Railfan Technology > Canon 100-400mm Autofocus Problems

I have a Canon 100-400m lens that has great difficulty autofocusing while shooting at longer distances.
It has problems jumping around trying to find a focus point.
All suggestions welcomed.
Phil

I'm guessing you are letting the camera choose from any of its maximum 9 or 23 or 61 AF points rather than 'locking it down' to just a few possible focus points. That's one of the major problems when shooting in Auto mode. The AF will most often choose the closest item to focus on, perhaps a tree leaf 20 feet away, or a nearby building rather than on the train that's 100 yards away. For what it's worth, I've set my camera to use only the center focus point. I rarely miss focus as a result.

Also, if your camera has such AF settings, ensure you have set the AI Servo image priorities to either the middle or 'focus' settings. Also set the 'lens drive when AF impossible' to OFF, otherwise your lens and camera will 'go nuts' trying to focus when it cannot do so, such as quite low lighting.

If memory serves me, the Canon 100-400 also has a multiple Image Stablization setting switch. Perhaps that's in the wrong position for your shooting. It's also possible that you've inadvertently moved the AF switch to MF. That one 'got me' a couple months ago.

Also, rule one for all Canon cameras...if it moves, use AI-SERVO. No exceptions! Although ONE SHOT may make sense, during the fraction of a second between focus lock and shutter open in ONE SHOT, the train moved, and will be slightly blurred as a result. AI-SERVO keeps the focus lock on the moving subject. The only time I use ONE SHOT is to photograph buildings, bridges, and distant scenery.

Lastly, if you're 'just a tad' out of focus, did you micro focus adjust (MFA) that lens to that camera? One of the things I learned was to perform MFA at approximately the shooting distances I use the lens for. The higher-end Canon cameras also permit separate MFA settings at the wide and tele ends of their zooms.

Thanks for the very useful info.
Another friend mentioned the AI Servo setting, which I will try.
That may do the trick.
How do you do the MFA?
Phil

philhoov Wrote:
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> Thanks for the very useful info.
> Another friend mentioned the AI Servo setting,
> which I will try.
> That may do the trick.
> How do you do the MFA?
> Phil

What body are you using? Micro Focus Adjustment is only available in some bodies. It is not recommended that people mess with it, unless they absolutely know what they are doing.

Posted from Android

I'm running a Canon 6D.
Never heard of MFA.
Phil

Micro focus adjustment is adjusting the the in camera focusing mechanism very slightly to compensate for being a tad front- or back-focused. In other words, the sharpest plane of focus is a little in front of or behind where it should be. Lenses and camera bodies alike are manufactured to specific tolerance 'ranges' which may result in slightly mis-focused images. Unless you are a 'pixel peeper' like me, you'll not be aware of the minor mis-focusing. As you are paying for the sharpest glass and high quality full frame sensor (I have a 5Diii and L glass), it makes sense (to me) to get the absolutely sharpest results possible from it. It should be noted that every lens on every body will give different results and must be individually MFA'd. IE, MFA of lens A on body A will not be the same as lens A on body B, or vice versa.

To my knowledge, there are 3 'general' methods of performing MFA: Dot Com, (semi-) automatic, and fully manual (backward-slant ruler method). Each has their benefits and drawbacks as far as I'm concerned.

As the Dot Com method came about after I did my MFA 'exercise', I've never used it and cannot comment on how good/bad it is.

I first used semi-automatic online purchased software that had me print out a 'target' and tape it to a vertical surface. With camera tethered to my computer via USB connection, the software would automatically fire multiple shots and automatically adjust the camera MFA for that lens. Except for the 5Diii, which it could not automatically set the camera, and I had to make the choice myself of 'sharpest photo'. I thought I had done everything correctly with all 4 of my L lenses, but in my opinion, the 16-35 and 24-105 were less sharp afterward, in looking at the results of a shoot. I blame it on having the target closer to the camera than my typical shooting distance with those lenses.

So, I found an inclined ruler MFA tool on ebay and used that outdoors from about 50 feet away and was very satisfied with the results. The process I use is to take shots at -10, -5, -3, -1, 0, +1, +3, +5 and +10 MFA settings and view the results blown up on my computer. If need be, I can take 'middle' settings once I figure out the 'ballpark' to use. Zoom lenses get separate wide and tele MFA settings (5Diii, maybe 6D, too). It's slow, it's tedious, but it worked for me. As my 24-105 went to Canon for the well-documented internal cable failure and they replaced the entire focusing mechanism, I had to re-MFA the lens with my camera. I dropped my camera with the 16-35 mounted and 'split' the lens open, and after getting it back from Canon, I still have to re-MFA that one, too.

