Panasonic 7-14mm Flare - Case Study for a solution

Discussion in 'Native Lenses' started by Steve-H, Sep 15, 2012.

  1. Steve-H

    Steve-H Mu-43 Regular

    29
    Sep 3, 2012
    All,
    I like UW lenses, and the images I can produce with them. Unfortunately, for those of us who want a non-fisheye lens, we really have one choice - the Panasonic 7-14mm f/4.0 zoom. As has been documented all over the net, this lens produces a nasty purple flare when used in combination with the E-M5 body. While I have a theory behind why this is only seen on the E-M5 there's nothing that I can personally do to prove it - so I'll leave that be.
    What I am going to try to do is figure out a method to minimizing the impact, as for the moment this is all we have to work with for the foreseeable future of UW lenses.

    Some examples:
    #1
    P9150010.JPG
    1000iso 7mm @ f/6.3

    #2
    P9150012.JPG
    1000iso 7mm @ f/6.3

    #3
    P9150009.JPG
    1000iso, 7mm @ f/4.0

    #4 (no flare)
    P9150013.JPG
    1000iso 7mm @ f/6.3

    More in the next post...
     
  2. Steve-H

    Steve-H Mu-43 Regular

    29
    Sep 3, 2012
    Breaking it down, if we look at example #1, we have an example there the main light source is directly in front of the camera, about 30-40 degrees off the vertical axis from the center of the lens. By all rough estimates, the flare is directly in the middle of those two points, about 15 degrees off center.
    In example #2, this exhibits what I guess we can consider 'typical' lens flare, with a main light source off to the horizontal axis, and a streaking effect across the lens. If this flare were not purpleish in nature, Im sure most would find it acceptable.
    Example #3 - this one is special. Here we have all sorts of things going on, but you can clearly see the impact of two main light sources adjacent to both the vertical and horizontal planes of the lens. Interestingly enough - I was almost able to get them to perfectly bisect the image.
    Example #4 - I started out framing this photo as I had done on image #3. However, I slowly rotated about 10 degrees and took a shot. Roughly 60 degrees and I was able to get it flare free.

    So, here's my thoughts....
    Creating a larger lens hood would potentially remove the horizontal axis flare from image 3. Images 1, 2, and the vertical flare in image 3 all come from light sources within the frame, and thus cannot be shielded.
    If we look at the way some of the flare looks in detail, its quite irregular and may not lend itself to software correction:
    flare_example_1.
     
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  3. Steve-H

    Steve-H Mu-43 Regular

    29
    Sep 3, 2012
    So first things first - Im going to try to create a lens shade that will at least assist in shielding light coming from sources outside of the shot. My requirements are:
    -no vignetting
    -easily portable
    Im going to hit up the local arts and crafts store. I plan on getting some foam strips and buttons.....

    In the meantime - for those much smarter than I - is this something that maybe fixed with a firmware update ? Akin to the fuju X10 orb issue ? Im wondering if it is possible, as the color of these reflections are always the same...
     
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  4. jloden

    jloden Mu-43 Hall of Famer

    May 15, 2012
    Hunterdon County, NJ
    Jay
    Could you try one of the collapsible lens hoods? IIRC someone was using one already with the 7-14mm to make a DIY filter holder setup, so I believe there's at least one known to fit.

    Ideally you could come up with a reproducible "worst case scenario" test setup with a tripod and controlled light source, and do some before & after testing with the new hood.
     
  5. addieleman

    addieleman Mu-43 All-Pro

    Aug 5, 2010
    The Netherlands
    Ad
    Your hand may be a powerful tool too: use it to shade the lens from the brightest light source. I used to do that a lot but modern lenses hardly ever need that kind of measures. For the record, I don't have the E-M5/7-14 combo.
     
