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Thread: Does Proper Exposure Prevent Noise

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    Brownbear's Avatar
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    Does Proper Exposure Prevent Noise

    As many people on this forum probably know, I have been trying to get a good photo of black bellied whistling ducks in flight against a blue sky for 2-3 months with no success...

    If I use a Aperture Priority, with a low aperture (6 is about the lowest I can go with my camera) I experience chromatic aberrations on the ducks that is not so easy to fix...

    Program Exposure mode does not work at all nor does the sports setting.

    In manual mode when I use a higher aperture say F8-F10 combined with a slower shutter speed the photo is blurry.

    If I try to use a shutter speed priority, even just 800 the photo is very underexposed... (the ducks fly at dawn and dusk)

    So it seems my only option is to use a higher iso but even at iso 800 the photo is full of noise (and sometimes still too dark).. If I overexpose the photo a little the sky is washed out... I have tried every setting M, A, S, P with no success...

    I believe I read somewhere on this forum (Colin?), and that if you set your exposure correctly, you will experience no problems with noise. Is this true? If yes, how does one set exposure correctly for high contrast action photos in poor lighting conditions (ie; my nemesis... the black-bellied whistling ducks)

    I have a Sony Alpha 200 DSLR (100-300mm) and a Nikon D80 that I use with a Tamron 200-400 mm lens. I experience the chromatic aberration and noise etc (as above with both camera lens)

    Thank you...

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    FrankMi's Avatar
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    Re: Does Proper Exposure Prevent Noise

    There are more experienced voices here than mine so this may not be the best approach.

    I would kick up the ISO to 1600 or higher and do everything to get a good sharp, well exposed image of the duck at the expense of the sky. I would then also take a properly exposed sky without the duck.

    In post processing I would use a noise reduction program and minimize the noise on just the duck then sharpen the image as needed. Once the duck was as good as I could get it, I would replace the sky with the properly exposed one I had taken.

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    jprzybyla's Avatar
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    Re: Does Proper Exposure Prevent Noise

    Hello Christina, In response to your question...Does proper exposure prevent noise, I would say yes and no. What is exposed correctly will not have noise, but the dark shadow areas in that image may have noise. Take a look at my post below titled...More From The Day Before Yesterday. In the shadow areas of the wings there was noise that I had to deal with in post processing using the Adjustment Brush in Lightroom 4. Those images were shot with Shutter Priority set to 1/2000. I would not shoot any bird moving without a shutter speed of at least 1/1600. The camera will choose the aperature needed, unless very bright light most likely the maximum of 5.6 for the lens I used and your Tamron. Concerning the Chromatic Aberation I find that that only occurs on edges that are soft. If an image is in sharp focus there is no Chromatic Aberation with good glass. I shoot a lot of birds and find early dawn and dusk difficult because of not enough light, difficult to get correct exposure and difficult for the camera to focus with a maximum aperature of 5.6. I hope this helps, you need a high shutter speed and let the camera choose the ISO it needs.

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    Administrator Manfred M's Avatar
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    Re: Does Proper Exposure Prevent Noise

    No, noise in the image is related to the ISO setting and is not related to the lens.

    A digital camera sensor is effectively a combination of photosensors and analog amplifiers. The higher the ISO level, the higher the level of amplification required. This means that any extraneous signals that the sensor picks up, including the noise created by the electronic circuitry itself, such as photodiode leakage, gets amplified. This is the noise we see in the image.

    When you take a picture of a relatively consistently coloured area, like the sky, the noise appears to be more visible, just because a more random background will tend to hide the noise. The problem with the sky is that the blue channel in a photodetector is the least responsive of the channels (as compared to the red and green channels), so the level of gain required is higher than the other channels, which means your skies, with the high blue content is going to be more noisy.

    The chromatic aberation comes from your lenses; and is generally more of a problem with longer lenses. Looking at your images, I suspect that you are doing some fairly significant cropping; and this will accentuate both noise and the CA.

