Basic DSLR techniques - interactive course

Basic DSLR techniques

Improve your DSLR skills by following a hands on course!

(c) Dyxum 2007
-----------------------------------

INTRODUCTION

Is this course suitable for me?
You copy your images to your computer...
Do you set about deleteing the ones that are too dark, too bright, blurred, harshly flashed?

Yes? Then welcome aboard!

Why do we think this is important?
1) Sometimes the only way you can create the image you want is by knowing some of the technicalities.
2) You are free to concentrate on your creativity if getting technically good images is second nature.

How is this course different?

Interactive.           Your examples will be used in the guide, your questions can be answered.
Hands on.           Get your camera ready.
Accessible.           task will be clearly directed, email can be used to contribute.
Community extensible.     You will have the chance to make contributions that will help others.
Differentiated.      Ideas for extension work will be provided where possible.
Progressive.           Simple tasks will be used as building blocks to approach more difficult ideas and techniques.

Due to the interactive nature of the course, you may want to bookmark this thread now and check back every day or so. Go on, I'll wait!

Thanks. :)

If something is not clear then it is my fault.
Do not feel shy about asking questions or seeking clarification.
If a particular setting is not mentioned, leave it as it is.

Right, lets get started...

-----------------------------------

PART 1
Aim: To be able to control the brightness of our images

Objectives:
1) to find and evaluate exif data
2) to improve awareness of exposure settings when they take a photograph
3) to see how big a difference in brightness there can be within a simple everyday scene.
4) to practise using A, S and M modes.
5) understanding flashing shutter speed warnings
6) understand the 2 functions of the AEL button
7) use the AEL button in practical situations
8) expose a backlit portrait
9) shoot silhouettes


TASK 1a (no matter how easy it seems, pick that camera up!):

Outside should be daylight, your room lights should be off. Your flash should be OFF.
1) Set the camera to A mode (KM7D top right dial). Set the aperture to f8 using the front control wheel.
2) Take a shot out of the window, focusing on something outside and framing the shot so that the window frame / curtains are on the edges of the image.
3) Take a shot of the wall next to the window, include a fraction of the window on one side.

-----------------------------------

If you want to email me images for any task it might be worth setting the camera to take small standard quality jpgs: On the 7D. 1) press the menu button. 2) press down on the directional thumbpad (D-pad) to select "Image size". 3) press right on the D-pad 4) press down to select "S: 1504x1000" 5) press the set button To set the quality: 1) press the menu button 2) press down (twice) on the directional thumbpad (D-pad) to select "Quality". 3) press right on the D-pad 4) press down to select "Standard" 5) press the set button The menu positions are very similar on the A700: (contributed by sdblanchet, thankyou!) File size for a700 Quality setting for a700 Remember to change your settings back afterwards!

checking exif checking exif in vista: 1) The very basic exif data is shown at the bottom of a explorer window when you highlight an image file. OR 2) Right click the image in an explorer window, click on the details tab: checking exif in photoshop: Open the image, go to File --> File info Click on "Camera Data 1" on the left-hand side. You can see the raw exif data in the "advanced" section it has more details but is much hard to read. Community request Could someone extend this and post quick details of finding the exif in XP, paintshop pro, OSX.

We were comapring two images like the two below:



The basic exif data (see above) for the two images is as follows:
Outside: ISO200, f8, 1/250s
Inside: ISO200, f8, 1s (ONE SECOND!)
So the only thing that changed in this example was the shutter speed.

ISO, aperture used and shutter speed (or expose time if you prefer) are nearly always the three most important values to examine.


1) how many times brighter was it outside?
The camera sensor recieved 250 times more light for the second shot.
250 times brighter outside would probably be an over estimate because the inside image is overexposed.
Actually the outside is around 50 to 100 times brighter.
100times!!
Wow.
Ever turn on a light bulb in a sunlit room and not notice the difference?
Our eyes adapt so well to different light levels its hard to realise how big the difference in brightness can be in different scenes.

Top tip: if you want a photograph of a building with a blue sky, photograph the sunlit side of the building, not the shadow side.
This greatly reduces the difference in brightness between building and sky and both can be well exposed at the same time.


2) how many "stops" brighter was it outside?
One "stop" brighter means the brightness is doubled , (2 times brighter)
Another stop increase (two stops) and we have doubled the brightness again (4 times brighter)
Another stop increase (three stops) and we have doubled the brightness again (8 times brighter)
Keep doubling and you find:
Four stops more is 16 times brighter
Five stops more is 32 times brighter
Six stops more is 64 times brighter
Seven stops more is 128 times brighter.
So in our example it was approx 6 or 7 stops brighter outside.

