Problem with "back focus"?

S

shank

New member
I've been a lurker here for a few months and learned a ton. Thanks for all the good discussions.

Have any of you noticed the focus to drift on your DVX when you pull out? Looking back on several projects I've completed, I'm disappointed to see that the focus is fairly soft on a wide shot, when I know for certain it was in focus when I was zoomed in. This is a "back focus" problem in my opinion, but the DVX has no obvious adjustment.

I didn't find an answer to this question when performing a search, but I know I'm not the only one who's ever experienced this.

Any comments or solutions would be appreciated.
 
I know this is a stupid question but you are shooting in Manual focus mode right?
I've had focus drift problems when in auto mode and zooming out.
 
My DVX had a back focus problem when we got. I sent it to get it looked at and sure enough they said my camera had a back focus problem very similar to yours. Well we luckly still had warranty on the camera and got it repaired. Now it works fine. I can zoom in all the way, focus, and zoom out while everything is still in focused. Check your warranty and make sure its not jacked!
 
Yes, I'm shooting in manual focus mode so the auto focus shouldn't be an issue.

I'll have to see if I'm still covered on my warranty. Glad to know others have had the same problem.

Thanks for the response guys!
 
I have the same problem.
I zoom in at 100%. I manually focus.
Then i go to 80% zoom and i have no focus!
But if i go for example 50% or 0% i do have focus.

It only happens in around 80%, Why?
 
My camera has this issue as well. Note to Panasonic:

a) Have a backfocus that actually works from the factory; (or)

b) Make backfocus field adjustable

:angry:
 
I spoke with one of the Authorized Service Centers today about my back focus problem. He said this may be correctable with his computer setup - 2hrs at $100/hr. If not I will need a new lens assemby - $538 on panny's website.
I also asked how many of these problems he has seen, the reply was "hundreds". I did not ask if these were all DVXs - I assume not.
Since this problem only recently appeared, and I have babied the cam from day one, I'd really like to know what can cause the issue and how to possibly prevent a recurrence.
 
Don't drop the camera! Anything that gives a decent jolt could cause a problem with alignment. Other than that things should be ok. Of course, things drift and you may eventually need to have it set again (most likely years - longer than you have the camera).
 
Thanks Shaw.
I was thinking condensation may have formed on a PCB temporarily shorting a control circuit. When the problem occurred I had been shooting out in the cold wind before going inside where the issue developed. I just now finished a test with DVRack and am unable to duplicate the focus problem. So, I am going to test again tomorrow (if I have time) by taking some shots outside in the cold for half an hour or so and then more inside to see if it comes back. If it does not I think I'll forget to send it in.
I'll post the result here when I have it.
 
Ah! You may be experiencing changes in the optics due to the cold. I believe the DVX (and most every prosumer camera) has "plastic" optics which are much more susceptible to changes in temperate than glass. This could easily cause weird focus problems.
 
..another small thing to note is that a wide shot just by nature of the glass is going to be softer than a longer shot. most zoom lenses have the tendency to be softer in the wide range. so if its just a loss of that extra crispy cripness... its likely not a focus issue as much as it is a general optics issue.
 
iamloser said:
..another small thing to note is that a wide shot just by nature of the glass is going to be softer than a longer shot. most zoom lenses have the tendency to be softer in the wide range. so if its just a loss of that extra crispy cripness... its likely not a focus issue as much as it is a general optics issue.
Click to expand...

Several of the shots were in sharp focus at full zoom with subject more than 30 meters distant. But when pull back finished all but the closest objects are way out of focus. The problem is made more evident by the fact of the low light conditions I was in at the time(open iris-little DOF)
The weather here has warmed a bit the last couple of days, so testing my theory will have to wait for cooler temps..
 
does the focus # actualy change for the camera when your zooming out, or does the focus just shift without the # changing?
 
When this was happening I was on a 'personal pleasure' shoot outside Dayton, OH at the USAF Museum and really was not paying too much (any?) attention to the numbers. I was having too much fun trying to get some decent dolly shots using the electric scooter I had kicked my elderly father out of ...
:evil:

When I am able to test my condensation idea I'll keep an eye on the numbers for sure. Thanks!
 
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