Green pixels within my blacks, why?

Discussion in 'Digital Darkroom' started by marissa_c._boucher', Feb 17, 2006.

  1. Some of my images appear to have weird color problems in the pixels when magnifying. For example, if I magnify a groom's black lapel, I'll see all sorts of pixel discoloration of greens. To better explain, take a look at a close up view of this groom's lapel. By the way I see this is lots of my images. They're shot on a 20D and 10D on L lenses. Just switched to shooting RAW so maybe it's JPG related, these images you see were shot JPG though.
    00FJfT-28271484.jpg
     
  2. Here's the image bigger.
    00FJfV-28271684.jpg
     
  3. I think you need to calibrate your monitor. Mine is calibrated and if I see any coloration it is towards blue. I double checked this by downloading both your examples and looked at them in the "info" area (where the "navigator" is in photoshop) and it indeed confirmed my "seeing" as a little towards blue. This actually is to be expected as it looks like you might have been in the shade a bit and maybe using electronic flash as fill....both have a slight blue shift as compared to daylight. Daylight is 5200 K (Kelvin degrees), shade is 7000 K, and flash is 6000 K (depending on the flash). On the 20D you have besides the normal WB controls, there is a white balance correction graph controlled by the joystick to tweak this all in if necessary if you shoot nothing but jpeg. You can also do a custom WB....read the manual for details. But if you are intent on switching to RAW, then all this WB can be easily tweaked in the Photoshop's ACR (RAW converter). Although that is not saying that setting the WB as above in RAW IN camera is a bad idea...you can still use it in the RAW converter via the "as shot" set up.

    anyhow, it's definitely not green shifted, that's for sure.
     
  4. Well, green or blue, it looks like noise to me. Did you shoot it at a higher ISO? Even if you didn't, if you read all the explanations of the "Expose to the right" techniques, there aren't very many bits left once you get into the shadows to differentiate various tones and colours. I say it's camera noise.
     
  5. You know that the black cloth is being lit by natural light, yes? And that the color of the sky is a nice cyan, yes? It should not be surprising then to see some cyan reflections from surfaces with a little gloss to them, like satin lapels, or shiny leaves.

    Film (or digits) records what is actually there without the visual processing our eye/brain system provides. Where our visual system drops colors casts continually, the camera does not. And therein lies your problem.
     
  6. That's just noise.

    But at least you were shooting with L glass. Be sure to name that in the future in case anyone suspects your technical ability in the future.
     
  7. Could be JPG. I would expect the internal raw conversion to clip the shadows to get rid of noise, but maybe it leaves some noise in the deepest shadows. If you shoot RAW and boost the exposure, you should be able to clearly see if this is noise or not. Set your exposure with a grey card and shoot something black (like a suit).
     
  8. Is it in the RAW file as well? This looks like what one gets with incamera jpegs. Scroll down to the middle of this page to see the differences between jpeg and RAW noise from a Panasonic LX1: Jpeg and RAW noise compared
     
  9. Thomas...I've already been running a fully, regularly calibrated setup for years now so I don't think it's related to that. I also am informed on WB methods and processing. The WB on that photo still needs some work though, I agree. Thanks though.

    I'm not going to sweat this too much because I just switched to shooting 100% RAW so if the problem persists then I'll be more worried.

    The shot was actually taken at 100 ISO, 180 shutter at f4.5, which is why I'm shocked that noise would appear. No flash was used according to the properties data. I agree that it could be related to JPG in some way.

    I don't think it's reflection from the sky creating those green pixels though because I've seen this problem on indoor shots as well.

    I agree that it's probably noise even though it was at 100 ISO. I'm looking to get two Canon 5D's this year anyway and they produce less noise throughout each ISO range so that could help a little combined with shooting RAW too.

    Thanks for help everyone.
     
  10. Tim...I think you nailed it with that comparison link you posted, thanks! That is exactly what some of my other shots look like magnified as well. It's the in-camera JPG problem, you're right. Thank you! Well, I don't shoot JPG anymore so problem solved!
     

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