Spots on image

dont worry about dust too much unless it actually affects your image sensor.check it by pointing to a white wall or sky with f put to it maximum like 32/22 , focus and take pictures.. if its problem with the lens then it will make prominent dark speckles on the image.. but if you get dark speckles even at lower f - stops like 1.4/3.5/5.6 then its dust in the sensor.

dont try cleaning your sensor yourself as you may spoil it and finally have to refer a service center of the brand .

The image sensor in the camera needs cleaning. You can buy cleaning kits, but often you'll just make the problem worse until you gain experience. Many camera shops now offer professional sensor cleaning so you might decide that it's better to pay someone else to do it for you. If you join a local camera club there's also usually at least one sensor cleaning guru who can do it really well if you buy him or her a beer.

Prevention is better than cure, so always blow dust off the camera and lenses before changing them, and never leave the camera for any length of time without either a lens or a body cap on the front.

The spots can be in the inside of the lens settings to the CCD/imager.
If the cleaning of the lens is done well it can be a speck of dust logged in to the screen and having it on the image.
A careful cleaning in a dust proof set up is required.

Your lens would need to be absolutely filthy with enormous dirt specks to cause the fault you describe. Dust, fingerprints, and regular minor debris simply doesn't show in the final image. In any case, you cannot clean inside the lens without dismantling it and that is a job for experienced specialists only.

Your fault is a dirty image sensor. You can buy sensor cleaning kits, but if you're inexperienced with them or trying to clean the sensor in a dusty environment you'll just make matters worse. Many camera shops offer sensor cleaning while you wait at relatively low cost. The reason you don't see the dirt when taking the picture is either because you're looking through the optical viewfinder or because the LCD screen simply doesn't magnify the image enough to show the marks which are present in the image.

You can prevent the dirt from reoccurring by never leaving the camera with the lens throat open for more than strictly necessary, and by always trying to keep the open lens throat pointing slightly down when swapping lenses.

I hope that I've helped, please take a moment to rate my answer.

Blue polarizer has gone bad.

It sounds like the projection lamp is beginning to show its age. How many hours of use does the unit have on the bulb? The bulb are typically rated for about 800-1600 hours of use before they go bad. The bluish image on the screen image is a typical tell-tale sign that the bulb is going to need replacing.

Most of your better projection units will have an internal time counter of the bulb life from the time the unit is first used or when a bulb is replaced. Check to see if your unit has this feature, if so it will show you on the screen display what is the total number of hours on the bulb and the estimated remaining hours of life.

Be aware that the replacement bulbs are NOT cheap and usually will cost you several hundred dollars, I have seen bulbs for professional projection units used for large convention/presentations have bulbs costing as much as $500.00 USD.

One other last thing to check is to clean the lens of the unit both inside and outside. To clean the inside, you will need to remove the bulb (be sure to wear a rubber glove as the oils from your skin will cause the lamp to blow, (causes a hot spot)). Then using a cleaning wipe, just as one used for cleaning microscopes or glasses, wipe the lenses. The discoloration might also being caused by dirt and oils on the lenses.

I hope this shed some light on your church's projection problem.

If you go to turn on your laptop and loads to your os and the spots on the screen remain there then most likely you have ruptured the liquid crystals in the screen by pressing too hard when you were cleaning the screen with the computer off. you could lightly touch the black spots with your finger and if it displaces the black with a white halo effect around your finger (DO NOT PRESS TOO HARD OR WITH FINGERNAILS DIRECTLY ON THE SCREEN) then it will mean that you will have to replace the screen because it has busted the crystals definately. DARK

If Alex's comment didn't resolve your problem, check for dust inside the camera body and on the part of the lens that goes into the camera body. The highlight indicator he speaks of will show on the LCD screen, but should not show up on your final picture once downloaded from the camera. Since the optics on that end of the lens are smaller, they are more susceptible to dust and dirt. If there is dirt or dust inside the camera body and you are not familiar with how to clean it, same yourself some headaches and take it to a qualified camera shop. You can seriously damage the interior optics of your camera by attempting to clean it the wrong way.

There is a spec of dirt that made it inside the camera and has landed itself on your image sensor.

If you take a picture and the image has a spot on it, it could be the screen. If you transfer it to your computer and the spot is in the same spot, its something on the image sensor. You would have to send it out for cleaning, and a new camera would be cheaper.

This is probably caused by dust, either on the mirror, lens, or possibly inside the light engine. There is a 5" dia hole on the side of the back of the tv where you can take out one screw and take the door off. this is just big enough for you to put your hand through to clean the mirror and lens. Hope this helps.