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    Re: Does Proper Exposure Prevent Noise

    Hi Christina,

    Sorry - this is the first chance I've had all weekend to reply to your PM here.

    Unfortunately, when it comes to ISO settings and noise, there are a number of variables ... and this makes things a bit more complicated. High ISO modes don't "cause" noise per sec - the noise is present in the sensor anyway - it's the subsequent processing by the camera and by us that REVEALS that noise, but again, the "devil is in the detail" ...

    To go into it a little deeper ...

    Lets imagine you have an iPod - and you plug it into your car stereo using a lead plugged into the headphone jack on the iPod. Normally in this configuration you'd want to have the iPod set to maximum volume so that the stereo gets the best quality signal to work with as it blasts it around your car (this is like ISO 100) - but - if we set the volume control on the iPod to 1/2, you MAY be able to get the same volume of music in your car by cranking up the car's volume control twice as high (this is like ISO 200). As far as the car stereo is concerned, it needs to amplify the signal twice as much because it's only 1/2 as big to start with.

    Continuing this analogy, if you halve the iPod volume again (ISO 400) (so it's now down to only 1/4) - then the stereo needs to amplify it twice as much AGAIN (so 4 times as much compared to when the iPod was set to full volume). In this situation the stereo will possibly still be able to do it - but - because the signal strength is pretty weak - and the noise is constant - the signal-to-noise ratio has dropped. In this situation you'll find that loud passages of music are still OK (because they're still much stronger than the noise), but you'll hear a lot of "hiss" with the quieter portions of the music as the music and the noise becomes indistinguishable.

    In this situation you've reached a point where louder portions of the music are OK, but quieter portions aren't. Exactly the same with our cameras except that we're talking about brighter portions of a scene being OK, whereas darker portions have noise mixed in. What this means in camera terms is that the DYNAMIC RANGE of the scene that the camera is capable of recording is being reduced by pretty much 1 stop for every doubling of the ISO that we use. (Dynamic Range is the difference between the brightest and darkest thing we can capture) (any brighter and we lose detail because it's too bright to retain detail, and any darker and the signal is lost amongst the noise).

    Putting that into practical terms - if you have a scene with a high dynamic range then you need to be at a low ISO setting to be able to capture that dynamic range. However, having just said that, low ISO settings also mean low shutter speeds for a given F-Stop - which may also bring "consequences" - at which point the photographer needs to decide which is the lessor of the evils and compromise accordingly. It's also entirely possible that the camera isn't capable of sufficient dynamic range for a given ISO that gives sufficient shutter speed at a given F-Stop - and the whole exercise becomes one of "best compromise".

    Continuing "in practical terms" ...

    If you have a purely reflective scene (eg bride in white dress standing in the sun next to groom in black suit) then there will only be about 4 stops of dynamic range needed to capture the scene. And most modern cameras - even at their highest ISO settings can usually handle this type of scene without too much difficulty. However - if the scene has an active lighting component (say, if the sun is behind the subjects) - or if the scene has shadow detail (details that are in the shadows) that you want to preserve, then additional dynamic range will be required, and that's the point were one might start to see noise in shadow areas with high ISO modes even if the shot is correctly exposed.

    So to summarise what we've learned so far ... "the maximum ISO mode you can get away with depends on the dynamic range of the scene you want to capture". That's one of the variables anyway.

    Continuing on with Dynamic Range ...

