PetaPixel

A Great Graphic for Understanding How ISO, Aperture, and Shutter Speed Work

Check out this awesome exposure triangle graphic found in this Exposure Guide tutorial on the fundamentals of exposure:

When these three elements are combined, they represent a given exposure value (EV) for a given setting. Any change in any one of the three elements will have a measurable and specific impact on how the remaining two elements react to expose the film frame or image sensor and how the image ultimately looks. For example, if you increase the f-stop, you decrease the size of the lens’ diaphragm thus reducing the amount of light hitting the image sensor, but also increasing the DOF (depth of field) in the final image. Reducing the shutter speed affects how motion is captured, in that this can cause the background or subject to become blurry. However, reducing shutter speed (keeping the shutter open longer) also increases the amount of light hitting the image sensor, so everything is brighter. Increasing the ISO, allows for shooting in lower light situations, but you increase the amount of digital noise inherent in the photo. It is impossible to make an independent change in one of the elements and not obtain an opposite effect in how the other elements affect the image, and ultimately change the EV.

If you’re just starting out in photography, do yourself a favor and work through the Photography Basics page over on Exposure Guide. It’s a fantastic resource.

Exposure – ISO, Aperture and Shutter Speed Explained [Exposure Guide via Reddit]


 
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  • http://www.facebook.com/people/Daniel-Austin-Hoherd/576367461 Daniel Austin Hoherd

    This is *awesome*. Brilliant display of the relationships.

    The only change I would make is reversing the direction of the Shutter Speed panels. This would make it so that rotating the triangle counter-clockwise would decrease exposure and clockwise would increase exposure. As it is now, it’s inconsistent in that regard.

  • Renato Valenzuela

    i suppose it goes without saying (or one can only hope) that this is for digital cameras only. changing the ISO on a roll of film would require looking up the tables for pushing and pulling.

  • Bob

    There is an error in the graphic that is substantial:
    The + and – on the aperture arc should be reversed. Opening your aperture (say from f/16 to f/2.8) makes the image BRIGHTER not darker.
    Also, as Daniel said, it would make more sense if it were reorganized as well, so that it “rotated” the same way for all three things. With the aperture +/- mistake corrected, it could be fixed by flip-flopping the order of the items in the ISO arc.
    Editors, please post a retraction / clarification / update so that you don’t confuse new photographers even further with this poorly-made graph.

  • asdf

    The + and – speak to increasing or decreasing DOF as indicated by the blurring of the people. I think it is clear, but see how it could confuse a noob. If you follow the link to the full tutorial, it is explained much better.

  • purplepick

    love this. just what i need to use when people ask me about photography :).

  • http://www.bobcooleyphoto.com/ bob cooley

    Not so – They sell (or at least sold) film in different ISOs (ASAs)

  • http://www.bobcooleyphoto.com/ bob cooley

    Really interesting Idea, but as a teaching tool it would make more sense to stick to 1 stop increments. On this chart, the ISO starts at 100, then jumps 2 stops to 400, then 1 stop to 800, then 1 stop to 1600.

    While traditional ISOs, f-stops and shutter speeds are less relevant on digital cameras (where you can set the ISO, shutter or aperture to increments of stops, e.g. ISO 320, f/5, 1/100 sec.), The concepts of single-stop reciprocity is an important learning tool for people interested in knowing how to master their exposures. Skipping a stop will confuse beginners who really want to learn to expose properly, because of the beautiful linear and reciprocal nature of the stop…

  • Dave

    Reciprocity, the backbone of exposure.

  • Benn

    As far as I am concerned this looks nice but is fundamentally flawed. If you rotate the triangle to a wide aperture value it indicates you would need a higher ISO value which is incorrect. With a wider aperture you could use a lower value of ISO

  • Haplo

    It’s not great because it is actually wrong. ISO is not part of the exposure. Exposure is set by aperture opening and shutter speed only!

  • http://www.bobcooleyphoto.com/ bob cooley

    Exposure is set by aperture and shutter in direct relationship to the ISO. That’s what reciprocity is all about. Exposure is not only about the speed or depth of field, its also about the quality (grain/noise/contrast) of the image, determined by the ISO.

  • http://www.bobcooleyphoto.com/ bob cooley

    I would also change this so it followed 1 stop increments. The chart misses the whole point of reciprocity since they shutters and ISOs jump multiple stops (and don’t do consistently with each other).

  • Haplo

    I agree that you set aperture and shutter in relation to iso, but that still doesn’t mean iso is part of the exposure. Exposure is defined as the amount of light you let fall on a light sensitive medium. By increasing iso you’re actually lowering the exposure, as you let less light fall on the sensor/film.

  • Renato Valenzuela

    yes, but you were stuck shooting at that ISO for 36 frames, meaning if you overrode the DX coding on the camera (or manually changed the ASA/ISO by however many stops) for one shot, everything else will become under/overexposed because of that change.

  • cadius54

    werkt niet bij een EOS 7D, vaak overbelichte foto’s…..

  • Renato Valenzuela

    i guess what i’m trying to say is that, with digital you have the luxury of changing the ISO from frame to frame. it’s something most of us take for granted now that most newer photographers who’ve never tried film don’t even realize.

  • http://www.facebook.com/sagebrushfire Leon Cooper

    Right or Wrong, that’s not going to help anyone get properly exposed images. Sensor Gain (ISO), Exposure Time (shutter) and Aperture Diameter are the 3 determining factors in how the tonal values of your image will be weighted – period. ISO is tricky because its secondary effect is really just a detriment whereas motion blur and varying depth of field are sometimes useful, but it works the same nonetheless.

  • http://www.facebook.com/richard.horvath Richard Torque Horvath

    Oh sweet jesus it’s 3 settings, 3! how can people not keep track of 3 settings? The same people will need a graph on how to look into the eyepiece.

  • nick

    funny if you read comments from this repost of the actually article (link above) and everyone is saying what a crappy guide this is…go to the actual article and everyone says what a great article it is. I personally feel, after reading the whole article, the graphic is a great representation and is quite informative. Then again I waited till after I read the article to write this post.

  • nick

    too many noob posts here

  • http://www.unnaturaldesirez.blogspot.com/ Umar Jamil

    Wow! that’s cool! Which study is this?

  • Ahsan

    I still do not understand the -2 till +2 (right in the center of triangle, where ‘EV’ is written)..what does that explain and affect our photo?

  • Pedro Wilsoni

    I think the confusion is that this diagram is only really attempting to say that there is a relationship between ISO/shutter and aperture. The problem is the way it is presented – like a pseuso spin-wheel that you can use to dial a setting. It’s the wrong type of graphic to present such a basic concept, ans so is potentially misleading – note all the comments pointing out how if you turn the triangle, etc!

  • miroy

    if you are not a photographer, you will never understand the graphic presented. Very informative for a photog. A handy cheat sheet to bring along during funshoot.

  • Robert Mule

    Why is it aperture has become the language of DOF, rather than light input? And ISO has become the language of light, and not speed?

    Is it because sensors are instantaneous where as film reaction is not?

  • Robert Mule

    I think it has to do with the hipster obsession with DOF and people not needing to adjust aperture due to not being stuck with one ASA setting depending on the film in the camera?

    I still think pushing up the ISO speed to compensate for low light rather than opening up the aperture is shoddy as hell. So many picture end up all spotty, and grainy, and gross.