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8mm pro chromatic aberration question

Discussion in 'Native Lenses' started by Underwater, Feb 28, 2016.

  1. Underwater

    Underwater Mu-43 Regular

    100
    Jun 1, 2014
    Eugene, Oregon
    Paul
    So I picked up a refurb 8mm during the President's Day sale and took it on a snowshoeing trip last week. When I looked at the shots, I was surprised by the amount of CA, as well as lots of green and purple blobs in many of the pics with the sun in the frame (I was intentionally trying to get the starburst effect).

    Granted, a bright day in the snow is going to be challenging for any lens, especially something as wide as this. I don't remember having these kinds of issues with the Rokinon 7.5, however. The 8mm also doesn't seem to be as bitingly sharp as the 7.5.

    This poses kind of a dilemma for me, as I ordered it primarily for underwater. It turns out that I can't use it in the same dome port as my 12-40 without changing extensions, which I don't want to do (the fewer o-rings touched, the less likely I am to flood expensive gear). I was thinking of keeping it anyway both because of the astro possibilities and for just how much fun fisheye shooting can be. Now I'm wondering if I should just return it and get a 7-14. Are my expectations too high? Did I just get a bad sample? Also, I'd be interested in any tips on correcting CA in post, other than clicking the box in LR.

    Thanks in advance!
     
  2. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    Hi, there's 3 8mm in mu-43 mount... Which one do you have?
     
  3. ijm5012

    ijm5012 Mu-43 Hall of Famer

    Oct 2, 2013
    Pittsburgh, PA
    Ian
    Unless he modified the title, he said the 8mm PRO which I'm assuming is the Olympus (especially given the fact that he mentioned the President's Day sale, where Olympus was selling the refurb stuff at 20% off).
     
    • Informative Informative x 1
  4. wjiang

    wjiang Mu-43 Hall of Famer

    From all the online reviews I've seen the Oly does have more flare and CA, is a bit less sharp in the corners (maybe field curvature related) when compared to the 7.5FE *wide open*. Comparing f/1.8 to f/3.5 isn't entirely meaningful though, what happens when you stop down to f/2 - f/2.8? That's still faster than the 7.5.

    In ACR (LR should be similar enough), you can expand the colour range and size of the CA correction band for the magenta and green edges separately if the default autocorrect still isn't enough. There should also be an eye dropper tool that you can use to select and autodetect an offending magenta/green band to correct for. Failing all that, use an adjustment brush with defringe cranked up and brush the offending bands.
     
    • Like Like x 1
  5. Ig7

    Ig7 Mu-43 Veteran

    298
    Aug 24, 2011
    Just got a new Oly 8mm 1.8 pro and there are specs of dust inside the lens. Anyone else had the same problem?
     
  6. Joe Smith

    Joe Smith Mu-43 Regular

    123
    Mar 6, 2016
    Not directly referring to your lens, but Roger Cicala from Lensrentals.com wrote recently concerning the Sony FE 85mm f/1.4 G Master:
    Source: Sony FE 85mm f/1.4 GMaster Emergency Tear Down
     
    • Like Like x 1
  7. Ig7

    Ig7 Mu-43 Veteran

    298
    Aug 24, 2011
    Good to know, thank you
     
  8. Zee

    Zee Mu-43 Top Veteran

    Which housing are you using?

    First off, get over the port swapping thing. You've chosen to go into the most hostile environment possible for a camera, it's going to cost you, more than just money.

    I've been shooting underwater since about 2006, from P&S, to better P&S, then to DSLR, now looking for a housing for my EM-1, now that my 400D housing is well and truly dead (I blame dolphins) and my Canon gear sold off.

    Anyways, using a single dome for all your lenses is just limiting yourself. Port swaps are not hard, learn the method, practice, get it right and you'll have no issues. Heck, you'r eusing M43 - you probably are already opening the housing to change the battery after ever dive!

    I've changed ports in boats, on a beach, anywhere, just a matter of paying attention and making sure you are focused on the task with no distractions. Then, always pay attention as you submerge, watch for drips and leaks, tie your housing to your safety sausage if you have to, and float it tot he surface - less pressure = less/no leak.

    As for the lens, I personally went from the Rokfish tot he 8mm Pro because it gives me control underwater that I totally lose with the Rokfish - no focus, no aperture control... Which means I am probably stuck at F4 or above with infinity focus - which may or may not be fine for a surprise opportunity (like the turtle the swims up to your face...).

    I'd stick with the Oly Pro, personally, and I'd consider investing in a port for your 12-40. Though, I'd be more inclined to get an Oly 60mm Macro and port for it. Lenses are pennies compared to the damn housing setup!

    Oh, I hope you have strobes!

    Z...
     
  9. Jonathan F/2

    Jonathan F/2 Mu-43 Hall of Famer

    Aug 10, 2011
    Los Angeles, CA
    I currently have the 8mm 1.8 Pro and also owned the Rokinon/Samyang 7.5mm 3.5 FE prior. I did a comparison between the two awhile back if you do a search. I'd actually give the nod on sharpness to the Rokinon, especially stopped down to f/8. That lens excels in stop-down daytime shooting besting the 8mm 1.8. Where the 8mm 1.8 excels is shooting at 1.8 in low light. You can shoot some crazy slow shutter photos with that lens. You also have to CA correct it in post processing.

    I'd say the 7.5mm is better suited for most fisheye shooters. The 8mm 1.8 Pro is best suited for those shooting in extreme conditions.
     
    • Like Like x 1
  10. Underwater

    Underwater Mu-43 Regular

    100
    Jun 1, 2014
    Eugene, Oregon
    Paul
    I'm shooting an Inon 170mm dome and the Oly housing for my M1. I go back and forth between the dome and a flat port (I own 2 flat ports- the common one for the kit lens and the 4/3 flat port for the 12-40 with a swing away adapter for a wet lens), so changing ports is not a problem at all. With the Inon dome, I need a 2" extension for the 12-40 and 7-14 Pro lenses. To shoot the 8mm, I'd have to unthread the EP08 adapter, unthread the extension, etc. Time consuming, and it really is a bit of a PITA.

    Since I started this thread, I opted to go with the 7-14 for UWA both because I like the flexibility of a zoom and to avoid the extra work and risk. BTW, I also have the 60mm, and I shoot with 2 YS-D2 strobes. Most of my diving is in the cold low-viz waters of the PNW, so the 12-40 and the dome is generally the right choice. Really low viz means I go with the 12-40 and flat port /diopter, and 2' or less of viz means the 60mm.

    I originally posted this thread because of what I thought was excessive CA; further use tells me that it's not as bad as I initially thought. My first outing with the lens was a snowshoe trip on a sunny, cloudless day- funny how shooting treescapes in those conditions can put a UWA to the test. The reason I wanted to shoot the 8mm underwater was for a trip to Bonaire. I just got back a couple of days ago, and although I intended to give the 8mm a shot, it just made more sense to stick with the zooms. The turtle and my buddy (with his E-PM1) are with the 12-40, the other shot is with the 7-14.

    P4130994.

    P4120491.
     
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  11. Zee

    Zee Mu-43 Top Veteran

    Some very nice shots there! And, as mentioned, the infamous turtle in your face pic! I always love when that happens!

    Z...