Contax IIA - Zeiss 50mm f/2 minimal focusing distance

[popel75]

Hi testing one of my Dad's rangefinders. Perfectly working Contax IIa with a Zeiss 50mm f/2 lens.
Maybe a stupid question but I read here that those lenses / bodies may have focusing issues so I tried to check
So I measured with a meter the distance and checked whether the scale on the lens indicates the distance correctly when the RF patch matches.
It works at 1m and 2m and I think at infinity distance quite precisely, yet at MFD the measured distance is 0.85m rather than 0.8m.
I tested in on another 5cm f/2 lens (Zeiss Jena version, my Dad had plenty of lenses ) same results it's 5 cm off.

I guess there should be no issues but was wondering if it's just me or whether this is "normal"

Sorry for this maybe dumb question

 

[Kino]

I am by no means an expert on Contax rangefinders, but this document might have some answers for you:

"Near-focusing devices for the Contax"

The Zeiss Ikon Contax Camera Repair Website - Zeiss Ikon Close-Focusing Devices for the Contax Camera

Yes, it's about supplementary devices, but maybe within the pages there might be information you are looking for and it can't hurt to read it!

There are also many other documents of value about these cameras:

The Zeiss Ikon Contax Camera Repair Website - Articles & Links

 

[brbo]

I tested in on another 5cm f/2 lens (Zeiss Jena version, my Dad had plenty of lenses ) same results it's 5 cm off.

If we are talking about just reading the distance from the mount and not results on film, every lens will give the same result. Even if there is no lens mounted.


Otherwise, when precision is required, do not rely on the distance markings on any lens or camera. You need to check your camera/lens combination with film or ground glass to know for sure if your camera/lens combination is actually focusing according to what rangefinder shows you.

 

[popel75]

If we are talking about just reading the distance from the mount and not results on film, every lens will give the same result. Even if there is no lens mounted.


Otherwise, when precision is required, do not rely on the distance markings on any lens or camera. You need to check your camera/lens combination with film or ground glass to know for sure if your camera/lens combination is actually focusing according to what rangefinder shows you.

Oh OK, so just to make sure I understand: for a known distance of an object at 1M where the object appears in focus in the rangefinder and the focus ring on the lens indicates 1m, this still means that on film it could be out of focus ?

 

[Kino]

It means for very precise measurements, you have to measure from the film plane of the camera to the subject or use a ground glass across the film plane and check the focus scale while the shutter is open on "B".

The film plane is exactly that; the plane where the film rests within the camera. Some cameras have a circle with a line drawn through it to locate the film plane, but I don't think the Contax II has one.

Gross measurements of any unit such as a one, ten or twenty meters will typically be fine unless the rangefinder is severely out of adjustment. Shooting with the aperture wide-open also makes it harder to be precise, as negligible errors will be covered by the depth of field of a stopped-down lens.

When you get down to the minimum focus distance of the lens on a rangefinder, and you know you have a good infinity focus match on the rangefinder, it's best to actually check the minimum distance with a ground glass to see how an engraved scale matches.

Depending on the lens, it can be accurate or pretty far off. It is a rangefinder that has to operate across a large span of distances and with a variety of lenses, so it can vary somewhat at the minimum focus distance.

Checking each lens will give you the exact distance at minimum focus if you require that precision.

 

[brbo]

Oh OK, so just to make sure I understand: for a known distance of an object at 1M where the object appears in focus in the rangefinder and the focus ring on the lens indicates 1m, this still means that on film it could be out of focus ?

Exactly. For example, you could mount a Nikon S lens on your Contax II and it would be out of focus on film even though rangefinder and distance markings on the mount would agree.