Digital Diversity

Focus and exposure are the two most important technical parts of photography. If the focus is off you get a blurred shot and if the exposure is off then your image can have detail loss that you may not be able to recover.

Focus

Your camera (no matter what type) will more than likely offer you several focusing modes. Common ones include face detect, single area, multi area and spot. Some point and shoot fully auto compacts might not have spot but the other 3 are very common. So whats the difference?

Face detect – Your camera tries to focus on the faces of subjects in the pictures. Cameras can detect multiple faces at once and this is nice for group shots of friends and family.

Single area – Normally shown by a rectangle in the centre of your camera. This will focus on what ever you place within that rectangle.

Multi area – when you focus, anything from 1 to several rectangles will appear on the viewfinder / LCD. The camera has chosen several points focus on.

Spot - Normally represented by a small square in the very centre of the viewfinder / LCD. This will focus on that one small point.

Your camera may have some other focusing modes as well. For example the fz-28 comes with a tacking mode. This places a target on your screen. When you press a certain button it will try and lock on to a target. If successful then it will follow this target around the screen. Its is pretty much single area focus where the focal point follows a target around the viewfinder / LCD.

DSLRs will often have an even more advanced tracking where you can hold down a button so it constantly adjusts its focus on the fly meaning you don’t have to pre-focus. This is one of the advantages DSLR’s currently have.

Personally I almost always use spot focus. This is mainly because I try to keep as much control on the focus as I can without letting the camera try and choose what it thinks is the best focus point. On the FZ-28 you can move the spot focus target around the screen, giving you that extra control needed for shots such as landscape where you are set up on a tri-pod.

This next tip may sound obvious but a lot of people new to photography don’t realise it. Remember to pre-focus. Almost every camera these days allows you to pre-focus a shot with a half press (even my mobile phones camera does). This will lock the exposure and the focus so long as you keep the button half pressed. The advantage this gives you is that you can almost totally reduce the shutter lag. Shutter lag is the time it takes the camera to take the actual shot from the moment you press the button. In digital cameras this is often about half a second. This is more than enough time to miss that action shot. For example, on the FZ28, the total shutter lag is about 0.35 seconds. However the shutter lag when pre-focused is only 0.08 seconds.

Lets say I’m going to take a picture of some of the family dogs running about.

If I just try and press the button down at the point I want to capture the picture, it is likely that by the time the picture has been taken, the dogs will have run off the frame.

So pick a point in the distance at which you plan to take the shot. Then half press the button. When all the green signals appear (most point and shoot cameras will turn the focus symbols green to show its OK) you can now move the camera where ever you want and that exposure and focus is locked so long as you don’t let go of the button. Now follow your subject around and when they hit the right distance press the button the rest of the way and it will take the shot.

DLSR cameras tend to have much faster focusing times so pre-focusing is normally less of an issue. However, this is not always the case.

Exposure

There are 3 parts to getting correct exposure. The aperture, the shutter speed and the ISO.

Aperture – This is size of the hole in the lens that lets the light it. It works in a similar way to your eyes pupil. It gets larger to let more light in and smaller to let less light in. What can be confusing about aperture is that the smaller the number the larger it is. This means that an aperture of 2.8 is a large hole while and aperture of 16 is a small hole. So try and remember than when people tell you to use a large aperture then they mean to use a small number. The more light you have hitting your cameras sensor the faster a shutter speed you will be able to reach. So if your taking action shots people tend to use the largest aperture they can. There is another effect that changing the aperture has. This is the Depth of field. The larger the aperture the smaller the depth of field and the small the aperture the larger the depth of field. For those who don’t know, the depth of field is the distance at which objects can stay in focus and not blur out.

A large depth of field will look like this:

Notice how everything is kept in focus.

A shallow depth of field will look like this

Notice how the ape is in focus but the background is blurred.

