Best Drop-In Filter Adapter for Canon RF Mount

In the beginning, there was just one. Actually, there was the announcement of just one. The one – from Canon – took a very, very long time to actually get shipped. But then there was a Canon EF to RF drop-in filter adapter (above), allowing for previously-unfilterable lenses to be, well, filtered. And it was good. It is still good. But now there are options…

The Adapters

Meike and Kolari now make their own filter adapters. We’ll answer the questions of whether they’re any good; if they come with good filters; and if any of these things are compatible with Canon’s. On top of that, we have new removable filters from Breakthrough Photography. We’ll see how those compare to Canon’s, and if we can find any compatibility issues between the four brands.

One really nice thing about the Meike adapter is that the version we purchased came not just with a neutral density filter, but also an empty filter holder that can be placed in the opening when you wish to simply adapt a lens and not have an optical effect on the image. Canon, hilariously, charges $130 for a clear glass filter for its version. Kolari charges $25 to include an extra clear-glass filter. And, yes, the Meike empty filter holder fits the canon adapter, so you can get a Meike adapter – complete with filter and blank filter holder – for just over the cost ($150) of just Canon’s clear filter.

A word on that empty filter holder… Adjustable filters like variable neutral density (VND) filters and circular polarizer (CP) filters have some relatively thick layers of glass. Manufacturers can reasonably get them down to about 2mm. Canon and Kolari compensate for the effect of this glass by lengthening the adapter itself by 1mm. Meike takes a different strategy, leaving the length of the adapter just like that of the non-drop-in adapters. This means that, in theory, the Meike adapter is a bit of a compromise whether you are using the empty or full filter holder, as the optimal adapter length will be off by 1mm one way or the other. With the Canon and Kolari versions, an empty filter holder will be off by a more noticeable 2mm, and a full filter will be just about perfect. This is why they recommend using the clear glass filter (the element of which is precisely the thickness allowing for zero focus shift).

Our casual testing (done with a Sigma 135mm f/1.8 Art lens and a Sigma 28mm f/1.4 Art lens) did not show a noticeable image quality issue with the Meike adapter with the empty filter holder, but this will be partly dependent on the type of lens uses, and is an area we will test further.

The Meike adapter comes in a few flavors. The best bang-for-buck is the $150 package that includes the adapter, a VND filter and the blank filter. You can also get just the VND for $79 or just the polarizer for $70.

CPLs: Breakthrough on left; Canon on right; empty holder in the middle

The Meike build quality appears to be decent, but not as ultra-smooth as the $299 (PL) – $399 (VND) Canon version. As adapters, they appear to function identically, merely providing pin extensions from one side to the other, without mucking around with the electronics. We could detect no difference in autofocus speed between the two adapters.

As filter holders, neither appear to be weather-sealed adequately. They both have a gasket that will go between the body and the adapter, but the filter slot uses a simple friction fit, and is positioned on the side, the edge of which is ready to catch any and all mist and rain. The canon filters do have a little indented rim in the plastic that might give them a hair more protection, but it seems it would merely slow the flow to some degree if at all.

And then there’s the Kolari adapter. This is a significant upgrade from the Meike, and features better fit than even the Canon adapter. The Kolari system avoids the push-button latch on the filters in favor of an extremely-well-finished friction fit. If latching a filter in the Kolari adapter feels like closing a luxury car door, then latching the button mechanisms on the other filters is more like closing a refrigerator vegetable drawer.

The Kolari filters tested had a very small amount of play in the filter control wheel, similar to that of the Canon and Breakthrough brand equivalents, and less than that of the Meike.

Kolari designed the filter to have more flocking and a more gradually narrowed internal light path, allowing for more blocking of errant light rays that might otherwise bounce into frame from the adapter’s internals. In many aspects like this, it seems that Kolari was trying to maximize the engineering at each step.

The Filters

The Canon filter we tested worked great. The one minor complaint we saw was the typical Canon unwillingness to put much dampening in filter wheels. This means that when you’re using your left pointer finger to reach out and adjust the polarization, you’re more apt to over-shoot your desired correction. You get used to it, especially if you’ve been using the filter inserts used for the big whites for the last few decades. Nothing new there.

The polarizer version is a bit heavy-handed on the light reduction, suffering almost two stops of reduced light at the brightest polarization setting. But if you want to use a polarizer, you might as well go for it.

The Breakthrough Photography polarizer (we tested the X4 CPL model) is at least as well-built as the Canon original. The dampening is far superior, and the control wheel much larger and more exposed. The polarization effect isn’t as heavy, and that may be a pro or con, depending on your typical needs. The picture at left shows it maximally open, and the one at the right shows the filter set for maximum filtering. It lets through roughly a full stop more of light than the Canon version. Breakthrough’s controls on the filter are the best of the lot. They may be a little garrish, with their different lines showing bright metallic reds or oranges, but they’re crisp and clear. Nothing some spraypaint can’t fix for the wildlife photogs.

The Kolari polarizer is similar in effect to the Breakthrough X4, with a similar degree of polarizing effect. The build quality is excellent. At bottom right the table’s shine is removed where the light is polarized coming through the filter.

The Kolari model’s secondary cogwheel – the one that sits between the control wheel on the outside of the filter and the actual filter lens elements, as pictured at left – has about half a millimeter of play between the cog ring and the central post, which gives the Kolari filters a tiny bit of play in the wheels. That level of play is similar to the better of the other brands, but if Kolary were to make that post bigger, it would make all the more differentiation between them and the others in build quality.

