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Thread: the exposure triangle

  1. #1
    New Member ventodimare's Avatar
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    the exposure triangle

    Hi All,
    I am aware of the exposure triangle, but I still don't understand which configuration choose in a specific case.

    When the subject is still (so I do NOT need to play with shutter speed) and I do NOT want to play with the depth of field, assuming ISO 100 and EV=11 I could use:

    1) f/5.6 and 1/60 sec
    or
    2) f/4 and 1/125
    or
    3) f/2.8 and 1/250

    Which of the above combinations should I use?
    Are they really equivalent?

    Thank you and Cheers!

  2. #2

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    Re: the exposure triangle

    Hi there,

    What's your first name?

    The short answer is "it's really up to you" ... There's not necessarily a right or wrong, only consequences.

    In the example you give, the exposure shot at F5.6 will have a greater DOF than the other 2 - if that's not significant (but usually it is) - then it doesn't matter. Same goes for shutter speed.

    Often though, we're working with a compromise - where shutter speed needs to be in a certain range - as does aperture - as does ISO - that's where it starts to get "interesting"

  3. #3
    Mark von Kanel's Avatar
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    Re: the exposure triangle

    Hi,

    Dont forget to take your focal length into consideration, the longer the focal length your shooting at the faster your shutter speed will need to be.

    A useful rule of thumb i read about said to use a shutter speed the same as or greater than the focal length you shooting at so if you using a 200mm focal length shoot at a shutter speed of 1/200th of a second or faster.

    If your equipment is image stabilised, or your using a support the slower speeds may work as well.

    mark

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    Re: the exposure triangle

    Quote Originally Posted by Mark von Kanel View Post
    Hi,

    Dont forget to take your focal length into consideration, the longer the focal length your shooting at the faster your shutter speed will need to be.

    A useful rule of thumb i read about said to use a shutter speed the same as or greater than the focal length you shooting at so if you using a 200mm focal length shoot at a shutter speed of 1/200th of a second or faster.

    If your equipment is image stabilised, or your using a support the slower speeds may work as well.

    mark
    Hi Mark,

    You need to multiply this by the crop-factor as well, for for a typical Canon shooter it would typically be 1/320th at 200mm.

    PS: By the way, that's just a guide for minimising camera shake - to virtually guarantee that one will eliminate it then you need to go as much as 5 times faster again.

  5. #5
    Moderator Dave Humphries's Avatar
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    Re: the exposure triangle

    Quote Originally Posted by Mark von Kanel View Post
    A useful rule of thumb i read about said to use a shutter speed the same as or greater than the focal length you shooting at so if you using a 200mm focal length shoot at a shutter speed of 1/200th of a second or faster.
    Hi Mark and "ventodimare",

    The crop factor of the camera does also need to be factored into this rule of thumb, so for the majority of people these days shooting DX/APS-C cameras, that means x 1.5/1.6, and x2 for the various 4/3 format cameras.

    In the example given, that means 1/300s, or thereabouts, for DX/APS-C and 1/400s for 4/3.
    Even then, on a non-VR/IS lens will give say a 'better than average' change of a shot without camera shake, going even faster or using good technique (acquired through practice) and/or support, all improves the chances further.

    If you have VR/IS, obviously use it (except on a tripod) and it will help further and allow more liberties to be taken with shutter speed.

    EDIT, I see Colin has suggested the same thing while I was writing this!

    ... and finally; welcome to the CiC forums to both of you,

  6. #6
    Mark von Kanel's Avatar
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    Re: the exposure triangle

    Dave,

    Thanks for the welcome, im just loving it!

    Of course what you say is entirely logical but hadn't occurred to me. DOH! that should help with my sharpness..... Sooo much to learn... Now just to convince the wife to let me buy that full frame so that there are fewer rules of thumb to learn!

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    Moderator Dave Humphries's Avatar
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    Re: the exposure triangle

    Quote Originally Posted by Mark von Kanel View Post
    Dave,

    Thanks for the welcome, im just loving it!
    Good

    Quote Originally Posted by Mark von Kanel View Post
    Now just to convince the wife to let me buy that full frame so that there are fewer rules of thumb to learn!
    Ah, well, there's something else not to rush into, quite apart from the cost and more limited choice of lenses it brings compared to DX/APS-C. If you tend to shoot more 'telephoto' than 'wide angle', or prefer more DoF over less, you're possibly better off where you are and try harder with the memorising - but that's a whole new story

    Cheers,

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    Re: the exposure triangle

    One other thing to keep in mind -- just about every lens is a bit sharper less than wide open. It is often preferable to shoot a stop or two down from wide open to maximize sharpness, other things being equal.

