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Drop-in Filter Mount Adapter EF-EOS R with Drop-in Circular Polarizing Filter A

DhiCan
Contributor
I have a 90D with a hole bunch of very expensives EF lenses which I love very much, including a 11 24mm ultra wide angle.
So recently I got my EOS R5 with the
Drop-in Filter Mount Adapter EF-EOS R with the Drop-in Circular Polarizing Filter A, which works beautiful but the problem is that when I'm not using the polarizing filter I don't have a way of covering opening and it would be wonderful if Canon makes a cover at a reasonable price so I "we" Canon loyal stop using electric tape to prevent dust and dirt from entering the sensor.
1 ACCEPTED SOLUTION

There is a good scientific reason for the "dummy" glass filter requirement in this particular EF EOS R adapter:

 

The physical thickness of the mount adapter for drop in filters is slightly different then the  base EF-EOS R or EF-EOS R with Control Ring.  That difference is because the "Drop-in" Adapter is always designed to have a thickness of optical glass in the light path.  Optical glass typically has a refractive index of between 1.5 and 1.67.  which optically reduces the effective thickness of the optical path-length of the adapter. 

 

With the glass filter in place (doesn't matter if it's a ND, a polorizer or simply clear) the lens flange to focal plane distance is reduced. Ideal lens focus will be at a different position of the RF internal focus positioner.  That may make no difference for relatively close subjects, but may make perfect infinity focus poor for some EF lenses.

 

Ideally, not having an extra layer of glass with it's two partially reflective surfaces would be preferred when no filter is needed (like the other EF-EOS R adapters), but could also create the possible focus limit because the adapter is designed to always have the glass layer in place for proper infinity focus.

 

Your choice is a $100+ "dummy" glass "filter" or 1/10 of a cent's worth of electrical tape and a hope the that auto focus range of your particular lens will be able to fully compensate. Older, always mechanically-coupled EF lenses may not have enough range to work correctly.

 

Alternately, for the same or less cost than a drop in piece of clear glass, you can purchase the basic, no ring Canon EF-EOS R Adpater, which is the correct choice for when you don't need a drop in filter.

View solution in original post

9 REPLIES 9

kvbarkley
VIP

Or buy the mount adapter without the filter. It sould seem to get more use

MikeSowsun
Authority

There is supposed be an optical element in the drop in filter to maintain optical integrity.

 

There is a San Francisco company called "Breakthrough Photography" that makes compatible drop-in filters for the Canon EF to EOS R adapter. In addition to various CPL and VND filters, they have clear filters starting at $69. 

8201D304-8685-4283-99AB-C7C20DA223C8.jpeg

781F9138-0B3D-45E6-AE54-DB390B7FD2D6.jpeg

 

Mike Sowsun
80D, 5D Mk III

Canon also sells a clear drop in filter for $140. 

https://shop.usa.canon.com/shop/en/catalog/drop-in-clear-filter-a

 

84C21525-F67F-4AB8-9D5B-C593560B75EA.jpeg

Mike Sowsun
80D, 5D Mk III

DhiCan
Contributor
I know, thanks!
But I mean just a covering pieces without any glass interfering with the genuine construction of of the lens.
I mean just a simple cap, I was thinking of buying the clear US$99.00 and cut off or grind it. A wild thought but so far I'm covering with black electric tape. Lol

DhiCan
Contributor
 

DhiCan
Contributor
I don't see what a clear filter really does in that position at least the one screwed in front of the lens protects it from the elements and from an accidental bump or impact.

There is a good scientific reason for the "dummy" glass filter requirement in this particular EF EOS R adapter:

 

The physical thickness of the mount adapter for drop in filters is slightly different then the  base EF-EOS R or EF-EOS R with Control Ring.  That difference is because the "Drop-in" Adapter is always designed to have a thickness of optical glass in the light path.  Optical glass typically has a refractive index of between 1.5 and 1.67.  which optically reduces the effective thickness of the optical path-length of the adapter. 

 

With the glass filter in place (doesn't matter if it's a ND, a polorizer or simply clear) the lens flange to focal plane distance is reduced. Ideal lens focus will be at a different position of the RF internal focus positioner.  That may make no difference for relatively close subjects, but may make perfect infinity focus poor for some EF lenses.

 

Ideally, not having an extra layer of glass with it's two partially reflective surfaces would be preferred when no filter is needed (like the other EF-EOS R adapters), but could also create the possible focus limit because the adapter is designed to always have the glass layer in place for proper infinity focus.

 

Your choice is a $100+ "dummy" glass "filter" or 1/10 of a cent's worth of electrical tape and a hope the that auto focus range of your particular lens will be able to fully compensate. Older, always mechanically-coupled EF lenses may not have enough range to work correctly.

 

Alternately, for the same or less cost than a drop in piece of clear glass, you can purchase the basic, no ring Canon EF-EOS R Adpater, which is the correct choice for when you don't need a drop in filter.

DhiCan
Contributor
Thank you so very much!
It makes sense, I based my suggestion on the fact that since Canon prices are not so affordable it'd be nice if they come up with just a simple cover, but then again the adapter will become like an extension tube that'd reduce or affect the focal operations in some ways.
Again thank you very much.

DhiCan
Contributor
 
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