Getting Some Great performance out of my Canon EF-S lenses by hacking them off!?!

Hello everyone!

A number of months ago I did something I wouldn’t normally do to a lens I own. I sawed off the back of it. More to the point, I sawed off the EF-S ring to make it EF mount. Why did i do this?
To get a usable telephoto solution from a lens I already owned adapted on my GH5!

I am all about finding ways to get extra value for using equipment or lenses you may already have lying around. The Canon EF-S lens collection I have was a consideration as adapting them to the GH5 with Viltrox F-M2 was a great solution. I mean who wants to keep buying new lenses when they don’t have to right?

**WARNING – This article is not for the faint of heart… Hacking off your lenses voids your warranty and may also damage your lens, please only follow this method if you are confident and can stand to loose your EF-S lens in the event of damaging it. DO SO AT YOUR OWN RISK **

As videographers we are constantly trying to build our collections of usable, low light and great image quality lenses for use on video and photography.

If you are like me, having a GH5 means having serious Photo and Video image quality when the right lens is attached. Getting versatility and good value for your dollar is important.. and some times its nice to be able to cut a corner to get what you need!

This time we are cutting for real! I mean actually cutting something… (more on that later)

For the most part you get what you pay for when it comes to lenses and for good reason. Today i’m going to show you how or rather tell you how you can take advantage of EF-S lenses on the GH5 using an unconventional method!

Still the thought of cutting something.. For me, i’d much prefer to have one of Canon’s larger 70-200mm F2.8 IS lenses but they are really too expensive… The quality is amazing and if i had the money for one i’d get one.. but i also wouldn’t like carrying the weight of one of those.. so what can I do?

My next best option is the 55-250mm IS STM which I already owned.. It was sitting idle most of the time.. but how to use it and is it worth it?

It turns out that this lens becomes an f2.8-f4.0  78mm to 355mm Full frame Equivalent when fitted on the Viltrox speedbooster on the GH5, NOT Bad, Definitely worth the effort!!!

Key requirements:

  • Must have a GH5 or other camera body that is supported.
  • Must have an EF-S lens you want to adapt and are willing to part with it in case you accidentally make a mistake. more on this later
  • Must have a hack saw with fine toothed blade
  • Somewhere to work on like a work bench
  • Strap and possibly some foam to hold the lens gently in place in the strap while cutting (find what works for you).
  • Must own a Speed booster – Viltrox EF-M2 (links at the bottom of the article) –
    **Notes:  I will be focusing specifically on the Viltrox EF-M2 (V1) with firmware ver 3.2 (as of December 2018) however as I have tested that config but do not know if EF-S lenses in-fact  work on any Metabones products. The newer Viltrox EF-M2II (ver 2) I suspect everything will work as the design and functionality are the same as the version 1 in terms of coding as they use the same firmware file. (I am waiting on confirmation from Viltrox on what the actual differences are to the product in version 2).
    The newer Viltrox EF-M2II (ver 2) physically has improved its Mount fitting on the Micro Four Thirds mount side as well as improved gold contacts (as that was a problem on some of the original EF-M2 units – however i did not experience that issue as others did)
  • Lots of courage and a steady hand

Viltrox’s EF-M2(s) Speedbooster Info

Original Compatibility List for the EF-M2 (ver 1) – As of February 2018

** Note: I realize this is old however it does show what original list of lenses were supported for the version 1 of the adapter
EF-S lenses were NOT supported originally until firmware 3.1 of the Viltrox EF-M2 according to my testing on version 1 of the speedbooster.

List of Compatible Lenses and cameras for EF-M2II (ver 2) as per Amazon’s website (** Keep in mind both EF-M2II and EF-M2 share the same firmware!)

A little more description of what i am doing….

For my Example today,

I’m adapting a Canon EF-S 55-250mm f4-5.6 Telephoto lens. (please see purchase links as the end of this article!)

What do i mean by Adapting?

EF-S lenses do not normally physically fit The Viltrox Speed boosters.

Regular EF lenses do but EF-S lenses don’t..

Why? An extra bit of plastic ring that Canon put in to control light and maintain its business sales of EF-S lenses – there are other differences as well such as the glass sizes being significantly smaller to accommodate Crop sensor cameras (not a problem for us on M43’s however!). ** Also, Please ignore the colored silicon lens bands on the lens in the image on the left, The bands are not part of lens or this review**

So I have cut off this ring physically without damaging the whole lens. At least that was the plan and I can tell you for the 55-250mm IS STM it works!
**Note: This is specific to Canon’s EF-S and EF compatibility. Please do not try this with any other Mount type!

A little about why this works…

But why would this work?

It all comes down to flange distance in the Canon lenses and compatibility of the speed booster. Canon has the shortest lens flange distance which makes its lenses adaptable and since EF-S and EF code is supported on the Viltrox speed boosters, were not changing that flange distance.

