Pages: [1] 2   Go Down

Author Topic: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!  (Read 1398 times)

Shiftworker

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 62

I've got a selection of adapters (3 metabones of various mk's and a Sigma MC-11)  in various thicknesses as measured using a digital caliper and  engineering surface plate and dial indicator contest paralellism. The thinnest is 25.75mm and the thickest is 26.1mm. After testing them all with the camera straight on to a large building facade I can tell you that if you want optimally sharp corners and edges esp on 17mm then the closer your adapter thickness is to the correct 26mm the better - even 0.1mm over or under is visible on critical inspection. Get the Sigma - it's the correct thickness, it's got better parallelism between the faces and it's a lot cheaper.
Logged

free1000

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 463
    • http://www.foliobook.mobi
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #1 on: August 07, 2019, 10:33:36 am »

Some sample files would be highly welcome if you can take the time to share
Logged
@foliobook
Foliobook professional photo

JaapD

  • Full Member
  • ***
  • Offline Offline
  • Posts: 239
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #2 on: August 08, 2019, 01:41:23 am »

My understanding is that the thickness only affects the focusing range, i.e. not being able to focus at infinity. Think about the function of macro extension tubes.

Regards,
Jaap.
Logged

free1000

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 463
    • http://www.foliobook.mobi
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #3 on: August 08, 2019, 04:51:01 am »

My understanding is that the thickness only affects the focusing range, i.e. not being able to focus at infinity. Think about the function of macro extension tubes.

Regards,
Jaap.

That seems right to me also.
Logged
@foliobook
Foliobook professional photo

Shiftworker

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 62
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #4 on: August 08, 2019, 05:21:46 am »

Lens designs that move parts of the optical group in relation to each other to achieve focus (so-called floating elements) require precise positioning in relation to the focal plane for optimal performance.
Logged

mcbroomf

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 949
    • Mike Broomfield
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #5 on: August 08, 2019, 09:03:16 am »

My understanding is that the thickness only affects the focusing range, i.e. not being able to focus at infinity. Think about the function of macro extension tubes.

Regards,
Jaap.

As Shiftworker wrote this isn't true as internal focusing of elements affect the final result if the correct flange distance is not maintained.  If the lens is unit focusing then that is so and an offset is all that is required.

I found this out like the OP when I bought a 14mm Rokinon SP/XP lens for use on a Sony.  The image was tack sharp into the corners with an MC-11 and just terrible with any of my Metabones adapters, and they all focused well past infinity while the Sigma adapter allowed the lens to focus to infinity just a hair past.  I shimmed all of my Metabones adapters to correct this and use the 17mm and 24mm with them now.

Mike
Logged

Shiftworker

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 62
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #6 on: August 08, 2019, 09:26:42 am »

I suspect Metabones intentionally undersize their adaptors as more customers complain that they can't reach infinity than complain their corners are not sharp enough.
Logged

Frederic_H

  • Full Member
  • ***
  • Offline Offline
  • Posts: 153
    • www.fredericharster.com
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #7 on: August 09, 2019, 06:02:17 am »

Interesting comparison.

Does the Sigma behave the same as the Metabones regarding mechanical vignetting and internal reflections ?

Thanks
Frederic
Logged

free1000

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 463
    • http://www.foliobook.mobi
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #8 on: August 09, 2019, 07:35:37 am »

As Shiftworker wrote this isn't true as internal focusing of elements affect the final result if the correct flange distance is not maintained.  If the lens is unit focusing then that is so and an offset is all that is required.

I found this out like the OP when I bought a 14mm Rokinon SP/XP lens for use on a Sony.  The image was tack sharp into the corners with an MC-11 and just terrible with any of my Metabones adapters, and they all focused well past infinity while the Sigma adapter allowed the lens to focus to infinity just a hair past.  I shimmed all of my Metabones adapters to correct this and use the 17mm and 24mm with them now.

Mike

Very interesting, thanks for the information
Logged
@foliobook
Foliobook professional photo

mcbroomf

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 949
    • Mike Broomfield
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #9 on: August 09, 2019, 08:21:59 am »

Interesting comparison.

Does the Sigma behave the same as the Metabones regarding mechanical vignetting and internal reflections ?

Thanks
Frederic

I'm not sure as I stuck to using the Metabones adapters on my TSE lenses.  I prefer them because I use the RRS L bracket that screws onto the adapter.  It supports the lens and protrudes below the camera L bracket (vertical and horizontal) so that I don't have to remove the camera l bracket.  Also I only have the mk IV Metabones.  They redesigned the mk V to give better performance for TSE lenses (less vignetting).
Logged

Dan Wells

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 981
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #10 on: August 12, 2019, 11:43:00 pm »

Could the Metabones not be quite straight? In addition to the floating lens elements (which could cause the strange behavior, especially in cases where two or more groups of elements move by different amounts), a slightly tilted adapter (as you say, tenths of a millimeter could screw this up) could introduce odd effects - especially if the tilt of the adapter is at a strange angle to the tilt you are deliberately introducing to the lens - there's no reason to assume the adapter's tilted only parallel or perpendicular to the lens tilt axis - it's just as likely to be at 37.963 degrees off axis (or any other random number).

In the world of (related) optical exotica, there were at least a couple of 1990s Zeiss lenses for Hasselblad that had separately adjustable floating groups. Almost always, a lens that has two or more groups moving has them cammed together in some way, so there's only one focus ring. These oddities (at least the 40mm and 50mm CF FLE and various updates) used two focusing rings - the main ring moved all the elements, while a separate FLE ring moved one group in relation to the others.
« Last Edit: August 12, 2019, 11:53:37 pm by Dan Wells »
Logged

Shiftworker

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 62
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #11 on: August 13, 2019, 02:57:22 am »

Could the Metabones not be quite straight? In addition to the floating lens elements (which could cause the strange behavior, especially in cases where two or more groups of elements move by different amounts), a slightly tilted adapter (as you say, tenths of a millimeter could screw this up) could introduce odd effects - especially if the tilt of the adapter is at a strange angle to the tilt you are deliberately introducing to the lens - there's no reason to assume the adapter's tilted only parallel or perpendicular to the lens tilt axis - it's just as likely to be at 37.963 degrees off axis (or any other random number).