3) why is the window frame in the first image so dark?
It was dark! To my eyes it did not look 100 times darker than the grass outside but the camera recorded it as it was.

4) why is the second image so blurred?
The shutter speed is too long to handhold. Looking at the exif data can tell us that this image suffers from camera movement rather than the image being out of focus.
Use the exif data alongside the image to identify the cause of a problem.

5) why did my eyes see both curtains and the outside clearly at the same time?
We have answer this pretty much already. The eye can cope with the approx 100:1 contrast ratio and the brain processes the image in a way that we see detail in bright and dark areas.
(The camera can probably handle the scene also if we use the RAW data or of the camera employs a processing algorithm such as sony's DRO)

sidenote:
I find it fascinating that photographers are using HDR to capture scenes with huge contrast ratios
and at the same time computer games and computer graphics cards are trying to simulate the LIMITATION of the eye using HDR rendering.





This second set of examples were contributed (thanks Wilfried):




6) What shutter speed and aperture were used in the two shots?
Outside: f8, 1/60s
Inside: f4.5, 1/90s
Same ISO for both.

7) Why do you think there was less difference in outside and "inside" brightness than in the first pair of images?
This is a tricky one! The first example was a mildly sunny day. I am going to guess the second was on a cloudy day.
Comparing the shutter speeds it was certainly brighter outside in the first example.
The cloudy sky is likely to reflect more light back into the room and maybe there is some direct light from outside.

8) Why do you think the camera operator chose f4.5 for the second image?
Accidentally a trick question. :)
The answer is in the exif, the camera chose f4.5 and not the operator (you can see "program mode" was used rather than aperture priority as I had suggested)
When taking the shot inside the camera prevented the shutter speed from being too slow by opening up the aperture.

----
Extension (advanced users):
Both the shutter speed and aperture have changed in this example.
Can you mathematically calculate the overall difference in the two exposures?

Looking only at aperture we can say it must have been (8/4.5)^2 times brighter outside = 3.2
Looking only at shutter speed we would say it must have been (1/90)/(1/60) times brighter outside = 0.67      (or if you prefer 1.5x brighter INSIDE).

Putting the two together 3.2 x 0.67 = 2.1 times brighter
Or approx one stop brighter outside.

(Values rounded to 2 significant figures)

Can you confirm your answer using the advanced exif data?
As nozzle pointed out the advanced exif shows that the answer of one stop apart (1EV) is reasonable.
----


----------------------------

So far we should know:
1) That even the simplest scene can be difficult to expose because of large difference in brightnesses
2) That these differences can be hard to jugde "by eye"
3) How to read the exif data to find out what settings were used when the photograph was taken

What I would like you to do now is very simple.
Get a pencil and paper.
Pick up the camera. Set Aperture Priority mode and fix the aperture at f8. Make sure the ISO is NOT on auto ISO. Set the ISO to 400 if in doubt.
Look through the viewfinder and point the camera around the room, or even better try it outside.

Watch closely as the shutter speed changes
Which part of your room (or outside scene) is darkest? Which is brightest?
write down where you pointed at and what the shutter speed was
Does the shutter speed change is you keep the same direction and zoom in and out?

Next, change the metering mode on the camera to spot metering.
On the KM7D the metering mode has a dedicated dial and spot metering is the bottom option.
community request: some brief directions here for KM5D/A100/A700 would be nice
Repeat the exercise and see if your new maximum and minimum shutter speeds are different.
Is there now a greater sensitivity to the direction you point the camera?
Does the shutter speed ever start to flash if you point the camera at something like a light bulb?

Then post your experiences here! (thanks DennisP, well done)



Even though this is a simple task its a large step towards thinking about getting a good exposure BEFORE taking the shot.

What I hope you got from the exercise is:
1) a greater awareness of the basic viewfinder and how it changes as you compose in different ways
2) the idea that it might be worth finding more than more metered value to be able to pick the average value or a value that is suitable for the part of the scene that is most important.
3) that spot metering meters the very center of your scene and will be very sensitive to what you point it at
4) that evaluative metering is not foolproof, just a small change in direction can trigger a large change in the metered exposure value.

