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Thread: half stop versus third stop

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    half stop versus third stop

    I did a little searching to see if this has been discussed, but I couldn't find anything. It certai

    A month or so ago, I shifted my 500D from 1/3-stop increments to 1/2-stop increments. I reasoned that 1/2 a stop is fine enough control for 99% of all situations, and I could always switch back on the fly. And 1/2-stop increments means that moving from blown to good exposure is fewer clicks of the dial. It seems fine for me: I've had no urge to change back.

    Am I just discovering that the earth is round? That is, do most experienced photographers simply set 1/2-stop and laugh about the camera manufacturers' marketing departments that sell 1/3-stop adjustments? Or do people find 1/3-stop useful, and I just haven't gotten to that level of fine-tuning exposure? Or is it a matter of taste? All the things affected by this setting are controlled by the "main dial" on the 500D, so it isn't just that I'm stuck with cross keys instead of a quick control dial.

    Cheers,
    Rick

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    Re: half stop versus third stop

    You'd have to have rocks in your head to leave a camera set to 1/2 stop increments!

    OK - now that I've got your attention

    ... I suspect that it probably doesn't make any difference in real-world terms. In reality I have mine set to 1/3 ... probably just the perfectionist in me ... often when shooting landscape it's all that's needed to tweak between blown highlight and "just in". I like to think that it's not so much an issue at the highlight end as it is getting me just a little bit further away from the noise floor at the shadows end.

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    Re: half stop versus third stop

    Well, if it is any consolation/reassurance, I went to 1/2 stop intervals (EC and shutter speed) on my D5000 for all the reasons you say Rick.

    If I avoid the blinkies by half a stop, the rest, shooting RAW, can usually be sorted in PP.
    It was one of the first defaults I changed on the camera.

    It'll be interesting to see whether folks who take more time over their shots find any benefit in 1/3 stop increments.
    EDIT: Oh looky, Colin has just proved my theory
    So that's what the rattling noise is every time I move

    You can often tell by the EXIF who uses what, you won't see me using "1/640", I go from 1/500 to 1/750 to 1/1000

    Cheers,
    Last edited by Dave Humphries; 11th June 2010 at 11:59 PM.

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    Re: half stop versus third stop

    Colin, if I were consistently setting up my exposure with a light meter, I could see the sense in 1/3-stop: why bother with the electronics, then say, "Eh, it's close enough"? Like the old joke we had in the army: Close enough for government work means measure it with a micrometer, mark it with chalk, and cut it with an axe. And I know you work to accurately, even outside the studio.

    Dave, I'm going to check EXIFs. Better than a poll: a better sample.

    Cheers,
    Rick

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    Re: half stop versus third stop

    The only reason I did half stops was because I couldn't work out third stops in my head, but then I thought sod it and do it now anyway. It is much better to be closer to the right on the histogram without blowing highlights, than having an easy sum to work out.

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    Re: half stop versus third stop

    Quote Originally Posted by rick55 View Post
    Colin, if I were consistently setting up my exposure with a light meter, I could see the sense in 1/3-stop: why bother with the electronics, then say, "Eh, it's close enough"? Like the old joke we had in the army: Close enough for government work means measure it with a micrometer, mark it with chalk, and cut it with an axe. And I know you work to accurately, even outside the studio.
    Although now you mention it, I do have my light meter set to 1/3 stops as well.

  7. #7

    Re: half stop versus third stop

    Not that my comments are worth anything but...

    I use 1/3 because a complete rotation of the dial gives me 1 stop increaments. IE, from the extreme left to right or vice versa.

    Just like to add that you can have one stop increaments for the ISO (which is recommended by most, including Colin) while leaving shutter and aperature in 1/3 stops. This can save some time while giving you finer control.

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    Re: half stop versus third stop

    The difference between a half stop and a third stop is a sixth. Remembering that a full stop represents a doubling or halving of light then a sixth stop represents about 16% more or less light. That would be considered in most scientific contexts as a very significant amount and probably most reasonable cameras would notice the difference. Thus, while it seems to me mostly a matter of personal preference which interval you use, there clearly could be occasions when the finer control offered by a third stop might be important.

    David
    Last edited by David; 13th June 2010 at 07:32 AM. Reason: spelling

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    Re: half stop versus third stop

    Quote Originally Posted by David View Post
    The difference between a half stop and a third stop is a sixth. Remembering that a full stop represents a doubling or halving of light then a sixth stop represents about 16% more or less light. That would be considered in most scientific contexts as a very significant amount and probably most reasonable cameras would notice the difference.
    Hi David,

    I hate to say it, but in experiments I've done it's difficult for the human eye to really notice even a couple of stops -- strange as it may sound (although from a technical point of view the camera sure notices). I often encourage people to grab their camera -- open their favourite lens right up as wide as it will go -- and then close it down a couple of stops -- and then repeatedly press and release the DoF preview button whilst looking through the viewfinder to see how much the scene dims (or more importantly doesn't dim) when the light you're seeing is cut to only 1/4 or what it was.

