Focus issue--what's going on here?

[Takkun]

I swear, I'm driving myself silly trying to figure this out.

I've got an ELCAN 90 Elmarit that I've mentioned in previous threads. A while back, I wasn't sure if it was focusing right, so I took it to CameraTechs in Ballard, who said everything was A-OK and it was my eyes playing tricks on me.
However, now I'm starting to second-guess myself again. I can't tell if it's my camera back-focusing or the lens, or just me.

The other night I was shooting an al fresco theatre performance around dusk, and there was enough light to shoot wide open, so I did.

I swore I was spot-on; my M5 has a nice, bright RF patch.

Guess not.

So while I was scanning, I found another image, same lens, same camera, that I snapped off at the local high school, focused at infinity. (ignore the awful subject matter)

And yet, I can't tell if it's in critical focus.

What's throwing me off is that every other shot on those rolls were with a 35, stopped down in daylight except for two with a 50 which I attribute being out of focus from shooting carelessly wide-open, and a third with the 50 that's spot on.

Pointing it out my front window to the same office tower appears to be in focus in the VF.

Complicating matters further: my Bessa. The vertical RF is out of alignment on it already, so there's a strike against it. Second, with the 90 mounted on it at infinity, the RF doesn't align fully. And yet the only shot I recall taking with that combo recently is just fine (wet printed; I don't have a scan yet).

I know that it's not a DIY and the obvious solution is sending something in, I just don't know what the weak link is, and I'm dragging my feet.

What are you guys seeing here? I apologize for the graininess, it was Delta 400 pushed two stops, so that isn't helping the analysis. If I shoot a test roll and process at home, what procedure should I use?

 

[Landshark]

check focus with a ground glass held at the film plane. With a sharp image on the GG(use a magnifier) check your RF image. If they disagree, try the 35 too. If both lenses checkout on the GG, the RF needs a tweak or nudge.
Frosted Scotch tape can also work well to focus on.

 

[Chriscrawfordphoto]

It might be your camera, not the lens. I have seen A LOT of rangefinder cameras whose rangefinder is out of adjustment, causing backfocus. Lenses rarely go out of adjustment, but cameras do because the RF mechanism is one of the more delicate parts of a camera, and being banged about, vibrations, etc. can cause them to need recalibration.

 

[peterm1]

Here is how you can check and be able to give accurate info to your camera technician.

I was having problems with my M8 (and pretty much all of my lenses) which looked like bad back focusing on the M8. The symptoms made it pretty certain it was a camera body issue but I needed to confirm this and to know to what extent (ie by how many centimeres at each aperture and distance).

So I bought a plank of planed pine wood maybe 2.4 metres in length and marked it off in one centimetre intevals around a cental mark that I made on the plank. The central mark was emboldened to make it more obvious and this became my aiming point for all tests.

I then numbered some of the centimetre marks behind (+1,+2,+3 etc) and in front (-1,-2,-3 etc) out to perhaps 60 centimetres in front and behind the central point. Sounds like a lot of work but all took perhaps 30 minutes to do once I had bought the plank.

Then I set up the camera on a tripod and placed the board on the floor in front of it in a well lit garage with the aiming point an exactly measured 3 metres from the film plane of the camera (which is marked on the camera body). Of course the distance can be varied for testing purposes. And of course with this set up the camera is angled down at about 45 degrees, give or take. This does not matter for these purposes.

Then I set about shooting a range of images, firstly using the measured distance, then using the rangefinder to focus on the marked aiming point.

To make sure I knew which shot was which, I wrote on a piece of paper the details of each test shot and placed this beside the aiming point so it was captured in each image (Name of lens, distance to target, whether that specific shot was measured distance or rangfinder focused and the aperture used). I did this several times with several lenses at various distances. Took maybe 1-2 hours for the entire preparation and test series.

Then I had the data I needed to be able to show my camera tech including whether the rangefinder was back focusing (yes it was), by how much (a lot) and how much this varied with different apertures and lenses

(Actually I just gave the tech a USB thumb drive with the pics on it - which included the paper with the details of each test shot's parameters - he was smart enough to work the rest out.)

When the camera came back it was spot on. The significance of measuring the distance and checking focus this way rather than just using the rangefinder was that it allowed me to confirm whether the problem was RF calibration or something else. If the measured distance focus was out it could not be a rangefinder problem and most likely would be the lens.

The same can be done with a film camera but of course you do not get instant feedback as you have to develop and print the images. But it will still work. Sounds like a heap of trouble - but serioussly all it took was a tiny bit of planning and some paiins taking measurement and discipline to stick to the test plan.

 

[Takkun]

Thanks, Peter. That's sort of the method I had in mind, I just wasn't sure if it was the best approach.

Though I think it might be safe to say it's the lens. Last month I was shooting in a helicopter and brought it and a roll along for ****s and giggles (never attempt to reload a Leica 900 feet in the air!), and I just got around to scanning. Every shot, at infinity, was out of focus.

Off to DAG, it seems..

 

[dct]

I have a similar problem with an old Elmar f4/90mm (one of the last produced ~1960 already with M mount). All my other lenses work spot on on my Hexar RF. That's why I'm 99 % sure the problem is the 90mm lens itself. With trial and error I understood: If the RF patch shows 10m, the lens shows only ~9m. Turning the lens to 10m gives perfect focus. I know the problem and try to avoid wide open narrow images or compensate manually for the shortcoming. But it is always a guessing work and very annoying.
Will have to test the same way as Peter mentioned to better understand where and what the issue is.

What if it's really this one lens only? Can an old Elmar be calibrated DIY?