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Thread: Help with AUTO ISO & settings

  1. #1

    Default Help with AUTO ISO & settings

    i'm using a nikon d90 and would like some help understanding ISO.
    Is my understanding of Auto ISO correct ... that the camera will leave ISO alone until the shutter speed would get slower than the min speed that has been set.
    Or does the camera bump up ISO, depending on light conditions, till the max sensitivity that has been set, then start adjusting speed.
    There seems to be some differing views on this.

    Also need opinions on settings. I've set it to ISO 3200, and speed 1/30. What do you guys set .. assuming you set your ISO to auto.

    thanx!

  2. #2
    Senior Member dennisc's Avatar
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    Default Re: Help with AUTO ISO & settings

    Go read up. ISO 3200, what you shooting? Grains?

  3. #3

    Default Re: Help with AUTO ISO & settings

    Quote Originally Posted by gazzatan View Post
    i'm using a nikon d90 and would like some help understanding ISO.
    Is my understanding of Auto ISO correct ... that the camera will leave ISO alone until the shutter speed would get slower than the min speed that has been set.
    Or does the camera bump up ISO, depending on light conditions, till the max sensitivity that has been set, then start adjusting speed.
    There seems to be some differing views on this.

    Also need opinions on settings. I've set it to ISO 3200, and speed 1/30. What do you guys set .. assuming you set your ISO to auto.

    thanx!
    also depending what r u shooting? imo i try out the iso mode by trial and error by shooting the same object and reading the thread from cs. as dennisc mention the best way is to read up then try out and still not sure post a question.
    shoot for fun

  4. #4
    Moderator Octarine's Avatar
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    Default Re: Help with AUTO ISO & settings

    What is stated in your manual? To me, it doesn't make any sense to bump up ISO to maximum, this defeats the idea of Auto ISO - which implies a gradual adjustment. So I guess (since I'm not using Nikon) that upon reaching the set minimum shutter speed the camera will gradually increase ISO to keep the shutter speed above or at the set limit.
    Read also zoossh's great Guide to DLSR photography for Newbies that also links to sulhan's Photography Notes for Newbies.
    After reading this you might want to reconsider using Auto ISO with your settings of ISO 3200 and 1/30s. The recommended shutter speed for stable handheld shooting is "faster or equal than 1/focal length" - do you always use a 30mm prime lens? Also, high ISO causes image noise. For taking images of static objects in dim light you better get a tripod and set ISO to lowest possible value.
    There are no magic settings. DSLR requires that you understand the details behind and make the right adjustments - even if a feature is called "Auto".

  5. #5
    Senior Member Diavonex's Avatar
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    Default Re: Help with AUTO ISO & settings

    Try and use low ISO whenever possible. See pictures below taken with ISO 100 and ISO 3200.




  6. #6

    Default Re: Help with AUTO ISO & settings

    thanks for the picture.

    i never realized high-iso can affect image quality even in fairly well-lit situations.

  7. #7

    Default Re: Help with AUTO ISO & settings

    auto ISO will usually select an ISO based on what the camera deems appropriate to get a good exposure in the fastest time (shutter open and close). usually auto ISO will select a setting from range like 64~800, and not go to the max setting.

  8. #8
    Senior Member sinned79's Avatar
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    Default Re: Help with AUTO ISO & settings

    Quote Originally Posted by sgstvoy View Post
    thanks for the picture.

    i never realized high-iso can affect image quality even in fairly well-lit situations.
    higher iso is usually used for more darker condition (eg night sceneries)...

  9. #9
    Moderator Octarine's Avatar
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    Default Re: Help with AUTO ISO & settings

    Quote Originally Posted by sgstvoy View Post
    i never realized high-iso can affect image quality even in fairly well-lit situations.
    It might appear well lit to your eye but for the camera it's quite dim. Fluorescent lamps don't emit enough light to make it bright enough for cameras. In addition, you might get colour casts since the light is not constant. During the phases of AC the light changes slightly. It is advisable to use a shutter speed close to the length of a single AC phase, ideally 1/50s to capture a full phase and eliminate color cast.

  10. #10

    Default Re: Help with AUTO ISO & settings

    I see, thanks for the info. I still have quite a lot to learn

  11. #11

    Default Re: Help with AUTO ISO & settings

    thank you for the advice. my preference is of course not to use ISO 3200. But sometimes in dimly lit conditions, if I don't have a tripod or flash .... and I don't want to miss the shot ... I have to be content with ISO3200. I believe the next auto setting on the d90 is 1600 - and set at that level the camera will probably pick a speed that is too slow for handheld and pic subject to too much shake. advice anyone ... still learning here so tips appreciated.

  12. #12

    Default Re: Help with AUTO ISO & settings

    Quote Originally Posted by gazzatan View Post
    thank you for the advice. my preference is of course not to use ISO 3200. But sometimes in dimly lit conditions, if I don't have a tripod or flash .... and I don't want to miss the shot ... I have to be content with ISO3200. I believe the next auto setting on the d90 is 1600 - and set at that level the camera will probably pick a speed that is too slow for handheld and pic subject to too much shake. advice anyone ... still learning here so tips appreciated.
    Then you may need a lens with a larger aperture.
    Alpha

  13. #13
    Moderator Octarine's Avatar
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    Default Re: Help with AUTO ISO & settings

    Quote Originally Posted by gazzatan View Post
    thank you for the advice. my preference is of course not to use ISO 3200. But sometimes in dimly lit conditions, if I don't have a tripod or flash .... and I don't want to miss the shot ... I have to be content with ISO3200. I believe the next auto setting on the d90 is 1600 - and set at that level the camera will probably pick a speed that is too slow for handheld and pic subject to too much shake. advice anyone ... still learning here so tips appreciated.
    The pop-up flash can be helpful at times, just need to learn how and when to use it. Use a diffuser, cheapest way is a paper tissue (one layer only). Balanced with ambient light you can achieve good results.

