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Thread: NEX iso step:

  1. #1
    Senior Member Rawfa's Avatar
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    NEX iso step:

    Hi,

    I just got my NEX5 and even though I have yet to take to the streets for a real test I've spent a couple of hours playing with it and getting to know it. I have to say I'm glad to find out it's interface is not horrendous as most people were saying (actually the new firmware makes it pretty easy to use it).
    I was just wondering if there is a way to increase the steps between ISO values. Right now it's 200, 400, 800, 1600, etc. Is there a way to make it like 200, 300, 400, 500, 600, well you get the idea. I really don't like having to go from 800 straight to 1600 or from 1600 straight to 3200.

    cheers

    Rafa

  2. #2
    uhligfd
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    Re: NEX iso step:

    Well, these NEX ISO values go up by a factor of two; so the exposure time will decrease to half or the aperture will close one stop when going from 800 to 1600 ISO.

    A fractional stop makes very little difference since ordinarily no one can tell an off-exposure of 1 stop. And going from 800 to 1600 in 100 ISO steps - as you suggest - would give us control down to 1/8 of a stop variation: quite ridiculous penny pinching in my mind.

  3. #3
    Super Duper
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    Re: NEX iso step:

    The incremental divisions between full ISO stops can help fine tune noise levels, I think that is what Rafa is getting at.

  4. #4
    meilicke
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    Re: NEX iso step:

    I have not been able to set it manually. I do see the camera is able to do this when set on auto iso. It sure would be nice to have the option.

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    Senior Member simonclivehughes's Avatar
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    Re: NEX iso step:

    Can't you use EV adjustment to effectively do the same thing?

    Cheers,

  6. #6
    meilicke
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    Re: NEX iso step:

    Quote Originally Posted by simonclivehughes View Post
    Can't you use EV adjustment to effectively do the same thing?

    Cheers,
    How would that work?

    EV would change just the shutter speed, affecting exposure, where changing ISO (and still using A, or P) would change both the ISO and shutter speed (or aperture if using S), keeping exposure constant.

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    Senior Member douglasf13's Avatar
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    Re: NEX iso step:

    The good thing is that your camera only has one ISO, and everything else is a result of a boost from an analogue or digital amp (or combination of both.) Camera makers were just kind enough to represent this gain as ISOs, so that it made sense to film shooters. Depending on the quality of the camera's amps and the RAW converter that you use, you may be better off exposing only at certain ISOs and boosting in your RAW converter after that. Of course, that won't work if you're a jpeg shooter.

  8. #8
    Senior Member simonclivehughes's Avatar
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    Re: NEX iso step:

    Quote Originally Posted by meilicke View Post
    How would that work?

    EV would change just the shutter speed, affecting exposure, where changing ISO (and still using A, or P) would change both the ISO and shutter speed (or aperture if using S), keeping exposure constant.
    But you're still affecting exposure by the same f-stop equivalent. A doubling in ISO is a 1 f-stop difference. Any exposure is a combo of those 3 things: shutter, aperture and ISO. They are therefore interchangeable.

    Cheers,

  9. #9
    meilicke
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    Re: NEX iso step:

    Quote Originally Posted by simonclivehughes View Post
    But you're still affecting exposure by the same f-stop equivalent. A doubling in ISO is a 1 f-stop difference. Any exposure is a combo of those 3 things: shutter, aperture and ISO. They are therefore interchangeable.

    Cheers,
    I do agree with this. But I think to use EV comp. in place of changing ISO is only valid if the file has the room to pull the details when adjusting back in post. So within 1 EV or so, and an image without *too* much contrast, and you could probably be fine, which I think was the intent of your original post?

  10. #10
    Senior Member simonclivehughes's Avatar
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    Re: NEX iso step:

    Quote Originally Posted by meilicke View Post
    I do agree with this. But I think to use EV comp. in place of changing ISO is only valid if the file has the room to pull the details when adjusting back in post. So within 1 EV or so, and an image without *too* much contrast, and you could probably be fine, which I think was the intent of your original post?
    Exactly... using +/-EV you can effectively fine tune the ISO in 1/3 EV steps, which gives you an even finer increment than the OP asked for.

    Ciao,

  11. #11
    Senior Member douglasf13's Avatar
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    Re: NEX iso step:

    Quote Originally Posted by simonclivehughes View Post
    But you're still affecting exposure by the same f-stop equivalent. A doubling in ISO is a 1 f-stop difference. Any exposure is a combo of those 3 things: shutter, aperture and ISO. They are therefore interchangeable.

    Cheers,
    Exposure is actually only the amount of light hitting the sensor. ie, Shutter and aperture. ISO is the amount of gain that is added to the sensor after the fact (or none at all at base ISO,) and is not a part of exposure itself.

