• Welcome to ScubaBoard


  1. Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

    Benefits of registering include

    • Ability to post and comment on topics and discussions.
    • A Free photo gallery to share your dive photos with the world.
    • You can make this box go away

    Joining is quick and easy. Login or Register now by clicking on the button

Panasonic 7-14 mm

Discussion in 'Panasonic Planet' started by fabgo, Mar 14, 2012.

  1. Puffer Fish

    Puffer Fish Captain Happy ScubaBoard Supporter

    # of Dives:
    Location: Knoxville, TN
    8,072
    144
    Sorry Phil, my fault. Let me try a bit clearer:

    The 7-14 lens, when used for really close focus has blurry corners on land, domes might make it worse, but it is there already.

    The reason appears to be because of a physics issue of the lens having a curved field of focus when really close, a known issue with flat field, really wide angle lens. Corners will look the worse, because they are the farthest away.

    Fish eye lens do not have this issue.

    Zooming out will make it go away, but you obviously loose all that lovely wide angle. Being farther away also makes it go away.

    Bottom line, if you bought the lens to do really close, really wide angle, it sucks (unless the objects in view fall along a three dimensional curved space.

    Oh, and it is very easy to demonstrate.

    PS I still really like the lens.

    ---------- Post added ----------

    Stopping down will reduce it, but not completely

    ---------- Post added ----------

    And the engineer in me can tell you that the field curvature is actually a good deal more than half corrected(meaning the curve is not as bad as it could be), and is an unavoidable byproduct of the lens design. This is not the only lens with this issue.
     
  2. PHIL RUDIN

    PHIL RUDIN Contributor

    # of Dives:
    Location: West Palm Beach, Florida
    1,221
    265
    PHILRUDIN-AUGMASTR-1.JPG-1204705.jpg PHILRUDIN-AUGMASTR-1.JPG-1060023.jpg PHILRUDIN-AUGMASTR-1.JPG-1060065.jpg PHILRUDIN-AUGMASTR-1.JPG-1060102.jpg Thank you for making this a little more clear to me. I think we are both on the same page about this and all wide lenses. First the image quality of the lens will not be improved on by putting it behind a dome port and inside a housing, however some port and extension combinations work better than others. Second I agree that physics has everything to do with issues of how these lenses will perform above and below water.

    One of the first things I teach in my workshops is that in photography everything is a tradeoff. ISO, F/stops, shutter speed are all tradeoffs to get to the results you are shooting for.

    My parents were both engineers and of the four kids I don't think any of us got much past algebra I. Since I ended up as a Police Officer for thirty years I discovered some lessons that apply as both a movie line and in life. The most appropriate for this lens issue comes from Dirty Harry "A man's got to know his limitations" 1973 the year I became a police officer.

    The same holds true for these lenses, if you bought the 7-14 zoom thinking you would go around shooting the lens at a distance of four or five inches then you don't know the limitations of the lens. If you buy a fisheye and think you will photograph a wreck or a large animal and not get an extreme amount of barrel distortion you don't know the limitations of your lens. The 7-14 is made for very wide undistorted views and I would not push this lens much closer to the subject than about the 10-12 inches it is designed for. For the same reasons I would not take my 45 macro and shoot through ten or fifteen feet of water at a wreck or large animal to make it fit the frame.

    Anyway with a proper dome system I think the 7-14 can produce some awesome images in spite of a little corner softness. I also tend to shoot this lens in the mid-range of F/stops as it has excellent depth of field without going to high and having to deal with lens diffraction.

    I have attached some photos taken with the 7-14 on a Panasonic GF-1 in an Inon X-2 housing with the MRS magnetic base port extension and the 115 132mm (5.2") glass dome port. These are my vision of how I think the lens works best underwater.

    All images are taken within 1 to 3 feet of the subject, the jacks are at 18mm to fill the frame, the rest are at 7mm. The pineapple shot was taken at 7mm with the 7-14 4/3 lens for Olympus DSLR's using a 230mm dome port. The images are cropped less than 2% and only to level the horizon.

    Phil Rudin
     
    BoltSnap likes this.
  3. Puffer Fish

    Puffer Fish Captain Happy ScubaBoard Supporter

    # of Dives:
    Location: Knoxville, TN
    8,072
    144
    Phil, We are. First off, lovely use of that lens. The pinapple image takes advantage of the curved focus effect (which is much less the farther you are away). The second is about as good as it gets showing how this type of lens can show the "big picture". The third is why people should have a wide angle lens and the last is a classic image.

    What I particularly liked was that you picked images that showed the len's strength, rather than complain about what it cannot do.

    Have to change computers, but will see if I still have an example to post (seems only fair).

    ---------- Post added ----------

    group 1b small.jpg Here is an example of another use for this lens.
     
