Why are photos sometimes not sharp?

Why are photos sometimes not sharp?

At times we all get photos that are a little disappointing. One of the biggest problems when starting out with photography is knowing why your photos aren’t sharp sometimes. Everything looked good through the viewfinder or on your screen, so why is the final image not sharp?

1. Your camera has focussed in the wrong place

It can be hard to tell if everything is completely accurate from just a small screen on the back of your camera. You might not notice until you see the image on a big screen that the camera hasn’t focussed precisely where you thought it had. Generally speaking, cameras focus better on areas of contrast and hard edges. So, for example, if you are trying to focus on a bird that is in front of tall reeds then there is a chance that your camera will be distracted by the reeds as they are easier for it to focus on. Similarly, if your subject is low contrast and all a similar colour, the camera might focus on something else that has higher amounts of contrast.

How to overcome this – if your camera allows you to, choose single point autofocus and place the focal point yourself over your subject. Area autofocus is much more likely to end up picking up the distractions. Also, try changing your composition if possible so that your subject stands out more to make it easier for the camera to focus. Check your focus either before or after you’ve taken the picture by zooming in on your screen so you can see the details more clearly. Consider switching to manual focus to override the autofocus. It is easy to be scared of focussing manually, but if you are taking a picture of something that isn’t moving, this slower approach can really help nail the focus where you want it.

2. Your shutter speed is too slow

Movement can increase the chances of you getting photos that are not sharp. There are 2 types of movement you need to overcome: 1. subject movement, 2. your movement. The faster either of these becomes, the faster the shutter speed you need to get a sharp photo. If your shutter speed is too slow, the subject will move in the short time the shutter is open and this will show in the final image.

How to overcome this – if your camera allows you to, increase the shutter speed. This can be done in Shutter Priority Mode (S or Tv), Programme Mode (P) or Manual Mode (M). Your camera will be limited by 2 things – its maximum shutter speed and the available light. If you go for a faster shutter speed then you allow less light in. So, this needs to be compensated for by having a wider aperture or a higher ISO. Otherwise, you will end up with dark images that are no use. In some situations it simply may not be possible to achieve the right shutter speed. If you want to take pictures of sports and do other types of high speed photography you might like to read this article on action and sports photography.

3. Your camera is not properly stabilised

This is linked to number 2 – shutter speed too slow. It isn’t only your subject’s movement that can cause problems. If you move at all then you risk losing sharpness. Sometimes the answer is a high shutter speed. However, this is not always possible or desirable.

How to overcome this – if your camera or lens features a form of vibration reduction (VR), image stabilisation (IS) or the like then activate it. This enables you to use slower shutter speeds with less chance of camera shake giving images that are not sharp. Normally you will be able to shoot a couple of stops or more slower than without this function (e.g. at 1/50th second instead of 1/200th). It is also important to consider your posture and see if you can hold the camera in a more stable fashion. If you are unsure about this then I would suggest getting tips from a professional or highly experienced hobbyist. You can stabilise your camera further by using a monopod or tripod. If you want or need very slow shutter speeds (e.g. 1/20th of a second or longer) then you will need to use a sturdy tripod. It is impossible to hold a camera still for several seconds so you must use a tripod or find a firm surface for your camera to sit on. Additionally, make sure you use timer delay so that any bounce from you pressing the button doesn’t affect sharpness. Make sure you switch off any VR or IS when using a tripod. These techniques are vital for long exposure photography, such as blurring water, photographing light trails, etc.

4. Environmental Factors

The weather can have an effect on your photos. For example, your camera may find it hard to focus through heavy rain. Even on a hot day, however, things can go wrong. Sometimes heat haze can result in images that are not as sharp as you would want them. When photographing things that are a long way away (e.g. birds flying around), any haze in the sky can affect your camera’s ability not just to focus accurately but to render a sharp image. There is unfortunately not much you can do with images on a hazy day. If you are using a long lens to photograph a bird far away and the haze distorts things slightly then there isn’t much you can do. Another problem that can arise is steamed up lenses. You might not notice it, but in some conditions the lens can get fogged up and this can affect your images.

How to overcome this – take a good lens cleaning cloth with you whenever you go out and make sure to keep your lens surface clean and clear of fog. It is particularly likely to happen when your camera experiences contrasts in hot and cold or when there is higher humidity in the air. Don’t forget to check any filters you are using as well as these too can get fogged up. If you are having problems focussing through the rain using autofocus then try focussing manually.

5. Lens Quality & “pixel peeping”

Some lenses are better than others – hence the difference in price tags! To get the best quality of contrast and sharpness you will need good quality glass (good lenses). This is especially the case if you are cropping in quite a lot when processing your images. You will start to see an image is softer with lower quality lenses the more you zoom in. However, even with the best lenses you can only crop in so far before you notice the image quality start to degrade. You cannot crop in an infinite amount and still get a wonderful picture (even though TV films like to make you believe you can…!). If you are viewing an image at 200% or more then it is likely that some of it is not sharp any more. There are limits. Going in that close when editing is sometimes referred to as “pixel peeping”. Yes, you want there to still be some detail if possible, but don’t expect it to be as clear when you’re that zoomed in. Eventually, after all, you will reach the pixels themselves which are just a series of squares!

6. They need sharpening in post production

Many digital cameras feature something called an “anti-aliasing filter” in front of the sensor. This is essentially something that slightly blurs the light reaching the sensor. That may sound daft, but it helps the camera to avoid certain problems such as moire (an unusual effect that can occur when photographing patterns).

How to overcome this – add some sharpening when you edit your photos. Be careful not to overdo things, but this is an important step. Images will not be quite as sharp as they can be until you have tweaked them in Photoshop or Lightroom or another editing programme. Even cameras without an anti-aliasing filter still benefit from some sharpening being applied to images.

7. They sometimes aren’t meant to be

Yes, sometimes people do deliberately take out of focus photos. There are a range of techniques that are designed to produce artistic interpretations rather than easily recognisable facsimiles. For example, sometimes you might want to use just colours and patterns rather than details to create an image. Intentional blur is a real photography technique!

I hope this might help you work out why some of your images are not sharp. As you get more experienced you will be able to work out the problem more quickly and hopefully avoid it happening in the first place. So, rather than simply deleting unsharp images straight away, use them as a way to improve your photography by working out what went wrong.

 

© Joe Lenton, September 2016

 

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