  6. Steve-H

    Steve-H Mu-43 Regular

    29
    Sep 3, 2012
    I did see the collapsible lens hood idea. Unfortunately none of my local camera places had it, so before I pay S&H I'll ghetto one up to see if it helps, and how tall I can go.
    I do plan on heading back to the machine shop to replicate the shots once I feel I've made progress.
    The thing is.....it really IS a nice lens ! Hopefully we can collectively come up with something. Is there anyone on the board who knows an Oly/Panny rep ? I'd be good to get in their ear to see what they have to say
     
  7. flash

    flash Mu-43 Hall of Famer

    Apr 29, 2010
    1 hour from Sydney Australia.
    Gordon
    The purple fringing in 1 and 3 are easily removed in Lightroom 4 or Capture 1. That type of LoCa is fairly common with sharp lenses with very bright light sources behind a darker subject. Stopping down wil also reduce/remove it.

    The other two are much harder to deal with. I'm not sure a large hood will do it as it's just as likely to be an internal reflection inside the lens.

    Gordon
     
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  8. Steve-H

    Steve-H Mu-43 Regular

    29
    Sep 3, 2012
    Well as with most things - I was wrong. Very happily wrong....Thanks Gordon. Here's the scoop:
    I purchased LR4. I took Image #1, imported into LR, and corrected CA. It got 99% of the purple tint out - Im sure I could have done better, I'll need to spend some nights learning the ins/outs of LR. Here's a 200% snapshot after LR:

    LR4_export_CA.

    I found it very interesting that for the most part, what is left was a straight line. I then brought the image into GIMP and did some correction - 100% shot:

    [​IMG]

    While it may not be 100% perfect, Im sure with some practice I can get better. Here's the final image:

    [​IMG]

    Tomorrow, I will setup a test rig to see what can be done about an additional lens hood. I'll post the details as soon as I think it all through. But for now, I think this is pretty promising.
     
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  9. Steve-H

    Steve-H Mu-43 Regular

    29
    Sep 3, 2012
    Also, here's image #2 out of LR:

    P9150009.
     
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  10. Iconindustries

    Iconindustries Mu-43 Hall of Famer

    Thanks for discussing this Steve. I have an OM-D and 7-14 and experience the same problem.

    The last picture looks really good.
     
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  11. TDP

    TDP Guest

    I've been using my left hand and shooting with my right....LR 4 sounds like a much better idea (I'm still on 3).
     
  12. hkpzee

    hkpzee Mu-43 All-Pro

    Sep 5, 2011
    Hong Kong
    Patrick
    This look promising. I might need to upgrade my LR3 to LR4. I cannot remove the purple flare with LR3 at all.

    BTW, what is GIMP?
     
  13. ajohnw

    ajohnw Mu-43 Rookie

    12
    Sep 16, 2012
    Birmigham UK
    John
    When I saw the mention of flare I initially looked at the star round one of the lights in a shot and lost window frame and detail etc where light levels are too high. Then I noticed the purple but I wouldn't describe that as flare or fringing as mentioned in one post - that usually only occurs on very high contrast changes across borders. The purple is in low contrast areas.

    I suppose that they might be due to internal reflections that may be prevented by using a much larger lens hood but I suspect that they are more down to camera lens correction software. This lens needs rather a lot of it and is receiving some looking at the straightness of various items in the shots. It would be interesting to know if the same problems occur when used on a Panasonic camera.

    I suspect that these are camera jpg's? If not I'm still inclined to think it's a software problem.


    If I'm correct I believe Adobe produce add ons for specific lenses but that may involve working from raw and I don't know which packages they are used with. Also CaptureOne maybe. Panasonics own raw processing software should also deal with it.

    If you want to see what an uncorrected image looks like a free program called rawtherapee will open a raw file without doing anything to it.

