M50ii + EF-S 55-250mm STM + Kenko SHQ 1.5x Teleconverter

Congratulations on a tidy little project with great results! I still have my modified 55-250 and take it out once in a while.

JasonS70 wrote:

Hi all,

Well after some procrasination I finally followed some advice given on previous posts about modifying my lens to work with the Kenko adapter

The thing I did different is a did not chop up the mount, instead I bought a EF mount replacement part from fleabay that screwed on perfectly. It it well built and has given me no issues

As for the Kenko adapter, taking the chip out so it would work with the lens proved to be fun and games but in the end everything came together and works with not problems. Of course the information about the lens F stop and focal length is not correct but that does not bother me

As for the results I am pretty happy with them, there is a small hit to image quality but with the plethora of software out there today that small hit is more than manageable. Plus for the $100 Aus odd dollars spent who can complain.

So here are some recent examples, of course to get the correct exif data you will need to do some math, I am to lazy

Cheers

Jason

The EF mount part

Nice images! Great job. It is a fun little project for sure.

Welcome to the small but growing club of EF-S 55-250 + teleconverter users. It's a great, light combo.

The back of your EF-S 55-250 IS STM sure looks a lot better than my hacked off mount.

You are correct that the image quality is slightly degraded using the TC, but it's not much and partly due to the fact that the proper lens corrections are not applied in post-processing or in the camera for the combo.

I have found using DxO PhotoLab 5 that setting the global sharpening to about 30-50, maxing out the CA corrections including enabling purple fringing correction, and using an unsharp mask with intensity 25-50, Radius 0.91, and threshold zero will yeild results that look very much like the lens without the teleconverter, they will be pretty sharp at the pixel level. Also using Deep prime de-noise even at low ISOs seems to always give a cleaner, sharper image... for low ISOs a low value of 10-25 is often about right.

For other post-processing software, applying a little more sharpning and more CA correction should help.

For those who might be interested in this conversion, here is a link to a past thread where this was discussed a bit, and the posts have links to other threads where I detail how to remove the chip from the Kenko 1.5x SHQ teleconverter.

https://www.dpreview.com/forums/post/65817791

Really nice pictures, Jason.

I got the stuff together a few months ago, but ran out of time to do the conversion in time for the need. The need will arise again, however.

Larry, can you remind us again why you needed to remove the electronics from the teleconverter?  Was it because autofocus didn't work at all or didn't work well?

I found the thread.  It's here:  https://www.dpreview.com/forums/post/65219570

ThrillaMozilla wrote:

Really nice pictures, Jason.

I got the stuff together a few months ago, but ran out of time to do the conversion in time for the need. The need will arise again, however.

Larry, can you remind us again why you needed to remove the electronics from the teleconverter? Was it because autofocus didn't work at all or didn't work well?

I found the thread. It's here: https://www.dpreview.com/forums/post/65219570

It has been a while, but I seem to remember the combo just didn't work, it would focus hunt or something like that and it might have given errors. With no chip everything just works (except EXIF data isn't accurate).

Thanks, and thanks for doing the hard work to develop that.

JasonS70 wrote:

Hi all,

Well after some procrasination I finally followed some advice given on previous posts about modifying my lens to work with the Kenko adapter

The thing I did different is a did not chop up the mount, instead I bought a EF mount replacement part from fleabay that screwed on perfectly. It it well built and has given me no issues

As for the Kenko adapter, taking the chip out so it would work with the lens proved to be fun and games but in the end everything came together and works with not problems. Of course the information about the lens F stop and focal length is not correct but that does not bother me

As for the results I am pretty happy with them, there is a small hit to image quality but with the plethora of software out there today that small hit is more than manageable. Plus for the $100 Aus odd dollars spent who can complain.

So here are some recent examples, of course to get the correct exif data you will need to do some math, I am to lazy

Big congrats!  Great set of pictures. I too did the 55-250 "Rexley TC Special" (with the fleabay back cap).  Worked like a charm!

Enjoy your new rig!  (and thanks for posting)

R2

Well after some procrasination I finally followed some advice given on previous posts about modifying my lens to work with the Kenko adapter

Great! I hope you get as much a joy out of your extended 55-250 as I do out of mine.

The thing I did different is a did not chop up the mount, instead I bought a EF mount replacement part from fleabay that screwed on perfectly. It it well built and has given me no issues.

That's very interesting. Over in the Adapted Lens forum, Tom Caldwell did a similar replacement to mount the EF-S 55-250 IS STM on a focal reducer for M43. The EF-S extension back towards the sensor interferes with the optics in the focal reducer, just as it does in most extenders. However, he had problems with it being a very tight fit. Can you share the listing on Ebay? Perhaps there are some which are less tight? Or perhaps it's just a different fit between the extender and focal reducer?

Regards,

Alan

As for the Kenko adapter, taking the chip out so it would work with the lens proved to be fun and games but in the end everything came together and works with not problems. Of course the information about the lens F stop and focal length is not correct but that does not bother me

I use the Kenko "1.4x Teleplus HD DGX" extender, released in 2015, which has a simple optical design (3 elements in 2 groups) but is mechanically compatible with EF-S and has no problems with EXIF or AF.

