DIY Photography

Your one stop shop for everything photo-video

  • News
  • Inspiration
  • Reviews
  • Tutorials
  • DIY
  • Gear
Search

Submit A Story

It’s not a triangle: it’s the exposure quadrangle

Oct 8, 2018 by Edward Crim 2 Comments

  • Share
  • Tweet
  • Flipboard
  • WhatsApp

The Exposure Triangle; you’ve heard of it, I’m sure. It’s fabled in story and song and celebrated by photo instructors everywhere. We can even buy t-shirts commemorating the concept! There have been countless articles written about the “exposure triangle” (try a web search and see for yourself), all with the intent of helping newcomers to photography figure out how exposure works in their cameras.

Some of these articles are obscure and pedantic and, as my friend Shaw would put it, indulge in technobabble to impress the reader with the writer’s expertise. Others make a sincere effort to communicate important information to the reader, but all of them fail to acknowledge that beyond ISO, aperture and shutter speed, there is a fourth part of the exposure equation, the part without which there would be no exposure at all; and that part is light.

Weston exposure meter from 1950’s

The concept of a triangle to explain exposure is a recent one, and it falls short of reality in that it only deals with the writing implements and leaves out the medium with which we write. ISO, aperture and shutter speed are our way of handling the intensity of the light we encounter in order to get our optimum exposure brightness. Older photography books have charts and even dials to help us calculate proper exposure, and all of these do factor light into the equation.

Daylight Exposure Computer from the 1956 version of the Kodak Master Photo Guide

Light is, after all, not constant. In the days of film, when men were men and cameras were cameras, refraining from fielding calls from your friends, and giving your location away to the NSA, each box of film that we opened had instructions on how to deal with light, the most fickle member of the previously well-known exposure quadrangle. For direct sun, use these settings, on sand or snow, do this, in open shade set your camera this way, and when the sky is overcast, try this combination of shutter speed and aperture. For those who wanted to be able to shoot in other circumstances (indoors or at night, for instance, or in the middle of a hurricane), there were light meters. Starting in the early 1930’s, hand-held exposure meters allowed precise measurement of light, and for only $3.95 (the price of a week’s groceries in 1956) there was also the Kodak Master Photoguide with its exposure calculators; rotatable dials that allowed the matching of ISO to the current light level to determine a range of suitable aperture & shutter speed combinations. My 1956 copy of the Master Photoguide has dials for daylight, floodlights (incandescent), and flash as well as pages of recommendations for “unusual daylight situations” and “color photography at night.” The films of this era ranged in ISO rating from 10 for Kodachrome transparency (slide), to 32 for Kodacolor print film, to 100 for Ektachrome transparency film.

Exposure Value, or EV, is key to understanding exposure and the fact there is no one right ISO/aperture/shutter speed  combination for a given level of light, but rather several, depending on the look you want to give your image.

Exposure Value chart shows many different combinations result in the same image brightness.

The Sunny 16 rule is an easy place to start in understanding this chart. If you know it already, please forgive the repetition, but for those of you who don’t, here it is:

Direct sunlight during most of the day = f16 @ shutter speed of 1/ISO. In other words, ISO 500 = 1/500 sec at f16. Looking at the chart above we see that 1/500 sec @f16 has an exposure value (EV) of 17. Every other combination of shutter speed and aperture that has an EV of 17 will give the same exposure. Likewise, ISO of 64 equals an exposure of 1/60 @f16 and an EV of 13. This means that you can use any EV of 13 to get the exposure you want, but your photo will look very different at 1/4000 sec @f1.4 (movements stopped and background out of focus) than it will at 1/8 sec @f32 (moving objects blurred and background in focus to infinity and beyond). The EV of these two settings is the same, and both (as well as all the other EV 13 combinations) are correct exposures in direct sunlight for ISO 64. If clouds roll in and your light fades, however, that fourth part of the Exposure Quadrangle requires readjustment of the other three and a new EV will reign.

Gossen Luna Pro exposure meter with EV readout – useful for setting your Hasselblad.

Most exposure meters will calculate scene brightness in EV. My Sekonic meters do, my old Minolta meters did and my even older Gossen and Weston meters did as well. And many of the leaf shutter cameras of previous generations had an EV scale that would lock the shutter speed and aperture together in the same EV, enabling quick and easy shift from one combination to another. Of course, we can do the same thing now (shift from one combination to another) with our digital cameras in the auto modes of aperture priority, shutter priority and program.