In the world of (related) optical exotica, there were at least a couple of 1990s Zeiss lenses for Hasselblad that had separately adjustable floating groups. Almost always, a lens that has two or more groups moving has them cammed together in some way, so there's only one focus ring. These oddities (at least the 40mm and 50mm CF FLE and various updates) used two focusing rings - the main ring moved all the elements, while a separate FLE ring moved one group in relation to the others.
Yes tilt can be a problem too and this is inherent in the TS-E lenses themselves as the mechanism is not that accurate for zeroing the tilt. With the adapters and the TS-E mechanisms I tested these for tilt on my engineering surface palate with a dial indicator which measures in (100th's of a mm) but you can do it yourself by simply rotating the whole lens group via the lens mechanism and looking for changes across the frame. I've got the 50mm FLE which has the floating front element and I use this with a Mirex shift adapter alongside my TS-E lenses. The floating element compensates for field curvature at different focusing distances and it does make a big difference to the resolution at the outer edges of the frame when you don't set it correctly but when set correctly it makes the lens a much better performer than the non FLE version which I used to own. Infact the 50mm FLE is such a good performer that I can't see any reason to upgrade to the new TS-E 50 at the moment which is testament to it's design. Maybe when the A7r4 is my main camera will it finally be retired.
Logged

mcbroomf

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 949
    • Mike Broomfield
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #12 on: August 13, 2019, 04:47:41 am »

Could the Metabones not be quite straight? In addition to the floating lens elements (which could cause the strange behavior, especially in cases where two or more groups of elements move by different amounts), a slightly tilted adapter (as you say, tenths of a millimeter could screw this up) could introduce odd effects - especially if the tilt of the adapter is at a strange angle to the tilt you are deliberately introducing to the lens - there's no reason to assume the adapter's tilted only parallel or perpendicular to the lens tilt axis - it's just as likely to be at 37.963 degrees off axis (or any other random number).

In the world of (related) optical exotica, there were at least a couple of 1990s Zeiss lenses for Hasselblad that had separately adjustable floating groups. Almost always, a lens that has two or more groups moving has them cammed together in some way, so there's only one focus ring. These oddities (at least the 40mm and 50mm CF FLE and various updates) used two focusing rings - the main ring moved all the elements, while a separate FLE ring moved one group in relation to the others.

In my case with the 14mm lens all 4 corners were terrible (I could not even get sharp corners refocusing on them with high mag in the EVF) and I'd been using the Metabones on other lenses without too much of an issue (longer FL probably which seem to be affected less).  After shimming evenly around the adapter they (I did this on 2 of them) were fine with no noticeable issues.
Logged

free1000

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 463
    • http://www.foliobook.mobi
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #13 on: August 13, 2019, 11:54:47 am »

In my case with the 14mm lens all 4 corners were terrible (I could not even get sharp corners refocusing on them with high mag in the EVF) and I'd been using the Metabones on other lenses without too much of an issue (longer FL probably which seem to be affected less).  After shimming evenly around the adapter they (I did this on 2 of them) were fine with no noticeable issues.

What did you use for shimming? Did you make a ring or was it possible just to use segments of a ring in the right places?

I bought some shimming material that was super thin acrylic, that I was using for MF back shimming, it came in a variety of thicknesses.
Logged
@foliobook
Foliobook professional photo

Shiftworker

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 62
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #14 on: August 13, 2019, 01:56:17 pm »

I use feeler gauge for my shims. You can buy large sets on Ebay fairly cheaply and they come in a large range of thicknesses and can be cut fairly easily with some good scissors (the scissors will not last long doing this). It's important to shim the areas around the screws and not those between otherwise the flange can distort when you tighten it down.
Logged

Shiftworker

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 62
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #15 on: August 13, 2019, 02:23:49 pm »

BTW I'm having some problems with the MC-11 on the TS-E's. It's sometimes not showing the aperture, showing the wrong aperture or doing something very weird with the exposure. It may be the contact pins or it may be it's just not 100% compatible with these lenses. I've got the latest FW on the adapter and camera. For all my criticisms of the metabones on the engineering side it's been rock solid on the software and operational side.
Logged

mcbroomf

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 949
    • Mike Broomfield
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #16 on: August 13, 2019, 08:04:42 pm »

I bought a roll of thin stainless shim, so I made pieces.  Feeler gauge is a good idea too. 

I have 3 MC11's and don't have trouble with them, although I don't use them with my 17/24 TSE lenses.
Logged

Denis de Gannes

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 293
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #17 on: August 13, 2019, 09:54:37 pm »

Is this a real discussion? ??? ::) :(
Logged
Equip: iMac (Ret. 5K,27"Mid 2015),macOS 10.14.6

Shiftworker

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 62
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #18 on: August 14, 2019, 01:12:47 am »

Is this a real discussion? ??? ::) :(
Please join in if you have relevant information of value to contribute.
Logged

Shiftworker

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 62
Re: A7r2 + 24 and 17 TS-E lenses - correct adapter thickness is critical!
« Reply #19 on: August 14, 2019, 01:14:28 am »



I have 3 MC11's and don't have trouble with them, although I don't use them with my 17/24 TSE lenses.
That's encouraging. I've got 2 so I'll try the other one.
Logged
Pages: [1] 2   Go Up