Category Archives: Lenses

Summicron-M collapsible

I got a hold of a Leitz 5cm f/2 Summicron-M collapsible lens … one that was in really bad condition, which was the only way I could afford grabbing this type of lens. I have to say (and I knew for a long time) Leica M stuff is EXPENSIVE (I thought the LTM was over priced).

I did not do a complete dissasembly … like getting at the focus helicoid.

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The lens is actually not that difficult to work on, but just requires a bit of pre-info … since you really don’t want to damage a Leitz.

The front element is very soft so it is noted on being very easy to scratch when cleaning. This one has heavy haze and fungus.

 

 

 

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DSC00531To get to the aperture blades you can just unscrew the entire front group off.

Getting between the elements of this front group is something I did not even attempt to do.

 

 

 

 

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DSC00532You can remove the rear cap section, but you have to do one thing first. There is a small screw in the side of the lens barrel, loosen that first

It is a brass screw, so watch out !!!

 

 

 

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before using your spanner wrench to unscrew the rear retaining ring.

 

 

 

 

 

 

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The collapsible lens rides on two slots, and the rear focus ring has two bearings inside it … so try not to loose them … and when putting it back together you have to line up the slots.

You can see the two bearings (the left one is missing in this shot).

 

 

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Here is a picture of the end cap attached to show how the slot should line up.

The encap goes on after placing the focus ring on … so you will have to eye ball it.

Then screw the retaining ring back on with the spanner wrench without turning the end cap … then secure the side screw.

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Cron the destroyer …

The Leitz 50mm lens went through many different iterations since 1924, starting with the Anastigmat designed by Max Berek … the Summar was the first of the f/2 line in 1932, then Summitar, then finally the Summicron.

The Ernst Leitz Wetzlar Summacron 50mm (5cm) f/2.0 first production M-mount started 1954. The Leica part name for the m-mount version is SOOIC-M (don’t ask me about that). 7 elements in 4 groups … that’s a lotta glass !!! The original version started as a collapsible, later 1956 they also producted a rigid body.

Early 50mm Summicron’s had lens elements, made by Chance Brothers & Co., that had thorium oxide in it … very low radioactivity and it eventually turned the lens little yellow/brown over time … they quickly switched over to their own lanthanum oxide formula.

Marco Cavina has a great website about Leica, though it is in Italian … but I don’t think you will have any problems finding reading matrial about anything Leica.

Now I am not a Leica person, I was caught offguard when people use the suffix to talk about various lenses … and this one being the Summacron 50mm (5cm) f/2.0, it was refered to as a cron. It appears that a Summacron refers to the f/2.0 aperture size ? … obviously I am a Leica newbie … so what do I really know.

 

 

 

 


Cleaning the cat … 500mm reflex

I wanted to try out this oddity of a lens. I shoot a lot of wildlife, so a long focal length lens is handy. Even handier is a physically short and lightweight lens. I snagged this lens for a bit less than normal because there was obvious dust/stuff inside.

I first thought of just removing the front element by unscrewing the ring … but it would not budge. I checked the web, and others show a disassembly … Ok, doesn’t look that hard.

Tools – philiips screwdriver, cleaning stuff, and painters tape

First thing to do is get the tape out, set the lens to infinity focus and place a tape reference on the outside between outer focus ring and body.

TIP: try not to rotate anything during disassembly.

Next you need to take off the PCB board with the contacts. There are two screw holding it on and there is a spring underneath one side.

Next remove the screws from the mounting ring.

Pull off the mounting ring a bid and then maneuver the PCB through the hole to separate them.

The outer body is held on by the four screws.

Note that the PCB and chip are attached to this part, so try not to damage it … and it sits in a slotted area.

At this point you might want to get the tape out again and make more reference marks on any rotatable parts.

In order to remove this rotating focus collar you will need to remove some gears … make a tape reference to its position.

Tip: pull the lens while slowly unscrewing, and as soon as the two release place a tape marker. You’ll thank me when you put it back together.

Two screws hold the gears on.

Try not to lose any parts when you remove it … and also try to keep the lube.

Pull off the column.

Then just unscrew the two parts.

Clean up, and try not to scratch the mirrors.

