KoniOmegaflex Loc: Central KY

I have a Canon EOS 5D MKII. I'm having a problem with autofocus using a 28-135mm IS USM lens.
It only happens occasionally and it could be when taking a photo of a group or an object. It isn't limited to soft material, low light, or any of the usual suspects. I'm aware that with a Canon, the autofocus problem would be with the lens. Even happens when I switch focus point to hit a hard object. I typically use only one focus point.
I'm aware that the lens is no longer produced. I found a new lens on Amazon (from a third party) and one at Park Avenue Photo (that I wouldn't think of buying from.)
Any thoughts appreciated. Thanks for reading.

mwsilvers Loc: Central New Jersey

Are you shooting in raw or jpeg? Please upload some high resolution examples of the problem. Use the "store original" check box before attaching the images, and make sure they contain EXIF information.

KoniOmegaflex Loc: Central KY

I usually shoot in raw but when auto focus didn't lock, I just switched to manual focus. I don't have any o ut of focus shots to share. Thanks.

speters Loc: Grangeville/Idaho

I have no idea what you mean by hard or soft object/subject? Are you staying within your MFD range?

CHG_CANON Loc: the Windy City

It is an old lens, but it's hard to say what would be the problem from your description. A single point set on some aspect of the image should focus, period. An example image would help better explain the issue.

A lens to consider is the EF 24-105mm F/3.5-5.6 IS STM. You'd give up some length, but the would be a major jump in IS capability and overall sharpness.

KoniOmegaflex Loc: Central KY

In range definitely. By hard I mean an edge or something metallic; soft, a piece of cloth. Hard could even be a leaf. Thanks. I guess it's just an old lens and needs to be replaced.

KoniOmegaflex Loc: Central KY

Thanks for the suggestion of the 24-105. When the auto focus doesn't lock, there is no image to share. I just switch to manual focus and take the photo. Thanks again for the help.

joer Loc: Colorado/Illinois

The lens is old and so is the 5DII. Mechanical devices tend to wear out.

AzPicLady Loc: Behind the camera!

I've had a 28-135 since film days. It is my go-to lens and is always on my 5D MIII. I've never experienced the problem you describe except when I'm actually too close to my subject. I don't know what the minimum focusing is on that lens, but I've found it occasionally! Other than that, it is dead on every time. The only error is in the camera. When I had eye-controlled focus, it never failed. Without that, sometimes it chooses the wrong thing (like choosing the branches instead of the bird). Then I switch to center focusing point and make sure it's on what I want. I have yet to find a lens with that focal length that beats the one I have.

amfoto1 Loc: San Jose, Calif. USA

I've used several copies of the EF 28-135mm over the years.... presently have two of them. One of mine currently has a problem with the aperture, but I've never had an issue with the focus on any of them. It's fast "USM" and very reliable, very accurate.

Have you cleaned the lens contacts? Sometimes focus problems are solved by using a little isopropyl alcohol (plain "rubbing alcohol" works fine), dampen a clean, lint free cloth with a few drops and carefully wipe the contacts (keeping off the optics of the lens). Often it's oils... maybe finger oils or oil from the lens or camera lubrication.... that's on the contacts, causing disruption of the low voltages the camera and lens use to communicate. The alcohol is the best way to remove oils (don't use a pencil eraser, such as is sometimes recommended.... erasers are made from vegetable oils and will merely smear any oils already on the contacts).

It could be an internal problem with the lens, though I don't know of anything common to the 28-135 specifically. Many lenses use a ribbon cable from the contacts to the focus motor, aperture, etc. Those cables can fail over time and with use. It also could be the focusing motor going bad.

Do other lenses focus fine on your camera? Is it only the 28-135 that has problems? If so, that points to the lens being the source of the problem. Unfortunately, it would probably cost more to fix it than to replace it. 28-135s are pretty much a bargain on the used market. Is there any way you can test your lens on another camera, to see if there is similar problem? If so, that would pretty much narrow it down to an issue with the lens.