  9. #9
    Mark von Kanel's Avatar
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    Re: the exposure triangle

    Dave

    Not going to rush into anything for a change, just given up my job to spend more time at home with the wife doing Photography......so going from lots of money but no time to lots of time, no money... but waithing for Nikons D700 replacement with baited breath and little bits of drool at the corner of my mouth

    Dont really have a style and am not leaning toward one area of photog or another, going to try Colins school of portraiture next so a few lights might be needed.....

    Regarding memorising stuff, seems to get harder as i get older.... what were we talking about again?

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    rpcrowe's Avatar
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    Re: the exposure triangle

    Quote Originally Posted by Mark von Kanel View Post
    Regarding memorising stuff, seems to get harder as i get older.... what were we talking about again?
    I was going to answer this post but, I forgot what I was going to say!

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    Re: the exposure triangle

    Quote Originally Posted by Mark von Kanel View Post
    Hi,

    Dont forget to take your focal length into consideration, the longer the focal length your shooting at the faster your shutter speed will need to be.

    A useful rule of thumb i read about said to use a shutter speed the same as or greater than the focal length you shooting at so if you using a 200mm focal length shoot at a shutter speed of 1/200th of a second or faster.

    If your equipment is image stabilised, or your using a support the slower speeds may work as well.

    mark
    this old axiom may be true for 35 mm film & full frame dslr's, but with sub full frame digital sensors one has to figure the crop factor into the equation for the reciprocal of lens focal length when shooting handheld w/o IS,e.g. a dslr with a 1.6X image crop factor at 200mm needs 1/320s or greater to minimize user quiver that translates into image unsharpness; i was using the old formula for sometime & getting sub par captures with a eos 20D & 70-200mm non IS lens, i read a brief article about it & it made sense; one can also minimize user quiver with the camera's speedlight or an external flash; using a non ttl flash like my old vivitar 2800 on M i can set a camera shutter speed of 1/320s w/o shutter curtain clipping, while using 1/400s i get shutter curtain clipping in the lower 1/4 of the frame, this gives me a speed boost over my 50D's speedlight max synch of 1/250s. This comes in handy shooting critters in deep shade where i need the lens set at 200mm focal length & want to keep the iso under 1000. the Canon dslr ttlII dedicated hotshoe flash units may have a higher flash synch speed than 1/250s, but i have 2 perfectly functional flash units from my canon AE1 film slr days that adapt very well.

  12. #12
    shreds's Avatar
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    Re: the exposure triangle

    Two observations; anyone going for full frame may need to take weightlifting lessons, and just a word of warning on using older flash units from the film era, as many run at a different voltage to modern digital cameras and it is possible to fry the electrical circuits, so before you leap at that bargain Vivitar 285 (my old faithful in film days), check compatibility.

  13. #13
    FrankMi's Avatar
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    Re: the exposure triangle

    Quote Originally Posted by rpcrowe View Post
    I was going to answer this post but, I forgot what I was going to say!
    LOL! I love it. That's exactly the kind of thing I would do. Must be a side benefit of the ag.. er... maturity.

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    Re: the exposure triangle

    As a new member (and photographer) I am loving these little tidbits of information. There is obviously a wealth of experience here

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    mike the bike's Avatar
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    Re: the exposure triangle

    I agree with the last post . .although a lot of what has been said on this issue continues to evade me I was gonna post a question regarding Manual setting . . i recently went on a course up in Yorkshire to try and get me off . AV and onto Manual we were shooting landscapes on a tripod and here is what we did . .we set up the tripod along with some ND Grads and a polariser (Lee filters .) i selected Manual and set the ISO at 100 using my telephoto at 90mm I used live view and a thirds grid to focus a third of the way into the scene F/11 gave good exposure now . .as the light changed and crept across the vally the meter needle constantly changed and i had to constantly adjust the shutter speed to keep the needle in the centre of the dial and when the light hit and everything was ok i fired the shutter and got a great shot . everything sharp good DOF . . ( see the shot below ) is this the way one would use manual as i see it you set the ISO select the aperture you want to use half depress the shutter and adjust the meter to obtain the shot ? i cant seem to get my head around the exp triangle is there a trick to keep adjusting the compromises to obtain different exposures ?

    thanks

    the exposure triangle
    valley by mikethe8ike, on Flickr
    Last edited by mike the bike; 3rd November 2011 at 05:30 PM.

