How to set up the perfect focus for shooting jewelry in manual mode?

Please check if yu did set the camera in AF mode continuous. In that mode, the camera is focusing on whatever is aimed at. Even when the shutter button is not pressed, allowing you to shoot without missing opportunities.
The mode where you see the camera focus when the button is pressed half way, is called single. This setting will conserve battery power.
Look in the manual under Switching between Focus Settings. I can't tell you war page that is for your camera, in mine it is page 100.
On the last pages in the book are all settings for each shooting mode.

The D90 has three different autofocus modes. In the AF-S mode it will not shoot until it has focused. In the AF-C mode it will shoot when you press the shutter release button even if has not focused. In the AF-A mode the camera switches between the AF-S and AF-C modes so either can apply.Also, bear in mind that the camera doesn't really know what you're taking a picture of. It may focus on something other than your subject. If you're in the single-area AF mode then you control which of the eleven focus points the camera uses. In any of the dynamic-area AF modes the camera decides.For full details on how the various modes work, please consult your manual. You might also check out the Nikon D90 video tutorial.

I could be that your lens isn't focusing. If the Auto focus can't find something to focus on the shutter won't fire. If you are shooting in low light sometimes it has trouble try shooting something that is well lit. also your auto focus point may be somewhere other than the center. there is a button on the top of your camera that looks like this [ ][ ] [ ] [ ]
More or less that will switch where your focus point is. If you look in the view finder and see a red dot when you push on the shutter button that is your focus point. push the above button until the red dot is in the centre. that may fix your problem.

I would check IS(image stablization) setting and continous shooting setting to make sure these features are turned off. You want to experiment with different IS settings and definitely turn the continous shooting mode because the continouse mode may not focus 100% in order to shoot multiple shots. Hope this helps. -James. P.S. In my case it was too difficult to distinguish the quality of focus in the VF or LCD so you may not see the focus issue on them.

The shooting modes are described as follows: AUTO (Factory default setting) Auto mode is used for regular photography. The camera automatically makes the settings for natural color balance. Other functions, such as the flash mode and metering, can be adjusted manually. Portrait Portrait mode is suitable for taking a portrait-style picture of a person. The camera automatically sets the optimal shooting conditions. Night scene Night scene mode is suitable for shooting pictures in the evening or at night. The camera sets a slower shutter speed than is used in normal shooting. If you take a picture of a street at night in any other mode, the lack of brightness will result in a dark picture with only dots of light showing. In this mode, the true appearance of the street is captured. The camera automatically sets the optimal shooting conditions. If you use the flash, you can take pictures of both your subject and the night background. SCENE Scene mode enables you to select one of the following scene shooting modes available in the menu. Landscape + Scene shooting Landscape + Scene shooting is suitable for taking pictures of landscapes and other outdoor scenes. This mode produces clear, sharp pictures with excellent detail, making it ideal for shooting natural scenery. Landscape + Portrait shooting Landscape + Portrait shooting is suitable for taking photos of both your subject and the background. The picture is taken with the background as well as the subject in the foreground in focus. The camera automatically sets the optimal shooting settings QuickTime Movie Quicktime Movie mode lets you record movies. The focus and zoom are locked. If the distance to the subject changes, the focus may be compromised. Landscape Landscape mode is suitable for taking pictures of landscapes and other outdoor scenes. The camera automatically sets the optimal shooting conditions. Self-portrait Self-portrait mode enables you to take a picture of yourself while holding the camera. Point the lens towards yourself, and the focus will be locked on you. The camera automatically sets the optimal shooting conditions. The zoom is fixed in the wide position and cannot be changed. My Mode Enables you to make settings manually and register them in the mode dial's mode so you can call up your own shooting mode whenever you want. Program shooting (P) Program shooting allows you to shoot using an aperture and shutter speed that the camera sets. You can set the flash, white balance, or other functions manually. Aperture priority shooting (A) Aperture priority shooting allows you to set the aperture manually. The camera sets the shutter speed automatically. By decreasing the aperture value (F-number), the camera will focus within a smaller range, producing a picture with a blurred background. Increasing the value will let the camera focus over a wider range in the forward and backward directions, resulting in a picture in which