But, just in case, also inspect the "pins" inside the camera's lens mount, which correspond to the contacts on the rear of the lens. Those pins are spring loaded... Gently press each one and watch if it springs back into position correctly, doesn't get "stuck". It's rare, but can happen and cause issues with focus or other lens functions.

Be a little careful with both the contacts on the lens and the pins in the camera. Both are gold plated and you don't want to damage that. Never use anything abrasive to clean them. Gold plating is used because it's ideal to insure electronic communication between camera and lens. Gold doesn't oxidize the way other metals can do.

Finally, how are you setting up focus on the camera? Are you using One Shot, AI Servo or AI Focus? One Shot is only usable with stationary subjects. One Shot stops and "locks" as soon as focus is achieved (giving "Focus Confirmation"). If the subject is moving and distances between you and them is changing, with One Shot there's a good chance that a lot of images will miss focus.

AI Servo is used for moving subjects. It achieves focus, then continues to update and maintain focus (no Focus Confirmation)... The 5DII isn't the best camera doing this, particularly with anything other than the center AF point. That's the only higher performance "dual axis" type of AF point in the visible array. The other focus points are less sensitive "single axis" type.

5DII (and the original 5D) does have 6 invisible "Assist Points" which can be enabled in the menu. The Assist Points are closely clustered around the center point, sort of making the area delineated by the Spot Metering circle act like one big AF point. Two of the Assist Points are higher performance "dual axis".... the other four are single axis. But you can't select or see them AND THEY ONLY WORK IN AI SERVO MODE.

AF Focus isn't really a focus mode at all. It's automation where the camera is supposed to decide for you whether or not the subject is moving, then switch to use the correct mode: either One Shot or AI Servo. Frankly, I experimented with it many years ago and stopped using it. I found it caused a slight delay, sometimes didn't choose correctly and also sometimes failed to switch modes if a subject stopped or started moving after AF had started running. It might be a clue that the most "pro-oriented" Canon models don't even have AI Focus... they only have One Shot and AI Servo modes. Maybe it works better now on newer models. I wouldn't know because I got so much better results using the other modes... especially AI Servo in combination with Back Button Focusing... that I haven't tried AI Focus on more recent models. I don't think I've ever used it on my 5DII and know for certain I haven't on 50D, 7D, 7DII.

Your best focusing results will be using either One Shot or AI Servo, depending upon the subject.... and by pre-selecting a single AF point... especially the center point on the 5DII. The other points you can select on 5DII are slower and more likely to hunt or miss focus. Even so, it's not a fast focusing camera. I don't use mine very often for sports or wildlife. The AF system on my 7DIIs... and 7Ds, 50Ds previously.... are MUCH faster and better tracking movement. (5D Mark III got a much improved AF system... Unfortunately, the 5DII's was unchanged from the original 5D's.)

travisdeland Loc: deland, FL

Probably going to be an issue with the flex circuit inside the lens-or the AF motor, itself

KoniOmegaflex Loc: Central KY

Hi amfoto1, thanks for the time and effort and sharing your expertise with me. In a nutshell, I was shooting a Canon 5d MKII, 400 ISO, JPEG + RAW, 1/160, F/8, single focus point, shooting a small group of people in an outside setting. I tried a couple of times. Lens failed to lock twice so I switched to manual focus. A short time later, I was able to shoot this same small group using auto focus with no problem.
Before posting this problem, I tried the same lens on another body and another lens on this body with no problem. I used a silk like lens cloth to wipe the contact points and I checked the spring loaded pins inside the lens mount. The lens worked fine, no problem. I just now put a couple of drops of 91% Isopropyl alcohol and wiped the contact points again. It works fine with good light and very low light.
I thought I might have to buy a replacement. Of course I'm sure you know the lens is no longer produced. I found one on Amazon from a third party seller or associate "Camera Warehouse" that I have no knowledge of. I found another one at Park Ave. Photo in Manhattan but many negative reviews have convince me that is not a good option.
I know that an intermittent problem is the hardest one to find.
I guess for now I will just keep using it until I get a firm fail.
Thanks again for your knowledge. I appreciate it very much.