Is it harmful to continue using an EF 70-300mm lens with damaged IS?

[flamer800]

Hello, hope this is the right place to post.

I have a Canon 70-300mm f/4-5.6 IS USM (Mark I from 2005) and the IS seems to be malfunctioning when the lens is at 70mm. The image in the viewfinder will jump around and jitter, and the lens will also make loud noises. This problem disappears when the lens is zoomed in, or if the IS is turned off.

Video: https://youtu.be/XH9WljNelq8?feature=shared

I don’t mind that the lens cannot be used at 70mm anymore, but I am more worried that continued use will further damage the lens and make it unusable even when zoomed in.

Anyone have advice or solutions?

Thanks!

[flamer800]

Yes, I am pressing the button, seeing it dim, and hearing the sounds it makes as I move. However, I think you were right that it is an aperture problem (that appears at 70mm exclusively for whatever reason.) 

I can see in the viewfinder that during the tests, the aperture seems to be changing. The lighting still changes, and the aperture number in the viewfinder sometimes will rapidly flicker to a different number, even though it is on Manual mode and a set focal length. I think it goes to 5.6 whether or not I am above or below that value

[flamer800]

BTW, my apologies if my responses are confusing or not helpful. The problem isn’t happening every time so it’s difficult to replicate and describe

[deebatman316]

Are you zooming in the lens during the test. That will make the aperture change. Zooming in from 70mm to 100mm will make the aperture change from F/4 to F/4.5 which is normal. But if you’re still at 70mm and the F/# changes from F/4 to F/5.6 without you changing it something is wrong with the lens. If the lens falsely reports the F/ number it throws off the exposure. It can also affect the lens’ IS too. That’s probably why the exposure was jumping around anytime I heard the sound. Can you show a recording of the viewfinder when the F/# rapidly flickers. Does it rapidly flicker on the rear and top LCD screens too. Or just the viewfinder only.

[flamer800]

I spent a while trying to capture the f number changing on camera, and was only able to get a shot of it happening from f/4 changing to f/5.6 with live preview. It also changes in the viewfinder, though. I'd post a video but I can't recreate it consistently.

It happens with most often with rapid movement. I think focusing and zooming out the lens out to 70mm might also cause it happen right after, although I couldn’t get it on video.

https://youtube.com/shorts/hQY-Vi5C6tU?feature=shared

[deebatman316]

I saw in the video it switched between F/4 and F/5.6 without intervention multiple times. Ie you zooming in or out or manually changing the F/ number. Focusing won’t change the selected aperture. Only zooming in will. Because it’s a variable aperture lens. The lens works differently than others. The way your lens is designed is that at 70mm it’s physically longer than it is at 300mm. Your lens is what’s called a reverse zoom lens. As you zoom in the lens physically gets shorter not longer like most lenses do. Most of the time when you zoom in with a lens it physically gets longer. Then when you zoom out it gets shorter. The flex cable in the lens is physically longer at 70mm than 300mm. That’s why the aperture works correctly at 300mm or any focal length longer than 70mm. The flex cable is shortest at 300mm. But at 70mm it’s changing by itself and the aperture motor gets very loud.

[flamer800]

Thanks for the explanation.

Im not entirely sure what you mean about a reverse zoom though?

The lens is longer when it is at 300mm than when it is at 70mm.

I suppose if it is a cable issue like you’ve said then the lens will be fine at longer focal lengths.

 

 

[deebatman316 · Accepted solution]

I know it’s hard to understand. When you zoom in and out. Externally what you see is the exact opposite what happens inside the lens. Hence why it’s called reverse zoom. So even though zoomed in at 300mm the lens looks bigger. Internally the lens is actually smaller and vice versa. If you’re within the return period I would return the lens as it is not functioning properly. If it can’t be returned I would contact Canon to see if they can repair it. Get a quote first BEFORE repairing it. Repairing it can easily exceed the value of it. If they can’t or it exceeds the value. Look into the Canon EF 70-300mm F/4-5.6 IS II Nano USM lens. This lens is a great improvement over your current lens. It also uses a much faster Nano USM AF motor. Compared to the slower cheaper Micro Motor USM which doesn’t support Manual Focus Override in AF mode. Like the new version II lens does. Or you can look at the EF 70-300mm F/4-5.6L IS USM model but it will be much more expensive than the version II model because it’s geared to toward pros. This variant of the lens uses the original fast Ring Type USM AF motor. Focus can be overridden in AF by turning the focus ring at any time.

[flamer800]

Ty for the info and help. I’ll make do for now until I can get an upgrade

[deebatman316]

I’ll caution you though if you go down the repair route. Canon usually stocks parts for 10 years after the product is discontinued. That lens was discontinued back in 2015 or 2016. It’s very likely that they may not have parts for it anymore. I’ve seen some discontinued lenses only have support for 3 years after discontinuation. Canon ran out of parts for that lens quickly because it was a popular lens among professionals.