Help with Custom WB (and pics inside)

Discussion in 'Night, InfraRed, and UltraViolet Photography' started by lexiticus, May 15, 2007.

  1. I Have a D50 and D70s, both I use for IR every once in a while, but even setting a custom WB off of the blue Sky, a white porch, the Grass, Shrubs, I get blown highlights in the 3/4 + Range of the histogram
    These blown highlights aren't just white either, they are turquoise which makes them a very big pain to deal with!
    Anyone have any tips for finding the right Custom WB setting with an IR filter (On an unmodified D70s + D50)
    Pics show example

    BTW, IR filter is Hoya R72
    lenses I've used are the 50mm f1.8, 18-55 Af-s, Sigma 90mm f2.8 Macro and Tokina 28-75 f2.8

    I've got at my disposal, that i might try (to set the custom WB), a Circ polarizer, an ND8 filter, an ND400 filter and a few UV filters. Also since i rarely take my Tripod almost all pics are shot JPG and at ISO 1600. (RAW also does it, and it isn't any easier to fix IMO)

    D70 and Tamron 28-75
    blown1.

    D50 and 18-55 af-s
    blown2.
     
  2. BigPixel

    BigPixel Guest

    Might not be what you wanted but the first is beautiful.
     
  3. Thanks, Its just a tree in my backyard that had good lighting at the time (shadows all over the background yet it was well lit)
    So I used it to test

    I still can't figure out how to get the best WB setting though, Tried a few other things (and peices of paper) Still get blown turquoise highlights (at the top 25% of the histogram, so it shouldn't be that blown...)
     
  4. charliec

    charliec

    327
    Jan 17, 2006
    los angeles
    treat it the same as visible light and reduce your exposure just remember that 3/4 on the histogram is 'blown' and even if the camera is not blinking highlights it may be overexposed.

    If parts of your photo become to dark fix it with curves or a shadow/highlight tool. the problem with this for you will be shooting at iso 1600 introduces alot of noise in the post processessing stage when you make adjustments.

    I suggest to set out one day with IR in mind and use your tripod with iso 200 setting.
     
  5. Ya thats my backup plan, However my older camera's never blew the highlights like that, and I haven't heard of anyone else having this same problem so i figured maybe someone knew a fix.
     
  6. I have the same problem, if it makes you feel better.

    I shoot with D70s + 35mm f/2D + Hoya R72, custom white balance set off of grass. The only way I've found to reduce this issue is to underexpose a bit, try not to get past midpoint in histogram too far.

    I've not had it happen on foliage though, normally it happens to me on a completely white object (like streetlamp covers).

    I'll reset my WB and try setting it again on nicer grass now that we have some real green stuff around. Been raining the past 2 days though, and might rain again today so nothing doing for the next few.
     
  7. Ahh someone else with the same problem, So it isn't just me after all, Oh well I guess i'll have to just live with it then. (when setting custom WB, you can do it in manual mode and control the exposure, I will try messing with that a bit more till i get a borderline overexposed and borderline underexposed WB setting, see if that changes anything)
     
  8. Use a custom WB setting off of a healthy lawn. This has worked great for me and after setting it properly I have never had to go back and redo it.
     
  9. I shoot 'raw' and WB set to 'auto' - works for me. You can set your WB afterwards in PP.
     
  10. They both look like they might be improperly exposed.

    Take a custom white balance off a sunny patch of grass with the sun "bouncing" up into the lens, rather than with your back to the sun.

    I don't know about the D50, but my D70 accurately meters and autofocuses with the IR filter attached. Trust it. Use Manual mode to set the exposure parameters, and you should not get those polluted whites.

    Your mileage may vary.

    Good luck.
     
  11. Hmm, I have no such luck at all, Especially with Autofocus and metering.
    heres what I did (About half an hour ago)...

    Grass that I set the WB off of
    grass.

    Grass after WB set (histogram barely past the 1/2 way mark, this is +1.0 ev, Also notice the AF is a few cm too deep, Since it was set to center focus)
    grassir.

    Attempted proper exposure focusing on the foreground tree, (DOF is completely past it on the background, which all my lenses do (backfocus seriously) EV comp +2.7, Polluted whites)
    overexposed.

    Heres an example of the histogram, Its as if the 3/4 mark Is specifically for the Cyan "whites"
    histogram.
     
  12. I may not be understanding your reply properly, but just in case....

    Set your white balance of the grass with the IR filter installed. Set to manual metering and autofocus (M on the dial). Use meter to adjust aperture and shutter to center mark. Press and hold WB until you get the signal to shoot white balance frame. Shoot. Make sure you get the "Gd" signal flashing in display to indicate the camera is happy with the WB shot.

    As for the angle...

    Assume the sun is in the southeast (morning). Point your camera southeast to the grass so that the light will directly bounce from grass into your lens (with the IR filter in place).

    That ought to make things work better. IR light focuses at a different point than visible light, that's why I let the camera do the focusing. I compose (using a tripod because of shutter speeds), then carefully place the IR filter so as to not alter composition. Use the self-timer to avoid jiggling the camera.

    You can see a couple of my IR shots in my collection on PhotoSIG...

    Here...

    Good luck
     
    Last edited by a moderator: May 21, 2007

  13. Ya did all that (just now to make sure I had the exposure dead on the center), and I still get that overexposed cyan "blown whites" I guess i'll just have to underexpose my pictures to avoid this, Its not a big problem, I just have to be careful

    (I also didn't realize you meant autofocus before putting on the IR filter, I just use the distance markings and manual focus on my lenses now because of the inaccurate AF with it on)
     
  14. I didn't mean to autofocus without the filter. I compose the shot before putting on the filter. I use the autofocus after installing the filter. The IR light refracts different than visible light, that's why I let the camera autofocus. If I focused beforehand, the focus will be off due to the refractive differences.
     
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