    It's not only scenes and cameras that have dynamic range issues that we need to worry about -- what we display our images on also enters the equation. Surprisingly, most cameras can capture a dynamic range of around 12 stops at their native ISOs - but paper can only reproduce about 4 stops (it's purely reflective), and most monitors can only reproduce around 6 stops. What this means in practice is that if you've used a high ISO mode - and a shot looks noise on your screen, it'll probably look a lot less noisy in a print ... and sometimes that makes all the difference. It's another variable anyway (2 so far)

    The problem with scenes that contain a relatively high dynamic range is that although the camera may be capturing all the information, we can't see it unless we compress the (up to) 12 or so stops captured into the 4 to 6 that we need to print (4) or display (6) - and unfortunately this compression is pretty much the same as "amplification" in that it increases the noise along with the shadow detail. So in this circumstance, it's not so much that the capture was "noisy due to the high ISO mode" as it is that "we the photographers have chosen to REVEAL the noise captured in the hope of also revealing additional shadow detail). It's another variable anyway. (3 so far)

    A 4th thing to consider is that noise is a random variation - but ON AVERAGE - the signal is still OK ... you just need to average enough samples. What that means photographically is either "don't pixel peep" or "don't crop the shot excessively". Pixels are very very small things - but - if you crop an image excessively, then you end up stretching what remains to a bigger and bigger size until it becomes visibly obvious.

    Congrats on getting this far

    In the context of your bird shots, I'd say you probably have a "perfect storm" of things working against you:

    - If they're flying then you've going to have an active light source (the sky) that defines you're basic exposure, but against that, you're trying to capture an object that's not only reflective, but also contains shadow detail that you want to subsequently reveal (so it's a relatively high dynamic range scene).

    - If you follow the rules for high dynamic range photography and stick to a low ISO then you'll probably get motion blur and/or camera shake -- but if you up the ISO you lose dynamic range and then get noise.

    - Birds in Flight are tricky to frame correctly - so you're possibly using a shorter focal length to get a wider angle of view - and then having to crop more - which as we now know also contributes to how visible the noise is.

    So ideally, what's the best solution? In an ideal world - with unlimited funds - you'd get whatever camera gives you the best dynamic range - and best autofocus - and marry it to a lens that allows you to get the tightest composition possible; something like a Canon 1D X and a EF600mm lens - mounted on a sturdy tripod and a Wimberly head.

    Unfortunately, it's a compromise. With the rig I just described, it's still a compromise - with your existing gear it's probably more of a compromise. The trick is to get equipment and techniques that deliver a level of quality that you find acceptable, at the lowest price point.

    Welcome to photography

    Hope this helps

  6. #6
    Administrator Manfred M's Avatar
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    Re: Does Proper Exposure Prevent Noise

    Interesting analogy Colin, although I'm not sure how well that your explanation would do on an electrical engineering exam...

    I do agree with your conclusion; Christina is likely hitting the limits of what her equipment can deliver. The subject matter and shooting conditions are not working in her favour...

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    Brownbear's Avatar
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    Re: Does Proper Exposure Prevent Noise

    Thank you Frank... Great idea, but at this point the selecting the duck (well) is beyond my editing skills, but I will try.

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    Brownbear's Avatar
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    Re: Does Proper Exposure Prevent Noise

    Thank you everyone for your helpful replies.. I will focus on focusing, and faster shutter speeds for all my birds in flight..

    Colin thank you for taking the time to provide such a detailed reply, and a lesson in photography. I will be printing out your reply, so I may use it as a reference as I learn more about photography. Very much appreciated.

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    Re: Does Proper Exposure Prevent Noise

    Quote Originally Posted by GrumpyDiver View Post
    Interesting analogy Colin, although I'm not sure how well that your explanation would do on an electrical engineering exam...
    It was either that or the bath filling up with water analogy

    PS: Spent many years doing electrical engineering exams in the military (haven't had much use for things like calculating the impedance of a parallel tuned circuit since though!)

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    William W's Avatar
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    Re: Does Proper Exposure Prevent Noise

    Quote Originally Posted by Christina S View Post
    I have been trying to get a good photo of black bellied whistling ducks in flight against a blue sky for 2-3 months with no success . . . the ducks fly at dawn and dusk . . . it seems my only option is to use a higher iso but even at iso 800 the photo is full of noise . . . and sometimes [at ISO800 the photo is] still too dark . . .
    Commenting only as to how I would address this shooting scenario, in a simple manner, to make the most keepers:

    The SCENE you want to capture has two main SUBJECTS – the Sky and the Ducks.

