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Adjusting infinity focus on Alpa lenses

E

epforever

Member
One of my Alpa lenses isn't focusing at infinity when set at infinity, and I'd like to adjust it. Shimming won't help; it's focusing slightly closer than infinity, so shimming would only make it focus even closer. And my adapter is already nicely shimmed for my other lens.

I've seen past threads about how to do this (loosen the screws, turn the ribbed focusing ring for accurate focus, then tighten the screws), but those threads are for Cambo lenses. I messaged one of the original posters, and he confirmed that Cambo helicals are different from Alpa. On my Alpa lens, once I loosen the three screws in the distance ring, they come out completely, revealing three threaded holes in a round metal ring beneath (just barely visible through the small holes where the three screws were). When I turn the ribbed focusing ring independently, those three holes vanish; they're obviously attached to the ribbed focusing ring. It's no longer possible to re-attach the screws. There's nothing for them to screw into, just a solid brass-looking ring that's attached to the ribbed focusing ring.

Has anyone adjusted their infinity focus on an Alpa lens? Any suggestions?

thanks
ethan
 
B

Ben730

Active member
Ethan
As far as I know are the Alpa and Cambo helicals the same. You also can use the Alpa HPF rings on both systems.

Try to find the wholes of the inner ring. To find them precise you can use a needle and good light. The first screw will be easy to turn in again, but you need the right screwdriver. The third needs some pressure. When all three screws are in, loosen them only a bit. These screws are very short. Three turns are normally more than enough.
Then turn the ribbed focusing ring for accurate focus, then tighten the screws.....
Hope that helps.
Regards,
Ben
 
E

epforever

Member
Ben730 said:
Ethan
As far as I know are the Alpa and Cambo helicals the same. You also can use the Alpa HPF rings on both systems.

Try to find the wholes of the inner ring. To find them precise you can use a needle and good light. The first screw will be easy to turn in again, but you need the right screwdriver. The third needs some pressure. When all three screws are in, loosen them only a bit. These screws are very short. Three turns are normally more than enough.
Then turn the ribbed focusing ring for accurate focus, then tighten the screws.....
Hope that helps.
Regards,
Ben
Click to expand...
Ben -- thanks for the reply. See attached image. Do you mean these three screws? Or something else? I have tried removing these three screws, and it is like I described: when I remove them and rotate the ribbed focusing ring (separately from the ring with distance markings), the holes for the three screws disappear. They rotate away. Underneath the holes on the surface of the distance ring, there are second holes that the screws go into. Those second holes rotate away. Hope that is clear.

Let me know if it is something else that you are doing. Thanks again.

Alpa_schneider_lens_diagram_1000px.jpg
 
Pemihan

Pemihan

Well-known member
Ben730 said:
Yes these 3 screws. Don't remove them, only loosen them.
Regards,
Ben
Click to expand...
What Ben says. The first time I did it with my Cambo 40HR I too removed the screws and experienced exactly the same as you did Ethan. As Ben says don't remove the screws, only loosen them.
 
V

vjbelle

Well-known member
Ben.... the three screws you are referring to are the correct screws. I've had to adjust the infinity stops on most of my lenses with the only one not being adjustable being the 150mm which uses a different helical. Some of the rings are hard to move and I found that turning the lens to the stop (close or far depending on the adjustment need) helps as the stop allows only the outer ring to move.

Victor
 
V

vjbelle

Well-known member
I sure did mean 'Ethan'.....:salute:

To slightly expand on this...... as I mentioned the longer lenses (150 - 210mm) use a Linhof helical and are not user adjustable. I used that lens (150mm in my case) to adjust the back for infinity focus and then all other lenses would be adjusted to it by setting the infinity stops. Worked out very well for me but is totally moot now as there is no need for any of this with the newer CMOS backs. Now I advise to shim so that all lenses focus beyond infinity and always focus with live view at 100%.

Victor
 
N

narikin

New member
Can you describe the process a bit more for those of us who are not familiar, and never done it.
The basic steps would be useful

Which holes/screws are you revealing?
You turn the screws *in* to loosen them?! normally its out to unscrew, so this sounds odd.

thanks
 
Pemihan

Pemihan

Well-known member
Take a look here:

https://www.getdpi.com/forum/medium...acks/33610-cambo-sk-35mm-lens-adjustment.html

Also I copied this instruction a while back:

The focus ring consists of two rings (please see attachment): the ribbed ring that actually drives the helical focus and a second ring that shows the distance indication. Ring #2 locks ring #1 at infinity.
Just loosen the 3 screws on ring #2 and you can focus beyond the infinity lock.

