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Week 5: The Exposure Triangle


On Auto modes (including aperture and shutter priority), your camera decides what the correct exposure is. Remember the 18% grey exercise from week 1? That was your camera deciding which combination of aperture, shutter speed and ISO to use, to turn the whole scene a mid-grey tone.

The thing to remember this week is this: your camera will never, ever, ever pick an extreme aperture, shutter speed or ISO, if at all possible. If you're out during the day and you want to freeze the water in a fountain, it is just not possible in auto modes, because the camera will pick a safe, mid-range shutter speed. Want to blur the background on a portrait? Not possible - the camera will pick f8 always, when what you need is f4. The camera sees its only job to protect you from camera shake - it doesn't care about the creative effects you want to achieve.

This week you'll bring everything you've learnt together, and shoot on fully manual mode. We're doing this just so you know how to do it. You absolutely do not have to shoot on fully manual mode exclusively from this day onwards. I shoot on aperture priority mode 90% of the time, and you should choose whichever mode suits you, always bearing in mind that you *can* shoot on manual when you need to. I shoot on manual mode if a series of shots all need to have the same settings (eg. for a stitched panorama), or if I need the fine control (eg. macro).

WHAT IS THE EXPOSURE TRIANGLE?

This is one of the most complicated lessons of the entire year. Please take it one step at a time. You do not need to remember everything - as long as you understand it as you are reading it, that's fine. You have the rest of the year to commit it to memory, and we will do that by keep coming back to this lesson throughout the year.

Imagine a 3-way seesaw (teeter-totter). If one corner goes up, the other 2 corners have to go down by an equal and opposite amount. This is exactly the same for camera settings, and it's known as the exposure triangle.

If aperture, shutter speed and ISO are the 3 corners, and one goes up (let's say you want a shallow depth of field so you pick a large aperture), then, to keep the same exposure, the other 2 need to go down to compensate. If you are on aperture priority mode, or shutter priority mode, the camera does the compensation for you. If you want complete control, you will need to shoot on manual mode.

How to shoot on manual mode

Find the "M" setting on your dial. Now dial in all 3 settings - aperture, shutter speed and ISO (unless you  are using auto ISO). Use your camera manual if you need a reminder of how to change each setting.

Don't forget to put your camera back onto your preferred setting once you've finished (Program, Auto, Shutter priority or Aperture priority). If you don't do this, and aren't used to shooting on manual mode, you'll take some unexpectedly over or under exposed images the next time you go out with your camera.

Understanding Stops

Do you remember the list of aperture f-stops? And shutter speeds and ISOs? f4, f5.6, f8; 1/60th, 1/125th, 1/250th; 100, 200, 400?

The gap between these measures of aperture, shutter speed and ISO is important, and it's called a "stop".
From f4 to f5.6 is 1 stop. From 1/60th to 1/125th is 1 stop. From ISO 400 to ISO 800 is 1 stop. Each stop lets in the same amount of light. So 1 stop on the aperture scale corresponds to 1 stop on the shutter speed scale. Knowing this allows you to compensate accurately.

To keep this email manageable I'll carry on the explanation about stops and why they are important in this post over on the website: Understanding stops. Because this week's lesson is one you'll need to go over a couple of times, I've also included the whole of Chapter 5 from Workbook 1 as a downloadable pdf in the post. And, because it's easier to watch stops being explained than read about them, I've included an excerpt from the video lesson that accompanies this week's lesson.

You can re-read the information about shooting on manual mode, have all the information you need about stops handy, and also do a quiz to test your understanding of the exposure triangle:

THIS WEEK'S PROJECT

1. Select aperture priority mode, choose an aperture that is a full stop (eg f8) and take a photo.

2. Write down what settings the camera picks.

3. Go onto manual mode and dial in the settings that the camera picked, except change the aperture by 1 stop (bigger) to have a wider aperture, and a shallower depth of field.

4. If you leave the rest of the settings as they were in step 2, your photo will be slightly over exposed, because you have a bigger aperture. So you need to change the shutter speed or ISO by a corresponding 1 stop in the opposite direction (less light). In this case use shutter speed, and change it to 1 stop less light (faster). Take the photo again. Keep everything the same between photos - where you stand, what you're photographing, how much light there is.

Both the photos should have the same exposure, if the light hasn't changed and you focussed on the same spot. The only difference should be a slightly shallower depth of field in the second photo.

Have another go, this time on shutter priority. Try changing the settings by 2 stops, and by using a combination of both aperture and ISO to compensate.

This chart shows the 3 settings laid out in the same direction, from less light to more light (or for ISO, less sensitive to more sensitive), to help you with this exercise. It's important that you start on a full stop setting. Check the information in the blog post if your settings aren't shown here - you may be on a third or a half stop setting:


If you are struggling with this exercise, head over to the Facebook group for help. Describe exactly which settings your camera picked, and what you have dialled in when you try to shoot on manual mode.

Claim your subscriber's 50% discount now if you like to learn by watching. This lesson is covered in lesson 5 of the video series, and you can preview it in the blog post:

Modules will be added to the video course as we progress through the year. You will be able to claim a 50% discount for the duration of the current module (ie. this week and next week for the Get Off Auto module), then that module will revert to full price.

RECAP

1. Read this email, and the extra post. Download the pdf.

2. Remember that a "stop" is just a measure of light, like a gram is a measure of weight, and a centimetre is a measure of length.

3. Remember that your camera might show full stops, like f8 or 1/60th, or it might show third or half stops, like f6.7 or 1/400th

4. You do not need to remember all the numbers. I know the full stops, but I don't know the third and half stops.

5. Do the project. It won't sink in until you actually take the second photo.

6. This is the hardest email of the whole year. If you're still reading, you're winning.

Next week - it's the last lesson in the Get Off Auto module. We have a quick look at exactly how the camera decides how much light there is ("metering"), and how you can make very quick adjustments to photos that are too dark or too light by using exposure compensation instead of shooting fully manual.

See you in the Facebook group. Ask any questions you have about the project over there. Post your homework photos in the thread Homework thread 12 October. There will be a link to the thread in the pinned post.

Have fun, Emma

Some reminders...


Don't forget there's a new informal weekly challenge on the AYWMC Facebook page (different from the private Facebook group). This week the topic is "pets". Have a go if you want a break from the technicals this week. Visit the pets post here: AYWMC Facebook Page - share your pets post


If you're interested to find out all the stats behind the Class of 2017 (including whether Nikon has beaten Canon this time around), head over and look at this new post: Who Are The Class Of 2017?


There is a discount coupon available for the first module of the video version of AYWMC for this week and next week only: Claim 50% off Get Off Auto module

 
 
 
 
Emma Davies Photography, Marigold, East Bracklesham Drive, Bracklesham Bay, Chichester, PO20 8JW, United Kingdom

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