Gaoersi 6x17 Camera

Lens and metering quality are not relevant here because the camera doesn't’t come with lenses or a meter. I guess you could say that the camera should produce superb images with a high quality lens and appropriate metering.

Calibrating the lens may come easily but it can also become something of a Chinese puzzle because the instructions are terse to the point of cryptic. It took me quite some time to work out the procedure. However, once you understand what to do, it becomes relatively simple again.

The camera comes with a small piece of ground glass so once you have removed both the camera back and the dark slide, you can check the focus through the back of the camera. I also purchased the 8x loupe, as shown below:

Checking the focus through the back of the camera

At the front of the camera, the Lens adaptor fits onto the camera body and the Lens fits onto the Lens adaptor.

The whole mechanism that attaches the Lens to the camera is the Lens Adaptor.

Each Lens Adaptor has a Focus Ring and a Lens Ring, as shown below:

Lens with Focus ring, Lens ring and Lens adaptor (notice the Chinese spelling of Lens)

When the lens adaptor is correctly set up, the infinity sign will be on top and the lens will be focusing to infinity (as shown above). Then as you turn the lens up to half a turn clockwise towards the minimum focusing distance, the end part of the lens mount (together with the lens) moves away from the Focus Ring and changes the focus.

Briefly, these are the steps you need to follow to calibrate a lens:

Turn Focus Ring to Infinity (lens fully retracted)
Loosen lens ring
Unscrew barrel between lens ring and Focus Ring and focus to infinity using ground glass screen and loupe
Tighten lens Ring
Align focus ring and ensure that it’s tight

To loosen the Lens Ring you first have to loosen the two adjustment rings on each side of it. One of them is shown below:


Fixing screw on Lens Ring	Adjustment screw inside Lens

Notwithstanding the instructions, the Lens Ring doesn't’t change the focus; it’s just a locking ring. When you loosen it you can turn around the barrel of the adaptor between the Lens Ring and the Focus Ring. In this way you can screw the whole assembly out, thereby changing the focus.

The next task is to align the Lens so that when you are focused at infinity, the infinity sign is in the middle on top. There’s another issue associated with this. The Focus Ring should rotate between infinity and the minimum focus and stop at each end. Sometimes, though, it can just go round and round with no point of reference. This is because it is screwed into a separate small ring inside the barrel of the Lens Adaptor and it is possible for this to come undone – we will call this small ring the “Threading Ring”. You can use the little holes in the threading ring to screw it in but I found it difficult to get it tight enough. Then I found another trick for doing this. The Focus Ring can unscrew if you screw it too hard past infinity but provided the threading ring is still connected, you can also tighten it by screwing it past the minimum distance.

There are then two ways to align the Focus Ring. You can have it locked into in position but Infinity may not be on the top. By rotating the barrel of the Lens adaptor (i.e. everything outside the Lens ring) you may be able to get the Lens correctly aligned with the focus still correct. This may work because rotating the whole assembly causes very gradual changes in focus. However, a more accurate way is to get the focus you want by rotating the whole assembly and then adjust the alignment of the Focus Ring using the methods of the previous paragraph.

Though the instructions suggest focusing at infinity this is difficult because objects are so far away and very small for a wide-angle Lens However, if you carefully turn the Lens Ring around exactly half a turn and then calibrate the focusing on that distance it amounts to exactly the same thing. When you have the adaptor properly focused and aligned you should retighten the screws in the Lens Ring and align the Lens itself in the mount.

Then according to the instructions the last step is to tighten the two screws inside the Lens The white arrow in the picture above points to one of these screws. The screws just go up and down in a slot to restrict focusing to between infinity and the minimum distance. My guess is that the only purpose of tightening them is to make sure they don’t fall out. They didn't’t seem to want to be tightened so I just left them well alone.

(Above the white arrow in the diagram above you can also see one of the locking holes you can use to lock the Focus Ring against the “threading ring”, as discussed above).

The one significant problem I did encounter was with my 150mm lens. First the hole in the adaptor was too small to take the lens so I filed the adaptor hole out to size using a half-round file. But then I couldn’t get the lens to focus at all. At 6m the point of focus was about 16mm behind the film plane – far too much for any adjustment. The reason for this is that I was sent an adaptor for a current lens whereas my 150mm lens is 40 years old. No problem though. I was sent an additional spacer ring that screws in below the lens ring and now it’s correctly set up and focuses. Great service. I’m impressed.

One possible room for improvement is that it would be nice if the lens adaptors had a mark to align distances against and a depth of field scale. One of their illustrations on the Web does show this with what I think is a 90mm Super Angulon lens– perhaps this is only available with that lens Still, it might introduce another element of complication to the calibration process and I do not regard this as a big issue; depth-of-field tables are easy enough to come by on the Web.