I have been using iPhone's camera since a long time and I have always wondered, what coatings or filters do mobile cams have in place (if the have any). The reason I ask is sometimes my iPhone is able to take better pictures of sky, clouds and the beach than my SLR can. In the latter, I have to adjust exposure, add polarisers/NDs to get exact same kind of colours, contrast and saturation. Anyone having technical info?
The lens elements will have anti-reflective coatings, as all modern lenses do. There may or may not be an IR filter over the sensor, certainly many early camera phones didn't bother with IR filters (using the camera you could see IR LEDs such as the ones found in the wii sensor bar). Apparently Apple only introduced an IR filter in the iPhone 4S and later models.
The lack of an IR filter might actually improve your skies as there is less IR and move UV in the sky, so you ought to get slightly darker skies provided the metering picks up IR.
There may be a UV filter built in (though this is very unlikely if there's not even an IR filter), there certainly wont be a polarizing filter. The differences you observe are likely to do with the JPEG engine on camera phones which will be optimised to produce contrasty images with rich colour saturation, whereas DSLRs aim to produce more accurate, natural colours.
sometimes my iPhone is able to take better pictures of sky, clouds and the beach than my SLR can. In the latter, I have to adjust exposure, add polarisers/NDs to get exact same kind of colours, contrast and saturation.
This will not be due to the coatings on the lens but to the image processing, specifically the contrast and colour saturation. It appears that the default saturation and contrast settings applied in the iPhone are more pleasing to your eye than any of the contrast and saturation settings you are able to get on your SLR so far. Some people like contrasty, saturated colours, and it suits some types of pictures well.
The equivalent on your SLR is probably to turn the contrast and colour saturation right up. That said, on my SLR I leave my contrast and colour saturation at sane defaults and do any boosting in post-processing (indeed, I shoot in JPEG+RAW so I can even re-apply it to the raw image data if I wanted to).
I have been using iPhone's camera since a long time and I have always wondered, what coatings or filters do mobile cams have in place (if the have any)
They will have anti-reflective coatings. I don't know if the outside surface of the camera (the one constantly rubbing against the inside of your pocket) has such a coating, but it is normal for camera lenses, even on phones and compact cameras, to have anti-reflective coating on the surfaces of the lens elements. The only thing that anti-reflective coatings should do is reduce flare and ghosting. Scratches on the outside surface of the camera lens will increase fogging.