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Anatomy of the Leica M8 Framelines

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Eagerly awaited by at least one person on this forum, here is the latest in the "Anatomy of the Leica..." series.

 

The M8 upgrade program allows the framelines to be changed for ones which are calibrated at around 2m shooting distance instead of the closest focus of 0.7m. This has the effect of balancing the framing error between closest focus and infinity to provide a more acceptable result. If you're contemplating this update and want to know what's involved, or just wondered how they work, this thread is for you!

 

To begin...

 

The framelines work by projecting light through a series of slits in two metal masks; one is in a fixed position and the other slides diagonally behind it. By clever design, in each of three positions of the movable mask, slits in the two masks coincide to allow the light through. This then appears as a frameline injected into the viewfinder. In the M7 and M8, there is also an LED display (just like the old red LED calculators) to display the AE shutter speed, manual metering and flash indicators.

 

Here's the fixed mask...

 

 

You can see the familiar layout of the framelines; counting from the outside: 24mm, 28mm, 35mm, 50mm, 75mm, 90mm. Note that the 75mm frame is scarcely bigger than the 90mm frame; no wonder the 75mm frame is the most inaccurate. If you wanted to eliminate some of the frames, "all" you have to do is black out the slits you don't want.

 

The centre rectangle defines the rangefinder patch. It's through this aperture that the image from the rangefinder window is projected into the viewfinder. Without the masks in place, you see a much larger image with parts of it superimposing the main viewfinder image, other parts being split from it, depending on distance; confusing and the rectangle constrains the rangefinder image to the centre.

 

The two holes top left and bottom right are used to locate the mask in the carrier; only one round hole is required; the second is elongated to ensure the mask sits flat. The diagonal slot top left is used to locate a spring which provides the audible "click" when the framelines change.

 

This mask is tiny, around 15mm wide, so you can imagine how small the slits are and how accurately located. It's not clear how they are made. In former times, I expect they were stamped, now, it would make sense to cut them using a laser. Either way, an expensive component to make.

 

At the bottom, an identifier for this type of mask: M8, 0.68 (viewfinder magnification), 6 (frame count).

 

You can just make out a clear plastic block in front of the lower aperture. This is where the viewfinder LED display is mounted. It's not clear what it's for. I think it is some sort of light "pipe" to increase the display contrast.

 

Here's an oblique view of the same mask - you can see the plastic block super-glued on to the mask - at six points it turns out after mine fell apart. Easily re-glued using Loctite 4062, a very low viscosity cyanoacrylate. Steady hand required, easy on the Rioja the previous night!

 

 

Here is the moveable mask which sits behind the fixed mask and moves diagonally. The pattern of slits may look odd but keep in mind that their only purpose is to align with the slits in the fixed mask when the moveable mask is set to one of three positions.

 

 

There are now two diagonal slots top left and bottom right so the mask can move along this axis.

 

The strange shape top left is to allow the framelines to click into place. The spring expands into the zig-zag edges and causes this mask to settle into the correct position.

The diagonal slot right centre is used to set the position of the mask. A pin actuated by the frame selection lever engages in the slot and moves the mask in the required direction.

 

Now, here's the clever bit. The whole mask assembly can be shifted to provide parallax correction and that movement takes place in the other diagonal direction, bottom left to top right. Notice how the frame selection slot is parallel with that movement - the two directions of movement are orthogonal so that a movement in one direction (as you focus closely) is not affected by a movement in the other (as you select a new lens). Clever stuff!

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Here is the frame mask carrier, shown first from the back where the masks are assembled.

 

 

Key to note are the slots bottom left and top right which allow the whole assembly to move for parallax correction. There are also two chrome pins which are used to locate the masks. Top left is a diagonal slit through which the spring passes. You can see there's a sandwich - the spring passes through the fixed mask at the back, through the moveable mask and then through the mask carrier.

 

 

Looking at the other side, you can see the slot for the spring. At the bottom is a triangular protrusion. This engages with the camera focussing mechanism and causes the carrier to be moved up and to the left (viewed from this direction) as you focus more closely.

 

 

The final major component is the mounting bracket which holds the carrier relative to the rest of the camera and engages with both the focussing cam and frameline selector lever.

 

 

At the top are the two mounting holes to attach it to the top of the viewfinder in the camera. Key is the pivoted lever. The geometry of converts the up-down motion of the frame selector lever engaged by the pin bottom left and converts it into diagonal motion to move the moveable frameline mask. The rivet centre right is the back of the pin which engages with the slot in the moveable mask.

 

Here's an oblique view of the mounting bracket:

 

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That's the major components then. There are of course some other components, shown here with a centimetre rule for scale.

 

 

Moving clockwise from top left:

 

2 mounting screws and washers to secure the mounting frame to the top of the viewfinder.

 

The mirror which reflects light coming in through the centre window through the masks into the viewfinder.

 

A guide for the flex print of the LED display.

 

The LED display itself, a wonder of miniaturisation; you can see the display at the bottom. The central window is about 1 * 2.5mm. The connector at the top connects the display to the M16C processor on the top of the camera.

 

A plastic prism; it's not clear what this is for, possibly to provide even illumination of the framelines.

 

3 screws to mount the prism to the carrier, the carrier to the mounting bracket and the mirror, guide and flex-print to the mounting bracket.

 

An L-shaped spring which is used to return the parallax correction to the infinity position.

 

Finally, the famous spring. This tiny, minute spring, is what provides the audible clicks when the framelines are selected. It's inserted though the masks and the carrier. By springing outwards, it causes the moveable mask to settle in one of the three required positions.

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So, with this kit of parts, let's play Leica technician and build it all. First, attached the prism to the carrier with a mounting screw.

