Focus Tab for Zeiss Distagon (and other Zeiss ZM?)

krötenblender

krötenblender

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For years I have been switching between my two favourite fast 35mm/f1.4 lenses:
- The Leica Summilux ASPH. FLE and
- the Zeiss Distagon

With neither I was perfectly happy.

The Leica is not only extremely expensive for what it can do, it also delivers a little less perfect image-quality compared to the Zeiss (IMHO) and is a little bit more prone to flare. The Zeiss OTOH can not compete with the weight and the perfect ergonomics of the Leica, which is for me as important as the image quality. Because if I don't like handling a lens, it does not matter, if it gives me better image-quality, because I don't use it. The main reason for the bad ergonomics is the missing focus-tab. I know, many people actually like the typical Zeiss-"bump", but I genuinely hate it. I can focus perfectly and at least twice as fast with the proper focus-tab than with this strange n*pple.

So I switched back and forth multiple times between both lenses, owning them in black and silber both more than once and even in parallel sometimes, but never got quite happy. I searched the whole internet for the proverbial china-man to provide some focus-tab, that can be applied to the Zeiss, to finally have both in one lens: better images quality AND good ergonomics that makes me enjoy using the lens. Never found one. TAAB does not really fit over the bump and makes the lens really ugly... same for other generic tabs).

What do you do, when there is no help in sight after years...? Make your own. I thought of it for quite some time now (I think, since I first time got a Zeiss and immediatly started to hate the bump), but never really tried it. Until...
- I have a short vacation
- I can't really travel right now (at least where I would like to go)
- Family is off visiting other family
- The weather is really bad... :)

So I sat down at my computer, measured some numbers from the Zeiss and started to hack some lines of code into OpenSCAD, an Open Source 3D programm controlled by code not mouse. That fits me more, since I'm a coder.
It took me now about a half work day worth of time to come up with three evolutionary steps, which I printed on my 3d-printer. The last one is now good enough. Finally, I hope, I can settle down to the Zeiss, save some money and lots of switching.

You can see the three versions (left to right) and the linked gallery here.

- The first one was just an experiment, if my measurements were exact enough (they were) and looks a little bit "blocky". Also my index-finger did not fit comfortably.
- The second one is a improved with a wider finger-trough, that is also slightly tilted. A little bit inspired by the Voigtländer-Design af the tabs for the new 35mm f2 Ultron.
- The third one also considers the shape of the enclosed focus-bump better, so ther is no gap between the tab and the bump. Almost perfect...

I slightly sanded the sharp edges of, painted it black (pretty rough, but I consider this version as a test only) and glued it with removable glue to the lens for testing. If it works really good, I will order a Version printed from metal from a commercial service. I can only do PLA.
What do you think?

Update: I tested it now in real use and I love it! I can focus as quickly as with the Summilux or new new Voigtländers and it just feels great. I will definitely get a 3D-printed version (or CNC) made from metal.
attachment.php

If you have the same problem with the Zeiss, want to have the same tab, I'm happy to provide you either the original OpenSCAD-source or the ready-to-print stl-file. Just drop me a message or reply here.
 

Attachments

  • 20210802-22-40-49.jpg
    20210802-22-40-49.jpg
    38.7 KB · Views: 6
I love the "focusing bump" on my Zeiss ZM 35mm and 50mm lenses. I love it just the way it is. I can reach out with my finger, contact the focusing ring; and then I can either focus using the ring, which moves easily with a light touch, or else slide my finger a bit further to the bump. It's enough to make me prefer the ZM lenses just for that alone! It is to me the ideal lens, at least from the ergonomic viewpoint.
 
Good job krötenblender. I also have the 35mm Distagon and don't really get on with the quirky bump. Your solution looks pretty neat to me. You should make a batch of tabs and sell them. If you do, count me in :)
 
As I said, many like it. I have been involved in many discussions about the bump-ergonomics vs. the tab. For me, tab is superior and I skipped several lenses just because of that, although the lenses were very tempting otherwise. For me everything up to 50mm must have a tab. And beyond that, I usually use non-rangefinders.

Anyway: the good thing here is now, that even tab-addicts like me, can really enjoy the spectacular Distagon. :)
 
Monz said:
Good job krötenblender. I also have the 35mm Distagon and don't really get on with the quirky bump. Your solution looks pretty neat to me. You should make a batch of tabs and sell them. If you do, count me in :)
Click to expand...

Thank you very much. No need to buy, if you‘re interested, I can give you the print-data and you can either print it yourself or go to any copy-shop with a decent 3D-printer. Pretty cheap…
 
that looks EXCELLENT!

I would love to get some of those made, if you can also send me the 3D print-data, that would be much appreciated.