  14. #14
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    Default Re: Help with AUTO ISO & settings

    i use the Auto ISO quite often... maximum ISO always set to 1600, but slowest shutter speed depending on the lens mounted... normally 1/15s for UWA, 1/50s for 50mm, and 1/160s for 150mm macro... (according to the rule of thumb for the slowest shutter speed... i got shaky hands so these settings are fine... if you got stable hands you can slow down a bit further...)

    you have to take care of white balance and exposure, if you could please nail it right in field... because photos with more noise left you less room for editing... unless you're converting to black and white...

    hope this helps...

  15. #15

    Default Re: Help with AUTO ISO & settings

    It is puzzling too. The auto-iso algorithm between brands seemed to differ, same goes for compact too. Unlike some 2008 generation compacts which auto max the iso at first sight, the new models apply low iso priority. But sometimes my dSLRs shutters goes beyond comfort low 1/20 without changing. Sometime it does.

    If I never experience a particular dSLR model, my assumed visual acceptance for APS-C iso800-1600, FF iso3200 and compact iso200-400. But D90 should fare acceptable at iso3200 with PP imo. Nevertheless, you have to judge/process the picture yourself. Ultimately, you produce the picture that you deem fit for people to see. Unless everyone has taken that same photo, nobody really knows what is the exact scene.

    The noise becomes not obvious if you are posting a small picture or some get away with b/w. If you want to see faint pixels, just look at your LCD at high angle.

    Quote Originally Posted by gazzatan View Post
    i'm using a nikon d90 and would like some help understanding ISO.
    Is my understanding of Auto ISO correct ... that the camera will leave ISO alone until the shutter speed would get slower than the min speed that has been set.
    Or does the camera bump up ISO, depending on light conditions, till the max sensitivity that has been set, then start adjusting speed.
    There seems to be some differing views on this.

    Also need opinions on settings. I've set it to ISO 3200, and speed 1/30. What do you guys set .. assuming you set your ISO to auto.

    thanx!

  16. #16
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    Default Re: Help with AUTO ISO & settings

    Quote Originally Posted by gazzatan View Post
    i'm using a nikon d90 and would like some help understanding ISO.
    Is my understanding of Auto ISO correct ... that the camera will leave ISO alone until the shutter speed would get slower than the min speed that has been set.
    Or does the camera bump up ISO, depending on light conditions, till the max sensitivity that has been set, then start adjusting speed.
    There seems to be some differing views on this.

    Also need opinions on settings. I've set it to ISO 3200, and speed 1/30. What do you guys set .. assuming you set your ISO to auto.

    thanx!
    auto-ISO is one of my favorite features in Nikon

    the camera pulls down the shutter speed (to the minimum set by user) before it bumps up the ISO to obtain the correct exposure..
    when maximum ISO still cannot expose well (3200 in your case), a slower (than 1/30) shutter speed may kick-in..

    one thing though..the "minimum flash shutter speed" overrides the "minimum shutter speed assigned for auto-ISO" when you use flash and auto-ISO features simultaneously..
    lets say if you set flash shutter speed at 1/60, and when you use flash, the cam will fire at 1/60 (in A or P mode), regardless of the minimum shutter speed you have assigned for auto-ISO (1/30 in your case)..
    in such circumstances you may end up with unwanted hi-ISO pics = grainy/noisy ones..
    using larger apertures may avoid shooting at 3200 ISO which is a bit high IMHO

  17. #17
    Senior Member dennisc's Avatar
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    Default Re: Help with AUTO ISO & settings

    best to learn up on how to judge and shoot in full manual. I don't trust what the camera tells me when it comes to low light.

  18. #18

    Default Re: Help with AUTO ISO & settings

    mmm.. if u set ISO to 3200 in that pic example above on a tripod, will picture still turn out grainy?

  19. #19

    Default Re: Help with AUTO ISO & settings

    Quote Originally Posted by sinned79 View Post
    higher iso is usually used for more darker condition (eg night sceneries)...
    slight correction here.. night action shots should need higher iso, i.e. situations where you want to freeze motion reasonably well.

    night scenery.. is perhaps misused. most people would still use low iso to retain maximum image quality AND detail for landscapes/cityscapes and the like for low light photography.

  20. #20

    Default Re: Help with AUTO ISO & settings

    Quote Originally Posted by dysfunktional View Post
    mmm.. if u set ISO to 3200 in that pic example above on a tripod, will picture still turn out grainy?
    yes.

    the best way to minimise grain at iso3200, is to find an evenly exposed scene, and expose it WELL.

    it will look alright at web size but will not hold up LARGE. and the chances of you being able to do this at night are few and far between.

    as to why, digital noise usually gathers in shadow areas. minimise these, and you have minimised grain.

    the ONLY thing tripod does when used PROPERLY for its correct purpose, is to minimise blur from handshake. it is not magic. it cannot capture and freeze motion either.

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