Adding a depth of field preview on a Yashica FX-3

by Franz-Manfred Schüngel


The Yashica FX-3 is a pretty cheap, lightweight and reliable camera than can be equipped with the legendary Carl Zeiss Contax lenses. It is a useful back up body for Contax owners as well as a low-budget first step into the system.
Main disadvantages of the body are the non-interchangeable focussing screens and the lack of a depth of field preview. I overcame the latter problem by adding one to the camera myself, and want to pass on the way I did it in case anybody else would like to try it too. If so, you should have some experience with tinkering at cameras and be able to put together what you took apart before. You will also void the warranty. I have no experience with the FX-3 super 2000, but it should work the same way, and probably for the FX-D as well.

The basic idea

On cameras with aperture priority and fully manual ones (like the FX) the aperture is selected on the lens. To maintain a bright picture in the viewfinder the diaphragm is kept fully open until the shutter is released.  Looking at the bayonet of the camera with the lens taken off you will notice two things: A lever wich can be moved against a small spring force round in the bayonet (lever A in fig 1), this lever "tells" the camera (i.e.the internal meter) the selected aperture, and a second lever at the bottom (lever B in fig 1), that moves all the way when the shutter is released. The diaphragm is held open by this lever, it will close when the lever moves. You can move this second lever with your finger against the springs force, a depth of field preview button has nothing else to do.
Your camera will not know that the aperture is closed, the internal light meter will give you incorrect values as long as you press the dof-preview button (that is the case with most cameras).

Taking apart

Do not worry too much about this part, you do not have to remove a lot. Just make shure you have a tidy working place (I never do, and this makes things complicated sometimes) and do not loose any screws.
Remove the leather on both sides on the camera front. Try not to tear it (spare leather cover is really cheap, so its a good idea to replace it prior to selling a camera when it looks rotten, but you have to get it first).
Remove the batteries, then the base of the camera.
Remove the bayonet (4 screws, there should be only one way of putting it back on).
Remove the plastic housing around the bayonet which is held by the screws that were previously covered by the leather. Loosen (not actually remove) the top cover to get it off.

Two parts have to be made:
- A button part that pushes the lever in the stop down position
- A guidance part that keeps the button part in place.

Making the parts

The button part consists of round aluminium. Do not make it too short, its easy to shorten it later. I used a diameter of 5mm (I actually had 6mm material lathed down to 5mm to have it precise). You will notice that it will not fit in the space where it is supposed to live later. You will have to do some fine tuning with a file.
Flatten (according to fig 2) one side of the inner part of the button slightly and then file away quite a lot on the other side (almost half of the material). Try to get a smooth surface. When you are done, the part should fit in the space mentioned, and you should be able to move the lever in stop down position. It must not get stuck somewhere.
At this point you will notice that with the lever in stop down position you are unable to press the shutter release. This might not be too much of a problem, but the point is, that your camera will get stuck when the dof preview button is pressed (or moves accidentally) while the self timer runs. If your camera is not taken apart at that moment you are in trouble. You have to file off some more on the side you flattened only a bit to make space for the shutter release (see fig 3).
When the shutter can be released with no difficulty while the dof preview button is pressed, you are done.

The guidance part is a small metal block (I used aluminium) which keeps the button part in place. The dimensions I used are given in fig 4. I had it mill-cut, but you can saw it at the right angle almost as well using a mitre saw. The most precise thing about it is the hole that guides the button part. Use a drill on a solid stand. It should be done with a reamer, the diameter must allow the button part to move without resistance, but with as little looseness as possible.
When you hold the guidance part to the plastic casing and look at it from the underside, you will notice a small gap, because the plastic cover is not exactly at right angle while your guidance part probably is. The difference is pretty small, if you like filing a lot, you can make the guidance part fit precisely. I just used a bit of cardboard for sealing.
At last file the edges that will be on the outside nicely round. Do not forget the hole for the mounting screw. Its size depends on the size of screw you find, e.g. 2mm.

Put a small screw or similar into the button part at the right point to prevent it from falling out when mounted. If you have access to a lathe, you can lathe down only the "outer" part of the button part, i. e. the internal part is left at its original diameter of e. g. 6mm. This will save you putting in the screw. Shorten the button part (mine is 38 mm) and make a nice button-end. You can do this easily even without a lathe by mounting it in a drilling machine, let it rotate and press a file against the end.

When you are finished, paint all the inner parts black and the outside of the guidance part too, if you like. I would not paint the button part (other than the internal part of it) because it will get scratched.


Drill two holes into the plastic housing around the bayonet, one in the side for the button part (6mm) and one for the mounting screw (e.g. 2mm). Screw the guidance part to the housing with a screw and nut and glue the nut to the cover (backside). When the glue is hard unmount.

Mount the camera by reversing the above order. Mount the dof-gizmo at last, be careful not to break off the screw you glued on the backside or you will have to repeat these steps. Cut out a corner of the leather to make place for the mounting part.

When you are finished, take pics & have fun!

I have a picture of the camera and a more detailed view, the leather on this camera was replaced with thin aluminium sheets. It has been in use for a while, so the paint already wore off the edges a bit.

If you do not want to do this much tinkering, you can also release and turn the lens like taking it off - this will also stop down the lens. Just don't drop it then.

Your questions, comments and suggestions are welcome.


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(c) 1998 by Franz-Manfred Schüngel

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