 

 

Those tape marks will come in handy to make sure you correctly get the correct position of everything.


Holy Schmidt-Spiegel Batman … its the Minolta 500mm reflex !!!

The Minolta Maxxum AF 500mm f/8 Relex lens was brought out in 1989, and is a Schmidt-Cassegrain catadioptric lens.

In 1672, Laurent Cassegrain designed a telescope using two mirrors to reflect incoming light to the eyepiece. This design corrected spherical aberrations and also made the telescope shorter. Later on the Catadioptric system was created, and his utilized both refraction and reflection … corrective lenses and mirrors.  In 1930 Bernhard Schmidt redesigned the mirror shape and added an aspherical lens to correct for coma, and astigmatism aberrations. The Schmidt-Cassegrain design is currently one of the most popular telescope design used today … and it also caused many camera lens manufacturers to use that also. Almost everybody made one (well not really), but Minolta was the only one to incorporate it into their Auto Focus system.

The Maxxum 500mm reflex is a stubby barrel of a lens. Due to the way it is designed it can produce donut or crescent shaped bokeh … which probably explains why this lens is not more popular. As I mentioned before, this is an AF lens which can support centre point focus … and since this is a gear driven lens, the body has a direct influence on AF speed. You’ve got one aperture size of f8 so it can cause the AF to hunt … IQ is pretty good on this lens … you just have to know how to work the bokeh … overall I really like this small handful lens.


Separation, leads to divorce, and a new coupling.

Sometimes you encounter a lens that has some internal blemishes that you cannot seem to clean off … can look like rainbow rings (ring of fire), a cloudy ring round the edge, a crescent beige tint, bubbles, or even a flowery/snowflake pattern … and it always seems like it’s trapped between two lens elements.

This old LTM lens has an almost complete ring haze. Now, it could possibly be just haze on the back of the element … but I suspected it was more than that.  After talking it apart it was apparent that it was separation of the front two elements.

Yes, in fact it is between two lens elements. Most lens designs require two lens elements to be bonded/cemented together (doublet) with adhesive to eliminate the glass air gap. By reducing exposed surfaces, cementing reduces refraction and ghost images from reflections, and allows the use of thinner flint elements. 

Older lenses used Canada Balsam as it had a high index of refraction, which is optically a good thing to have. It is derived from good ol Canadian trees … yup good ol sap … yes, its not just only for maple syrup.

Development of resins to cement elements started in 1785. Eventually changed to a synthetic resin because of WWII … high altitude aerial photography caused issues with Canada balsalm, so they developed a synthetic cement that could handle low and high temperatures … this is the MIL-A-3920 standard optical adhesive. UV curing adhesives appeared in 1966 to reduce the curing time for high production.

When the “cement” has degraded and no longer seals the two elements together, the separation will create artifacts that will change the refractive properties of the lens. Sometimes it is not very visually apparent … sometimes it is. The only real solution is to separate and re-cement them.

This topic has been discussed much on the web … FotomozaicLargeFormatForumskgrimes

With Canada balsam, it requires heating to soften the resin so the elements can be separated. The newer synthetic resins require special chemicals … and in some cases the elements cannot be separated without damaging it.

Once separated, new resin can be applied to cement the elements. Then new resin can be applied to cement the elements … modern day resins are UV cured, so makes it much quicker to get a lens back to working condition.

Sounds easy … not !!! Heating sometimes does not work, or even worse causes the element to crack … and there are cemented group that are encased in a metal sleeve which has to be removed first (without damaging the glass, and you may have to find something to replace it) … or, as mentioned before, it just doesn’t work.

One day I will make a serious attempt at re-cementing … meaning, my half-ass attempt sucked, and I will try again.

Summers Optical makes many different types of synthetic resins for optical cementing … and you can still buy Canada Balsam, as it is still used for microscopic slide mounting and painting.

Sometimes the lens separation is not so bad in terms of affecting the image, especially if it is around the edges like the lens pictured above … but when it sits right in the centre, it will most likely cause apparent visual effects. Mounting this lens on my Sony NEX-6 and taking some shots, I could not really notice it until I got some light hitting the front and the separation starts adding some flaring/fogging.


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