You might also have found:
5) that zooming in narrows the size of the spot metered area (relative to the wider view before you zoomed in)
6) that the shutter speed will flash if the camera requires a shutter speed "faster" than the camera is capable of (faster than 1/4000s or 1/8000s depending on model)

-------------------------------------

Next Steps We are now going to: 1) Explore "S" mode, aka "shutter (speed) priority" 2) demystify M "manual" exposure mode. 3) practise using the AEL button to lock and shift exposure ----------------------------------- 1) Exploring S mode This is what I would like you to do. a) Set the camera mode to "S" on the top dial (some cameras use "Tv" instead of "S", I much prefer Tv***) b) Set ISO100 c) use the front control wheel to set 1/200s as the shutter speed. d) Point the camera around the room. Some questions to answer: What value does the aperture change to inside? How does this relate to the lens you are using? Is this value flashing? What happens if you take a shot when the aperture value is flashing? Move the control wheel to change the shutter speed until the aperture stops flashing. Take another shot. 2) demystify M "manual" exposure modes First lets think what happens using the other modes: P mode. The camera chooses BOTH the aperture AND shutter speed so that the combination gives a correct exposure as judged by the camera's light meter A mode. You choose the aperture and the camera chooses shutter speed AUTOMATICALLY so that the combination gives a correct exposure as judged by the camera's light meter S mode. You choose the shutter speed and the camera chooses the aperture AUTOMATICALLY so that the combination gives a correct exposure as judged by the camera's light meter M mode. You choose BOTH the aperture AND shutter speed so that the combination gives a correct exposure as RECOMMENDED by the camera's light meter In other words, all 4 rely on the camera's light meter for the result but when using M mode nothing is automatic, you have to change either the aperture or shutter speed so that the mark (or "needle") is aligned with the zero on the meter scale. Lets have a practice. Set the camera to M mode. Set the aperture to f5.6 Look at the meter in the viewfinder. Do you see a) a flashing triangle to the left of -2? --> your exposure is much too low, increase the exposure by choosing a longer shutter speed b) a mark to the left of zero --> increase the exposure by choosing a slower/longer shutter speed c) a mark to the right of zero --> decrease the exposure by choosing a faster/shorter shutter shutter speed d) a flashing triangle to the right of +2 --> your exposure is much too hight, decrease the exposure by choosing a longer shutter speed You can adjust the aperture as well as the shutter speed to help zero the meter. By default on the 7D the shutter speed is adjusted with the front dial and the aperture with the rear dial. There is a menu option to reverse this. A700 owners will let me know if this is the same, and 5D and A100 owners can tell me how their camera is different. Point the camera at diffent objects and get used to zeroing the meter as quickly as possible. time yourself at zeroing the meter on 10 different objects, if you have a partner get him/her to call out different objects. Maybe try to explain how to balance the meter to them and see if they are any faster! ********************* UPDATED 17th Nov 2007 ********************* 3) Using the AEL button to lock and shift exposure. First task: Use A mode on the camera. Focus on a object by half pressing the shutter button. Hold it there and move the camera around. 1) Does the shutter speed then vary when you are using evaluative metering? 2) Does the shutter speed then vary when you are using center weighted metering? 3) Does the shutter speed then vary when you are using spot metering? In two of the modes I think you will find that the exposure is NOT locked along with the focus (at least with the 7D). Second task: Position someone infront of a window. DO NOT USE FLASH (flash will be addressed in PART3) 4) put the face dead center. a) Take a shot with evaluative metering. b) Take a shot with spot metering. Which is the better exposure? 5) focus on the face and then recompose so that the window light is in the center of the scene (try both evaluative and spot metering). See the problem? Very dark images? We are all aware of that changing shutter speed as we compose after out earlier work I hope! The solution is to lock the exposure by pressing and holding the AEL button (auto exposure lock) 6) Go really close to the face so that it fills the frame. Hold the AEL button down to lock the exposure (it was designed for a thumb :)). Move back, focus (don't let go of the AEL button) and take the shot. Here are some of the things you might observe: Image 1. shows how bad evaluative metering can be with backlight (no matter what the manual says) Image 2. I have focused on the darker area but I did NOT lock my spot meter reading. When I recomposed the bright area above the head gave a faster shutter speed and the shot ends up way too dark Image 3. A possible strategy, zoom in or move so that the face fills the frame and LOCK THE EXPOSURE (I choose evaulative to give me a balance of the shadow and highlights on the face). Image 4. Locking a spot meter reading from the middle of the face. The face is well exposed but the brighter areas are too bright, a strong sign that the only way to get a good result here is with another light source or a reflector. I am not going to tell you what method you should use (because you will find it depends on the situation) but I would like you to see is that: 1) there are some scenes the camera will not meter well 2) there are some metering problems caused by user error when recomposing 3) you can try to be more precise on which area to meter by using spot metering. 4) you can lock a suitable exposure at any time by holding down the AEL button. 5) that the metering mode behave differently with respect to locking exposure as you focus. In order to practice this I would like you to produce some examples and post them. Examples might be... I locked exposure on the brightest part of the sky to get a silhouette. I spot metered the spot lit face at a stage show. etc.. It would be nice if some advanced users gave us some examples here as well. Intermediate and advanced users Personally when I am taking silhouettes I meter the brightest part of the sky and set that exposure in M mode. Another function of the AEL button is not as well known. Set the exposure in M mode and either control dial will shift the overall exposure by chnaging either aperture or shutter speed. Try holding the AEL button while you move a dial. Notice that you can shift the aperture but keep the same overall exposure. So once you have that perfect setting for your silhouettes you can change your aperture to control your depth of field without chnaging the exposure. Try it! PART2 will be when, why and how to use exposure compensation. (I am hoping we might pick up some more contributers at this stage now we have the preliminary stuff that might have been familiar to them) I hope to have this up by 23/11/07.