procedure:
- tether
- center the lens (resp. the back)
- point the camera to a subject at infinity. For the 72mm lens a subject at 70 meters (for every lens the focal length in meters is a good reference, so 28 meters for 28mm lens, 50 meters for the 47XL and so on); it's very helpful if the motif also contains clear distinguishable elements nearer and farer than your 70 meters spot (for instance a row of houses shot from an appropriate angle is perfect) so that you can clearly see where the actual focus spot is
- shoot wide open, set C1 to sharpening preset "version 3 soft look" (or something smooth) and vary the focus distance until infinity is sharp (i.e. tack sharp from 70meters and further)
- when you've adjusted the accurate focus setting carefully turn ring #2 back so that it locks at infinity
- tighten the 3 screws
… done. Takes you half an hour or so when you do it for the first time and maybe 15 minutes for the next lenses.
This is the first thing I do with every new lens… even very little adjustments may improve sharpness at infintiy significantly.
 
B

Ben730

Active member
vjbelle said:
I
Now I advise to shim so that all lenses focus beyond infinity and always focus with live view at 100%.
Click to expand...
I shimed all lenses beyond infinity and mounted an Alpa HPFRing exactly at infinity. So I stay flexible when I have to use another digiback.
The distance to the sensor is with my Hasselblad V adapter plate of Cambo closer than with my Phase plate.....


Pemihan said:
This is the first thing I do with every new lens… even very little adjustments may improve sharpness at infintiy significantly.
Click to expand...
:thumbup:

That's also my experience. Everybody should do that to get best performance.
When I hear/read of weak Schneider digitars and Rodenstock HRs I think miss adjustment is more often the reason than sample variation.
Regards,
Ben
 
Y

yatlee

Member
Pemihan said:
Take a look here:

https://www.getdpi.com/forum/medium...acks/33610-cambo-sk-35mm-lens-adjustment.html

Also I copied this instruction a while back:

The focus ring consists of two rings (please see attachment): the ribbed ring that actually drives the helical focus and a second ring that shows the distance indication. Ring #2 locks ring #1 at infinity.
Just loosen the 3 screws on ring #2 and you can focus beyond the infinity lock.

procedure:
- tether
- center the lens (resp. the back)
- point the camera to a subject at infinity. For the 72mm lens a subject at 70 meters (for every lens the focal length in meters is a good reference, so 28 meters for 28mm lens, 50 meters for the 47XL and so on); it's very helpful if the motif also contains clear distinguishable elements nearer and farer than your 70 meters spot (for instance a row of houses shot from an appropriate angle is perfect) so that you can clearly see where the actual focus spot is
- shoot wide open, set C1 to sharpening preset "version 3 soft look" (or something smooth) and vary the focus distance until infinity is sharp (i.e. tack sharp from 70meters and further)
- when you've adjusted the accurate focus setting carefully turn ring #2 back so that it locks at infinity
- tighten the 3 screws
… done. Takes you half an hour or so when you do it for the first time and maybe 15 minutes for the next lenses.
This is the first thing I do with every new lens… even very little adjustments may improve sharpness at infintiy significantly.
Click to expand...
Thanks Peter. Good instruction. One thing I would add, lens should be wide open while adjusting. So, it's not affect by depth of field when lens is stopped down.
 
V

vjbelle

Well-known member
narikin said:
Can you describe the process a bit more for those of us who are not familiar, and never done it.
The basic steps would be useful

Which holes/screws are you revealing?
You turn the screws *in* to loosen them?! normally its out to unscrew, so this sounds odd.

thanks
Click to expand...
You are not revealing anything. The three screws shown in the drawing are the correct screws and should 'JUST' be loosened (counter clockwise) about one turn each. Needless to say do not lose any of these screws. The outer scaled ring is now not in contact with the inner helical and can move in either direction to adjust the infinity stop. As I mentioned previously if you are using a CMOS back then I would not recommend any of this but instead shim so that ALL lenses focus beyond infinity and trust your eyes at 100% pixels for focus (with a loupe).

Victor
 
K

kinglang

Active member
Who knows how to adjust this kind of long barrel lens to infinity? Focus ring is different from wide-angle lens.
LUX_0926-940x730.jpg
 
dchew

dchew

Well-known member
That is the Linhof helical Victor was referring to above. I could not find a way to adjust it without going into disassembly that made even me uncomfortable. 🥵

I just shimmed to that lens and adjusted others to match. Or, as Victor suggested with CMOS backs, you can over compensate to your closest front-focusing lens and use LV.
Dave
 
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