Oly 12-40/2.8 with step-down rings: How bad is the vignetting?

Started Jun 9, 2014 | Discussions thread
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Anders W Forum Pro • Posts: 21,466
Oly 12-40/2.8 with step-down rings: How bad is the vignetting?
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Like many others, I have a lot of nice things to say about the Oly 12-40/2.8. One thing I don't particularly like, however, is the filter thread size: 62 mm.

Not only is that bigger than any of the filters I already have and might like to use with it. It's also bigger than I would need for any other lens. Even my Pany 100-300 with 67 mm filter threads work well with step-down rings. Perhaps you lose a tiny bit of light in that case but the long FL means that there will be no problem with vignetting. Not so, unfortunately, when we move to the 12-40 and the WA side of things. So what to do about the situation?

Before deciding that, I figured it would be a good idea to check how bad things actually get with step-down rings. And since I have now done that, I thought it would be a good idea to report the results to help those others who share my predicament. So below you find my little test report.

My current filters and other close-up attachments (I also have some close-up lenses) are all 55 or 58 mm so I ordered step down rings from 62 to 58 and 62 to 55. Of course, I looked for as thin step-down rings as I could find. But making an informed decision about that is not easy since noone includes it in the specs and items like these may not conform to the picture you see in the ad. At any rate, those I ordered were these:

http://www.ebay.co.uk/itm/200774984091?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

http://www.ebay.co.uk/itm/200910488294?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

The 62-58 I received looks about as thin as I have seen these things get and protrudes about 3 mm from the lens barrel when screwed in. The 62-55 is regrettably a little thicker and protrudes about 4 mm.

I tested three different combos:

1. The 62-58 with a Formatt CC70M magenta filter. The filter frame protrudes about 5 mm when screwed in so the total protrusion is about 8 mm.

2. The 62-55 with a Hoya HD circular polarizer. In this case too, the filter frame protrudes about 5 mm when screwed in so with the somewhat thicker step-down ring, the total protrusion is now 9 mm.

3. The 62-55 with the same Hoya HD circular polarizer plus an old "PRO" linear polarizer that I sometimes combine with the Hoya to create a variable ND filter. This old thing has a pretty thick frame that protrudes 8 mm when screwed in. That means the total protrusion is no less than 17 mm in this case.

Ideally, one might of course hope that at least the first combo wouldn't vignette at all. Still, that's not really to be expected. After all, Oly is not likely to have expanded the filter thread from 58 to 62 for no good reason. So the bad but expected news is that all three combos show some vignetting. But the good new is that it isn't so bad, particularly in the first case. The case-by-case results are as follows.

Combo 1: Shows vignetting at 12 mm which is gone more or less completely just at the point where the camera indication changes from 12 to 13 mm. If you crop at the top and bottom at 12 mm, the vignetting is also pretty much gone once you get to an aspect ratio of 2:3. If you stop down to f/5.6, you don't see much of it even midway between 3:4 and 2:3.

Combo 2: In this case, you have to go the point where the camera indication changes from 13 to 14 mm in order to get rid of the vignetting. At 13 mm and f/5.6, you don't have to crop much at the top and bottom to get rid of it. You don't see much of it at this setting once you are midway between 3:4 and 2:3.

Combo 3: Here, the vignetting remains rather noticeable until you reach 16 mm and f/5.6. At f/2.8, you need to go to 17 mm before things start looking reasonably normal.

In short: It looks like combo 1 (step-down ring plus a single filter) keeps the lens almost completely useable. Further down, the losses quickly become increasingly noticeable.

Questions and commens are welcome as usual.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
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