*** Personal aside: I prefer "Tv" (time value) rather than "S" (shutter speed) Here are my reasons... Problems with shutter speed: 1) it has nothing to do with the speed of the shutter, it has to do with how long the shutter is open. 2) What does "increase/faster/higher shutter speed mean?" increase the value from 1/20s to 1/10s? Make the shutter move faster? Of course it means neither. 3) speed is not measured in seconds If you use "exposure time" or "time value" instead: 1) it is clear that it is the time taken for the exposure 2) "increasing/longer exposure time" means an increase in the value. 3) time is measured in seconds However, "shutter speed" to mean the length of the exposure is so common that I use this terminology also.

Please feel free to ask any questions about the tasks or subject matter covered so far.

This is a further example of the kind of feature that we add to Dyxum for the benefit of members. In fact we have been trying for some time to hook Andrew into doing this after he made the mistake of suggesting it. At last count nearly 150 members had indicated their interest in particpating in such a "course". Even if you did not respond to the poll ("A new series of tutorials...") check this out and see if you might benefit. Participation is encouraged, don't hestitate to ask questions, don't feel embarrassed by your perceived skill levels. Andrew will have the backing of the full Admin team in terms of contributing our collective knowledge to answer questions as they arise. The Forum Rules and Guidelines contain info on how to post pics here, and if you need other assistance first check out the Dyxum Knowledge Base index. I hope that all who particpate not only learn, but learn to enjoy their photography all the more for taking part.                             ---brettania (for the admin team)

Edited by Andrew - 17 November 2007 at 18:34

In Elements 3 the Exif can be obtained in the Metadata via the File Browser [ignore the red lines from the Vista "Snipping Tool"].



Edited by brettania - 05 November 2007 at 07:54

Thanks Andrew for the extension

I´ll try my best.

Exposures for the pictures are
1:f8 @ 1/60 sec
2:f4,5 @ 1/90 sec

@ ISO 200

Exposure value (EV)for ISO 100 is calculated as

where N is the aperture
and t is the exposure time

so this would equal for pic
1: EV 4,6
2: EV 4,3

BUT the advanced EXIF info is showing an EV of 6 for the first pic and an EV of 5.12 for the sec. picture. So more or less 1 EV

I guess me and my calculator are doing something wrong
I can´t remember when I last calculated "logs"

Edited by nozzle - 05 November 2007 at 21:31

I know I’m making this too complicated, but I’d rather participate than be right. LOL

1)how many times brighter was it outside?

According to the EXIF data, the outside shot had a Brightness Value (Bv) of 6, whereas the inside shot had a Bv of 5.12.

But after a lot of reading, I couldn’t determine if changes in Bv are linear (6 / 5.12 = 17% brighter) or non-linear. Before this course, I’d not even noticed Bv, so I’m not sure if Bv is even the right measure for brightness.

2) how many "stops" brighter was it outside?

SHUTTER SPEED
The outside shot was taken at 1/60 seconds versus the inside shot at 1/90 seconds. Since 1/90 seconds lets in less light than 1/60 seconds, the shutter speed of the inside shot was stopped down relative to the outside shutter speed. How much? Doubling the outside speed would give 1/120 seconds, which is one stop. The inside shot used 30 units (90-60) of the 60 (120-60) available, which is 50%, or half a stop.

Question: should I have used 1/125s as the doubling of 1/60s, rather than 1/120s?

APERTURE
The outside shot used an aperture of f/8 versus the inside shot’s aperture of f/4.5. That means the outside shot used a smaller aperture, letting in less light, than the inside shot used.

Therefore, the inside shot’s aperture went in the opposite direction of the shutter speed. The inside shot used a faster shutter speed (1/90s let in less light than 1/60s) but a wider aperture (f/4.5 let in more light than f/8) than the outside shot.