  4. fabgo

    fabgo Registered

    # of Dives: 25 - 49
    Location: San Francisco, CA
    12
    0
    The 7-14mm focuses closer at 7mm than at 14mm. I measure a minimum focusing distance (in air) of about 7" at 7mm, 8" at 14mm, less than the 9.84" (25cm) listed by Panasonic.

    So you should be able to focus on something just inches from the front of the dome, as long as the focus point is in the center of the frame.

    However, if you are trying to focus on something towards the corners, or use a large focusing point, I can see how the camera encounters problems.

    When using a dome port the lens focuses on a virtual image some distance behind the port. This virtual image is curved (same shape as the dome), so the corners are much closer than the center. This is also why sharp corners are so tricky to achieve when using a dome port.

    The smaller the dome, the steeper the curvature. 4" is a very small dome. So I can see how the camera could encounter problems focusing.

    Another thing is I don't think it's physically possible to correctly position a 4" dome in front of the Panasonic 7-14mm lens. I measure the entrance pupil of the 7-14mm lens to be about 2.5" inches from the focal plane (imaging sensor). That means the front of the 4" subal dome must be approx 4.5" inches (2.5" + 2" dome radius) from the sensor in order to be correctly positioned. And I don't see how the dome can be positioned that close without banging into the built-in lens hood. Not sure how that affects focus, but for sure it's going to affect corner sharpness. Do you use an extension ring with this port?

    ---------- Post Merged at 05:26 PM ---------- Previous Post was at 05:04 PM ----------

    I think you are right. I did some crude measurements on mine. It does indeed look like it is a section of a 9" dome. Which would be great if the dome was correctly positioned. But from what I can tell the port is too short, meaning too close to the lens. As I mentioned above, the entrance pupil of the 7-14mm lens is about 2.5" from the focal plane, which means the front of the 9" dome would have to be positioned 2.5" + 4.5" = 7" in front of the sensor. I measure roughly 6", so it's an inch short.

    This is all according to this WetPixel article:
    http://wetpixel.com/i.php/full/proper-dome-size-and-placement/

    Btw, I tried contacting Nauticam regarding this and never got any good answer. I can't figure out why they wouldn't position it correctly when they went through all the trouble of making a dedicated port. I just got mine and haven't taken it into the water yet, but inproper positioning would explain some of the reports of soft corners with this dome.

    The Panasonic 7-14mm should be an excellent lens for underwater use. It's sharp, it focuses very close, 7" or so at 7mm, much closer than the listed spec, and due to the smaller sensor you have a two-stop depth-of-field advantage over full frame. But if it's not correctly positioned, what's the use?

    - Fabian

    ---------- Post Merged at 05:43 PM ---------- Previous Post was at 05:04 PM ----------

    Not sure I understand this. When using a dome port you want to have field curvature. This is because the virtual image created by the dome is also curved. So if the lens focuses closer towards the corners, it's easier to get the corners sharp under water. And my understanding is that one of the reasons fisheye lenses are so popular for underwater use is because they tend to have a large amount of field curvature.

    - Fabian
     
  5. PHIL RUDIN

    PHIL RUDIN Contributor

    # of Dives:
    Location: West Palm Beach, Florida
    1,221
    265
    Hi Fabian,

    You may also want to read about hyperfocal distance, I have attached a DOF graph-ulator here, Digital Diver Network's Depth of Field Graphing Utility

    Each lens has a hyperfocal distance for each F/stop. An area both in front of and behind the point of focus which is itself still in focus. This is offen expressed as depth of field. The wider the lens the greater the DOF for the given sensor/film size. The DOF gets greater with each incrses in the F/stop range, so F/4 has less DOF than say F/22. The standard minimum focus used by the lens maker is the point of best focus not the closest point of focus within the DOF range at the highest F/stop. It is constant over the zoom range from 7-14mm what changes is the hyperfocal distance or DOF.

    I think before you just assume that the Nauticam port for the 7-14mm zoom is not "positioned correctly" you need to do your own tests and define what your expectations for the lens are. If you and others are expecting it to do work like a fisheye because it is a very wide lens that is just not the case.

    Phil Rudin
     
    BoltSnap likes this.
  6. shaker

    shaker Contributor

    75
    21
  7. PHIL RUDIN

    PHIL RUDIN Contributor

    # of Dives:
    Location: West Palm Beach, Florida
    1,221
    265
    "The smaller the dome, the steeper the curvature. 4" is a very small dome. So I can see how the camera could encounter problems focusing.

    Another thing is I don't think it's physically possible to correctly position a 4" dome in front of the Panasonic 7-14mm lens. I measure the entrance pupil of the 7-14mm lens to be about 2.5" inches from the focal plane (imaging sensor). That means the front of the 4" subal dome must be approx 4.5" inches (2.5" + 2" dome radius) from the sensor in order to be correctly positioned. And I don't see how the dome can be positioned that close without banging into the built-in lens hood. Not sure how that affects focus, but for sure it's going to affect corner sharpness. Do you use an extension ring with this port?"

