Contax G1 Soft focus problem

[RSilva]

Hi,
I own a Contax G1 plus the 2.8/28 and 2/45 G lenses. I wrote on a previous post my first impressions where that the lenses where too soft.
First, I believed that maybe it was because I didn't understand the camera but I use the focus and recompose technic. Sometimes I would press the focus mode button to "cf" while shooting portrait but I have solved that.
Then maybe it could be the scanner that was not on focus so I scanned some old film from a nikon fm2 that came out pretty sharp.
Because my film came from the lab with a magenta cast I believed the problem resided there - wrong again! I develop 5 rolls myself ever since and still 90% of my images came out soft.
For near objects (about 1 meter) the rangefinder will give me a 1cm error against a tape measurement.
For objects 4 meters away the error in measurement is about 10cm.
This errors seem normal to me, so, can anyone tell me what´s going wrong?:bang:

 

[Bob Michaels]

...................... For near objects (about 1 meter) the rangefinder will give me a 1cm error against a tape measurement.
For objects 4 meters away the error in measurement is about 10cm.
This errors seem normal to me, so, can anyone tell me what´s going wrong?:bang:

Are you determining this by analysis of negatives containing information that would allow you to determine exactly where the lens was focused? Or, is this a determination from reading the digital information displayed on the camera and comparing it to the actual distance? If the latter, be aware that the digitally displayed distance is only an approximation of where the lens is actually focused.

 

[RSilva]

Are you determining this by analysis of negatives containing information that would allow you to determine exactly where the lens was focused? Or, is this a determination from reading the digital information displayed on the camera and comparing it to the actual distance? If the latter, be aware that the digitally displayed distance is only an approximation of where the lens is actually focused.

Yes, this was made using the digital info that was displayed, but i think that such error is between the DOF margin.

 

[Bob Michaels]

Yes, this was made using the digital info that was displayed, but i think that such error is between the DOF margin.

While there is a direct connection and correlation between the distance measured by the AF part of the G1 and positioning the lens to accurately focus to that distance, the values displayed are some approximate afterthought.

I found the built in AF system was more precise than actually measuring the distance and then dialing in the value.

 

[Monochrom]

For what you state i asume the error is a back focus issue.

Always back focus will give you more softness than front focus.

10 cm misfocus is too much.

Many times the AF system on the g´s are off....

IF...the error is back focus then you have to put a shimm in order to solve this back focus problem...if the contrary you must put optical elements closer....

The right way should be to align and reset the AF system...but never knew of such fixing...nor if someone performs it.

On M lenses i do shimming all the time...they´re always off....but´s that another story...

I´ve never dismantled G lenses...but sure it´s not so difficult. the elemnts arrangements should be a screwd in rear element whcih can be undoen to set a shim.

Cheers and good luck!

 

[Monochrom]

oh oh oh...i forgot another thing.....

remember i wrote about af system mislaignmente...well it can be that your camera is not focusing ON the marks of the viewfinder...maybe it´s off, for ionstance i had this g2 that focused on the left corner upper side....so when i believed the camera focues on the centrer marks it just didn´t....so every single shot was out of focus...

As i learned where the focus was really aliegned i was able to shoot correctly....
Try making a simple test to know for sure if this is another case!

Bye!

 

[RSilva]

I have noticed that it´s a back focus problem.
On a closeup photo if I focus the nearest eye of a person, then the focus point will be the other eye.
If I focus a subject on the first plane, the second plane will be sharp.
Subjects placed far away seem not to be affected by this problem.
The problem is more notorious with the 28mm rather than with the 45mm lens.
I have noticed some few dust specs inside the rangefinder lens, could this be fooling the system?
Thank you all for the help.