February 2019 – Light Matters

Olympus OM-D E-M5 Mark II Astrophotography Part 2

I wrote earlier about my astrophotography attempts with the Olympus OM-D E-M5 Mark II. Over the Christmas holidays, I had a couple of chances to use the SkyWatcher Star Adventurer. However, they were very short chances. It turns out that polar alignment in the southern hemisphere is rather difficult, even with a polar scope. It took me several nights before I found the right stars and achieved an acceptable alignment. And then, just as I could start taking well-aligned photos, the camera battery died. I usually have a backup battery charged — not this time. I had only managed one set of 10 and a few other test photos. But this is one of the tests:

This is a crop of an out-of-camera JPEG that shows the Carina Nebula taken from Canberra. It was a 50s exposure taken with a Nikkor-H 85mm f1.8 lens (vintage ftw). Click through to Flickr to see it properly – there’s no noticeable star trailing, and the increase in definition of the nebula compared to Deep Sky Stacker stacks of single-digit seconds exposures is quite satisfying. Obviously there are still several issues, particularly fringing and overal sharpness; I think my techniques in both cameracraft and photoshop are to blame there.

Unfortunately, it was fairly rainy for the rest of the holiday, so I didn’t get any more chances for astrophotography. C’est la vie.

Canon A-1 wheeze fix

There’s a well-known issue with Canon A series cameras where the mirror damper mechanism’s lubrication dries out and the mechanism becomes slow and noisy. The noise sounds to me like a wheeze, but other people call it a squawk or a squeal or a screech. The human ability to be flexible with onomatopoeic terminology is still an advantage that we have over the computers that will one day rule us, but it does make it a little bit more challenging to google.

I bought an A-1 recently, and apart from the wheeze it was in pretty good condition. I decided to fix the wheeze. There are quite a lot of methods going around the internet, but they fall into one of two categories based on how you re-lubricate the mirror damper:

– Through the bottom of the camera

– Through one of the lens mount screw holes

There’s also a lot of really bad advice out there about spraying WD-40 in towards the mechanism. This is like using a shotgun to nail a picture to the wall. It’s not the right kind of tool, in the first place; even though a shotgun and a hammer/nail combo would both end up putting a hole of some kind in the wall, the shotgun will make the wrong kind of hole. WD-40 is only partly a lubricant; when sprayed, it goes everywhere and gets sticky over time. See my previous posts for what I think about sticky substances around cameras. For this fix, you need a tiny drop of the right kind of lubricant in a very precise location. Other fixes online suggested dropping oil into the camera body from the bottom of the camera, and that’s bad because it’s not precise, and there are things (i.e. the focusing screen) that you really don’t want to get oil on.

The most precise fixes involved using a long needle to place a tiny drop of oil on the mirror damper mechanism. Using a long, straight needle from the bottom of the camera seems to be a fairly common way to do this; however, this seemed to require a fairly precise guess about where the end of the needle was. If you go in via the top-left (looking at the front of the camera) lens mount screw with a curved needle, as described in this video, you can get a bit more feedback.

I used a 25-gauge needle that I curved a little more than the needle in the video. With this curvature, I could find the axle that needed lubrication and feel that the end of the needle was in the right place by moving it back and forth across the curved top of the axle. With the needle on top of the axle, I could also move it side to side to make sure that the needle point was close to the gear. I practiced this a few times before applying the oil. I also practiced making a tiny bead of oil on the end of the needle so I knew how much pressure to apply to the syringe – really not much at all!

The first few shutter releases sounded about the same. I waited about a minute, tried again, and the noise was getting softer but was still there. After about 5 minutes, the noise was gone, and has stayed gone.

I would very much recommend the method of re-lubricating the mirror damper mechanism through the screw hole. A blunt-end syringe needle of the kind I used here can be gently curved with some careful pressure from round-nosed pliers, giving a tool that provides enough feedback to be sure of your accuracy.

Tokina SD 28-70mm lens focus ring repair

A little while ago, I wrote about fixing the zoom ring on the Tokina SD 28-70mm lens that I got with a parts camera. Fixing the focus ring took a little more effort, and it needed to be done during the day so I could test infinity focus with a distant object, but it followed roughly the same principles.

As with the zoom ring, the focus ring was held together by scotch tape as suggested in this MFlenses forum post. The scotch tape’s adhesive had degraded to the point it was a slimy mess. However, the focus ring’s function is a little different. Below the focus ring rubber is a join between two parts: the rearmost is a metal ring that bears the distance markers and the focus stops, and the foremost is a metal ring that forms part of the front lens group’s mounting (on this lens, the front group rotates when focusing). The ring with the markings can come away from the front ring and move a considerable way down the lens barrel, which lets the front group move freely. Calibration of focus depends on sticking the two rings together in just the right alignment, ideally aligning the infinity marking with the correct focus stop when the lens is perfectly focused at infinity.

Because the ring with the markings can move a long way down the lens barrel, the scotch tape adhesive had a lot more scope to get into the wrong places. It soon became evident that I needed to remove the front element to clean it all up. And it’s just as well I did — it seems that someone had attempted this repair in the past, as there was a great big fingerprint on the rear lens element of the front group. I hadn’t noticed this when inspecting the lens optics, but I was grateful for the opportunity to clean it up.

Once cleaned up, I reattached the front element (I don’t think I got the alignment correct, but as the front element rotates on this lens I don’t think it matters greatly), then put it on a camera and went outside. I focused the lens on an apartment block about 10km away by rotating the front element directly, using the camera’s split image to get a decent focus. Then, I aligned the markings ring with the infinity focus stop and used a small piece of scotch tape to fix it in place. Then I checked by focusing on closer things then back to the apartment block, and also by focusing at 28mm zoom instead of 70mm. I got it as close as I could, erring beyond infinity slightly if anything.

I fixed the ring in place more securely with two more pieces of scotch tape, then put the focus ring rubber back on. This one hadn’t stretched like the zoom one had, so it didn’t need any padding.

With both rings repaired, the lens is now basically back to normal. It’s not the most amazing of lenses, and it has a strange rotational feeling when taking a photo (possibly the aperture mechanism is a bit out of alignment), so it might need some further work. However, it’s much more usable than when I got it, so I count it as a win so far.