Noisy Sky with New Lens?

Discussion in 'Digital Photography' started by twodeko, Jul 11, 2007.

  1. twodeko macrumors newbie

    Joined:
    Jul 11, 2007
    #1
    I recently bought a Canon 17-40mm f/4.0L lens for my Rebel XTi. After shooting some outdoor shots with and without a circular polarizer filter, I noticed that the sky was very noisy. I was curious if this is me being too paranoid, if there is something wrong with my camera/lens or that I need to change about the way I take pictures.

    The following two urls show outdoor pictures taken with two different lenses. The noise that I am wondering about can be seen in the first link (besides the firework shot, which was taken with the kit lens).

    Canon 17-40mm f/4.0L

    Canon IS 28-135mm *It is worth noting that this lens had focusing issues and was returned. Also, all shots were taken with a cpf as well.

    Thanks!
     
  2. timnosenzo macrumors 6502a

    timnosenzo

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    ct, us
    #2
    Lenses can't really make "noise". You may be noticing more noise in shots IMG_1953.jpg & IMG_1955.jpg because the color is darker/richer. The 2 shots I mentioned have noticeable JPG artifacts and it looks like you may have clipped the color channel a bit. Either way, lenses can't make noise like cranking up the ISO does.
     
  3. twodeko thread starter macrumors newbie

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    Jul 11, 2007
    #3
    nosen,

    The JPEG's were created at the 100% quality setting (Adobe Lightroom), and many of the qualities seen in those photos are also present in the original raw files. I could post the raw images as well, but I can assure you that it was in there as well. It has the ISO grainy look to it almost, but I am not sure if that is typical of a digital SLR. I understand that the lens cannot make a picture noisy, but how would richer/darker color produce this "effect" in photos?

    Would you say the overall quality looks on par for that lens? I have been learning quite a bit about my camera, but want to make sure that I am getting the most out of it. (Hence, this post :p)

    Thanks!
     
  4. mrkramer macrumors 603

    mrkramer

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    #4
    did you accidentally have the ISO left up too high from the last time you had gone out to take pictures? I have occasionally done that and come out with noisy pictures.
     
  5. adrianblaine macrumors 65816

    adrianblaine

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    #5
    I would think this is the culprit. Since the sky is such a dark blue, if the ISO is at 1600 or so, it could cause some noise in the darker parts of the picture.
     
  6. Abstract macrumors Penryn

    Abstract

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    #6
    Did you edit the photo? I mean, did you increase the exposure using software (iPhoto, Lightroom, etc) because you underexposed? Sometimes, increasing the exposure, brightness, colour saturation, or any number of settings can add some noise. I don't know what your photos normally look like at ISO 200, but I don't think the sky would be that noisy even when zoomed in.

    Anyway, rest assured that it's not your lens. I don't see how it could be possible, but I'm sure someone else knows better.
     
  7. Father Jack macrumors 68020

    Father Jack

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    Ireland
    #7
    Lenses don't make noise, different lighting conditions do.
    Increasing brightness of a dark or underexposed picture will also increase noise.
     
  8. twodeko thread starter macrumors newbie

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    Jul 11, 2007
    #8
    Unfortunately the ISO was set to 200 for all those pictures and I agree that it should not be that noisy.

    I may have done a little post processing, but if anything it was minimal. I am fairly sure that at least a couple of those pictures were right from the memory card yet they all show similar amounts of noise.
     
  9. twodeko thread starter macrumors newbie

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    Jul 11, 2007
    #9
    took some new pictures this afternoon and have posted them.

    no alterations/post-processing done, just shooting and saving the pictures as JPEG now instead of RAW.

    i also set the ISO to 100, so sensor noise should be minimal.

    ISO 100, No post-processing
     
  10. Abstract macrumors Penryn

    Abstract

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    #10
    Check the preset settings on the camera. There may be in-built settings for colour saturation and such. Check to see if there's a setting for "Sharpness", and see if it's at the middle setting.

    Anyway, I checked one of your new photos at ISO 100, and it doesn't look noisy at all.
     
  11. twodeko thread starter macrumors newbie

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    Jul 11, 2007
    #11
    Abstract,

    I thought so too :) I played with some of the settings and noticed that I had it on landscape mode and with a circular polarizer, it seemed as though the sky was a bit noise given the increased saturation.

    I am glad to see that you agreed, off to take some pictures on a backpacking trip this weekend!
     
  12. timnosenzo macrumors 6502a

    timnosenzo

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    ct, us
    #12
    Again, I think you clipped the color channel by underexposing the image slightly, so the blue can't display properly. Check out the histogram.

    Picture 2.png

    I'm no expert, but I think it adds up...
     
  13. twodeko thread starter macrumors newbie

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    Jul 11, 2007
    #13
    nosen,

    i appreciate your advice, and don't mean to ask for a histogram lesson but what do you mean by "clipping"? i see that the blue is consistent until it hits an edge (and likewise, the red) and thought that it corresponded to the brightness of the red and blue within the picture. i was told that the human eye is tuned to appreciating colors that are in the middle of that spectrum, which brings about my error in exposing that picture, but how would clipping bring about significant noise and speckles in the sky?
     
  14. Shaduu macrumors 6502a

    Shaduu

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    #14
    It means the entire blue spectrum available isn't being displayed in the picture.
     
  15. ChrisA macrumors G4

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    Redondo Beach, California
    #15
    How do you know the RAW images are noisy? You can't look at a RAW file. You can only look at a converted RAW file. How do you know the nose is not added by the conversion process? The raw data very well may be noisy, not saying it isn't just that you can't display a raw file,
     

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