There is definitely noise in this image.  I looked at your EXIF information and found that it was shot at ISO 400.  You have noise in every part of the image, as well as a "stuck" or "hot" pixel in one of the grapes.

If by "standard settings" you mean fully automatic, you're not using the camera to best advantage.  I recommend buying an inexpensive, light tripod--with a shoulder carrying bag, if you can afford it--and shooting in aperture priority.  Failing that, shoot in shutter priority with a relatively high shutter speed.  Also, if you're shooting in JPEG mode, be sure to set the quality to high.  As a last resort, put the camera in "P" mode, which controls everything but doesn't automatically set the ISO for you, and set the ISO to 100.

How accurate are the standard settings the camera comes with?  (I have Canon Rebel XT)  I usually use the standard settings (unless I'm shooting in the studio) and actually have a very steady hand -- I thought the pictures I submitted to Shutterstock were noise free and they were accepted everywhere else.  (I'm not disputing their verdict, they just made me realize I need to look more closely at my pictures.)

I checked one of their rejected photos and now that I know what to look for, I spotted the noise -- but I think it is very slight.  Could you guys possibly check out one of the photos and let me know if I'm correct in thinking its a slight amount of noise?  Or if I've deluded myself and need a lot of work?  I put the photo here http://www.rachellcoe.com/grapes.htm (Its at 100% so you can see what ShutterStock saw) If the noise is only very slight, would I be better off using the noise software than changing my camera settings?

I can't thank you guys enough for all the information!  I had read through the manual, but until I had my own examples to apply it to it wasn't really coming together for me.  Now that I know what to look for, I'm going back over it and applying the settings you mention.  One other question -- will an ISO of 100 work with most shooting situations? 

outside it will generally always work, inside it will generally never work.

what lenses do you have?

If you don't have it allready, a fun little lens (and cheap) is This One - 50 1.8  Since it has an aperature as wide as 1.8, it can shoot is pretty dark situations.

OK, so the darker your shooting environment is, the wider you want the aperature?  And the higher the ISO?  So 100 ISO and a low aperature setting is good for well-lit situations, and maybe 400 ISO for dark?

I know I've deviated from the original noise post, but this information is priceless to me.  And you are putting it in such a way that I can understand -- unlike the manual

You'll generally want to use ISO 100 for all of your microstock shots.  For you own purposes, or for artistic shots, ISO 400 or even higher will be fine.  But, the microstock sites, especially SS, are a bit nuts about noise.

If you try to use high ISO, you'll get noise in your image.  If you underexpose your shot, as I expect happened with your grapes, then the noise is going to get stronger.  You're often going to underexpose your image if you try to use a high/hand-holdable shutter speed because your lens may not open wide enough.  Your best bet if the light is low is to use a tripod.  A tripod will allow you to get a good exposure without the worry of camera shake.  Most of my product shots are shot at 1/15 of second or longer; many of my landscapes are also longer exposures.  My tripod is a must, and until recently I sucessfully used a really cheap one from Ritz (boy am I happy I got a better one).

You say you don't want a tripod.  A good rule of thumb (but by no means set in stone) is to use a shutter speed at least the reciprocal of your focal length.  So, if you shoot with a 50 mm lens, you should have a shutter speed of 1/50 second or faster.  But, keep in mind that the faster the shutter speed, the wider the aperture (as leaf said); this means a smaller depth of field (the area in front of and behind the focus spot that is acceptably sharp).  Shutterstock sometimes has a problem with too little depth of field and will reject an image for it.

OK, so the darker your shooting environment is, the wider you want the aperature?  And the higher the ISO?  So 100 ISO and a low aperature setting is good for well-lit situations, and maybe 400 ISO for dark?

I know I've deviated from the original noise post, but this information is priceless to me.  And you are putting it in such a way that I can understand -- unlike the manual

Noise is a function of how your sensor works and how the camera processes the signal from the sensor.  While a RAW file can help with things like inaccurate white balance and exposure problems, it can't get rid of noise.  You need to minimize noise with low ISO and accurate exposure.  Those two things are your best weapons against noise.

