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Another way to rear-mount filters

Filters
13 replies to this topic

#1 Bernard Foot

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Posted 03 April 2021 - 20:12

Quite a few members have discussed how they attach filters to the rear of a lens for situations where the filter cannot be mounted in front of the lens or is too small. Here is another method, which I don't recall having been covered elsewhere.

The limitations where it will work are:
  • mirrorless cameras
  • use of camera lenses designed for (D)SLRs, inc. M42
  • use of camera lenses which have manual aperture control
  • maximum filter size mount of 49-52mm
You're probably aware of adapters like this which are designed to allow DSLR lenses to be used on mirrorless cameras:

Attached Image: IMG_1393.JPG

You can see the pass-through electrical contacts and the plastic housing around them. In fact there are cheaper versions which do not have the electrical contacts, which provide the fittings but not the electrical contacts (and so cannot be used for autofocus or aperture control):

Attached Image: IMG_1396.JPG

These are basically hollow tubes with space enough to hold a filter. So epoxying a filter step-up ring inside this allows a filter to be fitted inside the adapter:

Attached Image: With Step Ring.jpg

I have standardised on 49mm filters, so I used a 40.5mm-49mm step up ring. The 40.5mm end fits nicely into the rear throat of the adpter (42mm is too big). With this adapter, made for Canon EF/EF-S fitting lenses, you can fit 49mm filters like an R72 quite easily. My Baader U with 49mm step rings permanently fixed on each side can just be squeezed through the front mouth. Here is the Baader fitted:

Attached Image: IMG_1401.JPG

52mm filters are too big to get through the mouth, but can be fitted if you detach the adapter's front (lens) mount by removing the four small screws. I was able to fit my U340+S8612 sandwich, both 52mm, together with their 49mm-52mm step up ring.

In this photograph you can also see notches cut into the filter mount to help remove it if the filter is hard to unscrew.
Bernard Foot

#2 nfoto

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Posted 03 April 2021 - 20:43

I have used this approach for many years. Currently setups for Z-mount, Sony E, and m43.

#3 Bernard Foot

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Posted 03 April 2021 - 20:56

View Postnfoto, on 03 April 2021 - 20:43, said:

I have used this approach for many years.

Ahhh - there's nothing new in the world!
Bernard Foot

#4 dabateman

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Posted 03 April 2021 - 21:32

Yes for any one interested, the Metabones BT2 pass through adapter allows a 5mm C-mount adapter to be wedged inside. No glue needed. Then I can screw in filters behind and in front of the adapter.
This has allowed me to test 1mm ug11 and 2mm S8612 filters in 25mm size behind my Sigma 10-20mm f4/5.6 lens which seems to have a UV cut off of 378nm.

#5 nfoto

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Posted 03 April 2021 - 21:33

So very true.

The Baader U, removed from its filter ring, fits nicely inside an F-m43 adapter, to name one case. There is a flat inner surface towards the rear which supports the filter. Add a wire-type retaining ring and one is good to go. I think this design was first used by me with my converted Panasonic GH-2 in 2012, during the USA trip with Andrea.

I use similar for the other camera mounts these days.

#6 dabateman

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Posted 03 April 2021 - 21:49

I know this is why off topic, but I am super excited with my new to me modified Tc-16a for Nikon. My DF is now an APS-c camera that can autofocus all my manual lenses now.

Now I have to see how much UV this adapter passes.

An other fun adapter is the Meike reverse AF Canon EF mount adapter. With the fast autofocusing Metabones BT2 adapter, I can get in camera focus stacking with the Sigma 10-20mm f4/5.6 lens for some fun 10x macro. A uv filter still works between the lens and camera for UVA imaging.

Edited by dabateman, 03 April 2021 - 22:03.


#7 colinbm

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Posted 04 April 2021 - 05:40

I have wanted & waited for years to do this, to make a rear mounted filter holder for M42 lenses on short registration cameras.
Now that I have the Sigma fp, L mount, full frame, mirrorless camera, converted to full spectrum, I looked for an adapter.
RAFCAMERA, came to my rescue, https://rafcamera.com/
They have a M42 to L Mount adapter, M42 male to 52mm filter ring & 52mm filter ring to M42 female.
So I can place any 52mm filter inside.
These can be used with M42 tubes, helicoids or bellows... :grin:
All should arrive here in a few weeks.

https://rafcamera.co...2x1f-to-leica-t

https://rafcamera.co...0-75f-to-m42x1m

https://rafcamera.co...1f-to-m52x0-75m

I have used them before.

Sweet dreams.... :cool:

Edited by colinbm, 04 April 2021 - 05:41.


#8 Ural

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Posted 04 April 2021 - 12:31

I am so glad that this thread appeared, thanks, very useful information. When I was using Nikon DSLR camera I grinded off a special ring using BDB 32.5mm filter as a workpiece. This ring was then attached to the rear of Tamron 24-70. It is good to know that there are easier options for mirror less cameras.

Attached Images

  • Attached Image: 20201207_163315ss.jpg


#9 Andy Perrin

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Posted 04 April 2021 - 18:33

Rafcamera is always fantastic. Very fast turnaround and good construction.

#10 Andrea B.

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Posted 06 April 2021 - 21:01

Bernard, thank you for the write-up on rear-mounting a filter inside a mount adapter. It doesn't matter if it has been done before because we always have new readers who want to know how to do these things.

This is also useful for Nikon DSLRs when using a T2-to-F mount adapter. T2 lenses have a 55 mm flange focal distance and so can be used on my converted D610.
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#11 Andy Broomé

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Posted 07 April 2021 - 12:28

I suppose that rear-mounting the Baader means no discolouration at wider angles?

#12 Bernard Foot

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Posted 07 April 2021 - 12:41

View PostAndy Broomé, on 07 April 2021 - 12:28, said:

I suppose that rear-mounting the Baader means no discolouration at wider angles?

Yes, I think someone (Birna? Andrea?) mentioned that in another post.
Bernard Foot

#13 Andrea B.

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Posted 07 April 2021 - 17:31

If I recall correctly, it does help to rear mount the BaaderU. I'll ping Birna to stop by here to confirm.
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#14 nfoto

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Posted 07 April 2021 - 19:06

Rear-mounting the Baader certainly reduces the usual discolouration for wide angles. However, there might remain some vestiges. My hunch is this has to do with the retrofocal properties of the given lens thus according to this hypothesis, one would expect less issue with a retro- than a non-retrofocus design.