CMOS = The problem with rolling shutters

Ok, so everything i have read and watched so far about matchmove has said to watch out for rolling shutter cameras. first let me tell you what i have learned about rolling shutters.

A rudimentary explanation of what is going on is that instead of an old analog method of photography and filming where a single frame is affected absolutly in the imediacy of the shot (however long the shutter speed) the image is 'imprinted' onto the film at the same rate all over.

in a CMOS digital camera, when the shutter opens light passes into a chip and the chip then has to right this infomation in a sequence. (imagine holding down the A key in MS word and watching the page fill up.) each row takes a fractional amount of time to process and therefore there is an offset of time in the photo. This is fine for a single image, un noticeable. however at the bottom of the page i will include my own diagrams, then 2 videos to show the problem with this effect.

I have drawn a rudementry picture to explain this effect. bare in mind this happens on a pixel ROW basis, no where near the result of this diagram.

ORIGINAL ANALOGUE FILM CAMERA

1st (1.00 seconds) pixel row


2nd (1.00 seconds) pixel row


3rd (1.00 seconds) pixel row


4th (1.00 seconds) pixel row


5th (1.00 seconds) pixel row ect....





CMOS DIGITAL CAMERA ROLLING SHUTTER EFFECT

1st pixel row (1.00 seconds)



2nd pixel row (1.01 seconds)




3rd pixel row (1.02 seconds)



4th pixel row (1.03 seconds)




5th pixel row (1.04 seconds) ect....




 So as you can see there is a huge problem when it comes to film, the clips below are taken from a forum and are not mine, though they explain the problem with this effect perfectly:






If you own these videos please let me know and i will happily delete them, or credit you appropriatly, however im sure you'll understand i am taking no credit, simply helping make people aware of a problem.