    John
     
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  14. Steve-H

    Steve-H Mu-43 Regular

    29
    Sep 3, 2012
    Thanks again for all the help and input thus far.

    GIMP is a freeware 'PS-like' opensource tool: GIMP - The GNU Image Manipulation Program

    The more I think about John's post, the more I believe there are two problems as he mentions, one being true lens flare (seen in photo 2 and 3), and the other being internal reflections (seen in photo 1). Look at the 100% crop again, its more rectangular, 'blobish' in shape, and looks nothing like what we normally see as flare.
    Also, I re-read all of the helpful posts over on dpreview (helpful being about 5% of all the usual posts there...), and someone else brought up a good point that is demonstrated in photo 2 - most times the reflections/flare are exactly on the x or y axis, rarely are they diagonal.
    This afternoon Im going to get some foil and build a snoot for a shoplight I have. I'll set the camera up on a tripod and do a series of shots while rotating the shop light around the tripod position (shooting a shot every 15 degrees of rotation or so).
    Im also curious to re-try this experiment with a laser aimed into the lens. I'll need to consult a couple of friends to see how to execute this safely. While this won't help us in a practical sense, I think it would be great to better understand how the internal reflections are caused.

    Lastly - these were all in-camera jpgs. I will try some raws and see what is available in LR4.

    Thanks again !
     
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  15. TDP

    TDP Guest

    Laser into the lens?

    Back in Canon'ville I vaguely remember a couple of folks BBQ'ing their sensors while videoing some laser lights during a concert. Maybe a really bright, nefarious looking flashlight would be a better idea.
     
  16. ajohnw

    ajohnw Mu-43 Rookie

    12
    Sep 16, 2012
    Birmigham UK
    John
    Don't - there is a chance that you will damage the sensor using a laser of any type. The whole thing about lasers is that the light can be focused to a very small point with lots of energy over a very small area and that's the problem and the wonderful thing about them. They can cut and burn etc.

    The star flare is down to the iris and relates to the number of leaves it has and how round the hole it leaves when closed. It can some times be prevented by moving the source around in the image. The detail disappearing can be down to light bleeding into adjacent pixels or even jpg processing software confusion.

    I would download rawtherapee if I were you just to see what an uncorrected image looks like. There is another more basic one called ufraw. Simple to use but there are a number of curled arrow buttons to reset things to defaults and it always remains in the last used settings. Also usually the need to find and use the auto exposure button or even set it manually at times but that is one of the advantages of using raw. As the memory cards are huge these days I usually shoot with the jpg+raw setting and use raw when the jpg isn't good enough. The raw file is usually worth another 2 stops of exposure range but the shots need more processing than jpg's usually do,


    John
     
  17. hkpzee

    hkpzee Mu-43 All-Pro

    Sep 5, 2011
    Hong Kong
    Patrick
    I shot in RAW and the purple cast is still there. I am 99% sure it is some sort of internal reflection, as seen in the shot below. It is a reflection of the bright light from the window on the right:
    P8080018-5_01.
     
  18. Steve-H

    Steve-H Mu-43 Regular

    29
    Sep 3, 2012
    Do you have LR4 ? If not, can you send me the original image file, and I will see how far we can improve the picture ?
     
  19. ajohnw

    ajohnw Mu-43 Rookie

    12
    Sep 16, 2012
    Birmigham UK
    John
    I can see some distortion in that shot so it looks like you may well be correct. The full image viewed at 100% probably shows chromatic aberration as well?. A couple of silly thoughts based on these lenses not having this problem on a Panasonic camera. I don't hold out much hope though.

    Have you tried removing the UV filter if there is one fitted. Might make things better or worse.

    If anyone has one handy it might be worth trying a skylight or maybe a haze filter. The reflection is in the far blue so may have something to do with the uv/ir block filter on the sensor and a weak minus blue filter might cure that. The type of filter I am thinking about has a faint pink tint to it. Some are amberish or even yellowish. There is a decent article on these types of filters here. Saves me typing.

    UV Filters | BH inDepth

    John
     
  20. Steve-H

    Steve-H Mu-43 Regular

    29
    Sep 3, 2012
    Thing is - these lenses do not have a filter mount, so we'd need to rig one up. Worse yet, the lens hood is built into the lens itself (so the lens 'cap' slides over the hood !). I've seen a couple of people rig some up - but you'd be talking a significant distance away from the front element, which may introduce its own problems/reflections.