Larry, and I presume everyone else, uses the older Kenko "1.5X Teleplus AF SHQ" extender, perhaps released at the end of 1990s, which has more complex optical design (5 elements in 4 groups), but requires modifying EF-S lenses and removing the chip to get AF to work. The more complex optical design might well give better sharpness, especially towards the field edge.

There is also a Kenko "1.4x Teleplus HD Pro DGX" extender — note the additional "Pro". This again uses a more complex design (5 elements in 4 groups) and will require modifying EF-S lenses. My understanding is that the "DGX" refers to the electronics. So, I wonder if the EXIF and AF will work without remove the chip, as it does in my DGX adapter, and perhaps give better results because of the more complex optical design? Unfortunately, the extender costs about $250.

I further note that there are other Kenko extenders after the SHQ but before the latest versions which are cheaper but which also appear to have the DGX brand, such as the "TELEPLUS Pro 300 DGX" (unknown optics) and "TELEPLUS MC4 DGX " (4 elements in 4 groups), both for about $70 used at KEH. I wonder if these might be a good compromise?

Regards,

Alan

I sourced a low-profile rear baffle replacement part from eBay, and swapping it out was straightforward and took about ten minutes from start to finish. I believe I posted about it in this forum a couple of years ago. As I recall, it works with my Kenko Teleplus Pro 300, a 1.4x teleconverter, as well as a Viltrox speedbooster.

The part is still available on eBay now, for $32:

https://www.ebay.com/itm/273820970279?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=pP7pZlLuR6u&sssrc=2349624&ssuid=DsRZ8vpWRJ-&var=&widget_ver=artemis&media=COPY

JasonS70 wrote:

I bought the 1.5x SHQ one as Larry reported it didn't have a great affect on the image quality. I had previously bought and tried the Kenko 1.4x one you use but really did not like the results it gave, it was used with a EF 70-300mm USM lens though, which I was not happy with in itself so that may have been the issue.

Are you referring to the 75-300 USM or the 70-300 IS USM?

Regards,

Alan

JasonS70 wrote:

Well I finally managed to be in a position to take a couple of direct comparison photos of a bird, one with the converter one without. I had a very accommodating Kestrel hang around for me

I am redrawing my conclusion that there is isn't much of a difference in image quality between converter and non-converter photos. There is a clear difference, to the negative, when using the teleconverter. So for me it is going to be shelved and I will go back to relying on cropping

Both photos are straight from DPP with the same edits and are full size

Cheers

Jason

Teleconverter

No teleconverter

Thanks for sharing your results. There are several factors that can explain why you're seeing results that are not as good as what I typically get.

The shots are taken at f8, which is a little beyond the diffraction limit of the 24 MP sensor. If the chip from the TC was removed and the TC shot was really at f11 (f8 setting + 1 stop unreported loss from the TC) then it would most definitely look soft like that. From the exposure data alone, the TC shot appears to have had over a stop more exposure, yet looks darker, indicating it may have been shot at f11 since the lighting looks almost the same.

DPP will do a pretty good job for the raw EF-S 55-250 IS STM, but won't have the corrections right for the 55-250 + a teleconverter which needs different lens corrections, including a bit more CA correction. if you're comparing both images using the same set of DPP corrections, or if DPP didn't know what the lens + TC combo was and didn't use corrections, that could also explain why your TC shots don't look as good.

I've found that you can manually correct the TC images very nicely using DxO PL5, on top of the EF-S 55=250 optical corrections DxO has for that lens. TC images need a custom CA correction and also specific sharpening settings. Also in general DxO's de-mosaicing seems better that DPP 4.

Your comparison uses different focal lengths of the EF-S 55-250 to simulate the same final image size, so it's not really an apples to apples comparison. The performance of the 55-250 mm, or perhaps your copy, may be worse optically at the focal length used for the TC shot vs the one used for the non-TC shot.

The non-TC shot has the bird larger at the pixel level than it is in the TC shot, so it will show more detail since it is a more magnified, this will make the non-TC picture appear sharper since it can show slightly more fine detail in the feathers and branches.

JasonS70 wrote:

I am redrawing my conclusion that there is isn't much of a difference in image quality between converter and non-converter photos. There is a clear difference, to the negative, when using the teleconverter. So for me it is going to be shelved and I will go back to relying on cropping

I don't think you did the test very well.  There is evidence of camera motion or subject motion with the teleconverter.  Look at the reflection of the sun in the eye.

Second, you used different conditions for the two lenses.  For example, you used a longer exposure time with the TC, and this may be one reason for the motion.

I would use a static test target on a sturdy tripod.  For an even comparison you should use exactly the same lens aperture and shutter speed, except double the ISO setting with the TC to compensate for the difference in exposure.  That's how you are going to use the lens, after all -- probably wide open in most cases.  When I say the same aperture, I mean the same aperture diameter.  If you removed the electronics from the TC, that means the same f stop setting.