Questions about focus accuracy, CLA, etc

Started 10 months ago | Discussions
Petter Salvesen
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Questions about focus accuracy, CLA, etc
10 months ago

Hi everyone. I recently bought a used M9 as my first digital rangefinder. I got the Summarit 50mm F/2.5 with it, and it worked great. However, when I bought the Voigtländer 50 1.1 (F/2.5 in Norway is not very useful this time of year, seeing as the sun hasn't risen when I go to work, and has set when I go home from work), I noticed the focus was way off.

I thought the lens had to be faulty, since the focus with the Summarit was perfect (I am aware of the DOF differences from F/1.1 to 2.5, but stopping down the Voigtländer doesn't help at all, I am also aware of focus shift, please read on!). I tried my Voigtländer 35mm F/2.5 Color-Skopar that I use on my Bessa, and it seemed to be backfocusing, same as the 50.

As a dSLR user, this rangefinder stuff is all new to me, but could it be that the M9 has earlier been adjusted to focus perfectly with the Summarit, which might be slightly off compared to what's "right"?

I asked about the possibility of sending camera + lens in for adjustment, to which the reply was "Leica doesn't adjust their cameras with voigtländer lenses", meaning that I would have to send it in without the lens and hope for the best.

Any help would be appreciated, I don't want to return the lens if it turns out to be the camera that's in need of a CLA.

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JDLaing
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Re: Questions about focus accuracy, CLA, etc
In reply to Petter Salvesen, 10 months ago

Lenses and bodies are each adjusted to a tolerance individually. They are not done as a pair. IE: Lenses are not calibrated to an individual body Or vice versa.

In your case I would suspect the Voightlander lenses are calibrated for a film body and the tolerance is greater. The fact that the Summarit focuses correctly is the hint.

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jeff hladun
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Re: Questions about focus accuracy, CLA, etc
In reply to Petter Salvesen, 10 months ago

Have you tried setting the camera on a tripod, placing a ruler in line with the camera, measuring the distance of a set mark on the ruler to the sensor plane, and then comparing all that to the distance scale on each lens? This should indicate whether it's the camera or the particular lens which is out of whack.

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bosjohn
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Re: Questions about focus accuracy, CLA, etc
In reply to JDLaing, 10 months ago

if the back focus is consistent you can soon learn to compensate for it close enough for all but the most critical of applications. I am surprised though that stopped down it doesn't look better.

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bosjohn aka John Shick bosjohn@yahoo.com

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Petter Salvesen
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Re: Questions about focus accuracy, CLA, etc
In reply to JDLaing, 10 months ago

JDLaing wrote:

Lenses and bodies are each adjusted to a tolerance individually. They are not done as a pair. IE: Lenses are not calibrated to an individual body Or vice versa.

In your case I would suspect the Voightlander lenses are calibrated for a film body and the tolerance is greater. The fact that the Summarit focuses correctly is the hint.

So it's not like with DSLRs where you can send in body + lens to get the camera calibrated to that specific lens?

I got told to return it to the shop where I got it, they would look at it and see if they could fix it. If not, they would refund me the money. There isn't a single repair center for Voigtländer in norway, it seems.

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Petter Salvesen
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Re: Questions about focus accuracy, CLA, etc
In reply to bosjohn, 10 months ago

bosjohn wrote:

if the back focus is consistent you can soon learn to compensate for it close enough for all but the most critical of applications. I am surprised though that stopped down it doesn't look better.

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bosjohn aka John Shick bosjohn@yahoo.com

I tried that, couldn't get a single shot that was in focus @ F/1.1. I would have to adjust differently at different focus distances anyway, so not a working solution

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JDLaing
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Re: Questions about focus accuracy, CLA, etc
In reply to Petter Salvesen, 10 months ago

Petter Salvesen wrote:

JDLaing wrote:

Lenses and bodies are each adjusted to a tolerance individually. They are not done as a pair. IE: Lenses are not calibrated to an individual body Or vice versa.

In your case I would suspect the Voightlander lenses are calibrated for a film body and the tolerance is greater. The fact that the Summarit focuses correctly is the hint.

So it's not like with DSLRs where you can send in body + lens to get the camera calibrated to that specific lens?

I got told to return it to the shop where I got it, they would look at it and see if they could fix it. If not, they would refund me the money. There isn't a single repair center for Voigtländer in norway, it seems.

That is correct. The rangefinder is calibrated to a tolerance level And so is the lens but independent of each other.

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