Understanding Exposure

Digital cameras can handle some exposure error, but understanding exposure properly can certainly help improve your photography.

Exposure is all about how much light you let into the camera.

Too much, and your photos will be washed out, too little and they’ll be too dark.

It is possible to correct a poorly exposed image using software afterwards.

However, there are a few reasons why you should avoid this. Some of those reasons are listed below:

• If you’ve overexposed you’ll end up with blown highlights – you can never recover detail in these areas of a photograph.
• If you’ve underexposed, the same applies as with blown highlights. There’s no data recorded in these areas, and you can never recover any detail.
• It’s difficult to get good contrast in poorly exposed photos
• It’s difficult to get good colour saturation in poorly exposed photographs
• It takes up lots of your time correcting things later on! Better to get it right when you take the photo
• Light meters in cameras can be fooled by certain lighting conditions.

Consequently, it helps to have an understanding of exposure before you press the shutter!

The information here is aimed at digital SLR owners. This is because if you use a compact digital camera you have limited options when it comes to adjusting exposure.

Compact digital cameras will work out the exposure for you, so you don’t have to!

It’s still worth reading on though, as it might give you a better understanding of how your camera is working, and you never know, one day you might decide to splash out on a digital SLR!

And if all this talk of properly understanding exposure completely puts you off ever getting a digital SLR, don’t worry. You can always set a digital SLR to “auto”, and it will handle the exposure for you; or you can come back to this page and take control of setting exposure for yourself!

Understanding exposure – what affects exposure?

There are only three things that can make a difference to the exposure. And two of those involve how much light comes into the camera.

• The shutter speed
• The aperture
• The “film speed”

Understanding exposure – Shutter speed

In understanding exposure, you need to understand shutter speed. The shutter speed is a measure of how long the shutter stays open. All the time it is open, light can enter the camera and falls on the image sensor.

The longer it stays open, the more light enters. If it’s open for too long, the photo will be overexposed. Not open for long enough and your photo will be too dark.

It’s worth mentioning here that the amount of time we are talking about is usually measured in fractions of seconds. In fact, 1/30th of a second is considered slow! It’s common for a digital SLR to be capable of shutter speeds in excess of 1/4000th of a second!

Click to learn more on how shutter speed affects exposure and how to use the shutter speed for creative effects.

Understanding exposure – Aperture

The Aperture? The what? In understanding exposure you need to know what the aperture is and does.

As with shutter speed, the aperture is also a way of controlling how much light enters the camera.

The aperture is an adjustable hole in the lens. It can open to allow more light in. Or it can close to become just a tiny hole, stopping so much light from entering.

Aperture and shutter speed work together – if you have a slow shutter speed (to let more light in) you have to close the aperture to compensate. And visa versa – if you have a fast shutter speed (letting less light in) you have to open the aperture to allow in more light to compensate.

Click for an explanation of how aperture can be used creatively to control depth of field.

Understanding exposure – “film speed”

Film speed? On a digital photography site? I must be kidding! Well. No. For understanding exposure it helps to know about film speed, or ISO. Let me explain . . .

In the old days we would load film into our cameras. The most common film was called ISO 100. The ISO rating was a measure of how sensitive the film was to light.

ISO 100 was fine for everyday use in good light. But if the light levels dropped, you had to compensate by having a slow shutter speed, and a nice wide aperture.

The problem? Once your aperture was fully open (to let as much light in as possible), and your shutter speed was as slow as you could manage and still hold the camera steady (to avoid blurring the shot), and there still wasn’t enough light . . . You loaded more sensitive film into your camera!

The sensitivity of film doubled from ISO 100 to ISO 200. It then doubled again to ISO 400 . . . and so on. The highest you could go as a consumer was ISO 1600. ISO 6400 was available, but only really sold in the pro shops.

So what’s this got to do with digital photography? Digital SLRs allow you to set the ISO manually. So if it gets dark, you can increase the ISO. The downside is digital noise – a speckling effect on photos.

This speckling occurred in the days of film too. The higher the film speed, the more speckling. Back then we called it film grain, and it can be used to good effect.

Source: Digital Photography Tips

Dealing With Backgrounds

Backgrounds present both opportunities and challenges to photographers. On the one hand they can put a subjects in context and make it stand out in a way that highlights it wonderfully – but on the other hand backgrounds can overwhelm subjects and distract from them.

