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Thread: How to avoid over-exposing red channel when shooting red flowers ?

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    Default How to avoid over-exposing red channel when shooting red flowers ?

    Find it a challenge in taking a close-up photo of bright red flowers without over-exposing the red channel resulting in a patch of red colors (losing fine details). Red-histogram is gear toward the right. Using matrix metering on a new D300 (similar issue with D70s previously with red colors).

    Any advice how on the capture the details without the blown out on red color ? Thanks.
    Good photography is not so much about what you use as the way that you use it.

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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Quote Originally Posted by JediKnight View Post
    Find it a challenge in taking a close-up photo of bright red flowers without over-exposing the red channel resulting in a patch of red colors (losing fine details). Red-histogram is gear toward the right. Using matrix metering on a new D300 (similar issue with D70s previously with red colors).

    Any advice how on the capture the details without the blown out on red color ?
    As you realize that the problem arises from overexposure, the solution is obviously to reduce the exposure. Where exactly is your problem?

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    Senior Member zac08's Avatar
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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    The sensors are geared more to the red colour. As such, you should try to consider using a lower saturation on your camera setting and adjusting it during PP phase.
    Michael Lim
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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Quote Originally Posted by JediKnight View Post
    Find it a challenge in taking a close-up photo of bright red flowers without over-exposing the red channel resulting in a patch of red colors (losing fine details). Red-histogram is gear toward the right. Using matrix metering on a new D300 (similar issue with D70s previously with red colors).

    Any advice how on the capture the details without the blown out on red color ? Thanks.
    trust the histogram. if in doubt use bracket exposure.
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    Senior Member zac08's Avatar
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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Guys....

    you are not READING carefully... he's talking about the colour histogram. And when shooting predominantly red subjects, the red histogram will get blown while the other 2 colours are ok and when combined, the exposure is just correct, so wat do you want him to correct then??

    In such a case, it's due to the fact that the sensor makers tend to emphasise more on red and thus, you have to work on the overall saturation to be lower and saturate the other 2 colours later.
    Michael Lim
    My Flickr Site

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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Quote Originally Posted by zac08 View Post
    the red histogram will get blown while the other 2 colours are ok and when combined, the exposure is just correct, so wat do you want him to correct then??
    Ugh. So to you blown channels arise from "correct" exposure?

    If the red channel, or for that matter any other channel is blown, it is overexposed, even if you follow the recommendation of the metering system. "Correct exposure" does NOT mean following the meter blindly. The metering system is only an aid in finding an acceptable exposure, and a meter reading requires interpretation. If the metering system is colour blind (as in most (d)SLRs), it will generally be off when metering highly saturated scenes.

  7. #7

    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Maybe to may it clearer: So if you were taking red flowers, how would you take the shot and what adjustment do you have to made since obiously only the red-channel is affected ?

    If the red channel is blown-out, the PP helps since the fine details are lost ?

    Thanks and appreciate your comments.
    Good photography is not so much about what you use as the way that you use it.

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    Senior Member azul123's Avatar
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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Tell us which metering did you use for that over-exposed red channel? could spot metering solve the problem?

    ../azul123

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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Quote Originally Posted by JediKnight View Post
    Maybe to may it clearer: So if you were taking red flowers, how would you take the shot and what adjustment do you have to made since obiously only the red-channel is affected ?
    Expose less. Simple and painless.

    (If you want to equalize the different channels, you can use colour filters, but it's pretty much pointless in the end. To get the brilliant colours back, you would have to undo the filtering later in software.)

    If the red channel is blown-out, the PP helps since the fine details are lost ?
    If you're talking about an existing overexposed picture, one can try to salvage some details by copying image details from the non-clipped channels to the clipped channel (based on the keen assumption that hue and saturation do not change much in the affected areas). This is how some raw converters salvage overexposed pictures. But this is only an emergency fix. And you will have to either reduce the saturation, or the brightness of the final image, as otherwise the colours cannot be represented (in the most popular colour spaces, that is).

    If you have the choice, don't overexpose in the first place.

    You cannot have a saturated colour patch that is simultaneously bright in RGB colour spaces that artificially restrict the brightness of the individual channels (such as sRGB or AdobeRGB). (Better RGB systems do not limit the brightness of channels and allow even negative RGB coordinates, but they are far from mainstream. The predominant colour space, i.e. sRGB, was not developed for good pictures, but for backward compatibility with legacy graphics systems. Adobe RGB is only a minor variation on sRGB and shares the same problems.)

    You'll have the same dilemma with prints - you cannot have a colourful print that is as bright as the white base paper. Neither can you have a slide that is colourful and at the same time as bright as a blank slide. As the brightness goes up, the possible colour saturation shrinks tremendously.

    If you want to circumvent the saturation limitations, you can rescale the brightness by declaring "white" as something less than the maximum you can get. I.e., keep your pictures a bit darker, and watch them with a dark (ideally black) background/frame.

    "Dark" is relative. Let's say you limit your sRGB brightness to 0...127 (instead of 0...255). This will allow to maintain more saturated colours. Noone will be able to tell that your image is "too dark", UNLESS they see something brighter as a reference. If you keep the border/frame/background of your pictures dark, there is no such brighter reference. Try it on your computer screen in a dark room.

    That's a big reason why projected slides, especially those with sparing exposure (-> helps saturation), look great to so many people when viewed in a dark room, and look sucky in a not-so-dark room. It also means photos will usually do better on dark (black) album pages (high key photos exempted). And it is also the reason why most better photo-related web sites use black (or at least a dark shade) as background in their colour scheme. Clubsnap's colour scheme, sad to say, is absolutely awful for photo viewing.
    Last edited by LittleWolf; 2nd January 2009 at 10:35 PM. Reason: typo

  10. #10

    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Thanks for all the replies. I do not usually shoot full red subjects like flowers though always impressed with photos showing red roses.

    Will try out the suggestion of having lower exposure (darker image) and do some PP.
    Good photography is not so much about what you use as the way that you use it.

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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    i think not shooting in vivid colour mode will help also..

    not too sure though.. =)

  12. #12

    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Managed to find one of the test photo and this is what I mean.


    Good photography is not so much about what you use as the way that you use it.

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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    the photo looks more like backfocus problem rather than over saturation of red channel

  14. #14

    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Another shot taken previously shows better details as compared with the above.


    Good photography is not so much about what you use as the way that you use it.

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    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    you need to compare same flower.
    the first I think the flower is quite small. the second shot is a lotus flower.
    what is the difference is setting? especially like apperture size (F number)? I believe for first shot, the appeture is very big (small F number) and for the second the apperture is medium (mid range F number).
    Big apperture (small F number) gives you thin Depth of Field (DOF) and thus if you mis-focus by a bit (the leaves look nicely focused - which is why I suspect backfocusing).
    Medium apperture (mid range F number) gives you more DOF than above and thus even if you mis-focus by a bit, more DOF is there to help (longer distance are somewhat focused).

  16. #16

    Default Re: How to avoid over-exposing red channel when shooting red flowers ?

    Manage to get the red tone right this time round after another attempt today.




    Thanks for all the comments.
    Good photography is not so much about what you use as the way that you use it.

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