blown highlights
 

hi all, i am using a canon eos 450d with the kit lens 18-55mm not the IS version.still learning and taking lots of shots of nothing in particular trying to understand exposure settings.one problem i'm seeing a lot of is blown out highlights particularly if the shot includes sky,i've tried exposure compensation and different apperture and shutter speeds but dont seem to be able to do anything about it.I do seem to remember reading somewhere that this is a problem with the 450d,is it the camera,me or the lens, i know the lens does'nt do great in reviews.I am looking to upgrade the lens to a 18-135mm IS (thats my budget) and seems to be a good all round lens.I also have the 75-300mm kit lens which does'nt seem to give me the same issue. any advice greatly appreciated.

You could us an nd grad filter to balance the exposure between the land and the sky to counteract this in camera or the graduated filter in ACR or photoshop when processing.

Hi njg39,

Blown highlights in photographs is something we all have to contend with no matter what make or model of camera we use. There are a number of methods you can employ to combat them, but first do you understand why the highlights are being blown out?

Well it all comes down to the camera's metering system, which basically analyses all the light values from the scene you're trying to photograph, from the shadows through to the highlights, but the range of values is too wide for it to control so it finds the average from all the values and records what it can from either side of the centre line. This means that it will clip both the shadows and highlights, ie those areas both above and below the sensors physical range.

One way to see this is more clearly is to use the histogram on your camera. The histogram displays all the different visible light frequencies as differing shades of grey, starting from 0 on the left-handside, which is absolute black, through to 255 on the extreme right-hand side, which is white. So to stop your camera from blowing the highlights you need to watch right-handside of the histogram and by adjusting either the aperture or shutterspeed or ISO to bring the vertical bars on the right-handside of it so they are just touching the far right-hand edge. Now this may mean that the rest of your image looks a bit under-exposed, but you can lighten the shadows using curves when you edit your shots with your photo-editing software to bring these back to where they should be.

Another method is to take two exposures and merge them together. With a landscape you will often find that the sky is sometimes 2 - 3 stops brighter than the land and the sky always gets blown out. So you take one shot metering on the sky and a second shot metering off the land and then merge them together. You will need to support your camera on a tripod and take two shots of exactly the same image so they will line up perfectly, because if the second shot is taken pointing at a different angle to the first you'll struggle to blend the images together.

The other answer is to use a filter to balance the sky with the land. The two most popular are an ND Graduated filter and a Circular Polariser. An ND Grad is usually a square filter that fits into a filter holder that clips to an adapter ring. Looking at the filter you will see that the top half of the filter has been darkened, like the lens in a pair of sunglasses, but it starts off very dark and it gets progressively lighter until after the middle where it is completely clear. This cuts down the amount of light entering the lens from the sky to balance it with the amount of light coming from the land. ND Grads come in a variety of different strengths depending on how many stops of light difference there is between the sky and land. They can normally be stacked if you need more than one filter to blance the sky and land light values. A Circular Polariser also cuts down the amount of light entering the lens by filtering out the polarised light that has reflected off a suface and is diluting the direct light. It can be adjusted, by twisting on half of the filter until the blue of the sky darkens and the clouds turn lighter. It works best when shooting at approximately 90 degrees to the sun. Its also used for removing reflections from non-metallic surfaces too.

Anyway, I hope that's given you some idea of what you need to do to stop the highlights from being blown out on your shots, but sometimes when you look at a scene you have to decide what detail in the highlights you don't mind blowing and what detail in the shadows you don't mind losing too.

thanks steve and ian for your comments very helpful ,i dont own a nd filter yet but i do have a circular polariser which i will start using now.i am beginning to understand histograms and have changed my display to show the histogram aswell as the picture ive just taken. very helpful advice thanks again, nick.

Nick, I think your camera also has a setting that shows any clipped areas of shadow or highlights by flashing the affected areas either blue or red. You may find this useful, because if you look at your shot with this set it will show you how much of your picture has blown highlights. You can then adjust your settings, take another shot and see if the blown areas have shrunk to a more acceptable level.

One way I work, where highlights and shadow compete, is to use a method I used when shooting slide film. Take a good look around the scene before you take the shot and determine where the midtones are. With a landscape this is usually in the grassy areas, and with a seascape it might be the sand. Point your camera into the midtone and use your camera's auto exposure lock to set exposure and then reframe and take the shot as you would normally. The locked exposure will remain locked until you have taken the shot and then it will return to normal. If you look at your histogram after taking a shot, you will see any clipping in the shadow, or highlighted areas.

One other thing...

The reason you don't suffer with as many clipped highlights with the 70-300mm is that the field of view is much narrower so the metering system in your camera has to average out at much smaller area.