  12. #12
    Senior Member Rawfa's Avatar
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    Re: NEX iso step:

    Man, this thread has grown my first post! A simple yes or no would sufice
    thanks everybody

  13. #13
    Senior Member Rawfa's Avatar
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    Re: NEX iso step:

    Quote Originally Posted by monza View Post
    The incremental divisions between full ISO stops can help fine tune noise levels, I think that is what Rafa is getting at.
    Thats is precisely what Ive meant.

  14. #14
    Senior Member simonclivehughes's Avatar
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    Re: NEX iso step:

    Quote Originally Posted by douglasf13 View Post
    Exposure is actually only the amount of light hitting the sensor. ie, Shutter and aperture. ISO is the amount of gain that is added to the sensor after the fact (or none at all at base ISO,) and is not a part of exposure itself.
    Yes, and if you alter the ISO for a given aperture/shutter setting, you alter the exposure. The fact that either aperture or shutter speed now needs to be changed to compensate shows this very clearly.

    For what Rafa's wanting to do, (within +/-1 EV) what I suggest will do the trick. A 1/3 EV adjustment is equivalent to a 1/3 stop ISO shift.

    Cheers,

  15. #15
    Senior Member Rawfa's Avatar
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    Re: NEX iso step:

    Im going to give this a try, Simon. I canno recall right now but Im not sure the EV adjustment is available in manual mode, though.

  16. #16
    Senior Member douglasf13's Avatar
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    Re: NEX iso step:

    Quote Originally Posted by simonclivehughes View Post
    Yes, and if you alter the ISO for a given aperture/shutter setting, you alter the exposure. The fact that either aperture or shutter speed now needs to be changed to compensate shows this very clearly.

    For what Rafa's wanting to do, (within +/-1 EV) what I suggest will do the trick. A 1/3 EV adjustment is equivalent to a 1/3 stop ISO shift.

    Cheers,
    We're getting technical here, but that is a common misunderstanding with digital photography. You never determine exposure by adjusting ISO in digital. You determine exposure by setting shutter speed and aperture. ISO is independent of exposure, and it simply changes gain amplification.

    Changing ISO with a film camera actually affects the sensitivity of the film itself. However, with digital, changing ISO simply changes the amount of amplification to the exposure after the fact, and it doesn't actually change the sensitivity of the sensor itself. Digital sensors only have one sensitivity, and changing ISO is more akin to pushing or pulling your exposure, like with film. With digital, some decide to change their ISO settings in order to push/pull their exposures while shooting, and others shoot their digital camera at only one ISO and allow their RAW converters to push/pull the exposure at a later time. Neither method is always superior, and deciding which one works for you is dependent on the camera's amp quality and your raw converter's quality.**

    When camera companies began with digital, they decided to show camera amplification in terms of ISO, in order for there to be a smooth transition in understanding from film to digital among users, but I think it is good to recognize the difference, if you're into the tech side of photography. As raw converters get better and better, we may someday see cameras with only one ISO.

    **obviously, with a live view camera, like the NEX-5, it makes more sense to change ISO in camera, because you're dependent on an LCD screen for viewing, and you'll probably need the gain applied immediately. ie. changing ISO.
    Last edited by douglasf13; 18th November 2010 at 10:03.

  17. #17
    curious80
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    Re: NEX iso step:

    Quote Originally Posted by douglasf13 View Post
    With digital, some decide to change their ISO settings in order to push/pull their exposures while shooting, and others shoot their digital camera at only one ISO and allow their RAW converters to push/pull the exposure at a later time. Neither method is always superior, and deciding which one works for you is dependent on the camera's amp quality and your raw converter's quality.**
    I don't think this is correct. The gain provided in hardware should pretty much always be better than doing it later in the RAW conversion (unless you are in one of the "extended" ISO modes which are done using software any way).

    The most important reason is that the amplification in hardware is done before quantization, whereas raw converter works on quantized data which is goign to give inferior results.

  18. #18
    Senior Member douglasf13's Avatar
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    Re: NEX iso step:

    Quote Originally Posted by curious80 View Post
    I don't think this is correct. The gain provided in hardware should pretty much always be better than doing it later in the RAW conversion (unless you are in one of the "extended" ISO modes which are done using software any way).
    It depends on the camera, the ISO used, and the raw converter being used. For example, with the A900 and RPP, there really isn't a need to shoot over ~ISO 400-800.

  19. #19
    meilicke
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    Re: NEX iso step:

    Quote Originally Posted by curious80 View Post
    I don't think this is correct. The gain provided in hardware should pretty much always be better than doing it later in the RAW conversion (unless you are in one of the "extended" ISO modes which are done using software any way).

