Unable to use AF on close up shots.

1. Your shutter speed's too slow

Take the effective focal length of your lens and divide it into 1 to get the minimum safe handheld shutter speed you should use. For example, with a 200mm equivalent lens, you shouldn't shoot any slower than 1/200sec or you risk camera shake. You might even get some shake at 1/500sec.

2. You're placing too much trust in VR

Nikon's Vibration Reduction system can let you shoot with shutter speeds four stops slower than usual - but don't count on it. This is a best-case scenario, and it's wise to assume no more than two stops. VR improves your success rate, it doesn't guarantee sharpness.

3. Your subject is moving

Moving subjects will appear blurred at slow shutter speeds, so even if you can hold your camera steady and even if the VR system does a great job, you will still need to use fast shutter speeds for moving subjects.

4. The ISO is too high

Sometimes you have to use really high ISOs just to avoid camera shake, but be aware that at the highest settings you will see a loss of detail. The camera uses noise reduction processes to reduce the appearance of noise, and these erode fine detail too.

field myths

Depth of field is the zone of near-to-far sharpness within your pictures, but it's only apparent sharpness, not real sharpness. Depth of field relies on objects looking sharp enough at normal viewing distances and magnifications even though they're ever so slightly out of focus. If you zoom in far enough, you will see that some objects aren't completely sharp even when they're technically within the depth of field limits.

6. Your lens aperture is too small

Small apertures used to be associated with better image quality. That was when lenses were comparatively unsophisticated and cameras used larger formats, such as 35mm and 120 roll film. But at small apertures an unavoidable optical effect called 'diffraction' sets in, where fine detail starts to blur. With today's smaller sensors and sophisticated zoom lens designs, you can see this as early as f/11. If you shoot at f/16 or f/22, your shots will be visibly softer than those shot at wider apertures.

7. You're focused on the wrong thing

Watch the AF points in the camera's viewfinder. If you're using auto-area AF, the camera will pick the nearest subject, which may not be what you intended. If you're using single-point AF, make sure the AF point's over the correct part of the scene. Tip: on some cameras, including the D3100, it's very easy to accidentally push the AF point to the right with the base of your thumb as you hold the camera and not notice.

8. Handheld close-ups shots are risky!

When you're really close to your subject, the depth of field is so small that the slightest movement on your part will throw your subject out of focus. The more you concentrate on staying still, the more you sway! Higher shutter speeds won't make the slightest difference - you need a tripod.

9. Focus/recompose errors

It's often useful to focus on one thing then keep the shutter button half-pressed so that you can recompose the picture and shoot. But in that time, you may have moved, the subject may have moved or, if the camera's in its default AF-A mode, it make think the subject is moving, switch to AF-C (continuous) operation and attempt to re-focus.

10. Is your lens clean?

If you walk into a humid indoor environment, your lens may mist up, producing a blurry, soft-focus effect. Other causes of blur are greasy smears and fingermarks - so check the front of your lens before blaming the camera.

A couple of possible reasons:
You are trying to take the shot with the lens too close to the subject. If you attempt to take a shot with AF on while too close then the camera won't take the photo. Try backing up from the subject a bit.
Which camera mode are you in? If you are using the green box (automatic) mode then in very low-light settings the camera may refuse to take the photo.
The AF on your lens might be broken. Try using a different lens (if you have one available). Do other lenses have the same problem?

This issue can occur in the following circumstances:
The subject is too close to the camera lens Insufficient lighting Subject movement Camera movement Incorrect camera settings Incorrect camera operation Follow the steps below to help prevent taking pictures that appear blurry, out-of-focus or distorted.

If the camera has both an auto focus and manual focus mode, make sure it is set to auto focus. Make sure there is enough lighting to allow the camera to focus on the subject. Make sure the camera settings are set appropriately. When taking close-up or macro-type shots, ensure the subject is not closer than the minimum focus distance of the lens. Also, if the camera has a zoom option, set it to the W (wide-angle) position. If you have a fast-moving subject and the camera has a Program AE mode with a higher shutter speed (such as Sports action), make sure it is enabled. Also, if the camera has an ISO control, set it to a higher setting. If your camera has a SteadyShot/anti-blur function, ensure it is enabled. Aim the camera at the subject. Press the shutter button halfway down. NOTES:
Pressing the shutter button halfway down allows the camera to focus automatically. A flashing green indicator will be visible in the LCD or viewfinder. When the indicator stops flashing, focusing is finished and the camera is ready to take the picture. Some camera models have a Monitoring AF setting that can be selected which allows the camera to focus without the need to hold the button halfway down. Consult the instruction manual of the camera for information whether or not this is applicable for your model.