Some of the common problems that photographers have with backgrounds include:

• Distracting Focal Points – we’ve all seen this happen – we line up a shot of a friend to take as a portrait and just as we press the shutter someone else pops their head up over their shoulder with a silly face. The result is that the real focal point of the shot becomes the face pulling person. This is an extreme example of distracting focal points in the background but it’s something that happens quite a lot.
• Protruding Elements from Subjects Heads – I nearly didn’t include this one but it’s so common that I just had to mention it. When shooting a portrait one of the common mistakes is for some background element to look like it’s sticking up out of a person’s head – like a horn. It’s often trees (as in the photo to the left) but could be anything. These shots can be quite comical but can also really throw the composition of a shot off.
• Competing Lines – if your subject has lines in it and your background also has strong lines they can compete in such a way that the image becomes busy or so that the lines clash with one another.

So how do we deal with these problems?

1. Check your Background Before Hitting the Shutter Release

Ok – this strategy isn’t rocket science, in fact you’d think it almost goes without saying – but unfortunately it doesn’t and many of the mistakes that I see in photographs could have been avoided simply by checking the background before taking the shot and taking some sort of evasive action.

Always scan the background of your shots before taking a shot. Look for colors that don’t fit with the rest of the image, bright patches that might distract the eye, lines that clash, people that don’t belong etc.

2. Move Your Subject

This is once again a fairly simple technique but is probably the first thing you should consider. Quite often asking a portrait subject to take a step to the left or right will fix things either by putting the distraction behind them or by putting it out of frame.

Photo by alterednate

3. Change your Shooting Angle

If you have distracting elements in the background of a shot but can’t move your subject another strategy is to move yourself and shoot from a new angle. This might mean rotating around your subject but could also include getting down low to make the sky the background or even getting up high and shooting down onto your subject to make the background the ground.

4. Using Aperture to Blur Backgrounds

One of the most useful things to learn as a way to combat distractions in backgrounds (and foregrounds) is to use the power of your lens to throw the background out of focus using depth of field. What you’re trying to achieve with this technique is a nice blurred background where you can’t really make out what’s going on there.

The easiest way to do this is to use a wide aperture (the smaller the number the wider the aperture). The wider your aperture the more blurry your background should become.

The quickest way to see the impact of this strategy is to switch your camera into aperture priority mode and to take a number of shots at different apertures. Start with an aperture of f/20 and work your way down – one stop at a time. Once you get down to under f/4 you’ll start seeing the background in your shots getting blurrier and blurrier.

5. Using Focal Length to Blur Backgrounds

Another way to help get your backgrounds nice and blurry is to use a lens with a long focal length. Longer tele-photo do help a little to get narrower depth of field (although the amount is less than many think). In actual fact the impact is smaller than it seems and the main reason for the change is that with a longer focal length the subject actually takes up more space in the frame. Lots of arguements have been had over whether focal length impacts this – you can read more about it here and here – I’ll leave it to the experts to discuss the finer points but will say that using longer focal lengths does seem to have some impact and is worth experimenting with.

6. Place Subjects In front of Open Spaces

Placing your subject a long way in front of other objects will also help to make those objects more blurry. For example if you have the choice between shooting your subject standing right in front of a brick wall or standing in front of an open field – the open field shot will have a much more blurred background simply because the brick wall is just centimeters from your subject and inside the focal range whereas an open field stretches off into the distance where everything will be out of focus.

7. Fill your frame with your subject

One of the most effective ways of removing distractions from backgrounds is to remove the background altogether by totally filling the frame with your subject. Get up close and/or use your zoom lens to tightly frame the shot and you’ll not only remove distractions but could end up with a high impact shot as well.

Photo by Keith Morris

8. Make your Own Background

Sometimes there just isn’t any suitable background and so you might want to consider making your own. This could range from buying a purpose built studio background or simply buying some cloth to do the job for you.

I know of one keep photographer who goes out shooting photographic portraits and carries large colored sheets of card with him to put up on walls to act as a background.

The other thing to keep in mind is that in many instances you can move things around in the background of your shots (especially if you’re shooting indoors). For example I was recently photographed in my home for a newspaper and the photographer had me move a number of pieces of furniture during the shoot because they were distracting in the shots. It took a little effort but the impact in the shots was quite incredible.

9. Post Processing

I’m no expert in using photo editing software but there are numerous ways of editing a shot after you’ve taken it to get rid of distracting elements. These can include blurring techniques, actual removing of elements and replacing them and techniques such as selective coloring (ie making your subject stand out by making your background black and white (or at least sucking some of the color out of it).

Source: Digital Photography School