. The justification for a good quality $100+ CP wasn't there.

Thanks all for the help and again, I apologize for not supplying enough detail.

[argyle]

It is the only 55mm lens I have and it is not used that often, so that is why I was attempting to adapt. The justification for a good quality $100+ CP wasn't there.

Since you say that its not used very often, then by all means the step-up ring is the way to go. If the lens would see a lot of use, then I'd strongly consider a separate CPL, especially when considering that a 55mm filter is widely available and relatively inexpensive.

In some cases, the filter size can be such an odd-ball that using a step ring is mandatory. For example, I have a Leica 35mm lens that I use on my 5D with an adapter. This lens has a Series VII (48mm) filter size, which I cannot find easily. I have no choice but to use a 48-49 step ring. It does get to be a PITA when trying to separate the step ring from the CPL when I want to use the CPL on my Olympus wide angle lenses. Luckily, I just picked up an Olympus 28/f2 lens that came with a CPL as a bonus...now the step ring stays affixed to the first filter. I'm not a fan of step rings due to the PITA factor, but sometimes they are a necessary evil. ;)

[gjl711]

One word of caution with the step rings though. It does create a point where the filter want to catch on things and if caught there is a possibility that you can damage the threads. When I use my step ring, I take the picture or pictures then remove the step ring and filter before I put the camera back in the bag. That way when I next remove the camera the lens does not have this overhang at the end.