More Super Ikonta A woes

[Arbitrarium]

So, after modifying the albada finder of my Super Ikonta A to better reflect what the lens was seeing, I shot a roll of expired XP2.

Every single shot is focused closer than I was expecting. Infinity shots are off infinity and shots I focused at about 10 metres are focused more like 5 or 6 metres away.

Thing is, the camera is freshly serviced by Miles Whitehead, and I've checked the focal plane with a ground glass and it's perfectly aligned with the rangefinder. Using a ground glass, everything seems to be aligned as it should be and the rangefinder is spot on at every distance.

But my shots are out of focus.

I've used rangefinders and folders plenty enough to know it's not just user error, I got more shots in focus on a scale focus Ikonta than on this coupled rangefinder roll.

The only causes I can think of are that there's something awry with the film pressure plate, or perhaps the focusing wheel has a bit of slack between the gears and I might be better of focusing with the front element, not the wheel.

But honestly I've no idea. I can't imagine the expired XP2 I shot can make much of a difference. Has anyone experienced a mystery focus issue like this? Any ideas what's going on?

Example. The rangefinder was perfectly focused on the 'predator' text, but the shot is focused on the pier in the foreground.

 

[retinax]

Wait, you can focus with the front element or the wheel? Any chance fiddling with the front element threw the rf coupling out of sync? You could feel it if the focusing mechanism had slack, right? That should mean you can turn it without anything happening at the focusing and/or the rf.
Other than that, the pressure plate could be the reason. But should be easy to check if the spring tension is sufficient and it's in the right place.

 

[Arbitrarium]

Yeah the wheel and front element are geared so it doesn't matter which you turn. Using the front element is better for critical focusing.

And true I should be able to feel if they're out of sync or slack. Like I say, with a ground glass the focus is accurate with the RF.

I'll check the pressure plate when I'm back home, but I'm not sure it would be so consistently out of focus if that was the issue. Gah!

 

[Gregm61]

I'd just send the camera back to the service guy, maybe with a few of the negatiuves so he can see what's happening.

I've had to send freshly serviced cameras back to shops for anything from miss-alignment issues, whether it was a mirror out of alignment on a Pentax MX, the feeler roller not set right on a Rolleiflex, etc.

Something's obviously not right and needs to be re-done, as painful as sending a camera back is after having done without it for some period of time already.

 

[p.giannakis]

As far as i know, Mr Mileshead offers 6 months warranty on the cameras he repairs. If i were you, i would contact him and email him with some pictures.

Ps: You're sure the negative was flat on the scanner when you were scanning it? I used to have this problem with my old negative holder on my Canon scanner.

 

[Arbitrarium]

I had a look at the pressure plate and put some more tension in the springs, but then realised something.

The pressure plate doesn't actually apply any pressure to the film. It rests on guides either side of the film that are about 0.8mm from the focal plane. There's no tension in the film when it's wound along, so it makes sense that the film would rest against the pressure plate, and therefore be at least 0.6mm off the focal plane, where my ground glass shows correct focus. Even half a mil would be enough to throw focus off a couple of metres.

So I don't know if you're supposed to calibrate focus from the film guides rather than the rollers/frame and let the film rest against the pressure plate, but that seems quite odd. My other guess is it's another issue of modern film being thinner, with thinner backing paper.

Anyway, I've applied a rectangle of light-seal felt to the pressure plate (~1mm thick) to hold the film against the rollers and image frame, which should in theory keep it where my ground glass shows is the correct focal plane.

Running a roll through to test...

 

[retinax]

Good, you know where the problem is. The distance seems too much to be because of thicker film and backing paper, no way that would have been almost 0.8 mm thick. Did the designers rely on the curve of the film to hold it against the pressure plate? Or is something not original there? The felt fix might curve your film forward through the gate if you applied it to the whole area, probably will through focus off a bit in the opposite direction, or allow it to curve backward if you just made a frame. Wouldn't it be better to apply it to the film rails to hold the film against the pressure plate and calibrate focus accordingly?

 

[Arbitrarium]

My guess is that the film is supposed to rest against the pressure plate, like you say, relying on its curvature. Presumably the lens was then collimated using the actual film gate (which would be the logical place to do it) rather than where the film will actually go, over half of a millimetre further back.

I am second guessing putting the felt across the whole negative... might be better to only apply it over the rollers. I guess I'll see when I finish the film! Guess it'll be a trial and error process.

 

[Steve M.]

I doubt the pressure plate is the problem. Me, I would send the camera back to be fixed properly. Or, put it on a tripod w/ the lens held open w/ a cable release and have it focused at infinity towards something at least 100' away. Then open the back door and tape a piece of GG across the film rails (two pieces of Scotch Magic tape pulled tautly will work if you have no GG), and w/ a loupe or a SLR lens turned around backwards, see if you have sharp focus.

Oh, I see now you have already done that. Then send it back. Even w/o a pressure plate at all, if the film is pulled tightly when you wind on, you should still have a sharp image on the GG. Did you remember to turn the GG coarse side toward the lens? I have accidentally turned it backwards when I was in a hurry. It's possible the rear element is flipped too. Other than that I am out of ideas, but I still think the best thing to do would be to send it back along w/ a scan of the above shot attached in an email to the repair person.

 

[Arbitrarium]

I'm talking to the repairman via email and he's totally fine with me sending it back, we're just discussing possible reasons for the problem because he collimated the lens properly. I made sure to have my ground glass the right way, yeah =P Checked it many, many times and it's perfect on the film rollers/inside film rails.

I think one of the problems is that the camera doesn't have any way to ensure the film is held tightly. The take-up side has a lock, but the feed side has no friction. I read a fix elsewhere where someone added foam disks top and bottom of the feed spool to provide friction and keep the film tight... Might be worth a try.

I've shot a roll this lunch time so I'll develop it tonight and see if my bodge fix has done anything, if not, it's off back to Miles.

 

[Arbitrarium]

Update: The extra felt seems to have worked. Much more accurate focus on this roll, only ever off by a few inches which is easily attributed to user error.

Seems to have slightly uneven focus across the frame, so the felt might indeed be squishing the film a little bit too much. I'll replace the felt with my original plan; an offcut of self adhesive leather that's about 0.6mm thick. Should fit the gap perfectly.

At any rate, shooting at 5.6 or smaller should now be completely fine, and as long as I don't shoot any flat brick walls I doubt I'll notice any uneven bits.

Examples shot today:

 

[johnnyrod]

Star fin evaporator!