The meter I use most often reads flash as well as ambient light and can give readout in EV.

EV scale connects shutter speed and aperture rings on my Hasselblad 500 C – 80mm f2.8 Zeiss Planar

The “exposure triangle” concept is flawed not only in that it overlooks the most important ingredient of photography, but it is also flawed in that the sides do not correlate in any meaningful way. In other words, they don’t tell you what exposure to use, which makes it, well, by definition, rather useless. It only deals with the camera controls and does not deal with light level. Of course, other than revealing the truth that there are four ingredients to every image’s brightness, a quadrangle doesn’t help you calculate exposure either any, better than the triangle.

Andrew Lawn of East Anglia certainly gets the concept. He is the creator of Andy’s Handy Exposure Calculator, a printable and very useful tool for greater understanding of the four horsemen of the, er, I mean four parts of every exposure. Here’s a link to download it.

Andy’s Handy Exposure Calculator – note f16 @ 1/125 second for bright sun at ISO 100

So, forget everything you’ve heard about the exposure triangle, throw out that obsolete T-shirt, and embrace the truth

There are actually four factors in controlling the exposure of every image you capture.

About the Author

Edward Crim is a long time photographer and teacher, and the director of the St. Louis Photo Authority. Prior to devoting himself full time to the mission of building community through photography, Edward devoted over 5 years to developing and teaching photography programs for St. Louis photo institutions. He is also a freelance event and studio photographer for the last 15 years and managed a full-service photo lab for 12 years before that. This article was also published here and shared with permission.

FIND THIS INTERESTING? SHARE IT WITH YOUR FRIENDS!

  • Share
  • Tweet
  • Flipboard
  • WhatsApp

Related posts:

Learn the exposure triangle easily with a little help from Kool-Aid Understanding the exposure triangle with a little help from Star Wars Lego Making sense of aperture, shutter speed and ISO with the exposure triangle Know The Difference Between Correct Exposure And Creatively Correct Exposure

Filed Under: Tutorials Tagged With: Edward Crim, exposure, exposure settings, exposure tiangle

Guest Author: from diyphotography.net

About Guest Author

This article was contributed to DIYP by a member of our community. If you would like to contribute an article, please contact us here.

« Film 35 is yet another solution that converts your old film camera into digital
Westcott’s new Flex Cine lights add full RGB colour to their flexible LED lighting range »

Submit A Story

Get our FREE Lighting Book

DIYP lighting book cover

* download requires newsletter signup
DIYPhotography

Recent Comments

Free Resources

Advanced lighting book

Recent Posts

  • Here’s a bullet time video booth you can build yourself
  • Ricoh has discontinued the HD PENTAX-DA 21mm F3.2AL Limited silver lens
  • This “stellar flower” unravels the twilight’s evolution in 360 degrees
  • Strobes vs Continuous LEDs – Which is right for you?
  • Wave goodbye to Apple’s My Photo Stream next month

Udi Tirosh: from diyphotography.netUdi Tirosh is an entrepreneur, photography inventor, journalist, educator, and writer based in Israel. With over 25 years of experience in the photo-video industry, Udi has built and sold several photography-related brands. Udi has a double degree in mass media communications and computer science.

Alex Baker: from diyphotography.netAlex Baker is a portrait and lifestyle driven photographer based in Valencia, Spain. She works on a range of projects from commercial to fine art and has had work featured in publications such as The Daily Mail, Conde Nast Traveller and El Mundo, and has exhibited work across Europe

David Williams: from diyphotography.netDave Williams is an accomplished travel photographer, writer, and best-selling author from the UK. He is also a photography educator and published Aurora expert. Dave has traveled extensively in recent years, capturing stunning images from around the world in a modified van. His work has been featured in various publications and he has worked with notable brands such as Skoda, EE, Boeing, Huawei, Microsoft, BMW, Conde Nast, Electronic Arts, Discovery, BBC, The Guardian, ESPN, NBC, and many others.

John Aldred: from diyphotography.netJohn Aldred is a photographer with over 20 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter - and occasional beta tester - of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.

Dunja Djudjic: from diyphotography.netDunja Djudjic is a multi-talented artist based in Novi Sad, Serbia. With 15 years of experience as a photographer, she specializes in capturing the beauty of nature, travel, and fine art. In addition to her photography, Dunja also expresses her creativity through writing, embroidery, and jewelry making.

Copyright © DIYPhotography 2006 - 2023 | About | Contact | Advertise | Write for DIYP | Full Disclosure | Privacy Policy