My HTsi Plus never seems to be able to Auto Focus on a subject, so when you push the shutter button half-way, it just flashes the focus indicator (telling you it is unable to focus). Try switching over to the "Manual Focus" mode. On the front of the camera there is a button labeled "AF/M". Push that button to switch to manual focus. If the camera is in manual focus, the external LCD screen will say "M.Focus". Now try to snap a shot. If that still does not work, there may be something wrong with the camera or the lens. So, try using a different lens in manual focus mode. If it still does not work, then I would say the problem is with the camera itself.

if the lens is removeable ensure it is fitted correctly.
if there is a manaul af setting make sure it is in af for autofocus.
ensure you are not in macro mode or close up mode as this will cause bluring on non close up pictures.
to test take a picture of a subject very close up and see if it is in focus if it is you need to change camera out of macro mode.
action mode is not available for macro mode so this maybe is the case.
action mode on cannon looks like a square with bottom right corner hilighted to look like a stack of images. make sure this is set for sequence shots.

My Fuji E550 manual says this icon indicates the autofocus cannot work effectively under the present conditions. If your image is too dark move to a distance of around 2m (6.6 ft) from the subject. Alternatively use AF lock to take the picture.
My thought -- might try taking the shot even if dark and lightening it extensively in a post production program like Picasa. I never discard a dark shot until I've tried this -- with many good results.

Performance wise, the camera has a couple of niggles. Start up to first shot time is around a second, and shot to shot (without flash) is good with three shots (the top three or the last three in a sequence are captured) in around 1.5 seconds unless the camera needs to refocus ort the flash fires. Flash recharge is around five seconds and disappointingly, the camera locks up as the flash charges, which is a shame.

But, focusing becomes an issue in low light too, where the camera will hunt trying to key on the subject or just continually fail to focus. So, beware in low light. There was another focus niggle on smaller subjects in macro mode where the camera would simply refuse to focus on anything in the frame smaller than the central AF area, and no matter what you do. Thanks

* Get AF off the shutter release and onto the * button using the custom function. * Use the center focus point only. Force yourself to pick what you want in focus, AF, then recompose and shoot, a habit far more effective than computer driven multiple AF points for just about everything. * AF performance degrades in low light no matter what camera you own. This is life. At least if you control the when/where of AF, you can try and choose high contrast points in the scene to focus on, points that will help mitigate the low light. * Not sure if this applies to you, but it does apply to many a pixel peeper...if something prints sharp at 8x10 or 11x14 then AF has succeeded even if it's a little off at 100% in Photoshop. AF is not perfect and the tolerances are not necessarily up to producing 40" enlargements, which is what 100% in Photoshop is. Having said that, in good lighting with good target contrast the AF on your 20D often will nail focus so perfectly that it will hold up even at 40".

If the camera is having a difficult time auto-focusing, you can try the FOCUS LOCK feature. This feature allows you to focus on another subject roughly the same distance from you and then move the camera back to the intended subject and take the picture without losing focus. First, turn the camera on and locate the Autofocus Target Mark in the center of the LCD. The AF Target Mark resembles an open and close bracket [ ]. Position this AF Target Mark on a subject roughly the same distance away as the subject the camera is having trouble focusing on. Press the shutter button halfway enabling the lens to focus. While holding the shutter button halfway down, aim the camera at the original subject and press the shutter button all the way down.

If the camera is having a difficult time auto-focusing you can try the FOCUS LOCK feature. This feature allows you to focus on another subject roughly the same distance from you and then move the camera back to the intended subject and take the picture without losing focus. First, turn the camera on and locate the Autofocus Target Mark in the center of the LCD. The AF Target Mark resembles an open and close bracket [ ]. Position this AF Target Mark on a subject roughly the same distance away as the subject the camera is having trouble focusing on. Press the shutter button halfway enabling the lens to focus. While holding the shutter button halfway down, aim the camera at the original subject and press the shutter button all the way down.