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Author Topic: Contax 645 focusing problems  (Read 9221 times)
william
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« on: November 13, 2006, 10:37:45 AM »
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Kind of a strange question, but I'd be interested in hearing theories on this.  I'm shooting with a Contax 645 + Phase One P30.  On waist-up and headshots, I can always nail sharp focus.  With full length shots, however, the images almost always look a bit soft.  It doesn't seem to be really "misfocused," because there's no area of critical sharpness on the full length shots I'm concerned with; rather, the whole image looks slightly soft.  So, I was thinking camera shake, but there's no reason why I'd get more camera shake with the same camera and lens (and f-stop and shutter speed) on a full length shot than with a waist-up or headshot, is there?  Same owuld go for subject movement; you'd expect to always see it if this was my problem.

So now I'm thinking that perhaps there's a problem with my lens in the far, but not near, distances.  E.g., focusing is perfect from 5-7 feet away for a headshot or waist up, but focus is off at the 10-15 feet needed for a full lenght shot?  (Do lenses behave this way?  Can they be out of alignment only at certain distances?)  Or perhaps it's the AF that's inaccurate int he far, but not near, distances?  But again, what I'm seeing in these full length shots is not misfocuing (e.g., where the focus point is behind or in front of what I'm aiming for), but an overall softness or lack of sharp focus anywhere.

I almost always shoot with the 140mm lens, so I'm not 100% sure if my other lenses display this issue on full length shots.  I guess I should do some "brick wall" tests at various focusing distances with various lenses...

Thoughts?
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Morgan_Moore
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« Reply #1 on: November 13, 2006, 11:18:47 AM »
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I had mamiya where I was sure that the chip was not alligned correctly with the focus plain of the mirror

The result was backfocusing using both AF and MF

My experience was that closer to infinity the effect was more obvious

------------

When shooting your brick wall shoot along it not at it then you can see if you are getting front or back focus

If your chip is missaligned (or the mirror of your Contax is not at 45 degrees) you have a problem

Firstly check that the back is properly mounted on the camera (a bit of sand will throw it off)

Next check that your groud glass is seated correctly (again checking for grit etc)

Check that you mirror is dropping to 45 degrees properly (grit or aging springs)

If all is good then you need to get the body/and or back checked out

Probably the C body is not that high tolerance - maybe try the back on another one

Sinar backs allow 'tuning' a back to a body via a shim system - current phase do not I believe - you may end up having to get another body because it is possible that everything is within manufacturers tolerance and still is 'off'

SMM
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James Russell
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« Reply #2 on: November 13, 2006, 11:43:49 AM »
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Kind of a strange question, but I'd be interested in hearing theories on this.  I'm shooting with a Contax 645 + Phase One P30.  On waist-up and headshots, I can always nail sharp focus.  With full length shots, however, the images almost always look a bit soft.  It doesn't seem to be really "misfocused," because there's no area of critical sharpness on the full length shots I'm concerned with; rather, the whole image looks slightly soft.  So, I was thinking camera shake, but there's no reason why I'd get more camera shake with the same camera and lens (and f-stop and shutter speed) on a full length shot than with a waist-up or headshot, is there?  Same owuld go for subject movement; you'd expect to always see it if this was my problem.

So now I'm thinking that perhaps there's a problem with my lens in the far, but not near, distances.  E.g., focusing is perfect from 5-7 feet away for a headshot or waist up, but focus is off at the 10-15 feet needed for a full lenght shot?  (Do lenses behave this way?  Can they be out of alignment only at certain distances?)  Or perhaps it's the AF that's inaccurate int he far, but not near, distances?  But again, what I'm seeing in these full length shots is not misfocuing (e.g., where the focus point is behind or in front of what I'm aiming for), but an overall softness or lack of sharp focus anywhere.

I almost always shoot with the 140mm lens, so I'm not 100% sure if my other lenses display this issue on full length shots.  I guess I should do some "brick wall" tests at various focusing distances with various lenses...

Thoughts?
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There is a lot your not mentioning, such as light source, fstop, shutter speed, auto focus or manual.

I have two Contax bodies mounted with two seperate backs.  One is brand new, one I bought used and has some wear and neither have focusing issues, or any form of slap or blur with the complete range of lenses.

