Odd CA with D5300+ 105VR + SB-800??

Discussion in 'Nikon' started by mike_halliwell, Oct 6, 2014.

  1. I was out shooting some early morning dew covered cobwebs with my D5300 + 105VR + SB-800 and got the following image.
    Shot in M 1/200 @ ISO 100 @ f4.5 and Manual Flash at maybe 1/16 power.
    I've over JPEGed it to make it fit here, but the 2 big angled magenta and green bands are equally visible on the RAW.
    Is this normal CA behavior with a high contrast subject like this or is there something wacky going on because it's flash and spherical water drops (I don't think so!) or what?
    00csFh-551623984.jpg
     
  2. Late Edit. I should add that I'm not parallel with the cobweb as the intention was kinda soft > sharp > soft through the image. It now looks like a 'failed' lens CA test shot of an inclined black and white graded ruler!! Incase it matters, from what I remember, VR was ON.
     
  3. Question, In waterdroplets you often see "miniatures"of subjects behind the droplets ( they are like little fish eye lenses). Are you sure it is not subjects behind the web that you are seeing here ? ( maginfy the droplets as much as possible and see if you recognise something...) .
     
  4. I've bumped up the saturation so you can see the effect more clearly..
    00csGb-551627784.jpg
     
  5. here's 2 more...the colour moves around too! Increases sat by 60%
    00csGd-551627884.jpg
     
  6. I would be wondering if you're getting some kind of prism effect with the water droplets and the light from your flash, along with the natural light of the scene.
     
  7. That'd be my guess too, that it's somehow prismatic/diffractive/scattering in origin.
     
  8. Mike, I have no idea what is causing the effect, but I really like your "Increased Saturation" image. Darken down the background in post, and you have a beautiful, creative image.
     
  9. It has nothing to do with Color Aberration, (CA) usually produced by most of the lenses at the corners, and visible in the sharp contrast line, extremely magnified, at left, kinda blueish, right pinkish line. This effect on your image, a results of those tiny prism, reflecting the background light, combining with the flash light you using. Try using natural light or add extra light with reflectors as a more natural light, then flash light. Which is s standard for close-up photography. Naturally, you need to use a steady tripod. I using the 105/2.8 VR, but, never using the VR mode, and always using tripod, camera and lens in manual mode. The 105/2.8 VR, one of the sharpest close-up lens after the AF 200/4ED.
     
  10. The reason I had to use flash was that the cobweb was gently swaying in the morning breeze.
    I was thinking more of Longitudinal Chromatic Aberration like this saturation increased Lensalign 'failure' image.
    This page shows Bad Long CA...
    http://www.lenstip.com/297.5-Lens_review-Samyang_35_mm_f_1.4_AS_UMC__Chromatic_aberration.html
    00csJa-551641584.jpg
     
  11. Thanks Brooks, it is pretty surreal!
    I'd not really looked at it in a positive way until you mentioned it...:)
     
  12. Mike, please post the (further still) edited surreal photo for a reference.
    I still think that what we are seeing is the LoCA alias axial CA. I if it was the prism effect of those water droplets, then the colour shift would have been different.
     
  13. This is longitudinal CA where subjects in front of the plane of focus are purple and the those behind are green. It has nothing to do with the water droplets. It will improve if you stop it down. Some copies of The Micro Nikkor 105mm f/2.8G have absolutely horrible Lo CA. I know, I had one that I bought new. I wasn't usable as a medium telephoto because of this. I had to stop it way down to get the CA to an acceptable lever.
    I sent it back to Nikon the day after I bought it and all they did tweaked the focus a little but didn't realign the lens. I talked to someone I know in NPS and she confirmed that this is a problem with this lens and some are much worse than others. I tested this lens against a "D" version and a Tamron 90mm, f/2.8. Both of these lenses had almost no Lo CA wide open. I sold the lens cheap just to get rid of it. It was by far the worst lens I have ever had in the nearly 50 years of shooting "pro" glass.
    Sorry about the rant. It still makes me mad to this day.
    John
     
  14. Mike, please post the (further still) edited surreal photo for a reference.​
    Kari, do you mean the further editing suggested by Brooks for a even darker background?
    John C, what's odd is I've never noticed this before. I guess I don't often use this lens at f4.5 either and maybe the high contrast has made it more obvious? Might be a silly question, but what can cause a lens to start doing this? Is it a decentred lens? Especially one of the ED ones?
    I'll see if I can replicate the problem with VR ON and OFF just incase it's those pesky prisms. Mine do seem to rattle around a bit.
     
  15. The lens I had was obviously a very bad copy. The effects are worse the higher the contrast and the wider the f-stop. I would not expect that a lens will change with time as long as it hasn't been dropped or experienced some other sever shock. People use this lens very successfully wide open for portraits which are typically relatively low contrast subjects and there is generally little, if anything, in front of the plane of focus. Mine was so bad that it was very obvious even on things like weathered wood.
     
  16. Purple and green and no intermediate colours? I'd put it down to LoCA. Not all otherwise good macro lenses are very good at LoCA, disappointingly - the old 90mm Tamron isn't, for example. I've not actually seen LoCA images from a 105mm VR, but Bjørn; says: "However, the optimum aperture range is still f/5.6 to f/11, and the IF design gives a some longitudinal CA, indicated by slight emphasis to reddish fringes in the foreground and the complementary greenish ones in the background of the focused zone". The 150mm Sigma is pretty good at the same problem, although not perfect. Short of going to Coastal Optics, or possibly a 125mm Voigtlander, I'm not sure you'll get perfection here. I'd just make the most of it creatively, or use Photoshop's LoCA desaturation controls. At least it's not as bad as my 135 DC was.
     
  17. Mike, yes as suggested by Brooks. If you cannot beat them, join them ;-)
     
  18. It's just "normal" LoCA IMO. The cobweb was obviously bellied out away from the camera (i.e. concave) and so you have the centre beyond the plane of best focus, and the outer part inside the plane of focus. The water droplets may have exaggerated the effect, but I see nothing unusual there.
    PS. The use of the DX format has obviously emphasised the LoCA of the lens. The same shot taken on Full-frame would doubtless show much less fringing. So one more thing to bear in mind when choosing formats.
     
  19. RJ, the only 'odd' thing is that I've never managed to show this in the 7 years I've had this lens at all apertures and on both formats!
    Does this mean it's had a knock without me knowing it..... like someone dropping my camera bag and not telling me?
     

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