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Author Topic: Much Anguish About Focus  (Read 11059 times)
John R Smith
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« Reply #60 on: May 10, 2010, 03:11:11 AM »
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There is not much wrong with the Hasselblad acutematte screens (of which I have three examples). I also have various earlier standard screens, and the difference is astonishing. If Maxwell's screens are better again, they would be well worth paying for.

The screen, I feel, is not really the problem with the V-system focus issues. It is more likely that there is not enough magnification using either the WLF or the prisms to actually see the very subtle variations in sharpness which we need to distinguish the absolute plane of focus. A 6x loupe would probably help, as others have suggested. The other issue is that the critical area of foucus for a great many compositions lies between say 20 feet and infinity, exactly the area of lens helicoid with the smallest movement and least finesse.

John
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Chris L
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« Reply #61 on: May 13, 2010, 02:49:38 PM »
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I too have been having problems with focusing lately, here is my story; I sold my medium format / digital back system because I was not having much luck manual focusing, I think my eyes are going bad. I have been shooting the Canon 1Dsmk3 and was noticing that certain lenses were front focusing, about 5 feet in front of the subject when the subject was at least 20 feet from the camera, and other similiar situations. It never seemed to happen when I was relatively close to the subject. It was only happening with my 300 F4 L and 85 1.2 L lens and 100 F2 non-L lens. My 50mm 1.4 non L seems to be work fine.

I called canon support  and had them walk me thru the micro-adjustments procedure, seemed to help a little bit but not really sure. Thats the problem, the front-focusing problem is not consistent. I called canon again, we did the lens test on the phone, I emailed him jpgs of a ruler shot at a 45 degree angle, everything checked out fine.

Then he said this, which surprised me, " for best results use the CENTER only AF focus point and recompose once you get focus. Do not use the other surrounding AF points, those are only for al servo mode when tracking a moving subject. Really? They told me that yesterday, I shot today with his advice and he seems to be right, I nailed focus more often than not, but it is too soon to tell.

Has anyone else heard this? I was thinking of sending all my lenses and camera body to canon to be checked out just to be sure there isnt an actual problem, but I would prefer not to obviously.

Just to re-iterate; the main focus problem seems happen when I am at least 20 feet away from the subject, and after focusing and recomposing from a non-centered AF point the camera places the focus a few feet front of where I focused.
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Rob C
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« Reply #62 on: May 13, 2010, 04:01:44 PM »
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I have no idea about the reason for christo's focussing problems, but on the MF slr cameras, I suspect that one reason some cameras are better than others in this respect is the way that focussing is done.

Take the Rollei TLR and the old Mamiyas: you wound a knob at the side of the body, a natural movement, quick to do and easy on the wrist. Contrast that with the helical focussing system of other such cameras, where the lens itself has to be messed around with in an unnatural, twisted wrist manner. I think the difference in comfort also carries over into how comfortable/confident the eye becomes when the wrist is not at ease. It's all connected, as they say.

Having had both the Rollei TLR and then the 'blad straight after it, though I was able to focus both well, I do think I remember the Rollei as quicker. And without doubt, once you start to 'hunt' with focussing, it goes nuts very quickly - or at least, you do!

Rob C
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Nick-T
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« Reply #63 on: May 13, 2010, 04:50:03 PM »
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Quote from: christo
Has anyone else heard this? I was thinking of sending all my lenses and camera body to canon to be checked out just to be sure there isnt an actual problem, but I would prefer not to obviously.

Yes this is what I've been told by the Hasselblad guys, AF gets more and more difficult the further from the centre of the frame you get. This is part of the rationale behind Hasselblad's focus/recompose compensation system (a.k.a "True Focus")

Nick-T
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Chris L
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« Reply #64 on: May 13, 2010, 05:10:15 PM »
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Quote from: Nick-T
Yes this is what I've been told by the Hasselblad guys, AF gets more and more difficult the further from the centre of the frame you get. This is part of the rationale behind Hasselblad's focus/recompose compensation system (a.k.a "True Focus")

Nick-T


I guess that makes sense then. I would love to hear from others who are shooting the 1Dsmk3 to see which AF points they use and their general experience. I thought AF on a Canon was a no brainer, I guess I was wrong. ( sorry in advance, I know this is a MF forum )
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John R Smith
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Still crazy, after all these years


« Reply #65 on: May 14, 2010, 02:36:41 AM »
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Quote from: Rob C
Take the Rollei TLR and the old Mamiyas: you wound a knob at the side of the body, a natural movement, quick to do and easy on the wrist. Contrast that with the helical focussing system of other such cameras, where the lens itself has to be messed around with in an unnatural, twisted wrist manner. I think the difference in comfort also carries over into how comfortable/confident the eye becomes when the wrist is not at ease. It's all connected, as they say.

Having had both the Rollei TLR and then the 'blad straight after it, though I was able to focus both well, I do think I remember the Rollei as quicker. And without doubt, once you start to 'hunt' with focussing, it goes nuts very quickly - or at least, you do!

Rob C

I agree completely with this, having also owned and used the Rollei TLRs and the 500 series 'Blads. The Rollei was a lovely thing to focus (well, lovely in a lot of other respects, too). Since I originally posted this thread, I have to say that I have improved my focus hit rate tremendously - from about 50% to nearer 80%. I have evolved a little 'trick' which seems to work for me, but I hesitate to suggest it because it may just be something to do with my particular eyesight / glasses / general ineptitude.

John
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philipmccormick
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« Reply #66 on: May 14, 2010, 04:28:10 AM »
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Quote from: John R Smith
I have evolved a little 'trick' which seems to work for me, but I hesitate to suggest it because it may just be something to do with my particular eyesight / glasses / general ineptitude.

John

Hey John, share your trick anyway please, it can't do any harm!

Philip
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Philip
John R Smith
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Still crazy, after all these years


« Reply #67 on: May 14, 2010, 04:46:35 AM »
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Quote from: philipmccormick
Hey John, share your trick anyway please, it can't do any harm!

Philip

Philip

OK, if you are really twisting my arm. But it is quite complicated to explain (though easy to do). So I will have to take a bit of time on it (I might start a new thread). But this is where Smith will get shot down in flames  

John
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Chris L
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« Reply #68 on: May 14, 2010, 10:13:42 AM »
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Quote from: christo
I guess that makes sense then. I would love to hear from others who are shooting the 1Dsmk3 to see which AF points they use and their general experience. I thought AF on a Canon was a no brainer, I guess I was wrong. ( sorry in advance, I know this is a MF forum )


still hoping for some feedback regarding my quote above
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billy
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« Reply #69 on: May 18, 2010, 07:33:51 PM »
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Quote from: christo
still hoping for some feedback regarding my quote above


might need to start another thread about that one, I am curious as well
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