Contax g1 'back focus' issue?

[simon_gabriel]

Hey, guys! I hope I'm posting this in the correct section. If

I'm not then please point me in the right direction.

So, a few days back I decided to test out my Contax g1

with the 45mm planar. All the labs were shut so I

developed my first c41 in a rollei digibase kit. The results

came out OK, but rather dirty as expected for my first

time. One thing that struck me though, was the fact that a

lot of the pictures day did come out appeared out of

focus. I wasn't very experimental in my practice and a

large portion of the photos that were out of focus were

very well taken on my behalf and I understand contax's AF

system so I don't feel like it was a skill set problem.

 

To make sure, I took the camera out today and took some

careful photos in all different apertures. I had the photos

scanned by a lab and have just had them back. The

photos again, are out of focus. The ones shot on f2 are

understandably the worst. Often the subject T is missed

slightly and the result is very soft.

 

From some research I learnt about a problem called 'back

fosusing' where the mirror and lens is slightly off causing

a miss of focus. Could this be my problem? I have read up

on the g1 and where some people have complained about

the G1's focusing, others praise it and claim they've never

missed with a careful eye. Let me illiterate here, I was very

careful with my shots! I am a decent photographer and

understand my shot. :)

 

I am away from my computer right now, so I will attach

my test photos for you to look at as soon as I can. In the

mean time, sound like anything anyone knows about?

Could this be a problem with my lens or is it a body thing?

Both lens and body are new to me.

Thanks!

[SCL]

<p>Simon - to really narrow down the cause, you should shoot a test roll on a tripod so as to eliminate any user shake issues. Likewise in that test you should take a series of test shots at the indicated point of focus. My understanding of the autofocus system in the G1 is that it works well with vertical lines and areas with distinct contrast, but not very well on horizontal lines - quite different than most modern af cameras. You can check backfocus with some elementary gear or a chart like this one http://regex.info/blog/photo-tech/focus-chart although you may have to modify the chart slightly with a vertical centerline. This one is the one I've used for years to check when I've had reason to suspect backfocus issues with my bodies http://www.kscameraclub.org/docs/pdfs/focus_test_chart_edited.pdf.</p>

[simon_gabriel]

<p>Thanks very much for the help, Stephen! I'll be sure to do another roll of more scientific tests.<br>

Here's a few that I carefully took on the roll today, most of which are focused centrally and with decent lighting. A few of these were f2, and some f2.8, f4.<br>

This, the camera should have been in focus for certain:</p>

<p><img src="http://imgur.com/1kj2k6z" alt="" /></p>

<p>This, no sharpness at all:</p>

<p><img src="http://i.imgur.com/rm4OflR.jpg" alt="" /></p>

<p>Again:</p>

<p><img src="http://i.imgur.com/Bq2QEsa.jpg" alt="" /></p>

<p>This one I made CERTAIN that I focused and shot it correctly, as I thought it was a good subject (f2):</p>

<p><img src="http://i.imgur.com/rkDjWkQ.jpg" alt="" /></p>

<p>And this, f2, looks like it slightly missed focus. No sharpness at all:</p>

<p><img src="http://i.imgur.com/r6rHJum.jpg" alt="" /></p>

<p>Again with this subject, focused well, carefully. Zero sharpness. Rubbish!</p>

<p><img src="http://i.imgur.com/E8X5aw8.jpg" alt="" /></p>

 

[simon_gabriel]

<p>Sorry, that first one where I said "<br>

This, the camera should have been in focus for certain:</p>

"

 

I was referring to this:

 

<img src="http://i.imgur.com/V9J4VSV.jpg" alt="" />

 

 

[simon_gabriel]

<p>The battery couldn't be responsible for anything like this could it?</p>

[Robin Smith]

<p>Are you sure the lab is scanning them nicely? Some labs are pretty bad at obtaining critical focus. Use a loupe or the 45mm lens off the body to see how sharp that lettering is on the negative before jumping to the conclusion that the AF is off. Use the lens as a magnifier, then report back.</p>

[SCL]

<p>Without seeing a 100% crop some are hard to tell for sure. It looks in the last one (mirror shot) that the rim of your glasses are in sharp focus, and if you were shooting at a wide aperture, which I'm guessing you were, there is razor thin DOF. The red PO box in the one above that is in sharp focus, but I'm again guessing you may have been trying to focus on the lower insert. If I recall my long ago research on this body, there is only 1 focus point ...dead center in the field and if you want to focus on something else which isn't dead center you need to lock it by initially focusing on it, using a continuous half shutter press and then recomposing.</p>

[simon_gabriel]

<p>Thanks for the replies. Robin, I do believe they're scanned property as my concern originally was that my home developed ones were blurred, also. I just checked the negative and it does seem that they're unsharp on them, also!</p>

<p>Stephen, thanks for the reply! If you drag and drop my photos on here (or right click and copy the image url) and put that into a browser then you should be able to see my photos in a larger resolution. I understand what you're saying, however my tests on focusing on these objects were so carefully done that the results should have not been like this. For example, the one of the missing car poster on the railings and the one of the post box were dead center focused. There is no way I missed.<br>

Likewise with the camera middle one. You mention that my glasses (and I see my shirt) are in focus. And this is what makes me believe it might be back focusing problem. It seems like my subject each time has been missed and on f2, sharpness is always slightly behind me.<br>

I'm very sure it's not a problem with how I'm taking the photos because it couldn't possibly be this hard to get a focused shot with such a camera. I'm able to get great results from much, much, much worse cameras!! What I'm saying is I need to rely on this camera and not worry that every time I take a shot, it's hit or miss with focusing (in this example, it's almost always miss even when I'm dead certain I got the shot)<br>

If it is back focusing, would that be a problem with my G1 and not the lens?<br>

.</p>

[donbright]

<p>Could be the focus motor, or an issue not allowing the lens to realize its full, or entire swing in and out. Contax G1s, and G2s are fine camera's, and of course the lenses are amazing. If you are interested in keeping your camera, send it off to: ToCad America in New Jersey. Thousands of Contax camera's run through there.</p>

[andrew_brown7]

<p>Hi,<br>

Can you focus manually with the camera?<br>

I've been looking at the pics enlarged and I'm hard pressed to find any lack of focus effort on the part of the camera, but certainly what looks like shake, or perhaps it's very shallow DoF.<br>

You should post some straight on pics when the DoF might not matter so much as regards focus, but these oblique shots are very difficult for the camera to get a grip on where to focus I would imagine.<br>

Is the camera focusing on the mirror glass itself, for instance? <br>

In the cat picture the lettering is not focussed but the metal column to the right of the sign is a bit better focussed, but again, the oblique nature of the shot at a small aperture makes it tough for the camera to choose a spot to go for.<br>

In the PO box shot, the enamelled plate is fairly sharp, as are the crown areas both sides of the box, whereas the front of the curve above the letter slot is not at all sharp. Perhaps the camera is focusing 3 or 4 inches behind where you think it's focusing? <br>

Andy.</p>

 

[philip_wilson]

<p>As a G1 (and G2 shooter) of many years I would make the following suggestions.<br>

1 Get into the habit of checking the top range display to see if you are focusing where you plan to. After a few weeks of doing this you will no longer need to do it.<br>

2 You will always have at least 1 or 2 shots on a roll where the focus is not what is intended with the G1 - especially if you shoot the 90mm a lot.<br>

3 The G1 focuses best on strong vertical lines in my experience. Be prepared to focus, lock focus and compose.</p>