 

 

Turn it over and place the moveable mask in the back. Note how the mask can slide diagonally, constrained by the chrome pins.

 

 

Then, put the fixed mask in; this cannot move because it is constrained by the pins. With the moveable mask in one position, the 28 and 90mm frames are visible...

 

 

With the moveable mask in the other extreme position, the 24 and 35mm frames are visible. Notice how the position of the slot centre right has changed between these two. The small spring is pushed into the stop top left through both masks and the frame carrier.

 

 

The carrier is then mounted on the mounting bracket using a screw top left; the L-shaped spring is installed and the carrier can move diagonally for parallax correction, returning to the infinity position under the force from the L-shaped spring.

 

 

Notice the tiny spring appearing through the slit, to the left of the pin, top right.

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Here's a picture of the back of the mounting bracket. The pin right centre has engaged with the slot in the moveable mask.

 

 

Here are two pictures of the display working outside the camera...

 

 

 

Don't forget that display window is just 2.5mm wide...

 

Finally, the mirror, guide and flex-print are mounted on the front of the frame carrier and here are two pictures of the completed assembly.

 

 

 

The question is, of course, what do Leica swap over when you send you camera in to have the framelines upgraded? One Leica "rep" suggested the entire viewfinder is exchanged which seems unlikely. The mounting bracket comes off with just two screws and one connector once the M16C board if off and just one screw allows them to salvage the cost of the mirror, guide and LED display.

 

Once the mounting bracket is out, it's a 5 minute job to switch the masks and re-install in the camera, so I think the frameline upgrade is probably just buying a new pair of masks plus the labour.

 

That's it!

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Well Mark another remarkable job, Thank You.

 

As to whether the frames only are replaced or the whole View/Rangefinder is swapped out I think they do change the whole thing for one reason. I think it's easier on the line to just change out the viewfinder. Then send the older viewfinder off to more capable/technical hands to have the frames replaced and then put back in the line to go into another camera, whether a M8u or M8.2 or it is left as is and used in a new M8C (that is if they are still making any of them (which I doubt)).

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Again a great job Mark!

 

I think the Leica Rep has told the truth- somehow.

To have a fast turnaround, Leica could

a) swap the old viewfinder for a modified one,

then

take the old finder to another working bench, where the new masks are inserted

and c) take the modified finder to the first bench where the next M8 is waiting for new framelines.

Regards,

Stefan

 

@shootist: you were faster ..... ;-)

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Mark,

 

I do not know what impresses me most, your skills to handle such small parts, the perfect way to make those macro pictures with such a large dof or your guts to take everyting apart an then back together.

 

Hans

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Yes, the downside of the lens stopped down to f57 is that you see the camera is not as clean as you would like!

 

For Nikon owners - D3, 105mm f2.8 VR micro lens, SBR1C1 macro flash.

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Guest DuquesneG

Thanks Mark for all your handy work and your time and for being generous enough to post it here for anyone who wishes to see it. A couple of minor comments, one, the new framelines are most definitely not calibrated even approximately for 2m. Others noticed that before, and I have now had the chance to do some test snaps with an M8.2 and confirmed it for myself. If anything, they are now calibrated approximately for the closest focus distance (0.7 for everything except 75mm and 90mm which are 1m ), and are very close to the M7/MP/M6. The earlier M8 framelines, for whatever reason, were even tighter than the 0.7/1m setting. I'm going to get both of my M8s upgraded at some point. Second comment, I had the framelines in a late-model M2 exchanged for M6 (M4P) frames by DAG a few years ago. He said it was not a difficult job, and it cost me nowhere near what Leica wants for the frame upgrade. I spoke to him and he said the mechanism is basically the same on the M8, which he has also delved into.

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I was just thinking Mark could have a gallery (on real wall) of Anatomy of M8. I think they would look great. Maybe Leica would object, but, another book, a small one (say CD size), of this would be great, too.

 

-T

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Mark,

 

thanks for sharing this. If I want to make custom framelines, do you think I can fill lines on the fixed mask with a gap-filling cyanolite glue and then use a black Sharpie to make it opaque?

 

If I do this with the 24,50 and 90 lines I should get an M2 style finder.

 

Jonathan

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Mark,

 

Some more questions. I haven't taken my toplate off yet, but from your pictures it looks like the frameline assembly is a straightforward unscrew from the rest of the rangefinder. Do I need anything more than a standard assortment of precision screwdrivers to get the framelines off? Did any of the screws have Loctite on them? Did any of the slot/pins have a lubricant on them?

 

Jonathan

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Excellent autopsy, Mark.

 

Now that you have explained it, I think I can see the sliding mask move across the fixed mask when operating very slowly the Frame Selector on the front of the body. The mask seems to move from southwest to northeast, when viewed through the rangefinder, as I move the Selector counter-clockwise, when viewed from the front. Very subtle indeed!

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Seeing all the complexity of just the frame line masks and all the tiny components involved which all have to be manufactured perhaps specifically in some cases does anyone doubt that the M8 is actually worth the money, (value wise that is as opposed to performance wise)?

 

Jeff

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Jonathan, go easy! The masks may look substantial but in reality they are tiny slivers of metal and that spring is ready to fly away and ruin your day. The plastic block detached very easily and I am extremely careful with these things.

 

You'll void your warranty of course if you do this...

 

You can see that the holes at the top of the mounting bracket are quite large and that the screws have flat tops meaning the position of the bracket is adjustable and I expect the centre hole is to locate some sort of alignment tool. The screws are secured with Loctite as perhaps you can see.

 

Important therefore that you record the position so that you can return it to the same position to keep the alignment.

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