Canon 70-200 4.0 front focus adjustment

jgoetz4

Good Afternoon Folks,
I was playin' around with the 5D2 and 70-200 4.0 w/Kenko Pro 1.4x tc over the weekend. After shooting around 30 or so pics, I downloaded them. I noticed the af point wasn't in focus in quite a few of the shots. Attached is one example. You can see the tree is in focus next to the actual focus point. The gentleman in the hat was approximately 800' away. Back yard shots of birds about 160' away look similar. Question is, is it time consuming if I adjust the lens with the 5D2, or is it something that can be done relatively quick ? Thanks in advance :thumb
Have a good day
Jim...

ziggy53

You cannot determine front focus or back focus with that sort of image.

These are the steps I take to check a lens for focus accuracy:

1) Basic AF accuracy is best accomplished using a flat target, i.e. a brick wall or other large textured surface. If a camera/lens cannot accomplish this task, it has no chance of passing any subsequent AF tests including real world use. Make sure that the target is at the typical distance for your normal use of the lens, meaning that a long focal length lens that you would normally use for wildlife at a distance should be tested at that same distance for AF accuracy. Always test a lens at least twice Minimum-Focus-Distance (MFD). Lenses rarely do their best at MFD (the exception being true "macro" lenses.)

If a lens shows consistent front or back focusing with the wall test, then use micro-focus adjust technique until you get consistent accuracy. If the particular camera body does not have a micro-focus option, it should be serviced, or the lens should be serviced. If you have consistent results with all lenses then send in the camera. If the problem only exists with a particular lens, it's the lens that needs service.

If the lens passes the wall test, proceed to the next test. If the lens fails the wall test and you cannot gain accurate AF with micro-adjust, send the lens back to where it came from or explore camera issues.

2) A fence line or similar, shot at an angle to the subject. Put a singular strong-contrast target on the top of the middle post and use a single focus point in the camera to focus against the target. This shows focus accuracy and/or how easily distracting for/aft objects influence AF accuracy (compared to the above wall shot). It also shows bokeh tendencies at different aperture settings.

3) A focus target/chart like in the following:

http://regex.info/blog/photo-tech/focus-chart

I do recommend testing these charts at twice minimum focus distance or greater. Most lenses, especially most zoom lenses, do not do their best at MFD. True macro lenses are the major exception.

4) A US stop sign, or similar very high contrast signage, both centered and off center and to the side and/or corner. This can show chromatic errors and off-axis errors.

5) Now just shoot "typical" subjects for your use of the lens(es). It's important that the lens perform correctly for your intended uses.

jgoetz4

Canon 70-200 4.0 front focus adjustment

ziggy53 wrote: »

You cannot determine front focus or back focus with that sort of image.

These are the steps I take to check a lens for focus accuracy:

1) Basic AF accuracy is best accomplished using a flat target, i.e. a brick wall or other large textured surface. If a camera/lens cannot accomplish this task, it has no chance of passing any subsequent AF tests including real world use. Make sure that the target is at the typical distance for your normal use of the lens, meaning that a long focal length lens that you would normally use for wildlife at a distance should be tested at that same distance for AF accuracy. Always test a lens at least twice Minimum-Focus-Distance (MFD). Lenses rarely do their best at MFD (the exception being true "macro" lenses.)

If a lens shows consistent front or back focusing with the wall test, then use micro-focus adjust technique until you get consistent accuracy. If the particular camera body does not have a micro-focus option, it should be serviced, or the lens should be serviced. If you have consistent results with all lenses then send in the camera. If the problem only exists with a particular lens, it's the lens that needs service.

If the lens passes the wall test, proceed to the next test. If the lens fails the wall test and you cannot gain accurate AF with micro-adjust, send the lens back to where it came from or explore camera issues.

2) A fence line or similar, shot at an angle to the subject. Put a singular strong-contrast target on the top of the middle post and use a single focus point in the camera to focus against the target. This shows focus accuracy and/or how easily distracting for/aft objects influence AF accuracy (compared to the above wall shot). It also shows bokeh tendencies at different aperture settings.

3) A focus target/chart like in the following:

http://regex.info/blog/photo-tech/focus-chart

I do recommend testing these charts at twice minimum focus distance or greater. Most lenses, especially most zoom lenses, do not do their best at MFD. True macro lenses are the major exception.

4) A US stop sign, or similar very high contrast signage, both centered and off center and to the side and/or corner. This can show chromatic errors and off-axis errors.

5) Now just shoot "typical" subjects for your use of the lens(es). It's important that the lens perform correctly for your intended uses.

Good Afternoon Ziggy,
Thanks for your response I have a few brick walls, and stop signs I will test the lens on. It's interesting to note that this particular lens never had any issues whatsoever when mounted on my 5D, Xti and 40D. When I would check the focus point in DPP using those cameras, af was spot on.
Again, thanks for your response and the link.
Have a good day
Jim...

jgoetz4

ziggy53 wrote: »

You cannot determine front focus or back focus with that sort of image.

These are the steps I take to check a lens for focus accuracy:

1) Basic AF accuracy is best accomplished using a flat target, i.e. a brick wall or other large textured surface. If a camera/lens cannot accomplish this task, it has no chance of passing any subsequent AF tests including real world use. Make sure that the target is at the typical distance for your normal use of the lens, meaning that a long focal length lens that you would normally use for wildlife at a distance should be tested at that same distance for AF accuracy. Always test a lens at least twice Minimum-Focus-Distance (MFD). Lenses rarely do their best at MFD (the exception being true "macro" lenses.)

If a lens shows consistent front or back focusing with the wall test, then use micro-focus adjust technique until you get consistent accuracy. If the particular camera body does not have a micro-focus option, it should be serviced, or the lens should be serviced. If you have consistent results with all lenses then send in the camera. If the problem only exists with a particular lens, it's the lens that needs service.

If the lens passes the wall test, proceed to the next test. If the lens fails the wall test and you cannot gain accurate AF with micro-adjust, send the lens back to where it came from or explore camera issues.

2) A fence line or similar, shot at an angle to the subject. Put a singular strong-contrast target on the top of the middle post and use a single focus point in the camera to focus against the target. This shows focus accuracy and/or how easily distracting for/aft objects influence AF accuracy (compared to the above wall shot). It also shows bokeh tendencies at different aperture settings.

3) A focus target/chart like in the following:

http://regex.info/blog/photo-tech/focus-chart

I do recommend testing these charts at twice minimum focus distance or greater. Most lenses, especially most zoom lenses, do not do their best at MFD. True macro lenses are the major exception.

4) A US stop sign, or similar very high contrast signage, both centered and off center and to the side and/or corner. This can show chromatic errors and off-axis errors.

5) Now just shoot "typical" subjects for your use of the lens(es). It's important that the lens perform correctly for your intended uses.

Good Evening Ziggy,
I shot a few flat signs and some various walls, with and w/o the 1.4x tc. After looking at the images, they were all in focus, and very sharp without the tc, not as sharp with it, but still in focus. I guess I had one to many cups of coffee last weekend
Have a good evening
Jim...