Contax G 45mm f2 back focusing?

[LeicaFoReVer]

Hi guys,

Is there such thing known for this lens? I recently bought G2 and finally tested my G equipment and realized that most shots at f2 are out of focus.

Can this be related to the G2 body or the lens? I believe it is with the lens. All other shots at f4 are ok. I havent tested thoroughly but planning to do so in couple of days.

The lens has a bit of wobble. Can this be the reason? see the shot below. I focused on the eye but the focus is on the ear.

 

[LeicaFoReVer]

No one to help me on that?

 

[LeicaFoReVer]

Still no comments, suggestions??

 

[Michel154]

how dose the 90 mm focus ? if it also front focuses that means it is the body not the lens
if it focuses well that means it is the 45mm that is not working out
that is all i can sugjest

 

[LeicaFoReVer]

I will test both lenses on the body with the focusing chart. However I heard that 90mm has a bad reputation at 2.8 with bad focusing so my test might be biased...Lets see.

 

[leicapixie]

http://www.rangefinderforum.com/forums/showthread.php?t=141892

http://www.rangefinderforum.com/forums/showthread.php?t=141892

The problem for me, is where is the thing focusing?
I know you see a mark, but there is parralex etc.
The 90mm shows off the problem of mis-focus more often..
It is for these reasons, that i never used the Contax G1 and G2.
Many are happy, but at that time i was a pro shooter.
I was not prepared to use a camera, which might/could fail in focus..
I was risking life and limb.
Many of you use them, should offer suggestions..

 

[Highway 61]

Still no comments, suggestions??

The Contax G autofocus isn't reliable : focus errors at close-up and unability to quickly/properly focus in front of many subjects, even at average distance.

The G lenses are stellar (including the 90/2.8), the 45/2 is for sure one of the best "normals" ever made, but how the body AF works is the culprit, were it with the G1 or the G2.

The suggestion would be that you jumped into another system if you cannot live with that.

 

[LeicaFoReVer]

I have returned 2 G1 bodies and 1 G2 body for those problems but this time I am determined. This is my second G2 body and second set of 45&90mm lenses and I need to figure this out. There are thousands of focused images of 45mm and 90mm people are taking at wide apertures so it should somehow happen. I like the system and I want to use it but I really need to rely and trust on the focusing at all times.

 

[Highway 61]

I have returned 2 G1 bodies and 1 G2 body for those problems but this time I am determined.

This sounds like an embedded contradiction, doesn't it ?

I have owned and used a G1 with the 28/45/90 lenses set. The tests I made at that time turned out to be an evidence of random and multiple focusing errors caused by the body at focusing distances for which DOF wasn't enough to cover the AF errors. Ditto for subjects in front of which the AF was struggling to focus.

Of course, if you take thousands of photos, you can get hundreds of them which will be properly focused.

You just cannot rely on 100% correct and repetitive focusing with the Contax G bodies. That's it. Nothing can be done.

Or - use the lenses DOF at its best. The typical G AF focusing errors can be covered by the lens DOF even at f/2. Given that you're at a certain distance from your subject. If you come close to your subject, close the diaphragm accordingly. And so on.

There used to be a cleverly made DOF chart for G lenses somewhere on the web.

At the end of the day, you will think that the Zeiss lenses for the Zeiss Ikon RF body are quite as good as the Zeiss G ones... and that you may like the ZI RF system as much as the Contax G one.

 

[LeicaFoReVer]

This sounds like an embedded contradiction, doesn't it ?

I have owned and used a G1 with the 28/45/90 lenses set. The tests I made at that time turned out to be an evidence of random and multiple focusing errors caused by the body at focusing distances for which DOF wasn't enough to cover the AF errors. Ditto for subjects in front of which the AF was struggling to focus.

Of course, if you take thousands of photos, you can get hundreds of them which will be properly focused.

You just cannot rely on 100% correct and repetitive focusing with the Contax G bodies. That's it. Nothing can be done.

Or - use the lenses DOF at its best. The typical G AF focusing errors can be covered by the lens DOF even at f/2. Given that you're at a certain distance from your subject. If you come close to your subject, close the diaphragm accordingly. And so on.

There used to be a cleverly made DOF chart for G lenses somewhere on the web.

At the end of the day, you will think that the Zeiss lenses for the Zeiss Ikon RF body are quite as good as the Zeiss G ones... and that you may like the ZI RF system as much as the Contax G one.

Not really a contradiction. I am in the group of people who believe the majority of the focusing errors occur due to the user error. In this particular case I am guessing that finally the focusing error I am having might be due to the defective lens. However I am going to test it.

 

[j j]

Yes, it is possible that either the camera or the lens is not working properly but G cameras are a little quirky and I would not give up yet.

I have used a G2 and 28/45/90 for a few years and cannot recall a single misfocus that was the fault of the camera. But that is looking back from now... when I first got the camera I thought it was misbehaving... now I know it was my inexperience.

It is a simple system with a single focus point and if you approach it expecting it to work like a modern autofocus camera you can be very disappointed. When I first got my camera I just expected it to work and missed focus fairly often. Rather than give up I got methodical.

I started to use the back button to focus. I gave the AF plenty of time to hit the mark before tripping the shutter. I trained myself to always check the focus distance in the viewfinder (much like I check the exposure).

