what make a high def lens a high def lens?

[Charles Perkins]

i know that the xlh1 comes with a hi definition lens but what does that mean? is the glass clearer, better quality and such?

if so, why can you use the adaptor and L series lenses from the SLR range, i mean, they must be ver good if they are recording around 12mp per pic.

[Tony Davies-Patrick]

Most pro-quality lenses made for SLR cameras are of a higher quality than lenses made for video cameras...they need to be.

[Ron Pfister]

This is an over-simplification. Using Canon EF-lenses with the XL-EF adapter makes use only of the glass at the very center of the lens. Thus the extension factor of 7.2 when compared to 35mm. As a result, only the very best EF-lenses are up to the task of HD-imaging on the XL-H1 (Canon only recommends EF-primes). This thread has more:

http://www.dvinfo.net/conf/showthread.php?t=56642

[Steve Rosen]

Additionally still camera lenses serve a huge population compared to "pro-sumer" HDV cameras, so they produce them in huge numbers and can rationalize the R&D and production costs better... Canon is fairly conservative in this arena and will wait until they're sure of a viable market before mass producing lenses for it... unfortunate (for us) but true.. that's what these forums are all about - hopefully someone from Canon reads them regularly...

[Stephan Ahonen]

Tighter manufacturing tolerances, a smaller circle of confusion and better control of chromatic abberation. Photographic lenses aren't as complicated to make since they're generally primes, and when they are zooms they don't have nearly the same zoom ratio as a video zoom lens. A video zoom lens capable of a 20x zoom ratio while keeping chromatic abberation to a minimum requires a ridiculous number of lens elements and precision engineering. The 50-100x zooms you see in a sports broadcasting truck can run over $1-200,000.

[A. J. deLange]

Originally Posted by Charles Perkins

i know that the xlh1 comes with a hi definition lens but what does that mean? is the glass clearer, better quality and such?

That's a very good question as those of us that have used the SD lenses from the XL series generally can't find any difference in sharpness - either perceived or measured - between them and the HD lens but no one has done a complete set of tests (MTF in all orientations at all apertures at all focal lengths) on either so it may well be that the HD lens performs better in some parts of its range than its SD brothers.

There are two definite differences. (1) The HD lens won't stop down as far as the SD ones because the diffraction limiting stop is at about f/9.3 for the HD sensor and appreciably smaller (aperture - not f number) for the SD sensor. (2) The HD lens can be controlled by the camera for taking still pictures. The SD ones can't.

The reasons one can use still photography lenses on the camera are because these, being genrally primes, are pretty sharp. It is a far, far easier thing to design a prime with focal length greater than the back focus distance than a 20:1 zoom with focal lengths at the short end appreciably smaller than the back focus distance.

If you do use a still camera or SD lens on the XL-H1 don't stop it down more than f/5.6 - 8. This will result in blur from diffraction. A simple experiment will convince you of this.

[Edited to correct f/stop values]

[Lauri Kettunen]

... just to add a detail to what A.J --whose comments I always highly appreciate-- said: For some reason the brights and darks of the 20x lens image are slightly brighter and darker than those of EF-series lenses as if the there was more constrast.

The other way around, I've not figured out any clear technical reason why XL H1 prevents one from taking still images with the EF-series lenses labelled HD incompatible. Instead of preventing from taking the stills, the camera could just warn about too small apertures --and in the ideal case, one could toggle such a message in the menus.

[Charles Perkins]

thanks for all of your replies.

really interesting info.