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Sony HVR-V1 / HDR-FX7
Pro and consumer versions of this Sony 3-CMOS HDV camcorder.


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Old October 30th, 2007, 12:27 PM   #1
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Back Focus Again

Once again the back focus does not seem to work properly on my V1U. In manual focus mode I should be able to zoom in on a static object, focus and stay in focus from telephoto to wide. As shown in the attached stills you can see I've focused sharply on the hat in the first image, however the image goes soft when zooming out to frame and then to wide in the second and third images. In the the last two focus is restored by racking the focus ring to infinity. I had this camera in to Sony a few months ago for the same problem and was told it was due to engagement of the macro focus function. Macro focus is off on these images and by the way it makes no difference if it's off or on. I guess it's back to Sony again. I hope I have better turnaround than Ralph :( BTW, select each image to see the full resolution version.
Attached Thumbnails
Back Focus Again-01zoom-focus.jpg   Back Focus Again-02zoom-out-soft.jpg  

Back Focus Again-03full-wide-soft.jpg   Back Focus Again-04focus-infinity.jpg  

Back Focus Again-05-wide-infinity.jpg  
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Old November 2nd, 2007, 03:09 AM   #2
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I haven't a macro/back-focus issue, even when the camera is focused at the minimum 0.8m: i.e the camera keeps focus over zooms regardless of macro engaged or not.
Good luck with your fix!
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Old November 2nd, 2007, 05:01 AM   #3
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I always find the V1 to be soft on full wide. My assumption was a kind of non-linearity in the interpolation system.

My reasoning was that to generate interpolated very fine detail there must be a certain amount of fine detail. When zoomed back, I assumed the amount of fine detail went to near zero. Think of an all gray sheet of paper. How can any interpolation system create detail from nothing?

But this may be a completely wrong concept. So I don't know if it is the lens (at WIDE) or what you call a "backfocus" problem.

In any case, I found wide shots to often be less than stunning in terms of fine detail.
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Old November 2nd, 2007, 07:38 AM   #4
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Quote:
Originally Posted by Steve Mullen View Post
I always find the V1 to be soft on full wide. My assumption was a kind of non-linearity in the interpolation system.
Steve,
Thanks for your input, but I believe you are referring to auto focus which in my opinion works great. My issue is with manual focus. At any focal length I can manually adjust the focus (usually to infinity) and get a reasonably sharp picture (as evidenced in my photos). On a static subject (such as in an interview) I should not have to readjust focus after zooming in fully and setting the focus. As long as the subject doesn't move toward or away from camera focus should be maintained throughout the zoom range. Even more so as the 1/4" CMOS imagers have a deep depth of field even at wide aperture.

"Back focus" refers to the focus distance from the rear lens element to the focal plane. On professional camcorders with interchangeable lenses, there is a user adjustment for this issue on rear of the lens. On fixed lens cameras it is a service issue.
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Old November 2nd, 2007, 07:40 AM   #5
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Originally Posted by Alnoor Dewshi View Post
I haven't a macro/back-focus issue, even when the camera is focused at the minimum 0.8m: i.e the camera keeps focus over zooms regardless of macro engaged or not.
Good luck with your fix!
Thanks Alnoor. That's good to hear. Originally when I sent the camera in last spring they told me the issue was due to having the Macro focus function engaged.
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Old November 2nd, 2007, 11:42 AM   #6
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I certainly have had a soft focus interview when macro was engaged - the proof is on the tape!

Typical - zoom in for sharp focus, zoom out to shot (not full wide), looks soft in post. This was one of about 12 interviews over 3 days, the rest were fine. It was definitely the macro setting and zoom in to focus.
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Old November 2nd, 2007, 12:55 PM   #7
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Originally Posted by Seth Bloombaum View Post
It was definitely the macro setting and zoom in to focus.
Seth,
I thought so too when I got the unit back from Sony last spring, however in my most recent observations it didn't make any difference if macro was on or off.
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Old November 2nd, 2007, 05:30 PM   #8
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Originally Posted by Lee Berger View Post
Steve,
Thanks for your input, but I believe you are referring to auto focus which in my opinion works great. My issue is with manual focus.
I understand what you were talking about -- backfocus. Although you can re-shoot your interviews -- when you zoom back and see it go softer -- can you make it sharper by a slight refocus.

If you can -- then you are right about backfocus issue.

However, with an inner-focus lens, I would not be surprised to find backfocus was not perfect over the FULL zoom range when in Manual focus. Over the last decade I've stopped using the traditional focus technique.

Now I zoom in only as far as I plan to during a shot -- which very unlikely to be a MAX zoom-in. Then I use One-touch AUTO or Manual to focus. (OT works best.) Now I zoom back to the point where the shot will start. This lets me be safe to do a zoom-in to the focus point as well as zoom full wide.
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Old November 2nd, 2007, 11:47 PM   #9
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Lee,

I had the exact problem just recently with my FX7. Same focus problem. I sent it in to Sony and they replaced parts and it seems to work pretty well now. There is a temporary way around it. Your probably using a f-stop between 1.8-2.6 if you go 2.8 or greater the image becomes sharp as a tack. Not sure why. Hope they fix it permanently this time.

