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Focus problem

Discussion in 'Projectors, Screens & Video Processors' started by zAndy1, Dec 22, 2003.

  1. zAndy1

    zAndy1
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    Hi all,
    I seem to have a problem with focus on my Z2 in that the bottom left hand corner of the screen is out of focus but the rest of the image is ok. Any ideas what could be causing this? Can it be expected when using the lens shift (wouldn't expect just one corner to be out though).

    Cheers,
    Andy.
     
  2. theritz

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    Andy,

    This is a common enough occurrence with PJs..... focus uniformity - I've read about it with other pJs..... Have no idea how it might affect/be affected by lens shift.


    Depending on how extreme the uniformity issue is it might be grounds for a swap.


    Sean G
     
  3. pacemaker

    pacemaker
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    i noticed same problem with z2
    not when watching films but on desktop
    start button out of focus!
    i also thought it was lens shift as mine is close to ceiling and lens shift almost right down
     
  4. zAndy1

    zAndy1
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    It's not just the start button but the whole area surrounding it too. And I admit it is more noticeable on the windows desktop/browsing than it is when watching films when it tends to not be noticeable really (can't explain why!). Anyway, least it's not just me...

    Cheers
    Andy
     
  5. Gary Lightfoot

    Gary Lightfoot
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    Is the screen square to the pj? It doesn't take much for the pj to be slightly off at an angle or the screen to a little too far/close in one corner for the focus to be out.

    I noticed that once, and it turned out to be the wall - the screen was flat to the wall, but the wall wasn't quite straight (my fault - I built it!). Using a spirit level and a smal piece of wood behind it straightened it out. It doesn't take much over a 4ft run (or more) to get it an inch or more out of true.

    Gary.
     
  6. Comer

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    I have the same problem using the Sony HS10 as I am using a little vertical keystone. It is only noticable when viewing the desktop so it doesn't bother me. I also notice that if I focus the pj just after it starts it is always slightly out of focus when I go back to the desktop at the end of the movie. This is due (i guess) to tiny expansion within the projector as it heats up throughout the movie. I read somewhere that this is normal. I recon that if I was not using a pc I would never have noticed it


    Conor
     
  7. WeirdFish

    WeirdFish
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    Does adjusting the iris make any difference? When its closed it'll increase depth of field I believe.
     
  8. buns

    buns
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    that shouldnt make difference to the focus. I have this also but once moving images are going, I cant see it and I dont believe that a new unit would be any better

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  9. WeirdFish

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    Far be it for me to disagree with Buns the Z2 tweaker ;) but I would have thought closing the iris would increase the depth of field therefore increasing the the margin of error when focusing. Effectively meaning you could have the bottom of the screen slighty further away than the top and both would be in focus.

    I realise this margin of error is probably still small.

    But then again I'm probably wrong. :blush:
     
  10. buns

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    Feel free to disagree...... im only learning so im quite likely wrong on many fronts. I can see what you are saying, but logic says that if you have a problem with an optical path, the solution does not lie in the light traversing it.

    An analogy. Consider two roads merging to one, but the merge area is long and somebody went and forgot to paint some lines..... with a whole load of cars (iris open), you have a problem cos no one is sure where to go and sheer volume means things slow down. But cut the trafffic (iris closed), well things will run smoothly, people have time to see whats going on and adapt. This doesnt mean that the latter situation has enhanced anything...... the same for the iris by your arguement (i think) because, although the problem may appear less, this is simply because you are limiting your ability to see it.

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  11. Kramer

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    buns,

    Shouldn't it start:

    " Two roads diverged in a wood....." :D
     
  12. WeirdFish

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    A good point buns, I think.:)

    All I'm basing my theory on is my knowledge of lens's in photography. If a lens, a 50mm for arguments sake, is set to f32 the opening is small and pretty much everything from a meter to infinity will be in focus. With the lens set to f2.8 the opening is large and focus is very precise, for instance a portrait photo would have the subject in focus but the background out of focus.
     
  13. buns

    buns
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    :p kramer! :D

    Weridfish,

    I'm stabbing here since im not into photography and such. Thinking further to what i said, i was perhaps not thinking of everything. Is the idea of the iris to use only the centre of the lens and not the extremities? What is the theory behind this? I assume it is a bit like amplifying the effect of the lens..... you close the iris then you effectively have increased focal range? This makes sense to me i guess...... excuse me if im confusing, im thinking this out as i type it!

    In any case, surely the aberation still exists, but is merely masked as i suggested?

    ...... im going mega geeky tonight....... god i love it :D

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  14. theritz

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    I wouldn't have thought that the iris would have changed the nature of the lens - rather that it affects the amount of light coming thru'- if the nature of the lens was changed, then surely one would need to re-focus......... :confused:


    Sean G.
     
  15. WeirdFish

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    It doesnt change the nature of the lens but it does change the way the light passes though it. The iris control is the same as changing the f-stop setting on a camera and basically controls depth of field. The side effect is it also cuts down light, which Sanyo have put a positive spin on this by saying it increases contrast, which is debated elsewhere eh buns? :)

    Changing the zoom will also affect depth of field but as the zoom on a PJ is relatively small its not worth complicating things.
     
  16. LV426

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    I'd tend to agree. The smaller the iris, the greater likelihood that things that are a different distance from the lens will be more equally in focus. The optical principles here are identical to those which apply to photography. Light paths (and the physics that govern them) are totally reversible.
     
  17. pacemaker

    pacemaker
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    well never mind the scientific stuff but can confirm that with iris closed my screen is better for focus
     

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