Internal Evening Q&A

Internal Evening: Q&As (The Exposure Triangle), presented by Jeff Fugler & Nicky Rhodes

Encouraging interest in, and knowledge of, photography is at the core of our photographic group. We have a wide rang of experience among members, from “Beginner” to “Expert”, so, where there are gaps in understanding, someone will usually have the answer. This evening was a great opportunity to use that expertise by asking questions about the basics.

Jeff began with a presentation on “The Exposure Triangle”. This is a way of setting your camera up for optimum exposure. Its all about light and balance - very Yin-Yang!!!

The three points of this imaginary triangle are:

Aperture: the size of the hole through which light enters the camera. This can be changed in “F” stops, with a lower number being a bigger hole (and a shallower depth of field - so things in the background or foreground may be out of focus).

Shutter: the time it takes for the shutter to open and close, letting light into the camera. This can be changed in stops of seconds and fractions of a second, with a shorter time letting in less light, (and capturing movement more sharply).

ISO: the sensitivity of the camera sensor to light. This can be changed in stops that double each time, from 100, to brighten an image in low light, (but, it will add “noise” to the image. Noise is a distortion, which makes the image look grainy).

Once a good exposure has been found, for a given situation, balancing these three points will result in continued good exposure, but different results. If one point is changed, then one or both of the others should be changed, by the same amount but in the opposite direction, to balance the exposure again.

In a very good handout, Jeff showed that moving the stops to the right on your camera will increase light and moving to the left with decrease light.

In Jeff's example below, you can see that the number of stop changes always balances out to make a correct exposure:


F11 (aperture) at 1/125 (shutter speed) with ISO 400 gives a good exposure

so will all of these:

F4 (4 stops right) at 1/1000 (4 stops left) with ISO 400 (left the same)

F4 (4 stops right) at 1/500 (2 stops left) with ISO 200 (2 stops left)

F16 (1 stop left) at 1/60 (1 stop right) with ISO 400 (left the same)

F16 (1 stop left) at 1/125 (left the same) with ISO 800 (1 stop right)

Having covered the Exposure Triangle, Jeff went on to talk about some of the camera settings that help photographers get the best results, depending on their aim. Most DSLR cameras have at least four settings, to help you produce well exposed images in different situations.

These are:

Fully Automatic: where the camera decides aperture size, shutter speed and ISO sensitivity, to get the optimum exposure, according to the scene. You can’t change any of these things.

Aperture Priority: where you can change the shutter speed and ISO, and the camera will automatically adjust the aperture to get the best exposure.

Shutter Priority: where you can change the aperture and ISO, and the camera will control the shutter speed to get the best exposure

Manual Mode: where you have control over all the settings and can decide to over or under expose if you wish, among many other things!

Each of these choices has its pluses and minuses and should be used according to the results you want. I.e., if you want to take photos of fast moving objects, (sport of wildlife, for instance), then controlling the speed of the shutter is important - you would not want to let the camera control that aspect. Manual or Aperture Priority would be the best settings for this. If, on the other hand, you want to capture a landscape, movement is less important than clarity, so you don’t want the camera to control the aperture. In this case, Shutter Priority or Manual are better settings.

Further details and explanations are available on the hand out, which is available from Jeff.

After tea and a chat, Nicky and Jo used a camera linked to Lightroom, displayed on the big screen, to give examples of setting and results, with and without flash. Adding flash to the mix can give more choices, and filters will also add another dimension, (making it a strangely square, or pentangle, triangle)!

Watching the screen, we could clearly see that a slow shutter speed resulted in motion blur, a wide open aperture resulted in unfocused background, (bokeh), and a high ISO resulted in a “noisy” image.

There was plenty of opportunity to ask questions, which were fielded very well by Nicky, Jeff and other expert members in the audience, and more ideas for further Q&A evenings as well. Unfortunately, I can’t remember what they were now - but Nicky will know and add some of them to the future programme!

At the end of the evening, Sue reminded us about entries to upcoming competitions. Please bring entries for the next print competition on the night, next week. Also bring or send to Jo, at, any PDI entries for the 19th October competition, by next week, 28th September.

Thank you very much to Jeff and Nicky, (and Jo), for a very informative and helpful session. It certainly cleared up some mysteries for me!

Next week we have the Round 1 Print Competition, judged be Alan Harris. You can bring entries on the night if you haven’t already handed them in.

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