Here's a quick Google on setting MFA in your 6D: https://www.google.com/search?q=micro+focus+adjustment&ie=utf-8&oe=utf-8#q=canon+6d+micro+focus+adjustment

Or, just Google: Canon 6D Micro Focus Adjustment



Edited 1 time(s). Last edit at 05/17/17 06:15 by BRAtkinson.

Thanks for the info on MFA.
Sounds more technical than I want to get into.
Phil

Hi Phil,
This sounds like getting your 100-400 lens setup correctly is what's needed.. Mine works great and is super fast in auto focus .

Things to do:

Make sure the Camera firmware is up to date Firmware 1.1.1 at least

Make sure the Lens Aberration has been setup

Use Al-Servo all the time video or still

Set the lens Focus Distance Range to 6.5, That way it's only trying to focus from 21ft to Infinity

Set Stabilizer mode to 2

If you are using a filter on the lens, make sure it's a circular filter and not linear

and as BRAkinson above said, use the single center point focus setting

See how that all goes, if its still a problem, I'd be glad to discuss it with in private message of via phone

Dave
Mount Joy, PA



Edited 1 time(s). Last edit at 05/18/17 05:03 by video7105.

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Thanks for all the info.
I will make those recommended changes and see if they help.
Phil

Many thanks to fellow TO members BRAtkinson and video7105 for your tips on my autofocus issues.
I updated firmware and made the various changes to the lens and camera settings, but that didn't fix the problem.
So, I called Canon Support and got an excellent tech support guy who confirmed that everything was set correctly.
His final suggestion, before giving up and sending the lens in for repair, was to polish the brass contacts on the lens with a microfiber cloth.
I did, and afterward, noticed a couple of small, dark smudges on the brand-new microfiber cloth.
That seems to have fixed it, based upon some basic testing it in front of my home while on the phone to Canon Support.
Next step is to get it out into the wild (railfanning) and confirm that it's now working properly.
I hope to do that this afternoon.
I may still try doing the MFA, but doubt that I need to do that.
Phil

My $0.02 worth... I would check the focus points. I have a 100 - 400 mm MkI and shooting trains (or planes) I use a single point focus and have little problem with getting a good focus quickly. The only caveat I would add is low light shooting, it sometimes has an issue but I think that's more to do with the camera than the lens. Good luck!

James Nelson
Thornton, CO
www.flickr.com/mojaveflyer

Thought I had it working until i got out and chased trains yesterday.
Everything I did still didn't fix it.
It still struggles to focus at longer focal lengths and jumps/clicks while trying to settle on a focus point.
It also does that set on One Shot.
I've updated firmware, set the camera to AI Servo, set single center focus point, lens is set to autofocus, stabilizer on and set to mode 2 and 6.5m to infinity.
And, I cleaned the contacts.
Two Canon Support techs say that is all correct.
I will be sending it to Canon Monday.
Thanks to everyone for your tips.
Phil

"while trying to settle on a focus point"

As others mentioned, choose a single focus point. What you are experiencing is operator error.

JW

Thanks for your input.
Single-point focus is set and confirmed.
Phil

After confirming that all settings were correct (during three calls to Canon Support last week), Canon asked me to send the lens to them.
Turns out that it wasn't "operator error", as stated by some on this thread.
Canon Repair has confirmed that the lens has a long-distance focusing issue and will be repairing it.
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If you're dealing with Canon Repair, don't accept their quoted price without asking for a better deal.
I got them to reduce their $285 quoted repair cost to $190 after working my way through two people with more authority.
My lens, while 7 years old, had been used little since new, and has led a very pampered life.
They took that into account and worked with me for a better repair cost.
Phil

You purchased this 7 years ago and just now realized there was an issue? - OR - You recently purchased it used and someone told you it was pampered??
Those pesky details.. they are often important to share when seeking advise. For example - "I bought a used Canon 100-400L version I and .... see sample image"

From the brevity in your original post it was assumed this lens was new. Many inexperienced with photography in general and especially those new to long telephoto lenses fail to understand the mechanics of use. Problems attaining focus are the #1 issue in these situations.

JW

I bought it new in 2010 for a trip to Yellowstone.
Seldom used it afterward, but noticed it didn't seem to focus correctly at long focal lengths.
I blamed myself for that and never bothered to look into it.
Canon Repair has diagnosed defective focus and will repair it.
Phil