I have been using stick-on tabs from 7Artisans and they are OK, this looks much better
 
leolab said:
that looks EXCELLENT!

I would love to get some of those made, if you can also send me the 3D print-data, that would be much appreciated.
Click to expand...

Thank you also and here you go: Focus Tab Files

There are now the 3D-files next to the pictures:
  • FocusTab.scad: Source file for OpenSCAD
  • FocusTab.stl: The stl-file, that your slicer needs to create the print-file for the printer (print-services need this file - or you know what to do with it, if you have a printer)
  • FocusTab.png: This is how it looks rendered in OpenSCAD

If I ever delete my files by accident, here is the plain text source for OpenSCAD, so it can reproduced any time:

HTML: 
<pre>
// Variables can be changed in case the used printer has a different precision than
// mine and/or my measured diameters are not precise enough.
//
//             |---------|
//             |_________|   -- variable d_c
//            |||||||||||||  -- variable d_b
//             |         |   -- variable d_a
//             \         /
// /---------------------------------------\
// |              ####          /-\   /-\  |
// |              ####          \_/   \_/  |
// \______________####________________//___/
//                              =====//
//
// d_a: Diameter of the ring printed with the distance numbers
// d_b: Diameter of the knurled focus ring
// d_c: Diameter of the ~2mm-width ring in front of d_b

d_a = 58.9;
d_b = 60.4;
d_c = 58.2;


difference() {
    // Tab block
    translate([0, -(d_c/2.0)-2, 17-10.7])
        linear_extrude(height = 12.7)
            square([24, 10], true);
    
    union() {
        linear_extrude(height = 20.7)
            circle(r=d_c/2.0, $fn=300);
        linear_extrude(height = 19)
            circle(r=d_a/2.0, $fn=300);
        translate([0, 0, 19-10.7])
            linear_extrude(height = 10.7)
                circle(r=d_b/2.0, $fn=300);

        difference() {
            translate([0, -((d_c-3.6)/2.0), 19-10.7])
                linear_extrude(height = 10.7)
                    circle(r=10.7/2.0, $fn=300);
            translate([0, -28, 0.1])
                rotate([-25, 0, 0]) {
                    linear_extrude(height = 7)
                        square([40, 25], true);
                }
        }
    }

    translate([0, -(d_c/2.0)-13.6, 16-10.7])
        rotate([-15, 0, 0]) {
            linear_extrude(height = 18.7)
                circle(r=9, $fn=300);
        }
        
    translate([-16.2, -30, 16-10.7])
        rotate([0, 0, 20]) {
            linear_extrude(height = 14.7)
                square([10, 20], true);
        }

    translate([16.2, -30, 16-10.7])
        rotate([0, 0, -20]) {
            linear_extrude(height = 14.7)
                square([10, 20], true);
        }

    translate([0, -28, 19.2])
        rotate([25, 0, 0]) {
            linear_extrude(height = 7)
                square([40, 25], true);
        }
}
</pre>
 

Attachments

  • FocusTab.jpg
    FocusTab.jpg
    12.2 KB · Views: 0
That is super cool! Although I'm fine with the Zeiss focus ring, your solution looks very workable.


Might I also say that I'm totally in love with the Distagon 35. It's a real endgame lens that can dissolve desire for other RF lenses.
 
krötenblender said:
Thank you also and here you go: Focus Tab Files

There are now the 3D-files next to the pictures:
  • FocusTab.scad: Source file for OpenSCAD
  • FocusTab.stl: The stl-file, that your slicer needs to create the print-file for the printer (print-services need this file - or you know what to do with it, if you have a printer)
  • FocusTab.png: This is how it looks rendered in OpenSCAD

If I ever delete my files by accident, here is the plain text source for OpenSCAD, so it can reproduced any time:

HTML: 
<pre>
// Variables can be changed in case the used printer has a different precision than
// mine and/or my measured diameters are not precise enough.
//
//             |---------|
//             |_________|   -- variable d_c
//            |||||||||||||  -- variable d_b
//             |         |   -- variable d_a
//             \         /
// /---------------------------------------\
// |              ####          /-\   /-\  |
// |              ####          \_/   \_/  |
// \______________####________________//___/
//                              =====//
//
// d_a: Diameter of the ring printed with the distance numbers
// d_b: Diameter of the knurled focus ring
// d_c: Diameter of the ~2mm-width ring in front of d_b

d_a = 58.9;
d_b = 60.4;
d_c = 58.2;


difference() {
    // Tab block
    translate([0, -(d_c/2.0)-2, 17-10.7])
        linear_extrude(height = 12.7)
            square([24, 10], true);
    
