How clean do I need to keep my Digital SLR camera lens?

I have a Nikon d90 and tamron 17-50mm lens. I keep it real clean I breathe hot air on it and wipe it with lint-free cloth and then blow the dust off with a hand help squeeze blower. But how clean do I need to keep it. No matter what there are always some type of dust particles and etc. I keep a HOYA 67mm UV filter on it always so I clean that. But how clean do I need it really? What point will I notice it in the photo. I always wipe off grease and fingerprints but will small dust particles and tiny scratches (they happen) really make a difference?

Also, I have never cleaned/touched my sensor, do I need to do that? I haven't noticed anything in my photos. Just let me know!

I have a Canon 30D. I also use a UV filter on all my lenses. I try to keep the filter clean. I wipe it off when its wet or snowy and if I notice big spots I clean it. Small stuff you won't notice, so don't worry about it too much.

I use compressed air to clean my sensor when its needed, like once a year. I want to get one of the newer cameras, like the 40D or 50D or even the new 5d mark 2 that all have built in sensor cleaning and even software to remove spots form stuff on the sensor it can't clean off. That is just awesome.

Don't worry about the little stuff. Use a good cloth that is made for lenses, so you don't scratch it.

It is best that when you go out shooting you use a lens cloth to make sure that there are no major spots on yoru lens (or filter if you are wise and are using a UV filter to protect the lens as you are).

Next thing to keep in mind is that those spots are not in an area that is focusable so they will just be a blur if they are large, and if they are small you won't see them unless you blow it up large. Also most people don't realize that with a crop sensor camera liek you are using it is only using a section of the image that you are getting thru the lens. So only that image that comes thru the center area are what make it to the sensor. That is why you get the extra reach compared to film. So that is the most important area to watch.

I will give my filter a good cleaning when I see it needs it, otherwise I normally do it twice a year, just to be safe. I clean all my filters, then, even my r25, and Cp filters.

As for the sensor. I send mine into Canon once a year for a good cleaning. Other wise I don't worry about it as most the canons are self cleaning, and the newer ones doe a great job at it. If you are seeing dust liek spots in yoru images, then you need to clean your sensor, or send it to the FACTORY for a real cleaning. You can blow it off with air, but other than that I don't suggest you do anymore. Take a photo os a clear blue sky or a white/cream wall. Proplery expose it and then look for spots int he images. If you look at a few shots you will notice the ones on the sensor are always in the same spot, that tells you its a sensor issue, esp if you change lens.

Hope this helps.

Happy Holidays

Re the lens - a UV filter will protect the lens from scratches or bumps but the cleanliness issue is exactly the same. What you are doing is fine. You don't want major greasy smears but you'll be surprised how little difference a little dust or a smudge makes on the front of a lens - the optics of the camera are such that the back of the lens or the sensor are much more important for visible effects on your images. Test for yourself - let the dust build up on your lens and take some shots and see if you can see anything. Likely not.

Re sensor - a dust speck on your sensor will very clearly show up as a light speck on images that always appears in the same place in the frame. You can eliminate one or two of these spots with software tools, but this eventually becomes a nuisance. It's probably safest to let a professional clean the sensor, as it is a somewhat tricky business and the cost is not outrageous, but if you're a handy person with tech you can get a cleaning kit at the photo store and do it yourself. You probably won't have major senor problems as long as you only have one lens and leave it on, but once you get more lenses and start switching them in the field, sensor cleaning will become a problem.