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Old November 3rd, 2007, 05:43 AM   #10
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Thanks Monday. The camera went to Sony on Wednesday and should be there by Monday. I'll keep my fingers crossed.
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Old November 8th, 2007, 09:43 PM   #11
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In order to test for back focus you should get a proper back focus chart. I found one recently by doing a yahoo search, so you should be able to find one easily. Don't pay for one, they are readily available for free. They are alternating converging black and white lines going to a fine point in the center.

Once you have a proper chart, set the camera on a tripod 15 ft. away from the chart and use only enough light to have the camera's aperature wide open (f1.6 or whatever the widest aperature setting is). This gives you the narrowest depth of field so focus is more critical. Zoom all the way in and manually focus to the most accurate focus. Then without changing any camera settings, zoom all the way out. Check to see If the focus is as good as it can be. If it is perfectly in focus, you don't have a back focus issue. If it isn't in focus your camcorder does have a back focus issue. Can Sony or anyone else fix a back focus problem when it is a fixed lens? I don't know.

When you test for back focus you can't close the aperature to say f4, because that increases your depth of field which might mask the problem. And since you should be testing from 15 ft away, that should prevent the camcorder from going into the macro mode, so that shouldn't be an issue. It should go without saying but just in case, remember all camera settings should be in manual mode so they can't re-adjust for you. Good luck.
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Old November 9th, 2007, 11:13 AM   #12
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Quote:
Originally Posted by Greg Laves View Post
In order to test for back focus you should get a proper back focus chart...
And since you should be testing from 15 ft away, that should prevent the camcorder from going into the macro mode...
You also need a monitor larger than the LCD to properly judge focus/backfocus issues.

Note that "macro mode" is a menu option setting on this camera.
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Old November 9th, 2007, 12:56 PM   #13
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Originally Posted by Seth Bloombaum View Post
You also need a monitor larger than the LCD to properly judge focus/backfocus issues.
Right! When I did my test I used my Sony PVM-14M4U edit monitor via the camera's component analog outputs.

Quote:
Originally Posted by Seth Bloombaum View Post
Note that "macro mode" is a menu option setting on this camera.
I made sure that macro mode was off as that is what Sony insisted was the issue. In fact, switching macro on and off made no difference in the back focus. The funny thing is that when I got this camera back from repair in June the back focus issue appeared to be fixed. I assume the new issue occurred between then and now and I really didn't use the camera all that much except for September.
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Old November 12th, 2007, 10:14 PM   #14
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Lee,

I'm still testing both V1U's. I now know that BOTH have back focus problems. Damn! The problem isn't as dramatic as your examples as shown with the skull and cross bones hat. But the issue completely takes away any detail in a face and hair, for example, when the zoom is taken from a tight shot to medium for example.

I took one of our consumer HDR-HC1 cameras and did the same test with it. And guess what . . . this experiment produced a razor sharp image from tight to wide with the HC1.

One thing too which is really strange. Like you I shot with the test subject 8.5' from the camera. When I did a tight focus and backed off to a little more than 1/2 way out I shot some footage and set the focus to infinity (which was too soft), BUT at 18' (a full 9.5' further than the actual subject was from camera) the image became much sharper. Something is wrong with this picture, for sure!

I suspect that there are a lot more V1U's with this problem than realised. I have two of them with the same problem. One interview I did with the Sony wide angle adapter is terrible - this is what alerted me to the initial problem.

Funny thing. A lot of folks suggest that the Canon A1 looks sharper than the V1U. I wonder if the lens or camera has a flaw making the camera just a little softer looking than other HDV cameras. My little Sony HC1 is right on the money holding tight focus right through the zoom. It's hard to believe that two expensive V1U's have a major limitation that I think might be hard to get Sony to acknowlege.

I'll let you know what the verdict is once I get word from Sony. I'll show them the HC1 test next to what I've shot with the V1U's. This is the only way one will really see how clearly soft the V1U image truly is.

When you get your camera back I'll be intersted to know if Sony has fixed the issue effectively. If you have an HC1 or A1U try to do a comparison. I was shocked at how much better the HC1 holds focus through the zoom range than my two new V1U's.

For those wondering ... I tested with both the macro mode engaged and also with macro disabled. Same poor result, either way. The V1U iris was f1.7 to f2 through the zoom range for this test.

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Old November 12th, 2007, 10:30 PM   #15
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Ian:
It's funny because in September I shot a great deal of SD and HDV footage in Western Idaho. Most of it was scenic vistas. Everything I shot was sharp. I also shot a Western Rattle Snake in HDV using the auto focus which did an excellent job of keeping the subject in focus. I shot some heavy logging equipment in action and am impressed at how well the detail in the machinery is resolved both in SD and HDV. I tried to keep everything around f 4. So it seems as if the V1 can produce a sharp picture, just not using manual focus :( I'm sorry you have two instances of the problem, but based on your tests it vindicates my problem. I just hope Sony will respond appropriately.

Lee
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