2 questions about noisy photographs

Discussion in 'Photography Beginners' Forum' started by TiaS, Feb 18, 2010.

  1. TiaS

    TiaS TPF Noob!

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    I have a Rebel XS and I often get noisy photographs when I use an ISO of 800 or 1600. Sometimes I will even get noise at 400. Is this common for the Canon XS or can I do something to help improve this?

    Also, when doing HDR, how I can aviod getting noisy photographs as my end result?
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    That's not surprising. Those are considered 'high' ISO levels and will typically give you noise on all but the best (most expensive) DSLR cameras.

    Part of the reason why you might get noise, is exposure....especially under exposure.
    If your shots are under exposed and you try to brighten them with software, that is where you will really see a lot of noise.

    Also, keep in mind that it's very easy to see noise if you are looking for it. You can zoom in and see some sort of digital noise on just about any digital image. A better way to judge an image would be to print it out and hold it at arm's length (for an 8x10, for example).
     
  3. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    Sounds perfectly normal to me as well - on my 400D (XTi) ISO 400 is the highest I work with for a shot that I expect to come out well (ie to my standards in terms of image quality). Pushing to ISO 800 is posible and in a print, with a good exposure, the noise is not so bad, but finer details are sadly often lost and its mostly a record shot ISO for me. ISO 1600 is just way too much noise for me - the finer details are almost totally lost and its just not pleasing to my eye - so I simply don't push that high.

    ISO 100 and 200 area where I mostly work, reading to 400 when needed and 800 for those record shots.
     
  4. robertwsimpson

    robertwsimpson No longer a newbie, moving up!

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    I took this at ISO1600 on my Rebel XTi:

    [​IMG]

    As you can see, this photo is very usable.


    The best way to avoid the noise is to expose correctly.
     
  5. tdiprincess

    tdiprincess TPF Noob!

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    That is a neat shot!
    Again, another thread that I'm happy to have seen! This will help me! Thank you!!
     
  6. Charles89

    Charles89 TPF Noob!

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    I dont know about the XS, but the XSi has a feature in the special menu, that reduce noise on high ISO setting. Funny thing is that I have had my camera for 1 year (1st DSLR) and I just noticed this special menu like 2 weeks ago. I am very pleased with the noise reduction it gives !

    The menu is called "custom functions" !

    Hope it helps !
     
  7. tdiprincess

    tdiprincess TPF Noob!

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    I will keep that in mind once I get mine. I will also be reading over the manual once I get my camera. I know it'll be boring, but hopefully I'll be able to find the functions a bit quicker..
     
  8. rufus5150

    rufus5150 TPF Noob!

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    You're better off blowing the cash and getting a decent NR program (Noiseware pro, etc) coupled with good exposure technique, images at 1600 are quite usable from that camera.

    (My old XTi had terrible noise at 800 and was actually better at 1600... I'm not sure if anyone else has experienced that, but I used 400 and 1600, but I never found 800 usable at all.)
     
  9. DennyCrane

    DennyCrane No longer a newbie, moving up!

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    Unless it's an object in motion, I'd simply use a tripod, lower ISO and longer exposure time.
     
  10. TiaS

    TiaS TPF Noob!

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    That is on the XS, I just checked. Thanks
     
  11. Dwig

    Dwig TPF Noob!

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    All digital images always have noise, period. Whether your brain notices the noise is affected, in part, by the detail in the image. In images with large middle-toned areas that lack detail (e.g. medium blue skies, ...) the noise is more noticeable. When there is a lot of fine sharp detail (e.g. the squirrel's fur in the pic in one of the other replies) you brain doesn't "see" the noise even when its rather significant.

    Also, any image processing to correct for white balance, other than "daylight", or underexposure is the equivalent of using a higher ISO and results in increased noise. A shot under common tungsten light requires a 2-3 stop amplification of the blue channel to accomplish WB. If shot at ISO 400, the blue channel would be effectively working as ISO 1600-3200 and would have the accompanying increased noise.

    Use only the lowest ISO available and, of course frame your pictures properly when shot so that there is no need to do any cropping other than to alter the aspect ratio to fit the composition.

    If you are using HDR techniques to produce true High Dynamic Range images you should NEVER use anything other than your camera's lowest ISO. Any increase in ISO will always reduce the dynamic range of the individual shots in the stack and is thus working against your goal.

    Using anything other than the lowest ISO when doing HDR should be for only those times that true HDR is not your goal, for times when you are using HDR techniques for solely its Tone Mapping to create exaggerated colors and tones.
     

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