    union() {
        linear_extrude(height = 20.7)
            circle(r=d_c/2.0, $fn=300);
        linear_extrude(height = 19)
            circle(r=d_a/2.0, $fn=300);
        translate([0, 0, 19-10.7])
            linear_extrude(height = 10.7)
                circle(r=d_b/2.0, $fn=300);

        difference() {
            translate([0, -((d_c-3.6)/2.0), 19-10.7])
                linear_extrude(height = 10.7)
                    circle(r=10.7/2.0, $fn=300);
            translate([0, -28, 0.1])
                rotate([-25, 0, 0]) {
                    linear_extrude(height = 7)
                        square([40, 25], true);
                }
        }
    }

    translate([0, -(d_c/2.0)-13.6, 16-10.7])
        rotate([-15, 0, 0]) {
            linear_extrude(height = 18.7)
                circle(r=9, $fn=300);
        }
        
    translate([-16.2, -30, 16-10.7])
        rotate([0, 0, 20]) {
            linear_extrude(height = 14.7)
                square([10, 20], true);
        }

    translate([16.2, -30, 16-10.7])
        rotate([0, 0, -20]) {
            linear_extrude(height = 14.7)
                square([10, 20], true);
        }

    translate([0, -28, 19.2])
        rotate([25, 0, 0]) {
            linear_extrude(height = 7)
                square([40, 25], true);
        }
}
</pre>
Click to expand...

Thank you very much krötenblender!
 
@krötenblender: do you have any recommendation as to what metal would be best for this tab? Choices from a local printer include stainless steel, copper, aluminium, tungsten, scalmalloy and inconel 718.

Thanks.
 
Monz said:
@krötenblender: do you have any recommendation as to what metal would be best for this tab? Choices from a local printer include stainless steel, copper, aluminium, tungsten, scalmalloy and inconel 718.

Thanks.
Click to expand...

No experience, yet. But AFAIK, the Distagon is made from aluminium, so I would probably choose that to avoid different expansion from temperature-changes, which could loosen the tab, if you have non-elastic glue. OTOH, copper and stainless steel sound pretty cool… so if you have elastic glue.

If you have it, please post a photo. I don‘t have a local print-shop, that can do it in metal. But I will order somewhere.
 
What I did with my 21mm f/2.8 Biogon was to take a 3rd party replacement focus tab from a 35mm Leica lens and use a rat tail file to remove enough material to clear the focus bump on the Zeiss. Stuck it on with some 3M double sided tape used for sticking address numbers on the outside of houses. It worked great and the person who bought it from me asked that I not remove it. I think I paid maybe $15 total for the tab, shipping, tape, and time spent with a file.

Phil Forrest
 
Ko.Fe. said:
Why not to file this rudiment off and place normal focus tab?
Click to expand...

You are not suggesting filing off the focusing bump, are you? Why deface the lens? The OP has found a non-invasive solution for those who prefer a conventional tab.
 
Phil_F_NM said:
What I did with my 21mm f/2.8 Biogon was to take a 3rd party replacement focus tab from a 35mm Leica lens and use a rat tail file to remove enough material to clear the focus bump on the Zeiss. Stuck it on with some 3M double sided tape used for sticking address numbers on the outside of houses. It worked great and the person who bought it from me asked that I not remove it. I think I paid maybe $15 total for the tab, shipping, tape, and time spent with a file.

Phil Forrest
Click to expand...

I tried similar ideas, but was never really happy with the results. This one is far better for me and it fits exactly.

The price for printing the plastic version is about 10 cent (Euro cent). The other part was just fun for me. :D
 
Krotenblender, I think your design is very elegant, almost genius level. Well done indeed.
Personally I have no issue with Zeiss bumps, and I have/had nearly the full set of ZM lenses, although not the 35 Distagon.
Thanks for being so generous in sharing.
 
Monz said:
@krötenblender: do you have any recommendation as to what metal would be best for this tab?
Click to expand...

I used mine now for a few days and the ergonomics speed and precision of focus is completely another level for me. So I ordered the Tab from a printing service and chose Alumide as material and laser-sintering. On the pictures, that material looks pretty nice and is not too expensive.
 
krötenblender said:
I used mine now for a few days and the ergonomics speed and precision of focus is completely another level for me. So I ordered the Tab from a printing service and chose Alumide as material and laser-sintering. On the pictures, that material looks pretty nice and is not too expensive.
Click to expand...

A picture of the end result please. I have been using my Biogon 35/2 lately and keep thinking I would like a tab similar to my Summicron 50 (also in the bag with the Biogon).

I'm not sure quite who to contact locally for printing, but maybe time to do a little investigating...
 
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