I practiced without film by focusing the camera on objects that were well separated from the background. I found road signs to be good for this as they have an easy target (the sign) and a trickier one (the post). I learned where exactly to aim to focus (the guide box in the viewfinder is not exact) by working my way from missing one side of the sign through hitting the target and missing on the other side. After that I moved to trickier objects such as a thin branch or single leaf.

When I loaded up with film I found that my camera was behaving much better! I took it slowly at first and soon enough my routine was second nature and I got faster. Now I just point my camera where I need to focus and it works. I hardly even notice the viewfinder target box let alone rely on it showing me where to point. I now find my camera to be quick and accurate.

When you took your example photo, did you take any others of your subject facing you? If the camera focused those easier photos correctly you know the camera/lens is working OK.

In your example shot (by the way it is a front focus error not back focus) your subject's eye is not positioned in the middle of frame where the camera focuses. Did you focus and recompose? That's a tricky job for any camera at f2 and for a viewfinder/rangefinder camera it is particularly difficult. To make sure of getting the shot I suggest take a few frames focused on slightly different areas of the face (nose, eye, cheek, forehead) to bracket the focus.

Another possibility is that you aimed at the eye and the camera focused on the near edge of the eye socket and missed the eyeball/eyelashes. The eye is a small target at this angle and I when using my G2 I would be tempted to focus on the front curve of the cheek (same plane of focus as the eye) as an easier target.

By the way, the G2 has a dual focus system and does not need contrast to judge focus so you can focus accurately on plain areas (it can focus in the dark and on transparent things such as window glass). This is often an advantage compared with my SLRs and mirrorless autofocus cameras as these can struggle with featureless targets.

This turned into a bit of a long post. I hope it is helpful and wish you luck with the camera. G cameras are not for everyone but I for one am glad I persevered with mine. I love using it and I love the results. I don't choose to use it for every occasion and, truth be told, if I were taking lots of shots like the one in your example I would prefer my SLR.

 

[LeicaFoReVer]

Thank you very much for your long message with lots of suggestions. Yes it is a quirky system and I gave up before without knowing those details blaiming the system so that is why I want to be more systematic this time. I made a test today and I will post my results later today.

As per your questions, yes I focused using the focus lock button and recomposed. Ok this was a rather quick shot and my wife wasnt posing really so it might be due to those as well. It was not a real test. There are 2-3 shots more where the focus was missed (at f2). Eye is tricky place to focus and thank you for your suggestion on focusing on cheek. It might better work.

However during my test today, I realized that indeed the G system suffers in focusing on plan subjects, particularly on the A4 page with vertical lines. It gave 8/10 0.64m and twice 0.6m. This is my observation.

And you are right. It is front focusing not back focusing in my example.

I will keep you posted.

 

[j j]

You are very welcome. Great pics and cameras in your flickriver. Hopefully you will be back with good news about your G2 soon. I shall look out for posts from G2FoReVer!

 

[LeicaFoReVer]

Hi guys,

After I finished my test, I shoot 14 shots with 90mm at 2.8 and 17 shots with 45mm at f2. 4 out of 14 shots with 90mm failed but it was when I centered the focus point btw focusing brackets. When I put the right bracket on the focus point, like recommended on internet, it is quite sharp and focuses bang on.

However 45mm gives quite a number of out of focus shots (13 out of 17) at different distances while the focus distance shown on lcd is right. So I tend to believe that I have a defective 45mm.

I bought it on rff and noted the wobble after I received (6 months ago) but as I didnt have a g2 body at that time I couldnt test it but used it on sony nex ever since.

 

[ianstamatic]

I have a g1 28 45 90 that i use a lot and dont experience any of the focus trouble discussed here.
I find it reliable and works just as expected, i also use the 90 wide open, close up with no problems.
i did however read the guides to using the g-system af to its best ability...
there is a method to it. and once your used to it, its very reliable.
if i where to miss more than 2shots per 38 exposure roll, i'd have an issue.

 

[LeicaFoReVer]

I have a g1 28 45 90 that i use a lot and dont experience any of the focus trouble discussed here.
I find it reliable and works just as expected, i also use the 90 wide open, close up with no problems.
i did however read the guides to using the g-system af to its best ability...
there is a method to it. and once your used to it, its very reliable.
if i where to miss more than 2shots per 38 exposure roll, i'd have an issue.

Hi Ian,

Could you please share the methodology you use which is not mentioned already here. I would like to learn it if it is something different than what we discuss.

In the end, I think my 45mm is probably faulty. I will share the images later on.

 

[LeicaFoReVer]

here are the photos:

crop of the image with 45mm:

90mm @f2.8:

and the crop of the above image:

 

[j j]

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?

 

[leicapixie]

http://www.rangefinderforum.com/forums/showthread.php?t=141892

http://www.rangefinderforum.com/forums/showthread.php?t=141892

I am still amazed after all that you have seen and seen,
think there is a solution to exact focus.
Even Leica M's can fail, as we see with digital..
The answer is not making rivers run uphill..
Realism is understanding (and that includes the Leica M)
are NOT scientific instruments..
The whole concept of the Contax was that it was a simpler,
to use,camera than the Leicas..
Get a lens-bench test at a repair facility.
Look thru the collimator, if you can..
Bracket your exposures, use depth of field..
stop pixel peeping.
Live happy.

 

[Monochrom]

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