The difference in apertures is (f/4 to f/5.6 is one stop, f/5.6 to f/8 is the second stop) so f/4.5 to f/8 is something less than two stops.

The difference between f/5.6 and f/4 is 1.6 units. The shot was taken at f/4.5, which is 0.5 units less than f/4. Dividing 0.5 by 1.6, I get 31%. Call it a third. So the difference in apertures is 1 2/3rds stops.

Putting them together, the inside shot was 1 2/3rds stops brighter aperture, but ? stop darker shutter speed, for a combined difference of 1 1/6 stops.

Question: if going to a darker exposure is stopping ‘down’, why isn’t going brighter stopping ‘up’?

3) why is the window frame in the first image so dark?

Judging from the second shot, the window frame had 0.88 units lower brightness than the outside portion of the shot, and would have required at least one more stop of exposure value to give it normal brightness.

4) why is the second image so blurred?

The curtain is not blurred, because that’s where the camera was focused. But since the photographer chose to acquire more light (the 1 1/6 stops calculated above) by using a wide aperture of f/4.5, he reduced the depth of field that would be in focus to a narrow band. That narrow band wasn’t deep enough to include the swing set in the background.

The photographer could have achieved the same exposure value with a narrower aperture, say f/22, that would have yielded a deeper field in focus, if he’d chosen a more sensitive ISO (risking noise) or a slower shutter speed (risking motion blur).

5) why did my eyes see both curtains and the outside clearly at the same time?

I wonder if they did. I find I concentrate on either the outside or the inside, but that the speed of switching from one to the other is so fast that normally I’m not aware that I’ve changed focus.

6) What shutter speed and aperture were used in the two shots?

Outside: 1/60s f/8
Inside: 1/90s f/4.5

7) Why do you think there was less difference in outside and "inside" brightness than in the first pair of images?

1.     It looks like a dull day, which might diminish the outside brightness.
2.     Even in the inside shot, the outside filled more than half the frame. So the outside brightness would still have registered in the inside shot, contributing to its overall brightness.

8) Why do you think the camera operator choose f4.5 for the second image?

Artistically, f/4.5 would have drawn the viewer to the only part in focus, namely the curtains, since the shallow depth of field would render the rest of the shot out of focus.

Technically, achieving the same exposure value through a slower shutter speed might have risked motion blur, and through a higher ISO might have created more noise.

Good timing with this cource: only had my camera for two weeks..

1) how many times brighter was it outside?
2) how many "stops" brighter was it outside?
3) why is the window frame in the first image so dark?
4) why is the second image so blurred?
5) why did my eyes see both curtains and the outside clearly at the same time?
6) What shutter speed and aperture were used in the two shots?
7) Why do you think there was less difference in outside and "inside" brightness than in the first pair of images?
8) Why do you think the camera operator choose f4.5 for the second image?

Answers;
A1) my guess is 8
A2) guessing on 8 times 3 equals 24 stops
A3) Becauce the camera metering systems decide that outside brightness is used to calculate camera settings. And the 24 stops difference makes the indoor lights to appeare dark in comparison. Especially since the camera didnt use any Dynamic range optimization
A4)probably due to vibrations during image recording (1" is long). May also be out of focus.
A5)Becauce the human eye is adaptive, call it DRO if you like. But the bottom line is that our eyes is far superior any given camera ever.
A6)inside: aperture F4.5 shutter 1/90; outside: Ap F8.0 shut 1/60
A7)The second pair had probably less light outside (cloudy) and stronger indoor lights.
A8) To reduce motion blurring

Originally posted by ahaveland A1) my guess is 8 A2) guessing on 8 times 3 equals 24 stops A3) Becauce the camera metering systems decide that outside brightness is used to calculate camera settings. And the 24 stops difference makes the indoor lights to appeare dark in comparison. Especially since the camera didnt use any Dynamic range optimization

Very good answers for 4-8. Our eyes are indeed amazing. Your answer to 3 is also good except for the value of the number of stops difference.

Interested to know where the "3" in 8 times 3 came from.

I've updated the post now with answers. Basically one stop more light means twice as bright. Each further extra stop doubles it again.
SO 4 stops more light is 16 times (2x2x2x2) more light.

Thanks for participating.

Edited by brettania - 10 November 2007 at 08:36

I didn't know this officially kicked off, but it is a great start to the tutorial. Excellent job Andrew, and keep up the good work. Your time and effort is indeed appreciated.

Don't forget to remind the 'students' that some functions can be 'toggled' in the menu, and not necessarily 'held' for the functions to work. I was always a toggler myself.