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.

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!

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.

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.

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.

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.

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.

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.

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.

Monday

Thanks Monday. The camera went to Sony on Wednesday and should be there by Monday. I'll keep my fingers crossed.

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.

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.

Right! When I did my test I used my Sony PVM-14M4U edit monitor via the camera's component analog outputs.

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.

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.

Ian

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

I spoke to another V1U user over the phone today. He reported the same back focus issues with his unit. He suggested it may be a design flaw.

Lee, now you're getting me interested! I've never spotted anything like that on my V1E, but am willing to check again... Could you sum up the best procedure (conditions when the problem is most evident; lighting, distances, iris values etc)?

Hi Piotr . . .

Do your testing with your V1 camera with the aperture as open as possible (my testing was in the f1.7 - f2) range. As someone rightly pointed out, doing a test at a higher f value will likely mask the focus issue due to the greater depth of field. As you know getting a shallow depth of field is a challenge with these small sensor camcorders.

I spotted the back focus problem in footage we just shot in Ethiopia (documentary shoot). The softness is subtle. When you pull out of a tightly focused shot (in my case interview footage) where the subject's face is in tight focus the reframed medium and wide shots are somewhat soft looking. Hair and facial detail seems to disappear -- totally taking the wind out of Hi-Def impact. I believe this is a design flaw (maybe only with the "U" (NTSC) cameras. Since both my cams do the same thing, I feel it's like the lens isn't properly matched to the sensor.

Piotr, I would be very intersted to know what your testing indicates.

As mentioned, one of our little HC1 cameras totally blew the V1U's out-of-the-water when it came to putting it through the same testing as the V1U's.
Your profile suggests that you used to have an HC1. If you still have access to one, try the comparison by doing the same tests with both model camcorders.

I used Lee's testing scenario by setting the camera 8.5 feet from the subject. Lee used a skull and cross bones hat . . . I used an embroidered pillow with a design. The pillow had lots of detail, texture and contrast which worked nicely. As I mentioned in a post from last night the focus is very puzzling.

Try this: Focus tightly on your subject. Pull out about 1/2 way from telephoto toward wide. Play back to compare this result with what you find by focusing at 5', 6' . . . 10', 11', etc. I found that the image looked sharp at 18' -- again this is when the subject was reframed to about half way through the zoom range. This is not aceptable. If you look at the footage on a good monitor you will see the difference IF you have the problem.

Since I have two of these defective units and didn't notice until several months after my purchase, I suspect that others will find the flaw too after close examination. The soft focas can be subtle. But with my Sony 0862k wide angle adapter some of the bad footage really jumped out as unusable.

Note: Today I took my two Sony V1U's to Sony Canada (their Canadian headquarters) and had the privilage to see a tech. I showed him some of the footage that is soft, BUT he only had CRT diagnostic equipment to view the footage on . . . which didn't show off the flaw easily. He said he could see the issue even on the small screen we watch on. He said that he might need to contact the Japan offices regarding the issue. He hasn't heard of this back focus issue with the V1U before, but did say that it might be something that needs investigation.

I hope I have the units back within a week since the project I'm shooting is for broadcast and the shoot isn't completed. The worst part . . . all the African material can't be reshot. With over 80 hrs. of footage shot, I'm not looking forward to looking at footage that can't be used due to a Sony flaw. Not good.

Note: Someone posted that Sony told them that the back focus problem was because the user left the camera in the default "macro" mode. Both Lee and I find that it dosn't matter.whether the macro is set to on or off. The footage is poor regardless.

Lee . . . if you require my support (or wish to talk about this issue) please feel free to write to me at ian.campbell@digitalplayhouse.ca. I would be happy to provide my phone number. I suspect that if this IS a more common problem than first realised we might need to help one another get the message to Sony.

Piotr . . . I do hope that your unit is perfect. I hope your testing gives you good results. Keep us posted.

Ian

Sure Piotr,
I did the test in my office, daylight coming through the window. I connected the analog component out to my Sony Professional NTSC monitor. I placed a hat on my desktop, approximately 8.5 feet away from my V1U set on a tripod. I set the focus to manual, and zoomed all the way in on the hat, adjusted the focus. Then I zoomed out to frame the hat. I noticed on the monitor the image appeared soft so I adjusted the focus to compensate (had to go to infinity). I then zoomed in again and the hat was out of focus. I repeated the test several times, from close up, to full shot, to wide shot. All were out of focus until I made a focus adjustment. I double checked to see if the macro mode was engaged and it was not (it didn't seem to make any difference anyway). The apateur was fully open (gain at 0db), but gaining up and choosing a smaller apateur made no difference. Here is my original link with pictures
http://www.dvinfo.net/conf/showpost....11&postcount=1

Here is a link to a site with a good back focus chart. I think you will find this is superior to other objects that you are currently using to test for back focus. I printed mine out on 11 X 17 photo paper and it worked great. If you don't have a large printer 8 1/2 X 11 will work also.

http://www.rondexter.com/focus_pattern.pdf

Thanks Greg! It would be even more useful if you could actually adjust the back focus.