    The most important reason is that the amplification in hardware is done before quantization, whereas raw converter works on quantized data which is goign to give inferior results.
    I agree with you here, but I think the benefits of using EV is to get just that little more (or less), between available ISO stops.

  20. #20
    uhligfd
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    Re: NEX iso step:

    Well, how then do you shoot lightning bugs at night with digital?

    With ISO 400 they are too dim to show up on a dark night in the fields. With ISO 6400 they do. Can the raw converter simply pull the light trails out of the digital file?

    Just wondering about the in camera gain versus in computer gain ...

  21. #21
    meilicke
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    Re: NEX iso step:

    Setting ISO (or gain) on the camera is best, as the gain-up is done in hardware, prior to the raw file being written. No amount of RAW manipulation of an iso400 file can get you to iso6400 like the hardware can.

  22. #22
    Senior Member douglasf13's Avatar
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    Re: NEX iso step:

    Quote Originally Posted by meilicke View Post
    Setting ISO (or gain) on the camera is best, as the gain-up is done in hardware, prior to the raw file being written. No amount of RAW manipulation of an iso400 file can get you to iso6400 like the hardware can.
    That is the common misconception, but it is not always the case. It depends on the camera, the ISO, and the RAW converter being used.

    Incidentally, the new D7000 and K5 are really pushing the limits of the need for ISO in-camera at all.

  23. #23
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    Re: NEX iso step:

    Quote Originally Posted by douglasf13 View Post
    That is the common misconception, but it is not always the case. It depends on the camera, the ISO, and the RAW converter being used.

    Incidentally, the new D7000 and K5 are really pushing the limits of the need for ISO in-camera at all.
    really, so are you saying that at the dynamic range in the shadow region of the D7000 and K5 are massive compared to other cameras, since as you said you don't really need ISO settings.

    A good test would be to set camera to full manual raw image capture, set ISO to 100, fix an aperture, and shutter speed to a fixed value, say 1/100, and go around taking images, even though on LCD review, they appear pitch black due to not enough light. Then after wards boost exposure using a "good" raw converter by say 5 stops to get an image that was meant to be taken at around ISO 3200. Are you certain then this image will have the same amount of detail in the shadow regions as an image taken at the proper ISO3200 and shutter 1/100 at the same aperture???

    MAz

  24. #24
    Senior Member douglasf13's Avatar
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    Re: NEX iso step:

    Yeah, Guillermo has already been running some tests. We're getting very close to that point. I'm not sure what Raw converter Guillermo used for the test on the second page of that thread.

    http://www.luminous-landscape.com/fo...?topic=49200.0

    Still, on some cameras, there is a cut off point. For example, I believe that Andrey ("hardloaf" in these forums,) the author of Raw Photo Processor, was the one who recommended not shooting the A900 past around ISO 400-800, and boosting past that in RPP with compressed exposure control. I tried it in the past, and it worked well and preserved DR.
    Last edited by douglasf13; 6th December 2010 at 13:12.

  25. #25
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    Re: NEX iso step:

    I also was making similar tests. I compared underexposed picture on 800 & 1600 against correctly exposed on 3200. First one gave me sometimes better results, RAWs processed in LR 3. It was on u43 body.

    But it make work differently on different cameras.

    Producers also apply noise removal on higher ISOs, so you may believe camera does it better, but is delusion...

    Coming back to NEX - I use Auto ISO without hesitations or 200 - when I need maximum IQ (plus tripod if needed).

  26. #26
    meilicke
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    Re: NEX iso step:

    Guillermo's post is really interesting. An extreme version of expose for the highlights, develop for the shadows. I will have to check some of my underexposed NEX shots when I get home. If the NEX shows a similar behavior, that will really change how I expose shots in some situations. Thanks Douglas.

  27. #27
    Senior Member douglasf13's Avatar
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    Re: NEX iso step:

    I haven't done much testing of this with the NEX-5, because it is a lot harder to focus the NEX with a dark screen, so this alternative way of shooting is less interesting for me with EVF/LCD cameras. With the A900, though, I frequently never shot past ISO 800 and let the raw converter do the rest. I don't imagine that the NEX-5 will compete with the newest generation of 16mp Sony sensors, as far as only using base ISO is concerned.

  28. #28
    meilicke
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    Re: NEX iso step:

    I would be happy with, say, two or three stops of easy recovery. To be honest, since getting the NEX about a month ago or so I have not dug very deeply into my raw files. In the cases I am thinking about several items in the scene are easy to focus on, but most of the scene is dark. For example, shooting outside at night with a few lights here and there.

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