    As already described, the “SCENE” has a very large dynamic range – that is to say it will be very difficult (impossible, sometimes perhaps) to make an exposure adequate for THE SKY and also adequate for the DUCKS.


    The Direction of the Light will be a major factor in how difficult it is to make a compromised exposure with which you are satisfied and or with which you can most easily work, in post production.

    The easiest shooting scenario will be if the light is coming onto the ducks, either directly onto them (Front Lit) or slightly to the side (Front Side Lit). I would choose my vantage point wisely, shooting with the light; i.e. primarily facing EAST, if shooting at Dusk.

    (To understand this concept further, please refer to Colin Southern’s explanation of the (white) Bride and (black) Groom, when they are shot together, in Front Lit Sun)

    ***

    It occurs to me that you are (mistakenly) of the opinion that different shooting modes will address the problems – they will not. What is required is an understanding of the different METERING MODES of the camera and how those metering modes drive the automatic functions: But that is a topic to research and or discuss in depth later: and with that reseach understanding how to use Exposure Compensation when using P, S and A modes

    Suffice to say that I would meter a green tree or green foliage that appears in the SAME lighting situation as the Ducks in Flight – and I would use THAT exposure as my BASE exposure.

    The next consideration is to understand that Dusk (and Dawn), are the two times of day when the EV (Intensity of the light) is CHANGING at the most RAPID RATE: so therefore you (or the camera) will need to be changing the exposure often. Assuming you mainly shoot at Dusk – you will be increasing the exposure as the evening progresses.

    Therefore I would select an ISO suitable to ensure a reasonable shot at the lowest EV – that would be at least ISO1600 – I do not know your cameras, but if they can make ISO3200 reasonably, I would use that.

    With that all set then it only remains, using M Mode, is to make the exposure readings on the green foliage and shoot away, ensuring that the Shutter Speed is always adequate to freeze the birds: ensuring that you make new exposure readings regularly.

    If you want to get fancy, a little more complicated and if you have exposure bracketing, then I would try Shutter Priority Mode and bracket ±⅔Stop and shoot in brackets of three shots: but remember that you will need to use Exposure Lock on the metering of the green foliage, before framing and shooting. Alternatively, you could still use M Mode and manually bracket opening and closing the aperture . . . if you have time.

    It is my expectation that most, if not all of your shots are underexposed (for the ducks): and mainly that is because the TTL Meter is driving your exposure and making those choices, when the camera is (predominately) metering the sky.

    WW
    Last edited by William W; 30th July 2012 at 04:31 AM.

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    Brownbear's Avatar
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    Re: Does Proper Exposure Prevent Noise

    Thank you William... Great practical information that I can try. There is lots of green foilage around for me to set the exposure with. And I have noticed that when I'm photographing other birds in flight it helps a lot if I can catch the light from a certain direction, and I will check out Colin Southern's explanation.

    There are not so many ducks around these days. They usually fly over the roof of my house in the early morning (at dusk they usually flying too high (out of range). I can't predict from what direction they will appear, but I can set the exposure for the direction with the best light and hope for a little luck.

    All said, the ducks and all the answers I have received on this forum have been a great learning experience for me.

    Thanks a million!

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    Administrator Manfred M's Avatar
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    Re: Does Proper Exposure Prevent Noise

    Christina: I think you are facing a situation that is a bit similar to what I ran into when I took this hand-held shot:

    Does Proper Exposure Prevent Noise

    This was around sunset and the bird was side / back lit; i.e the sun was setting to the right and behind the bird, so the lighting was downright awful and washed out the details. I was using a Sigma 150-500mm lens at 500mm on a full-frame camera (D800), so that would be fairly close to what you would be shooting on your Sony and your Tamron on your D80 would give you a bit tighter shot.