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    Re: the exposure triangle

    Quote Originally Posted by mike the bike View Post
    I agree with the last post . .although a lot of what has been said on this issue continues to evade me I was gonna post a question regarding Manual setting . . i recently went on a course up in Yorkshire to try and get me off . AV and onto Manual we were shooting landscapes on a tripod and here is what we did . .we set up the tripod along with some ND Grads and a polariser (Lee filters .) i selected Manual and set the ISO at 100 using my telephoto at 90mm I used live view and a thirds grid to focus a third of the way into the scene F/11 gave good exposure now . .as the light changed and crept across the vally the meter needle constantly changed and i had to constantly adjust the shutter speed to keep the needle in the centre of the dial and when the light hit and everything was ok i fired the shutter and got a great shot . everything sharp good DOF . . ( see the shot below ) is this the way one would use manual as i see it you set the ISO select the aperture you want to use half depress the shutter and adjust the meter to obtain the shot ? i cant seem to get my head around the exp triangle is there a trick to keep adjusting the compromises to obtain different exposures ?

    thanks

    the exposure triangle
    valley by mikethe8ike, on Flickr
    Hi Mike,

    In manual exposure mode you will have to keep adjusting things to compensate for changing conditions -- so my big question then becomes "why use manual mode at all in this situation?" If you use Av mode it's going to use exactly the same circuitry to measure the light (that's used to put "the needle in the centre"), but it'll do the shutterspeed for you -- so why not just use the automation? Automation is our assistant, not our master. And if you're wanting to bias the exposure that the camera selects in Av mode then it's a simple task to dial in a little exposure compensation ("EC").

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    Moderator Donald's Avatar
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    Re: the exposure triangle

    Quote Originally Posted by Colin Southern View Post
    In manual exposure mode you will have to keep adjusting things to compensate for changing conditions -- so my big question then becomes "why use manual mode at all in this situation?" If you use Av mode it's going to use exactly the same circuitry to measure the light (that's used to put "the needle in the centre"), but it'll do the shutterspeed for you -- so why not just use the automation? Automation is our assistant, not our master. And if you're wanting to bias the exposure that the camera selects in Av mode then it's a simple task to dial in a little exposure compensation ("EC").
    Mike I would go along with Colin's comments. However, I would deviate in terms of the final conclusion and say that the reason you do it in Manual is, a) it's a challenge and, b) it's fun. But, apart from that, as Colin suggests, there's no reason not to go into Av.

    The question of what constitutes 'fun' might, I am willing to concede, be a subjective matter and that my comments merely mean that I really do need to find more things to do in my life!

  18. #18
    mike the bike's Avatar
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    Re: the exposure triangle

    Hi Colin

    I seem to remember asking that same question . .and the answer was to use manual when the shot wasnt possible using AV this was demonstrated a couple of times and the exposure light was forever blinking in camera as i understand it . . once you select the right ISO for whatever your shooting (hand or tripod ) and you dial in the aperture to control DOF . .then all thats left is to is to regulate the shutter speed to ensure correct exposure ? what i cant seem to grasp is obtaining the same shot using different apertures etc . is it all about balancing things out to get the shot but how do you decide on the correct balance ?

  19. #19
    Moderator Donald's Avatar
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    Re: the exposure triangle

    Quote Originally Posted by mike the bike View Post
    what i cant seem to grasp is obtaining the same shot using different apertures etc
    Double one and half the other.

    So, for example, if one option is f8 at 1/60. Open the aperture up one stop (to f5.6) and you cut the shutter speed by one stop (to 1/125) and you have the same amount of light getting through.

    Does that make sense?

  20. #20
    mike the bike's Avatar
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    Re: the exposure triangle

    Kind of . .is this done for creative control or to tweak DOF i assume the latter im trying to get my head around this because on my shoot i used a s/speed of 1/250 and someone suggested i lower that to 1/160 to let more ambient light in there has to be some kinda table i can consult im afraid my mind has a mental block when numbers come up but im determined to understand this is it like driving i can do 30 mph in 1st gear but i can also do the same speed in all the gears obviously i labor the engine in the lower gears ? so to compensate i change gears but im still doing 30 mph does that make sense ??

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