Hi Blake,
Are you absolutely sure the problems is dust inside the lens? It's unlikely you'd see spots on images made with a dusty lens.
If they are fairly well defined black or dark brown spots in photos produced with a digital camera, then they are probably dust on the camera's sensor. Those show up most clearly when the lens is stopped down to f8, f11, f16, and are more obvious in large areas of even color, such as a blue sky.
If they are clearly defined spots on prints made from film, I'd suspect the film processor. Their equipment is dirty and their work is sloppy.
Dust on the front element of a lens will not have very much effect on a picture made with that lens. It can cause flare or loss of contrast, more if there is a lot of it, but won't show up clearly on images.
The same is true of a moderate amount of dust inside a lens, unless it get really dirty to the point photos look "hazy" and low in contrast. A lot of dust may cause an image to look soft, a bit out of focus.
Dust or scratches on the rear element of a lens are actually the most problematic. These cause stronger flare and spots of soft focus, overall soft focus if there is a lot of dust or damage, but also usually don't show up as clear spots.
If, in fact, your lens has severe dust inside, put it in the hands of a professional repair tech (like John at Focal Point) for a proper internal cleaning. The lens needs to be disassembled and that's not something most people can do themselves. No amount of blowing off or brushing is going to help.
Another thing that gets inside lenses is fungus. This is from moisture and humidity and storage in a dark closet. Fungus looks somewhat like spider webs or cob webs inside the lens. Fungus doesn't show up clearly on photos made with an infected lens, but rather there is overall image softening and loss of contrast. It's also a reason to give it to a professional, but sometimes is not repairable.
If your camera is digital and has dust on the sensor, it can be cleaned. This is a little tricky, but you can do it yourself. First look up how to do it in the manual. If there isn't any info there, search on the Internet if someone has instructions for sensor cleaning your particular model of camera.
You have to be careful that the shutter, mirror or sensor don't get damaged, if you choose to do it yourself. There are special cleaning kits sold for this purpose. And you need to "lock open" the shutter while cleaning, best done with an AC converter powering the camera. But, if you are quick about it, it can be done with freshly charged battery(ies). Canon cameras have a "sensor clean" mode. This holds the shutter open until the camera is turned off, but it can also close if the batteries don't have enough power. If the shutter closes on your cleaning tool, it will likely be damaged.
Hope this helps.
Alan