    I had set the ISO to 1600 and was shooting at 1/500th in shutter priority mode. I was trying to get a tiny bit of wing-tip motion in the image, rather than totally freeze the image. I played around with exposure compensation until I got something I liked on the histogram (I think I was around +1.7 stops compensation - the actual shot is at f/11). I had gotten the camera 2 weeks earlier and was still very much learning to use it at the time. I would shoot a bit differently if I were shooting today, now that I know the camera a lot better.

    The shot itself is cropped, with a tiny bit of PP to get rid of a few twigs from the nest. The original is below; I was about 30m / 100 ft from the bird / nest, so you can see that the image is a fairly small part of the overall image.

    Does Proper Exposure Prevent Noise
    Last edited by Manfred M; 30th July 2012 at 06:47 PM.

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    Re: Does Proper Exposure Prevent Noise

    Thank you. You're example is very helpful indeed. And I will try iso 1600, and your settings next time around...
    And personally, I love the photo.... both versions!

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    William W's Avatar
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    Re: Does Proper Exposure Prevent Noise

    These two examples perhaps better explain why I would place a lot of emphasis on Camera Position and waiting for the Birds to be in close to optimum light for shooting, rather than shooting willy-nilly at all the flying birds.

    Both are side lit and both are taken just minutes after sunrise. The (blue) water background can serve as the “nice coloured sky” you want in your photograph.

    In this first shot we have Blacks and Whites: both tones in shadow and also direct light. The point is, by setting up in a camera viewpoint and WAITING for the bird to be in good lighting, and then waiting for the moment; the Photographer could leverage the exposure to maximize shadow details in both the Blacks and also Whites and also keep a reasonably rich tone in the water – and also have greater leverage in any post production to enhance – even though the SCENE has quite a large Dynamic Range:
    Does Proper Exposure Prevent Noise

    ***

    In this second shot the camera is at the about same viewpoint and the flying Gull is almost in the same position as the Pelican in the previous shot – the two shots were taken a few minutes apart.
    Note here the light is still 90° camera right, but in this shot there is a little bleed in the tail of the flying gull where the tail is backlit – BUT keeping the same camera vantage point and keeping the same exposure - both the Blue in the water and MOST of the detail of the bird are kept intact – and a little blown white in the tail could be argued away as ‘artistic’:
    Does Proper Exposure Prevent Noise


    ***

    However ‘The Sky’ at dawn or dusk as a Subject is usually more difficult to manage than ‘The Water’ as a Subject – and this make the angle of the light an even more important consideration.

    As can be seen in Manfred’s sample – the light is also coming from camera right – but as he noted the light is slightly behind that bird, whereas (in the Pelican), the light is slightly in front of the bird – and those few degrees can make a lot of difference to how much detail can be captured

    A lot of this Photography stuff is good planning and preparation . . . and then waiting for the moment.

    By the way and as a personal comment: I can’t stand shooting Birds, so these shots for me are really hard work, but useful as an exercise and skills practice – but certainly not my idea of fun.

    If bird photography floats your boat then you should attack this with more gusto than I: it should be easier for you to do.

    WW
    Last edited by William W; 31st July 2012 at 12:07 AM.

  15. #15
    Brownbear's Avatar
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    Re: Does Proper Exposure Prevent Noise

    Thank you William. very helpful advice when accompanied by your photos. Yes, I admit my technique is a wee bet willy nilly, and I will start focusing on waiting for the right light.

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    William W's Avatar
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    Re: Does Proper Exposure Prevent Noise

    It is just about being a little patient - that doesn't mean you should let a good shot go by if the light isn't 'perfect' - if you see something interesting, then throw everything at it - even use ‘full auto mode’ if you are completely taken by surprise and have no time to think through.

    What I am getting at is having a general set of 'planning and prep rules' as a guideline to get to what you want to achieve.

    Good luck with it.

    WW

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    Brownbear's Avatar
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    Re: Does Proper Exposure Prevent Noise

    Thank you William

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