I do know that with the 140 if I stop to to F 16 I get a slight softness that I don't see at F8 or 11.

Since you are in focus some of the time and not other times I would check some other lenses, possibly renting another 140, before I changed cameras.

If you using autofocus it is my experience that the contax is "weighted" to focus to the center of a subject.  In other words if you focus on the middle of a full length, it easily pulls the face in focus even at wide open apertures, so if you focus on faces you should focus on the furthers point of a face such as the nose or lips.

JR
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william
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« Reply #3 on: November 13, 2006, 12:23:00 PM »
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Thanks for all your thoughts.  James, I'm shooting with Profoto D4 strobes, f8-11, 125th shutter speed, AF with manual focus tweaks as needed.

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There is a lot your not mentioning, such as light source, fstop, shutter speed, auto focus or manual.

I have two Contax bodies mounted with two seperate backs.  One is brand new, one I bought used and has some wear and neither have focusing issues, or any form of slap or blur with the complete range of lenses.

I do know that with the 140 if I stop to to F 16 I get a slight softness that I don't see at F8 or 11.

Since you are in focus some of the time and not other times I would check some other lenses, possibly renting another 140, before I changed cameras.

If you using autofocus it is my experience that the contax is "weighted" to focus to the center of a subject.  In other words if you focus on the middle of a full length, it easily pulls the face in focus even at wide open apertures, so if you focus on faces you should focus on the furthers point of a face such as the nose or lips.

JR
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James Russell
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« Reply #4 on: November 13, 2006, 12:35:21 PM »
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Thanks for all your thoughts.  James, I'm shooting with Profoto D4 strobes, f8-11, 125th shutter speed, AF with manual focus tweaks as needed.
[{POST_SNAPBACK}][/a]

You should isolate between manual and autofocus.

I find the autofocus on full length fashion to be dead on, in fact I find it the most accurate of any autofocus I've used.  Many people complain about the Contax autofocus as slow, but especially on continuous I have more in focus percentages than I do the Canons or Nikon.

JR
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RicAgu
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« Reply #5 on: November 13, 2006, 12:59:42 PM »
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Not sure about your Contax problem as I switched to the H1 when I went digital.  But int hte film days my Contax was tack sharp all over the place.

One problem i see right away though.  You are shooting with strobe at 125th shutter.  The contax only syncs at a 90th or 60th.  You have to stay on top of it but when ever you're shoot strobe. You have keep it on X and remember to take it off X when you are not shooting strobe.  Strobe sets it to 90th.

Best of Luck

 
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Thanks for all your thoughts.  James, I'm shooting with Profoto D4 strobes, f8-11, 125th shutter speed, AF with manual focus tweaks as needed.
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william
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« Reply #6 on: November 13, 2006, 01:05:12 PM »
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Huh?  I don't have a user's manual, but I thought I remembered from my film days that the COntax will sync at 125th or below when in manual exposure mode.  So, you're saying that (1) it only syncs up to 1/90th and (2) it has to be in "X" rather than "M" mode?  If so, I feel like an idiot.  But wait; if I were exceeding the flash sync speed, wouldn't I expect to see the shutter curtain/partial blackout of the image?

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Not sure about your Contax problem as I switched to the H1 when I went digital. But int hte film days my Contax was tack sharp all over the place.

One problem i see right away though. You are shooting with strobe at 125th shutter. The contax only syncs at a 90th or 60th. You have to stay on top of it but when ever you're shoot strobe. You have keep it on X and remember to take it off X when you are not shooting strobe. Strobe sets it to 90th.

Best of Luck

 
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william
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« Reply #7 on: November 13, 2006, 01:38:00 PM »
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Two examples of the problem I'm having are attached.  Specifically, the first is a full length shot where I used AF to focus on the near eye (no manual tweaks).  Nothing in the face appears in sharp focus.  The second is a tighter shot, also using AF w. no manual tweaks, where I focused on the near eye and it's tack sharp.  Everything was exactly the same except for my distance from the model (and obvious differences, like the use of gels).  Both are unprocessed, except for initial levels adjustment and converting to JPEG.
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RicAgu
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« Reply #8 on: November 13, 2006, 01:53:42 PM »
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It will sync at anything below 90th in manual mode.  But there is no 90th setting.  There is 60th or 125th.  When shooting with strobe keep it at 60th and on the X.  But make sure to remember to take it off X when not shooting with strobe.  As long as you shoot 60th and below you will be fine on X.

