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Thread: noise on long exposure

  1. #1

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    noise on long exposure

    hi everyone!
    i tried shooting in long exposure in my 50d camera (my first time) i don't know if this is right.
    what i got is an image that noise is noticeable, the settings are
    exposure time=8sec
    iso=500
    app=f/5
    please kindly comment on this shot
    noise on long exposure
    please kindly advise me the best practice in shooting long exposure...

  2. #2

    Re: noise on long exposure

    Hi Belong (is that your actual name?) I have a 50D, as well as a 5D. I find the 5d is much better at this type of shot as the pixel density is less (12mp against 15mp for the 50D) and it's full-frame so the pixel sites are larger. But there are things you can do with the 50d. Have you set the noise reduction in the menu to an appropriate level? Check your manual on how to do this.

    You might also want to try turning OFF the ALO (Auto Light Optimizer) Have a look at page 177 of the official manual. It tries to correct for low-light shadow areas in particular, but can (according to Canon) increase noise in a low light shot, especially on higher ISO. It's custom function II-4. Haven't tried it myself, but it might make a difference.

    Your shot doesn't help matters. Not sure what time it was shot (and how dark it was) but night shots like this work much better where there is more light available. It could be natural light (shoot just after sunset), or artificial light (say, house/street lights in a marina). In your shot I can see artificial lights but they are a long way off and are not going to make any difference to what the 50D records in terms of light strength. Try getting closer to a light source and shoot when there is more natural light available. That way your camera is having to work less to get what in needs for a decent exposure. Here's an example I shot to show getting closer and having natural and artificial light sources combined. Shot with a 350D... http://farm5.static.flickr.com/4063/...cfb87bd0_o.jpg
    Last edited by carregwen; 19th March 2010 at 06:13 AM.

  3. #3
    Moderator Dave Humphries's Avatar
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    Re: noise on long exposure

    Further to Rob's reply, might I suggest that 40 seconds at 100 iso would have reduced noise.

    However, if you were trying to grab 5 seconds stillness between wind gusts, then I understand the iso being that high.

    What PP software are you using?

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    Re: noise on long exposure

    Couple of things to add ...

    1. Avoid "odd" ISO settings like 500 (use 100, 200, 400, 800 etc) for lower noise.

    2. Noise is proportional to under-exposure - was the shot under-exposed and then the levels brought up in post-processing by any chance?

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    Re: noise on long exposure

    thank you very much carregwen, dave, and colin;
    first of all my real name is isabelo,
    i set the noise reduction on my camera on "standard" if i remembered it correctly, and i guess ALO was turned on. (thanks carregwen for the very detailed suggestions). it was shot i guess 2 hrs after sunset, and i could only see the distant lights far ahead.
    does my 50d capable of capturing such image like carregwen example?
    at 40 secs, 100 iso - can i capture much cleaner image than my example in 8secs, 500 iso?
    i am not aware of this 'odd' ISO settings, try to avoid this sooner...
    Last edited by belong; 20th March 2010 at 09:35 AM.

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    Re: noise on long exposure

    Hi Isabelo,

    Just to give you a quick demo of how noise shouldn't be a problem if you expose correctly ...

    The exposure on this first image of mine was 16 MINUTES @ ISO 200 ...

    noise on long exposure

    And 12 MINUTES @ ISO 200 on this one ...

    noise on long exposure

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    Re: noise on long exposure

    wow amazing!
    now i know that if i lower down the ISO to 100 or 200, i can get a cleaner image even in very long minutes. i guess i will have to just switch my "patience mood" then...
    thanks colin, you're always very helpful to a beginner like me!

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    Terry Tedor's Avatar
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    Re: noise on long exposure

    Hello! I have a 50D too. It is very capable of capturing images like carregwen and Colin have posted. I would recommend the same things that both gentlemen have said - lower ISO, longer exposure and turn off ALO. I'd also recommend turning on "High ISO Speed Noise Reduction" and set it to strong. This setting is under C.Fn II-2. Also, please be aware, with "Long Exposure Noise Reduction" turned on the camera takes 2 shots - the first one is the "normal" photo. The second one is called a dark noise exposure, where the shutter stays closed and the camera evaluates the noise from the sensor and then subtracts the noise data from the first image to effectively remove the noise from the first image. The second image may be "exposed" for as long as the first image was. In otherwords, if the first shot was exposed for 15 minutes, the second one will (most likely) take 15 minutes too. So the time spent waiting for the image to be completed will be 30 minutes. Before you turn this feature on, make sure you can wait that long.