    Fabian,

    I don't know about the Subal dome but the ZEN Underwater dome for the 7-14 is four inches and is a section of the 170mm (6.69 inch) dome so has the same results as below with the 6 inch Nauticam dome. The ZEN port also does a good job with such a wide lens for the size of the port. The ZEN 7-14 port is in fact shorter than the 9-18 zoom port which uses the same glass.

    Zen Underwater Pen Dome for Panasonic 7-14 in Olympus PT-EPxx Housings [zen.wa100.ep714] - $499.00 : Reef Photo & Video!, The Underwater Photo Pros

    ---------- Post Merged at 05:26 PM ---------- Previous Post was at 05:04 PM ---------

    "I think you are right. I did some crude measurements on mine. It does indeed look like it is a section of a 9" dome. Which would be great if the dome was correctly positioned. But from what I can tell the port is too short, meaning too close to the lens. As I mentioned above, the entrance pupil of the 7-14mm lens is about 2.5" from the focal plane, which means the front of the 9" dome would have to be positioned 2.5" + 4.5" = 7" in front of the sensor. I measure roughly 6", so it's an inch short."

    Also Fabian,

    Your problem here is in the math. Using your own figures for the 7-14mm of an entrance pupil of about 2.5" the dome radius would not be +4.5 inches it would be +3 inches because the Nauticam dome is not nine inches it is a six inch dome. At 2.5+3 inches you get 5.5 inches which is about balls on I think using your math.

    Phil Rudin
    ---------- Post Merged at 05:43 PM ---------- Previous Post was at 05:04 PM ----------


    - Fabian[/QUOTE]
     
    sunnymate likes this.
  8. sunnymate

    sunnymate Registered

    # of Dives: 200 - 499
    Location: Malta, Mediterranean
    24
    0
    Hi all, first of all, many thanks for lenghty explanations and all that technical back ground information - I find this thread extremy interesting and you guys seem to have really good undestanding of dome ports and WA lenses. Just to repeat my biggest problem I am having: I use the GF2 with 7-14mm in a Subal casing with subal dome and subal zoom/extension, and I can not focus under water closer than that earlier mentioned about 3..4 feets. At air I can focus very close. So reading your replies, I got an impression you can focus much closer under water ? Can someone tell me e.g. how close it focuses under water, and what kind of extension/dome combination is used (e.g. how much curved is the dome and how far from dome glass is the pupil of that lens in 7mm setting?) Will compare to my Subal setup and try to talk this again with Subal. Sorry to repeat the question here, but still for me looks like you all just confirmed the 7mm focuses close on air, but have someone really managed to focus it close under water ? e.g. bring it to 1...2 feets from object and take a picture ? Damn, im traveling 99% of my time next 3 weeks so will take a while before I get under water the next time - I ordered already the 8mm FE & extension ring to try if Im luckier with that combination. The 7mm lens is really great but at the moment can only take pictures from XXXL objects due to fact cant get close ! ... and its frustrating to see my photobuddies with other systems go next to a smaller object with their FE lenses and 8" dome to take the snap I cant... without going back home and change the 14mm & flat port. Thanks again for all those informative replys, gave me enough to read for 2 evenings while being on the road and bored. :) Cheers !!
     
    Last edited: Jun 26, 2012
  9. shaker

    shaker Contributor

    75
    21
    Hi Fabian,

    I asked a Subal representative about the 7-14mm at the BOOT schow in Dussedlorf (Germany), he told me that the 4" domeport (the one you have) is intended for people how need a compact system, those who are looking for better IQ should go for the 6" domeport. also, one can use all the Subal "3rd generation" ports with the GF2 housing. The 8mm lens can also be used with 4" domeport too.

    - 7-14mm: Zoom Extension Ring EXR-50/G3 (50mm) + 6" Domeport Subal DP-SWB/3 (or Domeport DP100/3)
    - 8mm Fisheye: Adapter/Extension Ring EXR-20/G3 (20mm) + Dome Port DP100/3
    - 45mm Macro: Planport FP-50T/G
     
  10. logic8482

    logic8482 Scuba Instructor

    # of Dives: 200 - 499
    Location: USA
    90
    18
    Hi,

    Any others around also using the Nauticam 7-14mm Dome Port with their casing besides Fabian? I'm looking at getting the Nauticam housing for the OMD, but don't want to invest in everything unless the edge softness is manageable when using the 6-inch 7-14mm Port. This thread is making me nervous that the 7-14mm is not performing optimally in the Nauticam dome.

    Thanks!

    Ryan
     
    Last edited: Jul 6, 2012

Share This Page