Lens adapter focus

[klompen914]

Thank you for this explanation. As soon as I can figure out why my systems won't allow me to give a thumbs-up, I'll be returning to add that. You rock!

[xpatUSA]

I would disagree, especially in the case of a SLR lens used on a mirrorless camera. [Registration 101 snipped]

In that case -and with it being so easy- it would appear that the OP has simply bought a bad adapter.

If you look at

[klompen914]

That was my conclusion. The purpose of the original question was to avoid that again. With the NEX-6, the solution eventually turned into the Metabones Speedbooster adapter - $$$, but worth it for the results that I got. Fortunately, the solution in this case is probably about $170. I can handle that!

[dje]

Thank you for this explanation. As soon as I can figure out why my systems won't allow me to give a thumbs-up, I'll be returning to add that. You rock!

Ernie I'm not sure about this but I have a feeling you have to have 10 posts up before you have access to the thumbs up button.
Dave

[xpatUSA]

What I am after is an adapter where infinity on the lens is infinity focus without any need of adjustment. Is there a full-frame adapter that will do this?

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lots of discussion ...
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it would appear that the OP has simply bought a bad adapter.

That was my conclusion. The purpose of the original question was to avoid that again.

Now it is clear, thanks Ernie.

[klompen914]

Thanks! This is my 10th post, so we'll see what happens. I really want to be able to recognize those who have been so helpful on this.

[William W]

Originally Posted by xpatUSA
finding an adapter that is focused exactly at infinity when your lens hits the stop under all conditions is a tall order

I would disagree, especially in the case of a SLR lens used on a mirrorless camera.

The adapter serves two purposes; allows a lens from one manufacturer to be used on a camera with a different lens mount and to provide the correct flange to sensor distance, which ensure focus at infinity for the old manual focus lenses with a hard stop at infinity.

Looking at the Canon FD mount, these have a 42.0mm flange focal distance whereas the Sony E mount has an 18.0 mm flange focal distance, so the adapter needs to make up for this 24.0mm difference. Not at all hard to do, as long as the manufacturer works at a high enough tolerance. I suspect that we are looking at a manufacturing tolerance of ±0.05mm or ±0.002".

IMO both Ted and Manfred are correct, however the point as to how easy an exact 24mm tube can be made, misses the point.

In theory the adapter needs to make up exactly 24mm difference and sure it is relatively easy to tool and manufacture a tube adapter to those tolerances Manfred mentioned.

Please refer to Post#4 Point #2.

WW

[William W]

On my 200mm lens, with the adapter that I have, when I focus the lens to infinity the focus mark is at about 100 ft/30 m. So the infinity mark has "moved past" the marker where I want it to stop.

I understand, thank you.

At infinity this is no big deal, but at other distances the f-stop marks are now useless. Even though I have focus peaking and can see focus on the screen, I still use those marks for a rough-cut idea of where I want to be. So the bottom line for me is that I want to use an adapter AND have the infinity mark line up where it is supposed to be.

I understand, this is the crux of your concerns, thank you.

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(extract from the OP)

. . . The tube type adapters I have tried are not calibrated so that infinity matches up. I am intrigued by the Fotodiox Pro Lens Mount Adapter because it mentions "guaranteed infinity focus", but I have seen some things about "focus past infinity" so I wonder if "guaranteed infinity focus" is what I want or if it is something else.

My position and my opinion have not changed.

I refer you to my Post #4 , Point #2.

I believe that you will find it a difficult task buying exactly what you want: I hope you do, but I have not found such an adapter, for FD and nFD Lenses.

I have not used the particular Fotodiox Pro Lens Mount Adapter you mention, because I do not have Sony Cameras, but I am familiar with FD and nFD Lens Mount adapters with no optical elements, i.e. what you refer to a "tube adapters".

As far as I am aware no manufactures' "tube adapter" allow for the calibration you want. Some adapters with optics, like the Metabones "Speed Booster" have that feature.

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The salient points are:

> considering that the lens adapter manufactures are making a precision instrument to mount to a old (read possibly worn and or skewed) Breech Mount Lens, they can ‘guarantee’ the user will attain infinity focus if they ensure that the Lens Adapter is slightly shorter than the technically correct additional Flange Distance which is required.

> Note (I think this point has being missed several times), the guarantee of “infinity Focus” does not mean the lens will be 'focused at infinity' when the line on the lens barrel aligns exactly with the middle of the infinity mark on the Focus Turret: The guarantee is simply that you are able to focus the lens to infinity.

> as I have previously mentioned, there is little real world impact in the focus at infinity being short of the infinity mark lining up on the lens barrel, except for a possible curvature of field when using some fast normal to W/A lenses. In your situation: I think, if the adapter is exceptionally short, you might have an issue with your 35/2 depending upon the generation of that lens, (there are several). Even though the 28 is wider, you probably will have less likelihood of an issue because (of the design of) this (slower) F/2.8 lens. Additionally, I think that your 50/1.4 will show no Curvature of Field.

***

Those points stated, it is understood that you want, what you want. Noted also, you might find that (with detailed interrogation) an adapter might perfectly conform to your requirements with one or several lenses, but not all of them.

Anyway - in the event that you cannot get an adapter(s) to suit your exact requirements for each of your lenses, then if you want to make a work around, my suggestions are:

> you must ensure the adapter you buy is slightly short (which as I have mentioned, many are).

> as previously mentioned, you can make a shim and insert that shim on the lens side of the adapter. Typically, I have found this fix is made by using a shim between 0.25mm and 1.25mm thick, depending upon the lens and the adapter being used. Aluminium Foil (i.e the stuff used in kitchens for cooking) makes a simple shim, though, the layers seem to compress with several on/off lens mountings. Consider choosing to buy several cheap adapters, one for each lens and leave them on once you have each smim's thickness perfect for each of your lenses.

2. as previously mentioned, you can reset/move the Lens's Focus Turret’s hard stop (if available), by releasing the locking screw, re-setting the turret and re-securing the locking screw. If the lens has an Hard Stop Locking screw, it is located under the Focus Turret’s rubber grip, which needs to be removed first, to access the recessed hole where you will see the locking screw. If you do this, do not remove the locking screw, just loosen it ¼ turn and re-set the lens's Focus Turret to the new required position.

3. Upon pondering your concerns over this last weekend, I think that the following is a practical cheap and the least invasive option: use (one) adapter for all your lenses and re-label each lens's Focus Turret with an overlay. I’ve use this method for Zone Focusing and Pre Set Focusing using marker points, but there is no reason it could not be adapted to simply re label the distance indicators. I use ‘painters’ tape’ that is the tape painters use to cut in around windows etc, it sticks but can be removed without residue.

***

Notwithstanding all of the above, I still stand by my original statement in Post #4 Point #5, to my mind this concern and the remedy for this concern will matter very little at all in the outcomes of real world photography, so, if you can’t buy, off the shelf what you want, consider not worrying about it at all and simply reform the processes/techniques that you use: as previously mentioned, my bold now for emphasis:

“The markings on a lens’s focus turret are spectacularly inefficient for accuracy and if one has (quality/premium) lenses which allow focus beyond infinity, then use that facility to accommodate precise focus, using focus peaking.”

WW