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    Re: noise on long exposure

    Quote Originally Posted by Terry Tedor View Post
    I'd also recommend turning on "High ISO Speed Noise Reduction" and set it to strong.
    Hi Terry,

    Just be aware that Hi ISO doesn't do a lot on low ISO settings

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    Re: noise on long exposure

    Quote Originally Posted by belong View Post
    wow amazing!
    now i know that if i lower down the ISO to 100 or 200, i can get a cleaner image even in very long minutes. i guess i will have to just switch my "patience mood" then...
    thanks colin, you're always very helpful to a beginner like me!
    No Worries Isobelo - the most important thing - no matter what ISO you use - is still to get a good exposure though. The good news is that the longer the exposure, the nicer the effect you get with water and clouds

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    Moderator Dave Humphries's Avatar
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    Re: noise on long exposure

    Hi Colin,

    I might be about to learn something here; why do you say -

    Quote Originally Posted by Colin Southern View Post
    Avoid "odd" ISO settings like 500 (use 100, 200, 400, 800 etc) for lower noise.
    If (most of*) the iso control range is a straight forward gain control on the analogue amplifier after the pixels (before we even get to the A-D), I don't see it makes any difference to the noise performance beyond the directly proportionate one. Surely the noise at 500 iso is less than at 800 iso? Obviously it will be a bit worse than 400 iso.

    * I am aware that at extremes, typically labeled Hi or Lo rather than an iso number, it achieves the effect of a higher or lower iso by shifting the bits, or multiplying the digits coming out of the A-D converter. This is a bad thing if the Dynamic Range is high because you are typically losing a stop of it.

    I can see that if the entire iso range was achieved through bit multiplication, then what you say would make perfect sense, as rounding errors would appear as noise (I think), so sticking to whole stops, allowing simple bit shifting, would be worthwhile.

    Or is there something in PP that you think works better on "whole stop isos"?

    I personally do use odd iso numbers, based on my assumption of how sensor gain controls work (admittedly based on how I was taught TV cameras work), so if I am wrong, it'd be nice to know

    Puzzled,
    Last edited by Dave Humphries; 20th March 2010 at 09:24 AM.

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    Re: noise on long exposure

    Hi Dave,

    In essence, they do the "odd ISO" by digital manipulation as well. Keith has a good article on it here if you're interested.

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    Re: noise on long exposure

    Quote Originally Posted by Colin Southern View Post
    In essence, they do the "odd ISO" by digital manipulation as well. Keith has a good article on it here if you're interested.
    Ahh, maybe I am OK with a Nikon, eh?

    Thanks, something for me to check on.

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    Re: noise on long exposure

    Quote Originally Posted by Dave Humphries View Post
    Ahh, maybe I am OK with a Nikon, eh?
    Doubt it - everyone knows that this years Nikons are just last years Canons

    Seriously (as the Cannon balls fly!) - Keith's tests look like they're something that could be easily repeated on your camera for you to test for yourself (if you're a bit bored at home).

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    Moderator Dave Humphries's Avatar
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    Re: noise on long exposure

    I'm never bored (now you mention it), but frequently worry about all the stuff I should be doing

    With Keiths pics, although there appeared to be a big jump from say 400 to 500 and 640 looked the same as 800, it wasn't quite as bad as I had imagined (mis-understood?) you meant. Never-the-less, it does seem to show that you might as well go straight to 800 from 400, at least with a Canon.

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    Re: noise on long exposure

    Quote Originally Posted by Colin Southern View Post
    Hi Terry,

    Just be aware that Hi ISO doesn't do a lot on low ISO settings
    Yes, that's correct, but it does do some.

    According to the 50D manual "Although noise reduction is applied at all ISO speeds, it is particularly effective at high ISO speeds. At low ISO speeds, the noise in the shadow areas is further reduced."
    Last edited by Terry Tedor; 20th March 2010 at 03:13 PM.

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    Re: noise on long exposure

    Great tips and links here although I am going to have to read and re-read the technical stuff a few times before I really get to grips with it. One thing I have noticed since doing long exposures is the difference in the level of detail you get - something you really see in Colin's 16min exposure

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    Re: noise on long exposure

    Quote Originally Posted by Terry Tedor View Post
    Yes, that's correct, but it does do some.

    According to the 50D manual "Although noise reduction is applied at all ISO speeds, it is particularly effective at high ISO speeds. At low ISO speeds, the noise in the shadow areas is further reduced."
    Also, it only works with JPEGs, not RAW captures

  19. #19

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    Re: noise on long exposure

    hi everyone,
    here's my shot on long exposure after i applied the recommendations/suggestions you all post.
    please have a comment on which i will improve further.
    thank you...
    noise on long exposure

    lens: 55-250 canon efs
    exposure: 4 secs
    f/25
    iso 100

  20. #20

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    Re: noise on long exposure

    Hi Isabelo,

    Looks good to me

    Probably a few minor post-processing improvements could be made - happy to give it one of my notorious "Photoshop 30-Second Makeovers (TM!)" if you'd like?

    If you're after even LONGER "exposures", another technique is to take several shots the same as you have, and them combine these in Photoshop for even less noise and smoother water.

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