In fact both Canon’s EF and EF-S lenses have the SAME flange distance, even though they put in an additional ring which optically means they are the same!

For those wanting to know what the flange distance is, its 44mm for both EF-S and EF lenses.

This is a major reason why doing this procedure and hacking a lens works here.. Canon’s EF-S lenses with a speed booster works because your infinity focus does not change!

Here is a link to Flange distances on Wikipedia to show you other mounts distances which is helpful in adapting lenses.

**Flange distance is the distance from the sensor to the rear of the glass element.

WARNING – I have only attempted this with the 55-250mm IS STM lens as its a relatively cheap lens and is known to work with the Viltrox adapter. DO AT YOUR OWN RISK. Cutting the lens invalidate your warranty immediately so don’t expect any help from Canon or the store in which you bought the lens from (if still under warranty). Also keep in mind cutting the lens is only required for lenses that have the EF-S ring (EF mounted EF-S lenses do not need this procedure – like the Sigma 18-35mm F1.8 which already has an EF mount).

** Also confirm that your Lens you are hacking actually works with the Viltrox Speedbooster as NOT ALL EF-S LENSES WORK!
As i do not own a Metabones Adapter, i am unable to test this on that adapter. Please do some Searching on google or reddit before attempting with other lenses!

The Lens

One final note is that there are several different version of the EF-S 55-250 lens from Canon. Specifically we are talking about the 55-250mm IS STM f4.0-f5.6 Zoom lens. Its plastic, light weight and relatively quiet and comes with Image stabilization. Released around 2013 i believe. They are still for sale and i do believe the newer one also works. This is the lens I am adapting today however and works without issue. Other versions may or may not work at all.

The Procedure

  1. First step is to ensure that you have upgraded your Viltrox EF-M2 speed booster’s Firmware to the latest version (or at least version 3.1) Follow online instructions on Viltrox’s website on how to do that properly. I can tell you that is very simple however, connect a usb cable to the port and download the latest firmware file (unzipped) to the adapter and wait until the file disappears and the adapter has time to reset (a good minute or so). Then unplug the adapter. Make sure to leave enough time for the firmware to write itself to the adapter or you can brick it. ** The speed booster must NOT be connected to any camera or lens when you do this procedure!**
    Viltrox’s Download for Firmware Updates (Click Here)
  2. Focus your EF-S lens so that the back piece of glass is extended further away from the plastic ring, usually zoomed out will do the trick. ** This will make sure you don’t damage the back glass element, if you do, your lens is history! Consider taping the back lens element with some removable tape like masking tape to protect it while cutting however keep in mind you will need to clean the lens again with an alcohol based lens cleaner to get any sticky bits form the tape. I didn’t use any tape when i did it and just carefully wiped the lens again with cleaner afterwards making sure not the scratch it.
  3. Take a deep breath and take a fine-toothed metal hacksaw blade to the ring and visually make sure you know where the saw will cut. Do not cut into the second ring or the EF mount itself because that will cause big problems for mounting the lens later. If you have any doubts about where to cut, grab an EF lens mount and compare the EF-S and EF mount for reference.

    Canon 50mm F1.8 STM **example of EF mount

    Make sure not to damage the metal contacts either. They should be retracted (on the 55-250mm Canon EF-S IS STM) when you zoom the lens prior to cutting it.

  4. Find a way to secure the lens so it doesn’t move while cutting it without damaging it or putting too much pressure on it. I recommend some kind of rubber strapping.
  5. Cut the ring off! Be careful!


The major benefit I found is that as long as you didn’t damage the EF ring when cutting, The EF-S lens is still usable on Canon’s EF-S crop sensor cameras and operates fine. No other light really gets in that i noticed and now its usable on the GH5 with Viltrox speed booster. For me it was a Win-win scenario and didn’t cost me anything additional. I now have greater range, good image quality on the 55-250 IS STM when used on the GH5 with speed booster and its very usable when Image stabilization is turned off on the lens and only Sensor image stabilizer is turned on (You can try to use both but i had mixed results). The GH5 has In-body image and sensor stabilization so this is a great thing for adapting all sorts of lenses too.

As long as you have a steady hand and don’t mind potentially damaging a relatively inexpensive lens, i encourage users to give it a try!

Till next article! Keep Shooting!

** Note: All links below are Brand New and warehoused by Amazon itself. You may be able to find cheaper options through other sellers. Please feel free to browse after clicking!
Also, I make a small commission from any purchases below. Please consider purchasing within 24 hours of adding to your cart or I loose the commission.. If you wish return to this page to order your products before checking out your cart when or if you decide to buy. I appreciate any and all support and it really helps!

** Note 2: It is extremely hard to find the original Viltrox EF-M2 (ver 1) now online. I suspect the 2nd version EF-M2II is in fact better in a several ways however i have not tested it and do not know if the Optical components are identical. Your mileage may vary.

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