DOF scales - Infinity Compensation Mark

[lordjim]

Hi everyone -

Most L lenses have what they call "infinity compensation marks" but do no longer have DOF scales. Why that? Could we get the same info from the infinity compensation marks? The manuals of the lenses are very unclear about how to use the mark, they just mention that the mark can be used "to compensate for shifting of the infinity focus that results from changes in temperature". Could someone explain to me why there should be an infinity compensation for a change in temperature?

It would seem to me that a DOF scale was a lot more useful than an infinity compensation mark. Am I missing something?

Thank you.

[Rob612]

That's something I am missing too, especially with the ultrawide lenses the scale was neat for setting the lens to hyperfocal.

[lordjim]

Well, I did not get any answer on this forum but I did on Fred Miranda's. So for those who are interested, you can look at:

http://www.fredmiranda.com/forum/topic/253361

[Tom W]

The DOF markings are still present on primes, though as you go longer, the markings are closer together and eventually disappear. Do note that they are based on using full-frame 35 mm film.

Here's the 24/1.4L's focus distance scale:

http://www.pbase.com/photosbytom/image/38286517.jpg

Zooms will not have such markings since the DOF is different at various focal lengths. The last lens I had with DOF-f/stop markings was a 35-80 f/2.8 Tamron push-pull zoom. The markings were curved lines that drew closer together as you zoomed to longer focal lengths.