Program Auto (Factory default setting) Program Auto mode is used for regular photography. The camera automatically makes the settings for natural color balance. Other functions, such as the flash mode and metering, can be adjusted manually. Portrait Portrait mode is suitable for taking a portrait-style picture of a person. The camera automatically sets the optimal shooting conditions. Landscape + Portrait Landscape + Portrait mode is suitable for taking photos which include both your subject and the landscape. The camera automatically sets the optimal shooting conditions. Landscape Landscape mode is suitable for taking pictures of landscapes and other outdoor scenes. The camera automatically sets the optimal shooting conditions. Night scene Night scene mode is suitable for shooting pictures in the evening or at night. The camera sets a slower shutter speed than is used in normal shooting. If you take a picture of a street at night in any other mode, the lack of brightness will result in a dark picture with only dots of light showing. In this mode, the true appearance of the street is captured. The camera automatically sets the optimal shooting conditions. If you use the flash, you can take pictures of both your subject and the night background. Indoor Indoor mode enables you to take pictures while indoors by allowing the flash to reach farther away. Beach & Snow Beach & Snow mode enables you to take pictures of scenery containing white sand or snow. Cuisine Cuisine mode enables you to take pictures of food by increasing the saturation, sharpness and contrast settings to take sharp, vivid pictures of the subject. Self-portrait Self-portrait mode enables you to take a picture of yourself while holding the camera. Point the lens towards yourself, and the focus will be locked on you. The camera automatically sets the optimal shooting conditions. The zoom is fixed in the wide position and cannot be changed. QuickTime Movie QuickTime Movie mode lets you record movies with sound. The focus and zoom are locked. If the distance to the subject changes, the focus may be compromised.

What is the best situation to use each of the shooting modes? The shooting modes are described as follows: Program Auto (Factory default setting) Program Auto mode is used for regular photography. The camera automatically makes the settings for natural color balance. Other functions, such as the flash mode and metering, can be adjusted manually. Portrait Portrait mode is suitable for taking a portrait-style picture of a person. The camera automatically sets the optimal shooting conditions. Landscape + Portrait Landscape + Portrait mode is suitable for taking photos which include both your subject and the landscape. The camera automatically sets the optimal shooting conditions. Landscape Landscape mode is suitable for taking pictures of landscapes and other outdoor scenes. The camera automatically sets the optimal shooting conditions. Night scene Night scene mode is suitable for shooting pictures in the evening or at night. The camera sets a slower shutter speed than is used in normal shooting. If you take a picture of a street at night in any other mode, the lack of brightness will result in a dark picture with only dots of light showing. In this mode, the true appearance of the street is captured. The camera automatically sets the optimal shooting conditions. If you use the flash, you can take pictures of both your subject and the night background. Self-portrait Self-portrait mode enables you to take a picture of yourself while holding the camera. Point the lens towards yourself, and the focus will be locked on you. The camera automatically sets the optimal shooting conditions. The zoom is fixed in the wide position and cannot be changed. QuickTime Movie QuickTime Movie mode lets you record movies with sound. The focus and zoom are locked. If the distance to the subject changes, the focus may be compromised.

The shooting modes are described as follows: PROGRAM AUTO (Factory default setting) Program Auto mode is used for regular photography. The camera automatically makes the settings for natural color balance. Other functions, such as the flash mode and metering, can be adjusted manually. Portrait Portrait mode is suitable for taking a portrait-style picture of a person. The camera automatically sets the optimal shooting conditions. Landscape Landscape mode is suitable for taking pictures of landscapes and other outdoor scenes. The camera automatically sets the optimal shooting conditions. Night scene Night scene mode is suitable for shooting pictures in the evening or at night. The camera sets a slower shutter speed than is used in normal shooting. If you take a picture of a street at night in any other mode, the lack of brightness will result in a dark picture with only dots of light showing. In this mode, the true appearance of the street is captured. The camera automatically sets the optimal shooting conditions. If you use the flash, you can take pictures of both your subject and the night background. Self-portrait Self-portrait mode enables you to take a picture of yourself while holding the camera. Point the lens towards yourself, and the focus will be locked on you. The camera automatically sets the optimal shooting conditions. The zoom is fixed in the wide position and cannot be changed. QuickTime Movie QuickTime Movie mode lets you record movies. The focus and zoom are locked. If the distance to the subject changes, the focus may be compromised.

1. Typical problem subjects for autofocus 1) Very low-contrast subjects 2) Overlapping nearby and distant objects 3) Very bright subjects in the center 4) Subjects moving very fast 5) Subjects through glass Focus on an object that is at the same distance as the desired subject, apply Focus Lock, and then recompose the picture. Or set the lens focus mode switch to (or), and focus manually. (Manual focus is only possible with cameras providing this feature.) 2. Attempting to take pictures out of the camera's shooting distance: When taking pictures out of the camera's shooting distance, the subject will be out of focus. The shooting distance differs from each camera model. Please check the specifications of your camera in the instruction manual to determine the shooting distance.

1. Typical problem subjects for autofocus 1) Very low-contrast subjects 2) Overlapping nearby and distant objects 3) Very bright subjects in the center 4) Subjects moving very fast 5) Subjects through glass Focus on an object that is at the same distance as the desired subject, apply Focus Lock, and then recompose the picture. Or set the lens focus mode switch to (or), and focus manually. (Manual focus is only possible with cameras providing this feature.) 2. Attempting to take pictures out of the camera's shooting distance: When taking pictures out of the camera's shooting distance, the subject will be out of focus. The shooting distance differs from each camera model. Please check the specifications of your camera in the instruction manual to determine the shooting distance.