If you have been shooting at 125th in M mode and you don't have half a black frame, then I am not sure.  You may want to check with JR about that.

Best of Luck

 

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Huh?  I don't have a user's manual, but I thought I remembered from my film days that the COntax will sync at 125th or below when in manual exposure mode.  So, you're saying that (1) it only syncs up to 1/90th and (2) it has to be in "X" rather than "M" mode?  If so, I feel like an idiot.  But wait; if I were exceeding the flash sync speed, wouldn't I expect to see the shutter curtain/partial blackout of the image?
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James Russell
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« Reply #9 on: November 13, 2006, 01:58:20 PM »
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Two examples of the problem I'm having are attached.  Specifically, the first is a full length shot where I used AF to focus on the near eye (no manual tweaks).  Nothing in the face appears in sharp focus.  The second is a tighter shot, also using AF w. no manual tweaks, where I focused on the near eye and it's tack sharp.  Everything was exactly the same except for my distance from the model (and obvious differences, like the use of gels).  Both are unprocessed, except for initial levels adjustment and converting to JPEG.
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Everybody tells me the Contax syncs at 1/90th and it does if you set it at X, but it will also sync at 125th.  In fact i've never shot in studio with flash at anything but 1/125th and never had a half black frame or any vignetting.

I believe his focus problems comes from setting autfocus on the full length on the face.  Just let the autofocus fall at the center of the subject and it will pull the face, at least it does for me.


JR
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william
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« Reply #10 on: November 13, 2006, 02:18:52 PM »
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James,

Let me be clear: you're suggesting, even at wide apertures, that you're getting sharp eyes by focusing on the lips or nose?  That just seems so counterintuitive to me...


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Everybody tells me the Contax syncs at 1/90th and it does if you set it at X, but it will also sync at 125th.  In fact i've never shot in studio with flash at anything but 1/125th and never had a half black frame or any vignetting.

I believe his focus problems comes from setting autfocus on the full length on the face.  Just let the autofocus fall at the center of the subject and it will pull the face, at least it does for me.
JR
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James Russell
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« Reply #11 on: November 13, 2006, 02:33:55 PM »
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Everybody tells me the Contax syncs at 1/90th and it does if you set it at X, but it will also sync at 125th.  In fact i've never shot in studio with flash at anything but 1/125th and never had a half black frame or any vignetting.

I believe his focus problems comes from setting autfocus on the full length on the face.  Just let the autofocus fall at the center of the subject and it will pull the face, at least it does for me.
JR
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I guess, you know I really don't think about it that much.  All these cameras and computers train us to the point we just kind of do what we do.

Just like if I fire too fast using the Aptus back it will lock up, so I never fire too fast and at this point I don't know what too fast is.  I do know I don't get anymore lockups.

Iin some instances I will autofocus on the center of a body, sometimes I manually focus on the bridge of the nose but for some reason it's in focus.

Actually in the few short focus tests I've done with the Canon vs. the Contax, I've found I can focus the contax more accurately, but then again I'm very use to using the contax.

Early on I sent all my Contax lenses and bodies to Leaf to check with the back and all came out exact so I figure at this point if I miss focus it's my fault.

Foucs has always been difficult in photography.

JR


JR
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damien
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« Reply #12 on: November 13, 2006, 02:36:02 PM »
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I recently had the same problem with my 80mm lens on my H1. The 35mm and the 210 were spot on both close and far but the 80 was soggy far, and good close. I say soggy because it was not clear where the principal point of sharp focus was on the pictures. I was no more sucessful on AF than MF. I sent the lens for calibration to Hasselblad and it came back tack sharp. I don't know what they did but it worked.

Damien.
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william
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« Reply #13 on: November 13, 2006, 02:47:04 PM »
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Hm.  Anyone know who still services Contax 645 items?


