Replacing the screen.....is it as simple as the four tiny screws and a couple clips?
No, it is not that simple. The image you focus with using your Rolleiflex finder is formed on the lower surface of the ground glass. Hold that thought for a moment.
When discussing the 1950s onwards Rolleicord or Rolleiflex models there are two kinds of focus hoods with screens fitted in two different ways. The older Rolleiflex models up to the E, and the Rolleicord models, except the Vb, have hoods fixed by four screws to the top of the camera body. Of course, this includes your Rolleiflex 2.8C. With these hoods, the focus screen is fixed to the underneath of the hood frame by two spring clips that retain it in place against the frame, where _____ is the frame and ==== is the focus screen.
_____
====
Because the screens of the older models are fixed to the underside of the frame, the height at which the lower surface of the screen is positioned, relative to the viewing lens, is directly impacted by the thickness of the screen. For example, if you remove a standard screen and replace it with another that is, say, one millimetre thicker than standard, the image forming surface is now situated a millimetre lower than it was.
The effect of this is to change the focus point of the viewing lens. Assuming the two camera lenses were previously correctly calibrated, the focus of the viewing lens will now diverge from that of the taking lens, making it impossible to critically focus the camera with the finder.
In this example you could restore the previously correct focus by using one millimetre shims between the hood and the camera body. This will have the effect of "lifting" the screen up by a millimetre and restoring the fitted height of the screen lower surface to what it previously was. I have never bothered to swap the screen of any of my Rolleis, however if I needed to, I would prefer to adjust the viewing lens back into agreement with the taking lens via the method the factory originally used to dial it in: that is to say, by adjusting the position of the viewing lens in its mounting threads on the lens board. This requires some dismantling of the front of the camera to access the locking screw for the viewing lens so that it may be loosened to adjust the lens. Of course, in the event a screen was being substituted by a thinner screen than stock this would be the
only way to make both lenses track together, since you can shim clearance to increase it, but cannot shim to
decrease it.
Later Rolleiflex models from the E2, F and T, as well as the Rolleicord Vb, and the Tele Rolleiflex and Wide Rolleiflex use the newer type of viewfinder hood. It is easily spotted by the two small plastic release grips on either side of the hood that permit the hood to be removed quickly and easily and Eg. replaced with a prism finder. These later types of hoods also have focus screens that are easily removable and (critically to this discussion) have screens that are clipped onto the top of the hood frame. Ie:
====
_____
If one replaces a screen with another of a different thickness, because the screen mounts on top of the frame, the top surface of the screen will of course be at a different height than the original, however this is of no consequence, because the image forms on the screen lower surface and, the screen sitting on top of the frame, the lower surface remains in contact with the frame at the same height (regardless of any change in its thickness).
In summary, if you change the screen in your 2.8C you will want to first check the thickness of it and compare it to that of the original. If there is a difference you will have to either adjust the viewing lens focus yourself or get a competent person to do this, otherwise your focus accuracy will not be maintained. There are a couple of other points to contemplate about that.
The viewing lens of a Rollei is fitted to the lens board, like the taking lens, and, as the taking lens focus is set by varying the relationship between the height of the board, and the position of the knob relative to the focus shaft, any adjustment to the taking lens automatically adjusts the viewing lens also. The taking lens adjustment, is therefore the master adjustment and must always be the first adjustment made (if necessary) in order to calibrate the two lenses of a Rollei. When the taking lens accurately focuses at infinity with the focus knob against the infinity stop, then, and only then, should any dialling in of the viewing lens be attempted because, should the taking lens focus not be correct, any re-adjustments of same will automatically defeat any setting of the viewing lens. To sum this up I think it is good practice to inspect taking lens focus whenever any aspect of the viewfinder focus is altered. There is no point at all trying to make your focus at the viewfinder accurate unless you know that the taking lens is actually correct, first. The basic and essential principle is that both lenses must focus together at all distances and, because the taking lens is the master adjustment, it should always be inspected for best possible focus accuracy and image sharpness unless it is definitively known to be correct.
Cheers,
Brett