03-01-2018 07:37 AM
So I just received my new Canon 5D MIV and I'm looking to for some clairity. I feel like I'm losing my mind.
First off, my camera is brand new and I'm curious if this is a focus setting I don't know about.
My old 24-105L kit lens was just recalibrated at Canon as well, so everything should be in perfect working order technically.
Usually when I want a subject to be in focus, I zoom in on the subject (105mm) and take focus. Lock it in manual on the lens, and then zoom back out so the subject is in focus.
I did this all yesterday with multiple portraits, and now that I'm reviewing the photos, the subjects seem to be blurry but objects in the back of the room are in focus.
Is this something I'm totally spacing on. Here's my examples below, just so you know my initial focus is sharp. Please note the second image, after focus has been locked on the subject in the first image... and he's suddenly out of focus, but the back left of the room is in focus. Take a look at the pots on the left hand side vs. his face. They shouldn't even be in focus.
Please help me save my brain from melting from my head.
Solved! Go to Solution.
03-01-2018 08:31 AM - edited 03-01-2018 09:11 AM
Your technique of zooming in to focus, and then zooming out to shoot is causing your problem. There are very few lenses that are safe to do this with.
A lens that can maintain focus at all focal lengths is called "Parfocal". Your 24-105 is not a true Parfocal and will not maintain focus as you zoom. Some people claim the 24-105 is a good lens for this technique, but it really isn't.
If you were doing this in the past with success, it was just blind luck, or you were shooting with a small aperture like f/11 where focus was not so critical. Or, it may have been because your old camera was not full frame or had fewer megapixels.
Having Canon recalibrate your lens could also have changed it just enough that it is no longer "parfocal" or is not "parfocal" with your new camera. (every camera and lens combo is going to have slight variations)
Here is what Roger Cicala of Lens Rentals .com says about parfocal lenses:
For one thing, parfocal is not an absolute definition. What is acceptable as parfocal to one person in one situation is unacceptable in another. Also, equipment has changed. A lens that might have appeared parfocal on a small sensor shooting standard definition video may be obviously not parfocal on a large modern sensor shooting 4k video. Finally, I’ve gotten older and wiser. Some things I wrote about years ago, I now realize are, um, well, less correct than I would have liked.
The ‘parfocalness’ of a photography zoom has significant copy-to-copy variation.
Cinema zooms are made with a moving compensating group that has the specific purpose of maintaining focus while the lens is zoomed. This group is adjustable to make certain it compensates properly.
Photography zooms do not have anything like this compensating group. Additionally, as Aaron and I often see, when we adjust a photography zoom for the best optical performance we often change the ‘best focusing’ point at different focal lengths.
What’s the takeaway point? No photo zoom is going to be absolutely parfocal. Some may well be close enough for your purposes, but check the copy in your hands on the camera you’re going to use. Remember, when someone tells you a certain photo zoom lens is parfocal, that means their copy on their camera held to their standards.
Roger Cicala and Aaron Closz
03-01-2018 10:04 AM