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I recently had the same problem with my 80mm lens on my H1. The 35mm and the 210 were spot on both close and far but the 80 was soggy far, and good close. I say soggy because it was not clear where the principal point of sharp focus was on the pictures. I was no more sucessful on AF than MF. I sent the lens for calibration to Hasselblad and it came back tack sharp. I don't know what they did but it worked.

Damien.
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James Russell
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« Reply #14 on: November 13, 2006, 02:51:12 PM »
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Hm.  Anyone know who still services Contax 645 items?
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Nippon, NY

But first go through a series of focus checks.  Learn how the camera reacts.

JR
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william
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« Reply #15 on: November 13, 2006, 02:58:12 PM »
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Thanks, James.  I will run some focus checks first.  If I discover a systemic problem, I'll see if Samy's will accept return of the lens at this point.  If not, I'll look into Nippon.

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Nippon, NY

But first go through a series of focus checks.  Learn how the camera reacts.

JR
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mikeseb
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« Reply #16 on: November 15, 2006, 03:56:00 PM »
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Just had one of my C 645 bodies CLA'd at KEH, so you could check with them if you need to have it serviced. They turned it around in no time.
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william
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« Reply #17 on: November 15, 2006, 05:38:38 PM »
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Great, thanks, I'll keep that in mind.  How much did the CLA cost, if I may ask?

BTW, the current status of things is that (1) I'm still having the focus/softness problems with the 140mm lens and therefore (2) I returned it to Samy's (who, I must say, were great - no problem with the return at all) and they're exchnaging it for another one.  I also purchased another Contax 645 body to have as a backup on hand, so I'll be testing the new 140mm on the new body this weekend.

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Just had one of my C 645 bodies CLA'd at KEH, so you could check with them if you need to have it serviced. They turned it around in no time.
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william
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« Reply #18 on: November 18, 2006, 08:42:18 PM »
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OK, I returned the 140mm lens and got a replacement from Samy's.  In the interim, I bought a backup Contax 645 body.  So, today, I tested the new 140mm lens on the new body.  Same problem: any time I'm within 5 or so feet of the subject (waist-up or headshot), it's razor sharp.  Any time I'm further away (full length), it's slightly blurred with no point of critically sharp focus.  To reiterate, all of this is with the same f-stop, shutter speed, lighting, etc.  The only variable is my distance to the subject.  

Having eliminated the lens and the body from the equation, that would seem to leave a couple other possibilities.  (1) Perhaps my shooting technique, e.g., how I hold the camera, is unconsciously different for full length shots than on tighter shots?  (I doubt that it's different enough that every tight shot would be sharp and every full length would be soft).  (2) Could it be the back?  I had assumed that the weak link here was somewhere in the camera/lenses, and not the back, but since I know now (or at least think I know) that the culprit isn't a particular 140mm lens or a particular camera body (or focusing screen, for that matter), the back itself is all that's left, right?  Or am I missing something?

(And I did try James' suggestion of focusing on the nose/lips.  Didn't make any difference.)

Thinking about it now, this seems particularly strange, given that my depth of field should be shallowest when I'm physically closer to the subject and the effects of focus inaccuracy would therefore be more visible; when I'm further away, I have a greater of depth of field at a given f-stop and you would therefore expect the greater depth of field to "hide" focus problems to a greater degree.  But the opposite is happening here.  But if you look at the samples I posted above, and my original description of the problem, Im becoming convinced that what I'm seeing isn't really mis-focusing (where an area other than the one I intended is in sharp focus); it's more akin to slight, but noticeable, motion blur or camera shake, in that NO single area of the image appears to be in sharp focus.

Help!!

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Great, thanks, I'll keep that in mind.  How much did the CLA cost, if I may ask?

BTW, the current status of things is that (1) I'm still having the focus/softness problems with the 140mm lens and therefore (2) I returned it to Samy's (who, I must say, were great - no problem with the return at all) and they're exchnaging it for another one.  I also purchased another Contax 645 body to have as a backup on hand, so I'll be testing the new 140mm on the new body this weekend.
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Morgan_Moore
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« Reply #19 on: November 19, 2006, 12:04:02 PM »
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Help!!
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Can you post some test images

F4, tripod,

you have those planks in your studio

Put a marker down, like a coin 3ft away and 10 ft away you should then ba able to see where is is acually focusing front or back

or if it is just going soft

SMM
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