Contax G 45mm f2 back focusing?

[LeicaFoReVer]

Hi, put your cmaera in a tripod or use a high speed underexpose 1 point.
put a ruler in a table perpendicular to the camera and focus at 3.5 feet 1 mtr

make 3 shots always at the same distance

1st f2
2nd f2.8
3rd f4

then you´ll see the truth

I have done that already. I had 36 shots with different distances and f values. As I said 45mm failed 13 times in 17 shots.

 

[LeicaFoReVer]

I think you would need to position the chessboard parallel to the film plane to be sure but it looks like your 45 is not performing as it should.

Maybe you can afford a repair or a replacement lens?

I may have had slight angle but I was trying to put it parallel to the film plane like you said. The background scale has 45 degree to it as explained here:

http://www.peleng8.com/how-to-detect-back-focus.html#.U1Z-PlWSz9V

 

[Steve M.]

I suspect it's a matter of learning how to focus your particular camera. I've owned quite a few of these, and found it helped me to point the camera at a well lit and contrasty object, and then lock focus on it repeatedly while keeping a watch on the distance readings. You want to lock focus on that well lit object w/ hard edges. then turn the camera to something else, get focus, then back to your bench mark and lock focus and observe the distance reading again. Do this a lot to get an idea of where you need to be focusing those little [ ] marks.

I found that if I didn't have the two focus points in exactly the correct place I would get variable distance readings, but once I found out where the "sweet spot" was the readings consistently were the same, and my focus problems disappeared. A tiny bit of difference from the ideal will get you a good strong focus lock, but an inaccurate focus. These are not good cameras in real low light unless you want to use the manual focus feature, which works but is a bit tedious in practice. Once I understood where my particular camera wanted the focus marks to be (and they all seem to be a little different in this regard) I had no issues, even w/ the 90 lens, which is known for difficulties in focusing. Keep your lens mount scrupulously clean too. A build up of that blue or green stuff, no matter how little, will affect the communication between your lens and the body and cause all sorts of random problems. Make sure your batteries are fresh too. If they are a little under the correct voltage, everything will still work, but again, random inaccuracies will happen. I found good prices online for the batteries. Buy 'em at the grocery store and you'll pay a fortune.

I loved my little G1, and always got sharp photos from it once I understood the camera's peculiarities, but that squinty little viewfinder always got to me, so I had to go to something different.

 

[LeicaFoReVer]

Yes! I was right. My previous 45mm was faulty. I think now I had luck this time and I received a non-faulty 45mm from KEH (although there are some dust specks between the lens elements... I bought the lens as EX category). I tested the lens on my G2 with Fomapan 100 film and only 1-2 shots missed the focus. Most shots were taken at f2 and some at f2.8). Look at the examples below. You can compare the chessboard patterned test chart with the previous lens posted previously above. The distance to the chart is almost the same, 70cm. This one is darn sharp, what is supposed to be. As usual, stand developed with Foma's rodinal.

So after changing two G1 bodies, and two G2 bodies, and several lenses (due to focusing troubles), I now have a functioning G2 body with 90 and 45mm lenses...