Hi Rod,
I asked Canon's Chuck Westfall a similiar question yesterday afternoon in the December issue of The Digital Journalist. I hope he answers, since I had always Micro Adjusted my 600 + 1.4/2/0 ex. at the mimimum focus distance, but he states in his article that Canon recomemnds the target should be 50x the focal length lens distance. Here's a link to his article:
I noticed that Chuck states that one should "Expect smaller microadjustment settings to have a greater effect with telephoto lenses". I would like to know a little bit more about that, with regards to say a 600, or in your case an 800mm lens.
Maybe if you too pose a similiar question in The Digital Journalist, he might answer quickly and give us Canon's best advice to fine tune the big guns!
Happy shooting,
Randy Wright
LAsurfpix.com
Randy Wright wrote:
I noticed that Chuck states that one should "Expect smaller microadjustment settings to have a greater effect with telephoto lenses". I would like to know a little bit more about that
I am guessing that this is due to the depth of field. With a (super)telephoto the dof is extremely narrow even at large distances therefore a smaller adjustment will have more effect.
This is probably why it is recommended that you shouldnt do the MA at infinity as the dof will be much larger here and it will be harder to get accurate adjustment.
Randy Wright wrote:
Hi Rod,
I asked Canon's Chuck Westfall a similiar question yesterday afternoon in the December issue of The Digital Journalist. I hope he answers, since I had always Micro Adjusted my 600 + 1.4/2/0 ex. at the mimimum focus distance, but he states in his article that Canon recomemnds the target should be 50x the focal length lens distance. Here's a link to his article:
I noticed that Chuck states that one should "Expect smaller microadjustment settings to have a greater effect with telephoto lenses". I would like to know a little bit more about that, with regards to say a 600, or in your case an 800mm lens.
Maybe if you too pose a similiar question in The Digital Journalist, he might answer quickly and give us Canon's best advice to fine tune the big guns!
Happy shooting,
Randy Wright
LAsurfpix.com
I mounted my 800L in a Wimberley II head on a Gitzo GT5541 Tripod, and set up a 9 inch bottle with a contrasty label on a stool. The stool was placed at 45 feet and 60 feet from the tripod with the bottle always being larger than the auto focus point in the viewfinder. The camera was focused in one-shot mode with no focal pt expansion. After the focus confirmation beep, I put the camera into live view mode and 10X magnification. I tried to make the image sharper by careful manual focus in both directions. My 800L required 0 microadjustment on both my 1DsMkIII's and both 1DMkIII's
rprouty wrote:
any suggestions on distance to do a micro adjustment with an 800 mm lens?
Thanks
Hi Rod,
I had sent a question to Chuck Westfall at The Digital Journalist the other day asking a similiar question. Chuck responded just a short time ago and said the following:
"The AF microadjustment method I posted above works with all EF lenses regardless of focal length, with or without extenders. As I mentioned, though, longer focal lengths are more sensitive to minor adjustments. It is tempting to perform the focusing tests at less than 50X focal length with telephoto lenses because of the longer focusing distances involved, but microadjustments performed at close range are less likely to remain accurate at longer distances. At 50X, you'll be splitting the difference, and maximizing the range over which the microadjustment is usable. That being said, if you have an EOS camera with Live View and you're working from a tripod with a stationary subject, you could use the 10X magnification feature in Live View to verify the accuracy of the camera's phase-detection AF system."
In case anyone else wants to read his info, here's the link again: http://digitaljournalist.org/issue0812/tech-tips.html
Randy Wright
LAsurfpix.com
800 millimeters x 50 = 131 feet or typical usage distance. For any lens, you can just type '800mm x 50 in feet'' (substitute in actual lens FL for 800mm) into google and it will do the calculations for you. If you are not using FF, then use the correct multiplier (ie 80 instead of 50 for 1.6 crop).
