HOWTO: Infinite Focus Adjustment for NEX Lens Turbo II

Started Apr 10, 2016 | Discussions
PkmX Junior Member • Posts: 38
HOWTO: Infinite Focus Adjustment for NEX Lens Turbo II
1

Since I got my FD-NEX Lens Turbo II, I've noticed that it isn't able to focus some of my lenses (particularly wide-angle ones) to infinity. That wasn't a big deal as stopping down to f/8~11 gains enough DoF to make far away objects in focus, so I never got around to fix the problem. Unfortunately, it wasn't the case for my Tamron SP 35-80/2.8-3.8. At 35mm, even after stopping down to f/16, far objects are still very well out of focus. (Interestingly, the infinity mark is quite spot on at 80mm.) My guess is that stacking two adapters accumulates way too much error on the registration distance.

I searched around the web and found no information about adjusting infinity focus on the LT II. AFAIK Metabones SBs have screws that allow users to fine tune the focus, but there isn't anything like that on the Lens Turbo II. So I decided to open it up and try to fix the problem by myself while documenting the process, and it turned out to be much easier than I thought.

First you need to unscrew 3 screws on the E-mount side. Take note of the orientation of the mount as you need to assemble it back in the right way later.

The mount is glued on the adapter. You can separate it by lifting the tab that hides the lens release button.

The open-lock ring is also glued; there are no screws to hold it in place. Separating it also pops off a rubber piece that protects the rear element.

This silver ring here can be turned to adjust the position of the optics. In my case, it was actually quite loose and I had to tighten it up completely in order to achieve infinity focus. Also note that you can't just leave the rear element in arbitrary orientation as it has to line up with the rectangle inside the mount. This kinda limits the precision of adjustment you have. I suppose turning the ring the other way will separate the elements, but I didn't investigate further since this is all I needed.

Finally, assemble everything back together, check focus with the distance scale and repeat adjustments if needed. After tightening up the rear element, all my lenses can now actually focus a little bit past infinity, which is fine for me and I'm willing to sacrifice a little MFD for that.

Hopefully this will help someone in the future as I wasn't able to find much info about this on the web.

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Tom Caldwell MOD Forum Pro • Posts: 30,278
Re: HOWTO: Infinite Focus Adjustment for NEX Lens Turbo II

Thanks for the Howto.  At one stage the adjustment was even easier and the "other'" manufacturers cheekily used to refer queries on this subject  to the "Howto" on the Metabones site.

Gluing parts in place is a nuisance problem but probably designed to frustrate bumblers fiddling with an adjustment and making things worse before screaming outrage about a deficient product and asking for their money back.

Luckily all my focal reduction adapters (from several brands) seem to have been properly adjusted out of the box as they were delivered.

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Tom Caldwell

bigley Ling Veteran Member • Posts: 3,475
Re: HOWTO: Infinite Focus Adjustment for NEX Lens Turbo II

The Metabones speed boosters all have a user accessible locking screw, that can be loosened, from which the lens element is free to be adjusted back and forth on a lens thread for infinite calibration. Afterward, a simple tighten of the locking screw and the speedbooster is ready for use. No glue or glue separation required.

ProfHankD
ProfHankD Veteran Member • Posts: 4,890
Re: HOWTO: Infinite Focus Adjustment for NEX Lens Turbo II

Nice little tutorial, kind of scary little focal reducer on the inside....

I have to say that overall, I prefer my original Lens Turbo to my II version. I understand that the clipped rear element and E-mounting without rotation of the adapter (essentially a breech lock) do allow them to get a little deeper into the E mount without risk of hitting anything, but clipped elements are never really a good idea. The Speed Boosters actually get a wider view angle without such evil mechanics, so it is possible... although I suspect the SB might be using more exotic glass to work that magic....

My primary issue with the LTII: it clips such that you can't get close to a full-height square image out of it on a FF sensor.  Yup; I sometimes use focal reducers on FF to get different aspect ratio crops with the full view angle.  

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bigley Ling Veteran Member • Posts: 3,475
Re: HOWTO: Infinite Focus Adjustment for NEX Lens Turbo II

ProfHankD wrote:

Nice little tutorial, kind of scary little focal reducer on the inside....

I have to say that overall, I prefer my original Lens Turbo to my II version. I understand that the clipped rear element and E-mounting without rotation of the adapter (essentially a breech lock) do allow them to get a little deeper into the E mount without risk of hitting anything, but clipped elements are never really a good idea. The Speed Boosters actually get a wider view angle without such evil mechanics, so it is possible... although I suspect the SB might be using more exotic glass to work that magic....

My primary issue with the LTII: it clips such that you can't get close to a full-height square image out of it on a FF sensor. Yup; I sometimes use focal reducers on FF to get different aspect ratio crops with the full view angle.

