Tips for DIY 6 bit lens coding

You will find plenty of articles about Leica's 6 bit lens coding system, what it does and how to DIY, I only have the following to add:

There is no need for buying or laboriously printing and cutting templates. All you need is a thin marker, some black nail polish and a toothpick. One more thing: late production Zeiss and afaik Voigtlander lenses have a groove cut in the lens mount which is in the right place and just deep enough to protect the paint from rubbing off. If your lenses are older, you might have to send them to a place that can machine the 6 dots.

First use the thin marker to mark the lens mount on the M8 (or 9) at the 2 ends of the 6 bit sensor. Then mount the lens and mark two dots in the same place on the lens mount. Next, mark a point exactly in the middle of the first 2 dots. "Exactly" is a relative term, but with a bit of care it will be plenty close enough. The 2 sections now remaining can contain 3 dots each. Here's what I mean:

  

None of the black or blue permanent markers I used worked because they still allowed enough IR to bounce off into the sensor, so the lens type was not detected. Thus, the black nail polish. There is no need to paint white dots, the bare metal will do nicely. Next, practice painting some other metal surface with the toothpick, as the brush included with the nail polish will be too thick. The results can be seen below, the Zeiss C Sonnar 50mm coded as a Summilux 50 pre ASPH, and the Zeiss 28mm Biogon coded as an Elmarit 28mm ASPH. It's not as neat as the original gear, but it's fully reversible, quick and durable.

 

Enjoy!

Zeiss C Sonnar 50mm f1.5 Focus issues

Sonnar

So, the first lens I tried on my new (to me) M8 is the Zeiss C Sonnar 50mm f1.5. It is an absolutely wonderful lens and there are plenty of blogs and sites on the web that will attest to that, so I won't dwell on it's qualities. I have only heard of one site that mentions the one significant issue this lens has: focus shift. This means that at wide apertures the plane of best focus is in front of the target indicated by the rangefinder patch.

I have done some tests using a template from Bob Atkins and I came up with some conclusions. I have shot dozens of frames doing focus bracketing every centimeter but for the sake of brevity here are the final results for the tests at 1 meter distance:

First at f 1.5, the first picture is focused on the center (un-numbered) vertical line, second one is focused on the line 5 cm behind it.

 
Since the depth of field at this aperture and distance is only 3 cm, if you focus exactly on your target, it will be entirely outside the lens' depth of field!

The situation at f2 is not much better. The first picture is focused on the center (un-numbered) vertical line, the second one is focused on the line 4 cm behind it. At f2 the DOF is 4 cm, so your subject will still be out of focus.

 

At f2.8 and up the focus accuracy improves dramatically to the point where you can focus normally using the rangefinder patch. I won't show any samples for that.

I've also done the same tests at 4m and the results are similar. In the pictures below taken at f1.5 and f2 the focus point was the small bolt circled in red. Again you can see it is outside the DOF.

So, what is one to do? You could come up with an index card of distances to back-focus at every aperture and distance and use that for every shot, but that would sap the living joy out of using this otherwise excellent lens. You could avoid shooting below f2.8, which would be an unspeakable waste.

Fortunately I happen to really like  the way this lens renders at f2, so I kept thinking there must be a better way, and I believe it is this: I noticed that the amount of back-focus required was approximately such that the double image in the RF patch is superimposed offset by about the same amount as the width of the 50mm frame line.

One way to do this is: focus on your subject then turn the ring slightly toward infinity until the patch defocuses by on frame line. As you get better, or with moving subjects, you can just focus offset directly.

This works quite well at f1.5, for f2 use a little less than one frame line width. Most importantly, this rule of thumb works quite well at both close (1m) and medium (3-5)m distances. I haven't noticed any issues at distances beyond that.

Here are the four shots of the wire fence focused exactly that way, at f1.5 and f2, focused on the bolt in the pictures in red and focused offset by one frameline width without the red circle:

F1.5

   

 

F2

....and F2.8 for comparison, focused on bolt:

Really though, the best way to fix this might be to use the Summilux 50mm ASPH, and it may come to that in the future, but for now I like this lens enough to give it a second chance.

In case you were wondering, my M8's previous owner (since new) assured me that the rangefinder was untouched from the factory and the focus was spot-on on his Noctilux, so I have no reason to believe it's an issue with the camera's rangefinder accuracy and not the lens.

A new crossroads to navigate!

I have been an amateur photographer pretty much as long as I've been able to afford it, meaning since I was about 8 or so. Oh how long ago that was, and how far we've come! It started with the cheapest possible russian Smena camera, and of course B&W developed at home. However, the point of this blog is not to bore you to tears, so I'll get to it.

What sparked the creation of this blog was a recent struggle to find the most enjoyable way to take pictures of the things and people that matter to me, and this search has brought me to a crossroads. I am a DSLR user who is somewhat unhappy with the DSLR way of doing things. Why am I unhappy? Mostly the size of the camera required to get a high IQ. It is next to impossible to get a small DSLR with a fast 50mm lens. In my case (Canon fan) I would have to get a full frame body (5D or the like) to be able to use the Canon 50mm f1.4. Those bodies are huge and heavy, meaning they will most likely sit in a drawer all the time. This is pretty much the fate of my present 400D with its ponderous 15-85 zoom.

The next logical step (or so I thought) was to get a small, fast prime. Of course, the Canon 50mm was excluded from he start because it's effectively an 80mm almost-telephoto. The 35mm is a better choice, focal length wise, but have you seen the size of that thing?

The root of the problem is the 400D's 1.6 crop factor, which means I have to use lenses that are not optimized for it, since Canon does not bother to make a 35mm f1.4 EF-S.

After a while, and not having come up with any better ideas, I decided to try a Voigtlander 40mm f2 Ultron, an overall excellent lens. However, another problem came up: since it is manual focus only, and most of the EOS line isn't designed with MF in mind, I end up with quite a few shots that are misfocused, or missed completely because I couldn't focus quickly enough.

Another ideea popped up, and I got myself a Fuji X100. A thoroughly outstanding camera, especially with the updated f/w. Still, the same problem crept up: slow focus. Enough times the camera would run through the focus range, only to stop at some seemingly random position, leaving the lens unfocused. Argggh! MF on the X100 is an exercise in futility as well.

So, what do do? More research was put in and an idea formed. Drumroll please:

Rangefinders! More specifically, the Leica M8!

The road to that conclusion was pretty long and I won't bore you with the details, but the next few posts on this blog will have to do with my experience comparing the 3 or 4 options on the table:

DSLR AF zoom
DSLR MF prime
X100
Leica M8


I've got an M8 coming, as well as 2 new lenses, the Zeiss 28mm Biogon and 50mm C Sonnar. I am particularly curious about comparing the M8/Biogon combo with the X100. At least spec wise they appear similar, 35mm effective FOV, 10 vs 12MP, both highly rated IQ. I will write new posts as I get more time with the Leica so stay tuned for that!


For those curious, I also plan to do some comparisons with the Voigtlander 40mm on the 400D and on my EOS Rebel film camera using Fuji Velvia! That should be interesting!