We have not yet had the opportunity to test the Canon variable neutral density filter, but intend to add that information in at a later time. We did get to test three non-Canon VND brands: the Meike version, the Kolari VND and one from Breakthrough Photography.

Breakthrough Photography VND

First up is the Meike version that came with the adapter. The upside is that it appears to have very little color effect on the image. Through the entire range of darkening available to its Breakthrough competitor, the Meike VND showed roughly the same lack of color cast. Even after a full 30 second exposure at maximum light reduction, there was just a very slight blue/greening of the tones consistently across the frame. It was only noticeable in comparison.

Meike VND

However, when shooting into the sun – admittedly an extreme test – the Meike filter showed much more flare, and this flare caused quite a rainbow of color effects. The pictures at right and left show the relative color cast and flare at about 6 stops of darkening. This is the worst case scenario, shooting into the sun, causing with the additional flaring effects. You mostly wouldn’t notice a difference if the sun weren’t in the shot.

At left is a picture at Meike’s maximum darkness – probably even a stop or two further than it is rated for, at 10 stops – at least according to the Canon R5’s meter. Remember that this is a shot that the Breakthrough filter couldn’t do at all because it doesn’t darken down this far. The flare can best be described as dominating, with a blue/green cast present more in the middle of the frame, all partly overcome with the massively magenta flaring. Again, this is a bit unfair, as when the filter is used only within its stated range of light reduction, these effects do not occur.

The downsides of the Meike are two-fold: 1) as you turn the filter wheel to make it darker, the darkening accelerates at a faster and faster pace, making large light reductions somewhat imprecise to adjust. It reminds me of old TV sets, when after decades of use the volume dial would do nothing from 0-3 and then would be full blast by 4. This acceleration of darkening is common to all VNDs, but the practical effect is made much worse when the dampening of the controls is poor. 2) The dampening of the control wheel is even poorer than Canon’s, and it has perhaps a millimeter of play in it. It is perfectly serviceable and convenient, but coupled with the first problem, it is noticeably more janky.

The amount of light stopped at maximum filtering is quite something to behold. It isn’t quite completely black when looking directly at a lamp, but it might take you a moment to locate the lamp. It is a proper 9 stops. To put this to the extreme, we placed a flash behind the filters at maximum filtered setting. The Breakthrough filter at left still blew out some highlights where the light peeks through the filter. At right, the Meike filter had a couple stops of highlight room to spare.

The pictures below show a scene taken at 30 second exposures with all three brands. This revealed that the

Kolari at Max

Breakthrough at Max

Meike at 10 Stops

Kolari filter is one half stop clearer at maximum darkness setting versus the Breakthrough VND filter, and that the Meike version is more than four stops darker than the both of them at maximum darkenting. The images also show that the Kolari filter shows the best vignetting performance, with the Breakthrough filter showing a little bit of inconsistency across the frame at the maximum setting, and the Meike filter quite uncontrolled when set to 10 stops of filtering.

Meike at Max

Just for reference, the darker shot shown below is the Meike filter used at maximum darkness with the same camera exposure settings, which shows the stark difference in VND maximum power.

The Breakthrough Photography variable neutral density filter is a masterpiece of dampening. It appears to be the best built of the three. It is rated for up to 7-9 stops of light reduction, but we find it takes only about 6 stops of light. There appears to be a very slight cooling color cast imparted on images taken at maximum reduction, to a lesser degree than the slight green cast of the Meike filter. Flaring is relatively well-controlled, but present, showing primarily vague purple streaks extending out from the sun.

The Kolari VND filter is rated from 2-10 stops of light reduction, and appears to perform very similarly to the Breakthrough filter, proving to be even a half-stop further short from the rated 9 stops. It has the better dampening of the Breakthrough filter, but also has a clever gauge on the filter itself that allows you to set a particular level of darkness, and then insert the filter into the adapter retaining that setting. The picture at left shows the numbered scale of stops on the outer ring and a little white dot on the ring that holds the filter.

Because the filter wheel is adequately dampened, and the build quality is so good, setting the darkness out of the adapter, and then inserting the filter into the adapter fails to change the setting.

The friction latching mechanism can be seen at right, compared to the Breakthrough mechanical design. Kolari version (left) has a super-simple nub that sits in the center providing a very precise friction latching mechanism. The Breakthrough version on the right has the user depress the button (top in red), which pushes a plunger, which can be seen threading through the other parts of the filter, which pushes on a slanted piece of plastic that then moves a latch mechanism. Both mechanisms involve wear, but the Kolari one is simpler, and – as seen above – the nub is replaceable, as it is a small part held in place with user-accessible screws.

So, What Would We Buy?

Before we tried out the Kolari, we thought we’d recommend the Meike, mostly because of price. Then, we could pick up an X2 drop-in polarizer from Breakthrough Photography. That would set us back just under $300 in total. And that’s still a great option. But after we had a chance to use the Kolari adapter and filter set, it was obvious that this was the one to get. It has the best build quality – even better than Canon’s – and an entire system, including VND, polarizer and glass filter costs $400 normally and $280 for Black Friday. To get the equivalent system, Canon’s versions would cost a total of $770. The Canon versions are great filters, although slightly harder to operate for lack of dampening, but ultimately there isn’t a quality they possess that isn’t topped by Kolari. Even after the price presumably goes back to $400 after the h0liday that is our recommendation versus either the cheaper Meike adapter/filter or the Canon adapter filter.