Didn't the LT version 1 had the blue dot issue with certain lenses? Also the performance of the LT2 with lenses wide open is known to produce higher quality especially towards the edges and sides.

ProfHankD
ProfHankD Veteran Member • Posts: 4,890
Re: HOWTO: Infinite Focus Adjustment for NEX Lens Turbo II

bigley Ling wrote:

Didn't the LT version 1 had the blue dot issue with certain lenses? Also the performance of the LT2 with lenses wide open is known to produce higher quality especially towards the edges and sides.

The blue dot problem is rarely an issue.

Optically, the LTII is a touch better (in fact, arguably a touch better than the Speed Booster Ultra), but, as I said, it actually isn't useful at all for getting different aspect ratios using a FF sensor. I evaluated all three in this research paper (along with use of teleconverters as APS-C->FF converters), and they're all competitive overall.

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bigley Ling Veteran Member • Posts: 3,475
Re: HOWTO: Infinite Focus Adjustment for NEX Lens Turbo II

ProfHankD wrote:

bigley Ling wrote:

Didn't the LT version 1 had the blue dot issue with certain lenses? Also the performance of the LT2 with lenses wide open is known to produce higher quality especially towards the edges and sides.

The blue dot problem is rarely an issue.

Optically, the LTII is a touch better (in fact, arguably a touch better than the Speed Booster Ultra), but, as I said, it actually isn't useful at all for getting different aspect ratios using a FF sensor. I evaluated all three in this research paper (along with use of teleconverters as APS-C->FF converters), and they're all competitive overall.

Will have to have a read of your research paper sometime ;). Thanks for the link. Noticed alot of posts and comparisons for different speed reducer adapters put emphasis on the corner performance. From image crops, the LT2 does seem to perform alot better in it's native aspect ratio than it's predecessor the LT1, but if one compares the center, the difference is less.

Tons o Glass 0 Class
Tons o Glass 0 Class Regular Member • Posts: 197
Re: HOWTO: Infinite Focus Adjustment for NEX Lens Turbo II
1

Sorry to resurrect an old-ish thread, but I have a couple of questions you or others who've adjusted these may be able to answer. I was lucky enough to get one of these MD to LT II reducers for a great price ($49.99 shipped, 0$ with an eBay coupon I earned [woooo!]) a few days ago - I really like what I see so far! However, I have rear element collisions with some of my lenses (confirmed via this list I discovered shortly after observing a collision), and my rear element is a little crooked.  I may try a disassembly and reassembly to at least realign the rear element, but if infinity could be improved or if rear element collisions could be reduced, that'd be great.

PkmX wrote:

Since I got my FD-NEX Lens Turbo II, I've noticed that it isn't able to focus some of my lenses (particularly wide-angle ones) to infinity. That wasn't a big deal as stopping down to f/8~11 gains enough DoF to make far away objects in focus, so I never got around to fix the problem. Unfortunately, it wasn't the case for my Tamron SP 35-80/2.8-3.8. At 35mm, even after stopping down to f/16, far objects are still very well out of focus. (Interestingly, the infinity mark is quite spot on at 80mm.) My guess is that stacking two adapters accumulates way too much error on the registration distance.

I searched around the web and found no information about adjusting infinity focus on the LT II. AFAIK Metabones SBs have screws that allow users to fine tune the focus, but there isn't anything like that on the Lens Turbo II. So I decided to open it up and try to fix the problem by myself while documenting the process, and it turned out to be much easier than I thought.

First you need to unscrew 3 screws on the E-mount side. Take note of the orientation of the mount as you need to assemble it back in the right way later.

The mount is glued on the adapter. You can separate it by lifting the tab that hides the lens release button.

The open-lock ring is also glued; there are no screws to hold it in place. Separating it also pops off a rubber piece that protects the rear element.

This silver ring here can be turned to adjust the position of the optics. In my case, it was actually quite loose and I had to tighten it up completely in order to achieve infinity focus. Also note that you can't just leave the rear element in arbitrary orientation as it has to line up with the rectangle inside the mount. This kinda limits the precision of adjustment you have. I suppose turning the ring the other way will separate the elements, but I didn't investigate further since this is all I needed.

In which direction did you have to shift the optics to correct infinity focus (towards the lens, or towards the camera)?

Does tightening this ring shift the entire optical assembly, or just the rear portion?

  • If entire assembly: Did shifting the optics exacerbate rear element collisions with the wide angles you were adjusting it for, or for any other lenses for that matter?
  • If rear portion: Did you notice any aberrations introduced after expanding/compressing the optical assembly?

Finally, assemble everything back together, check focus with the distance scale and repeat adjustments if needed. After tightening up the rear element, all my lenses can now actually focus a little bit past infinity, which is fine for me and I'm willing to sacrifice a little MFD for that.

Hopefully this will help someone in the future as I wasn't able to find much info about this on the web.

Thanks for posting!  This thread will be very helpful if/when I decide to pop mine open.

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