Shutter speed – This is quite simply the speed at which the shutter opens and closes. Each camera has a range of shutter speeds it can use. In cameras such as the fz28 it is anywhere from 60 seconds to 1/2000 of a second. You will want different shutter speeds for different types of photography. If you want to freeze fast moving action then you want fast shutter speeds. The faster the shutter the less blur you will have. Also the faster the subject the faster the speed needed to freeze it.

Sometimes people prefer to have a small amount of blur to give the sense of movement. So they will still use a fast shutter speed but reduce it just enough so some sense of movement is kept.

Then there is long exposure. This is when you use really long shutter speeds. This can be used to take night shots (for example of buildings) to let as much light in as possible. The shot below was a 60 second exposure. This means the shutter stayed open for 60 seconds.

It is also used to blur moving subjects against static subjects. For example when shooting water. The next shot was a 2 second exposure.

The longer shutter speed has made the water silky smooth while leaving the surrounding scenery sharp.

Of course a tri-pod is needed for long exposure shots like this. Also if your camera has image stabilisation you will need to turn it off. The stabilisation can try and stabilise even the slightest movements which can blur the rest of the shot.

ISO- International Organization for Standardization is how sensitive your cameras sensor is to light. The higher you make this, the more sensitive it will become. This in turn will allow you to use faster shutter speeds or smaller apertures. Doing this does come at a price. Image noise. That graininess and those colour spots that can appear. What ISO you can use without noise becoming a problem all depends on your camera. Most digicams (non-DSLRs) tend to be fairly noise free at ISO’s 100-200. Noise tends to start to appear at 400. By 800 things are looking a bit grotty but will be OK for small prints. Then by ISO’s of 1600 and above it becomes a real problem. Noise reduction software can help but sometimes its not enough. The below image has had some basic noise reduction but the result is a loss in detail.

Because DSLR (digital single lens reflex) cameras have larger sensors this is less of a problem. For your average modern entry level DSLR you will find up to ISO 800 is fairly noise free. By 1600 its starting to appear but isn’t too bad. Then as the ISO gets higher it just gets worse. As you wonder into semi pro and professional DSLR’s you will find they can use higher and higher ISO’s without noise being a problem.

Having said all that, using low ISO’s is perfectly fine for most situations. Its mainly when it comes to low light action photography. If you want to take pictures of your kids or friends playing an inside sport then you might be able to get away with using a compact. It will look a bit grainy but if you stick to small prints you should get some keepers. For something a bit better you are going to need to step into DSLR territory. This will give you nicer results and you should be able to print a bit larger. If you want to take any sort of professional looking, noise free, low light action shots that you might be able to sell, then you would want something like a canon 50d as well as a fast (large aperture) lens. Not cheap.

Shooting modes

So those are the 3 elements of getting correct exposure. That leads us into your shooting modes. No doubt your camera will have a lot of pre-set shooting modes such as beach, sport, portrait, party, etc etc. What these do is tell the camera the sort of situation you are in so it can best guess what options you want. So in sport mode it will know you want fast shutter speeds and therefore open the aperture and probably increase the ISO so that your shutter will be able to freeze the action.

Personally I’m not a huge fan of these. They are great for just shooting on the fly but your camera cannot read a situation like you can. In sport mode all it knows is you are shooting a moving target. It doesn’t know how fast its going or what type of action your shooting. Because of this i tend to stick to aperture priority (A), Shutter priority (P or TV on canon cameras) or manual (m). The way i look to shoot is have one of the 3 elements of exposure to be automated by the camera. This means i can set the other 2 how i want and let the 3rd one adjust automatically to get the correct exposure.

So in aperture priority i would set the aperture to 2.8 and the ISO to 100. Half pressing the button would let me know what shutter speed the camera is going to give me. If its not fast enough i increase the ISO until the shutter is fast enough. This gives me great control and is still very fast to adjust.

In shutter priority, its similar, except this time i set the shutter to what i want and the ISO to 100, then the camera will choose the aperture. Again if the shot is under or over exposed i will either adjust the ISO or the shutter to get it right.

