How accurate does an adapter have to be?

[Cap'n Bill]

I have just bought a tilt adapter (Nikon to Sony E), I only bought the adapter because it was about the only dumb adapter with a tripod foot. It works well enough but doesn't have a defined zero point at which the adapter has no tilt. I have tried setting it by eye aided by gravity, letting the lens hang vertically down then locking it, but measurements suggest it is often 1,0-0,5mm out of true.
How significant do you think this is? I have fixed (non tilt) adapters and out of alignment is <0.01mm generally.

Weather and time have prevented me from testing it photographically and I can see uses for the tilt function but wonder how usable it is for general purposes.

 

[HoppyUK]

Camera/tripod, frame something up and note what's under the centre AF point. Lock tripod. Fit the adapter and move the lens so the centre AF point is over the exact same subject.

 

[Cap'n Bill]

That's helpful. I'll try it tomorrow if time permits. Thanks.
I can foresee problems though in that the change of lens and adapters may move even my steadiest tripod head slightly, we are talking quite small differences here.

 

[sk66]

1mm (1*) out of alignment is enough to throw the focal plane out of critical alignment... but it might not be enough to be immediately obvious.

 

[AJQS]

What's not aligning? I'm struggling to understand this, is the tripod mount not a solid part of the adapter?

 

[HoppyUK]

1mm (1*) out of alignment is enough to throw the focal plane out of critical alignment... but it might not be enough to be immediately obvious.

1mm is quite an error, but how noticeable it is depends on depth-of-focus (not field). Long lenses have generous depth-of-focus, so less noticeable, but wide-angles, particularly at low f/numbers, have very, very shallow depth-of focus - like small fractions of a mm.

ps I was once told about a puzzle that Leica had with early versions of their 50mm f/1.0 Noctilux. There were curious and inconsistent out of focus areas, that turned out to be a film related problem. When the film was held in the jaws of the cassette overnight, it developed a very slight kink and wouldn't lie dead flat. When that piece of film was advanced to the frame, depth-of-focus at f/1.0 wasn't enough!

 

[HoppyUK]

That's helpful. I'll try it tomorrow if time permits. Thanks.
I can foresee problems though in that the change of lens and adapters may move even my steadiest tripod head slightly, we are talking quite small differences here.

You must not move the camera at all. Don't touch it! But with that achieved, the centre of the image will always be in exactly the same place, regardless of lens/focal length/adapter etc.

 

[pingu666]

actually i remmber reading some canon or nikon crop cameras actually have the sensor off center center of the lens, think to make the camera smaller

 

[Cap'n Bill]

What's not aligning? I'm struggling to understand this, is the tripod mount not a solid part of the adapter?

The adapter is a sort of ball and socket joint with a locking ring. Allows about 8 degrees swivel in any direction and rotation.Tripod foot is on the lens section, the camera is supported by the rear section of the adapter on the other side of the joint.. The problem is lack of any reference for alignment so getting it straight for normal use is well nigh impossible.

HoppyUK's solution is good in principle but to do it the camera and lens would have to be aligned with a good rigid adapter, the lens and good adaptor then removed and replaced by the lens and tilt adapter and the adapter aligned and locked in position. I suspect no matter how carefully this is done the camera may move slightly out of position during this operation.

I think I'll just write this off to experience and buy an alternative solution.

 

[sk66]

1mm is quite an error, but how noticeable it is depends on depth-of-focus (not field). Long lenses have generous depth-of-focus, so less noticeable, but wide-angles, particularly at low f/numbers, have very, very shallow depth-of focus - like small fractions of a mm.

I seldom use more than 3* (3mm) on my 24 PC-E...

I think I'll just write this off to experience and buy an alternative solution

I would probably keep it for tilt work, but it doesn't sound like it suits your intended purpose...

 

[Canon Bob]

I seldom use more than 3* (3mm) on my 24 PC-E...

Which implies that you seldom shoot from lower than 50cm. If you got down amongst the daisies then you'd need 7 or 8 degrees of tilt.

Bob

 

[sk66]

Which implies that you seldom shoot from lower than 50cm. If you got down amongst the daisies then you'd need 7 or 8 degrees of tilt.

Bob

I don't tend to use it for landscape type stuff. Mostly product work and the "thin slice" characteristic has to be heavily controlled... Often stacking is "better" than tilt for that kind of stuff (when it gets that close/small).

 

[Cap'n Bill]

I think you are right, Keep it for occasional tilt work. However, until I get another adapter with tripod foot or find a tripod collar of suitable diameter it will have to serve. I decided to remember a few engineering basics so used a surface plate and digital depth gauge to align it. Eventually got the flanges locked within under 0.1mm parallel. Very frustrating job because the act of tightening the locking ring moved the joint slightly each time.

While I had the gauge set up I checked a couple of other adapters. The worst was my Hawkes Factory Leica M to Sony E helicoid at 0.04mm out of true. All the other adapters were within 0.02 which is pretty good as they are all ebay cheapies.

 

[AJQS]

The adapter is a sort of ball and socket joint with a locking ring. Allows about 8 degrees swivel in any direction and rotation.Tripod foot is on the lens section, the camera is supported by the rear section of the adapter on the other side of the joint.. The problem is lack of any reference for alignment so getting it straight for normal use is well nigh impossible.

HoppyUK's solution is good in principle but to do it the camera and lens would have to be aligned with a good rigid adapter, the lens and good adaptor then removed and replaced by the lens and tilt adapter and the adapter aligned and locked in position. I suspect no matter how carefully this is done the camera may move slightly out of position during this operation.

I think I'll just write this off to experience and buy an alternative solution.

Oh I see, it's a tilt adapter. These are only meant for 'experimental' type shots for those who'd use a lensbaby, they are not meant to be serious precision tools, as I think you've probably gathered. I used this myself:

http://www.metabones.com/products/details/MB_NFG-E-BM1