    In fact ... I'll make it a challenge for someone here to give it a go and reply to us here on how the actual result compared to what they were expecting. Who's up for it?

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    Re: half stop versus third stop

    Quote Originally Posted by Blazing fire View Post

    I use 1/3 because a complete rotation of the dial gives me 1 stop increaments. IE, from the extreme left to right or vice versa.
    That's true, and pretty nice. At 1/2-stop, though, I get 2 stops from left to right, which is also nice.

    I try to adjust the ISO only when needed. I'm probably over-sensitive to noise, but I'm also using a 500D, which is probably noisier than some.

    Cheers,
    Rick

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    Re: half stop versus third stop

    Quote Originally Posted by Colin Southern View Post

    I hate to say it, but in experiments I've done it's difficult for the human eye to really notice even a couple of stops -- strange as it may sound (although from a technical point of view the camera sure notices). I often encourage people to grab their camera -- open their favourite lens right up as wide as it will go -- and then close it down a couple of stops -- and then repeatedly press and release the DoF preview button whilst looking through the viewfinder to see how much the scene dims (or more importantly doesn't dim) when the light you're seeing is cut to only 1/4 or what it was.

    In fact ... I'll make it a challenge for someone here to give it a go and reply to us here on how the actual result compared to what they were expecting. Who's up for it?
    I did this, and it's certainly true: pressing the DOF preview button makes minimal difference to the appearance in the viewfinder. It seems to make more of a vignette effect, more than a simple dimming, which I assume is an artifact of how the eye works at its focus point.

    I did an experiment with the camera, results about 5 posts down: the original version, which I posted here, was messed up. I goofed by using flashes in an attempt to get the light constant, forgetting that I couldn't then reliably control exposure by changing shutter speed.

    Cheers;
    Rick
    Last edited by rick55; 14th June 2010 at 08:46 PM.

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    Re: half stop versus third stop

    Colin, Rick - An extension to the experiment would be to take the above images and rapidly switch between them (is there an animation feature to do this?) I think the eye may then detect a difference, the brain seemingly is more sensitive to change than absolute values. But, we're getting far from the original point. To my mind use a half or a third stop change as you like.

    David

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    Re: half stop versus third stop

    As Dave pointed out (he was kind enough to do it in a PM), I'm an idiot. The flash is controlling the exposure here, and I was adjusting shutter speed. So unless I had the flash firing long enough to run the length of the shutter, and I'm not sure I did, these aren't really exposed properly.

    I'll redo it with tungsten light.

    Cheers,
    Rick

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    Re: half stop versus third stop

    Quote Originally Posted by rick55 View Post
    I'm an idiot.
    Oh good. That means there are at least two of us on here!

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    Re: half stop versus third stop

    Quote Originally Posted by rick55 View Post
    As Dave pointed out (he was kind enough to do it in a PM), I'm an idiot.
    All part of the service; if anyone else would like private abuse, I can provide it, just let me know

  16. #16

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    Re: half stop versus third stop

    I redid the example shots, using fixed (tungsten) lighting. I used two 100-watt bulbs in parabolic reflectors, one bounced off a flat reflector, one through an umbrella. I wanted to make sure the light was spread so that a fall-off of the "cone" wouldn't look like a change in overall light. One thing it shows is how powerful flashes are. I recall reading that a 580EX puts out 500W-seconds: I can believe it, because with 2 100W bulbs I'm cranked up 7 EV on the exposure from what I was shooting with a 580EX and a 430EX in the same configuration. Baseline before was f/11, 1/125, ISO 100, now it's f/5.6, 1/30, ISO 800.

    These three shots have the same two lights, ISO 800, fixed camera, f/5.6. The shutter speeds are 1/30, 1/40, and 1/45; giving baseline, - 1/3 stop, and -1/2 stop from baseline. The difference between 1/40 and 1/45 is the 1/6 that David mentioned. The only PP was to set tungsten white balance in ACR, crop out a section 1200 x 1200, then resize to 800x800 with bicubic resampling. I saved all of them at maximum jpg quality.

    The difference in lighting is visible, but the difference between 1/2 and 1/3 stop is pretty small.

    Cheers;
    Rick

    Baseline (1/30)
    half stop versus third stop

    - 1/3 (1/40)
    half stop versus third stop

    - 1/2 (1/45)
    half stop versus third stop

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