Then there is manual. In this mode i set the shutter and aperture to what i want and set the ISO to auto. This is the most accurate but it is the most fiddly to use. However if you know you need a shutter speed of 1/1000 and an aperture of 2.8 then its the best option.

With those 3 settings i pretty much have everything covered. For long exposure i always use manual mode. The only things i do different are to keep the aperture small for max depth of field, keep the ISO to 100 and turn off image stabilisation.

The most common setting i use is aperture priority. Even for action as long as its a sunny day. Adjusting the ISO to increase the shutter is a very quick and easy process.

After a bit of a practise you will work out which mode suits what kind of shots and you will find it just as fast as using a lot of the auto modes with a higher success rate. Just remember, you can judge a scene a lot better than a camera can. All the camera can do is look at the light readings it gets and guess.

Over and under exposure

When in A or S (TV) mode you will notice you also have an exposure compensation option. You can use this to over or under expose a shot. This does have its uses. You may find your camera tends to over expose and blow the highlights. If this is the case then use the exposure compensation to make sure nothing is overexposed.

There are other reasons to over and under expose a shot. To understand these you need to know the advantages and disadvantages of both.

underexposure – The advantage of this is that most of the underexposed parts of an image still tends to contain a lot of detail. It may look black to you but you can use a program like Photoshop to recover the detail. The disadvantage is that noise likes to hide in the shadows. This means that there is more noise in the darker parts (mainly the greys) of an image than the brighter parts. Recovering detail from these areas will also reveal the noise which can lead to a grainy image.

Overexposure – The advantage here is that you get less noise. For this reason some people like to overexpose there shots, then correct the exposure in post processing later on. The disadvantage is that if you over expose to much and blow the highlights then most of that detail can’t be recovered. Its lost, leaving you with pure white areas on your image.

You need to find a balance that suits you. Some cameras have an option that will actually point out where the highlights have blown. This will allow you to re-adjust the exposure slightly and retake the shot without going home and finding out the hard way.

Metering modes

Finally we have the metering modes. These are the ways in which your camera reads the scene and depicts how light or dark it is / needs to be. Most cameras come with at least these 3.

Evaluative, Area and Spot. Some compacts may not come with Spot (for example my Ixus 75 doesn’t have it)

Evaluative – your camera reads the whole scene and pics an exposure that’s in the middle to try and get an even result. This will often leave a sky that’s slightly overexposed and the ground slightly under, but these can be corrected in post processing.

Area – this is like evaluative except it uses a smaller area of the scene rather than the whole thing.

Spot – This uses the dead centre of the viewfinder / LCD to choose its metering. It tries to make what ever you point it at a midtone grey. So if you want a correctly exposed sky, point at it and take a shot, then use the exposure compensation to tweak the shot and from then on you will see it exposed correctly. But doing this you will notice how everything else gets very dark. This mode gives you the most freedom for adjustment and creativity but is also the most work.

For most cases I tend to use evaluative. I get a reading and then use the exposure compensation to tweak it. For more tricky situations i use the spot mode to get it perfect and then lock it using exposure lock ( most cameras should allow you to do this. Read your cameras manual and it should tell you how). On the FZ28 you will need to press the AF/AE lock button. This can be changed in the options to only lock the exposure, only lock the focus or lock both. A situation suitable for spot metering maybe a light flower on a dark background. To stop the flower being overexposed you need to just get the flower exposed properly by targeting a part on the flower that is a midtone using spot metering. You will find that your flower will be exposed perfectly but the background will be very dark. This can create a nice effect that singles out the flower nicely.

And there you have it. That should be almost everything you need to know to get you up and running with exposure and focusing like a pro. Even if it all seems a bit daunting at first, just keep at it, it will all become seconds nature after a while.

Tags: elements, flowers, highlights, layers, levels, lighting, macro, panasonic fz28, panasonic lumix fz28, photo editing, photography, photoshop, shadows, sharpening, thoughts, tutorial, tutorials

This entry was posted on Monday, August 17th, 2009 at 10:49 and is filed under photography. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.