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

Macro Photography Tips for Point and Shoot Digital Cameras

Much has been written on the topic of Macro photography for those photographers fortunate enough to own a DSLR with macro lenses – but what about if you own a compact point and shoot camera? Can you get great macro shots too?

While the results achievable with a point and shoot camera in macro mode probably won’t compare with a DSLR with a purpose built macro lens I’ve still seen some remarkably good shots with compact cameras (all three shots in this post were taken with compact cameras). Here are a few tips to help you get the most out of yours:

Select Macro Mode – this is a fairly obvious first step but I’m always surprised by how many digital camera owners haven’t explored the shooting modes that their camera has. Macro mode is generally symbolized with a little flower and when selected it will tell your camera that you want to focus on a subject closer to your lens than normal (the minimum distance allowed will vary from camera to camera – consult your instruction manual to find yours). Macro mode will also usually tell your camera to choose a large aperture so that your subject is in focus but the background is not.

Macro-Compact-Camera

Use a Tripod – in macro photography a tripod can be particularly useful, even if you’re just shooting with a compact camera. Keeping your camera still not only improves your shots (getting rid of camera shake) but it allows you to play around with different settings without losing your composition.

Aperture – once in macro mode some cameras will not allow you to make many other adjustments but if you are able to play with your aperture settings it can be well worthwhile to do so. As we’ve covered in our Aperture tutorials, the main thing that aperture impacts is the depth of field of your shots. Choose a small aperture (big number) if you want a large depth of field with everything in focus or a large aperture if you just want your main subject in focus. In macro photography you’ll probably want a shallow depth of field so select the largest aperture available.

Macro-Ladybirds

Focusing – I find that in macro photography it is helpful to have full control over focusing – especially when you have shallow depth of fields where it is all the more important to make sure the right part of your shot is in focus. If your camera allows manual focusing select this option and manually focus on the part of our subject that is the main point of interest.

Composition – remember some of the basic rules of composition like the Rule of Thirds. Make sure your image has a main point of interest and place that focal point in a smart position in your image in order to draw the eye of your viewer. Try to select a non cluttered or simple background for your main subject so as it doesn’t compete with it visually.

Flash – in many macro shots having some artificial light is important. The challenge with compact cameras is that most give you limited control of your flash. As a result choosing a good time of day when there is plenty of available light is probably your best bet. If you do need more light check to see if your camera allows you to pull back the level that your flash fires at. Alternatively you might like to try diffusing it in some way (tissue paper or cellotape over the flash for example). Another option might be to use some other source of artificial light or to invest in a reflector to help make the most of available light. Experiment with different methods of lighting your subject.

Macro-Flower

Take Your Shot – once you have your shot lined up and in focus take your shot. Make sure once you’ve taken it to take a good look at it on your LCD, zooming in to make sure that your focusing is sharp. Try shooting at slightly different apertures, with different compositions and focusing on different points of your subject to see what works best.

Macro Lens Attachments – some compact cameras actually have accessories available to help with macro/close up photography. These will enable you to enlarge your subject and/or decrease your minimum focal length. These might be worth investing in if you intend on doing a lot of macro work.

Self Timer – (this point was added as a result of comments below – thanks team!) when using my DSLR for Macro work I tend to use a shutter cable release and tripod to make sure my shots are completely still (to eliminate the small amount of camera shake from pressing the shutter). Most compact cameras don’t have cable releases but a simple way around this is to use your camera’s self timer on it’s shortest time setting which will similarly mean you have no movement of your camera when taking your shot (if you’re taking notice of the ‘use a tripod’ tip above).

PS: I’ve used the term ‘macro photography fairly loosely here. Technically ‘macro photography’ is actually when you produce an image where your subject is captured on your image sensor at life size (or bigger) with a 1:1 ratio.

In the case of most (all?) compact cameras this is not achieved and in fact ‘close up’ photography would be a better description. However as most manufacturers call their close up mode ‘macro mode’ I’ve used the term for the purposes of this article.

Source:  Digital Photography School