If I were in your shoes, I'd spend a bit of time goofing around with my camera.  I'd learn how to use my camera to best advantage--learn how it responds under different conditions, how the various program modes work, things like that--and then use RAW once I've mastered the camera.  RAW is a great tool, but it isn't a cure-all.  While I shoot RAW exclusively at this point, I know of others who only shoot JPEG and produce spectacular results.

Hope this helps.

I'm currently shooting large jpeg -- will shooting raw help to clear my photos up even more?  And how difficult is it to work with raw files?  (I have Photoshop CS)

I don't have a "favorite" settting.  However, I can say that the "incandescent" and "flourescent" white balance settings typically don't do a good job.  You'll want to manually white balance your camera under that kind of lighting.  The manual will tell you how to do this.

I do find myself using aperture priority with f 8.0 aperture a lot, as f8 produces the best images from my lenses.

This does help a lot!  I've already started playing around with my camera.

Do any of you have favorite settings for daylight, indoor, product, twilight?

I'm currently shooting large jpeg -- will shooting raw help to clear my photos up even more?� And how difficult is it to work with raw files?� (I have Photoshop CS)

Noise is a function of how your sensor works and how the camera processes the signal from the sensor.� While a RAW file can help with things like inaccurate white balance and exposure problems, it can't get rid of noise.

Actually, noise CAN be reduced by shooting with RAW.� How much it can be reduced depends on your camera settings in JPG.

JPG uses in-camera post-processing to create the image.� In other words, an image always starts out as a RAW within the camera.� But then if you shoot in JPG, the camera will post-process the image to create the result.� Usually, it will sharpen, apply contrast, saturate, and apply white balance.� It does all of this automatically.� It is during the sharpening phase that noise can increase in the image.

This can be solved in two ways: by shooting in RAW (thus eliminating the in-camera processing) or by turning off sharpening in-camera.� Not all cameras can do these things (since not all cameras can produce RAW and not all cameras can turn off post-processing).

I believe that the camera that you have (the Canon Rebel XT) can do either, so it is just a matter of how far you want to go.

And how difficult is it to work with raw files?� (I have Photoshop CS)

Shooting in RAW adds more steps to the process (since you need to convert the RAW to a JPG, and do the post-processing manually).

At first, I would suggest turning off some of the in-camera settings for post-processing.� Although cameras can post-process the RAW automatically (to produce a JPG), they apply the settings evenly no matter what type of image you take.� For example, if you have sharpening set at +2, then it will ALWAYS apply sharpening at that value.� No matter if the image is taken at ISO 100, or ISO 1600.� No matter if the image is taken in full daylight @ 1/250 sec or at night @ 30 secs.� As you can probably see, it would be better to apply sharpening manually depending on the conditions.� On top of that, digital editing programs such as Photoshop have better sharpening algorithms than cameras and allow many more options.

Turning off the in-camera settings will leave your JPG image the closest to the RAW as possible, without actually leaving it in RAW.� So for example, I would first suggest turning the sharpening setting to its lowest value (which I believe is -2 on your camera) and then apply sharpening to the image within PhotoShop.� This will give you much more control over the process.� Over time, you can then do the same with saturation and contrast as you become more experienced.

Hope that helps.

I was inspired after reading your posts last night (not to mention you helped me to understand a little more about the processes) so I made my poor sons model while I took 20 million pictures of them in the same pose using a ton of different settings.  (They got smart -- after about 20 minutes of this they substituted the dog for themselves while I was changing the setting on the camera)

Besides showing me ways to make the picture better, it also showed there is an almost mind-boggling amount of variables! 

I was inspired after reading your posts last night (not to mention you helped me to understand a little more about the processes) so I made my poor sons model while I took 20 million pictures of them in the same pose using a ton of different settings.  (They got smart -- after about 20 minutes of this they substituted the dog for themselves while I was changing the setting on the camera)

Besides showing me ways to make the picture better, it also showed there is an almost mind-boggling amount of variables! 

It always amazes me the number of people who don't do this basic experimentation when entering the world of SLR photography. It's even easier now with digital SLRs. Hope you got a couple of good pics of your boys and the dog!

Buy (and read) "Understanding Exposure" by Bryan Peterson. It's a great book for helping you understand what all the numbers mean and are doing to the final image. His other book "Learning To See Creatively" is also very good.