100-400 mk I tightness ring

[Tsleel2811]

Does anyone know if the **bleep** tightness ring can be moved without turning the focus too? Whoever designed this lens should be taken into a dark room and beaten

[TCampbell · Accepted solution]

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@Tsleel2811 wrote:
I'm having a pretty hard day with this lens. I can't use auto focus at f8. And I definitely can't auto focus on the sun. But I appreciate the input. I just thought there's a way to loosen and tighten without going out of focus. It's kinda pissing me off. Sorry if I seem mad or something. It's aggravating

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It sounds like you might be trying to use the camera to photograph the eclipse.

I'm hoping you have a solar filter for you lens (ND 5.0 is the most common but there are ND 4.0 and even some "18 stop" (which works out to ND 6.3).  You'll need one of those.

Also, exposures on the sun are _always_ done with manual focus and manual exposure (don't use automatic anything).  This is normal -- it wouldn't matter what camera you owned.

As for the lens, the tension ring is for the zoom... not the focus.  But if you change the zoom you will ALSO change the focus because the lens is not 'parfocal' (extremely few DSLR lenses are... 'parfocal' means that once you focus on a subject, you can zoom to another focal length and that original subject will still be focused. ). This is normal and nothing to worry about (it's not a defect.)

If you want to avoid bumping the focus ring.. a few rubber bands usually do the trick.  You can buy commercially made rubber bands designed just for this job... but any wide rubber band of appropriate size will work.  Put the rubber band on the lens so that part of it is on the focus ring and part on the non-moving part of the lens barrel.  This will make it harder (but not impossible) to shift focus... but each time you add another rubber band, you'll increase the tension.  Usually two rubber bands is enough... but you could do three.

[cicopo]

You loosen the tension ring by grasping it & the part diectly above it. Loosen until the barrel slides freely or with some drag (to your liking) & then leave it alone. Zoom in & out using the push / pull motion and let the AF do the rest.

[ebiggs1]

"Whoever designed this lens should be taken into a dark room and beaten"

WHOA !  Sounds like someone is having a bad day.  In its worst function ability it isn't that bad.  The design is well proven and some prefer it over other types.  I never had a moment of trouble with mine and I doubt cicopo has either.

[Tsleel2811]

I'm having a pretty hard day with this lens. I can't use auto focus at f8. And I definitely can't auto focus on the sun. But I appreciate the input. I just thought there's a way to loosen and tighten without going out of focus. It's kinda pissing me off. Sorry if I seem mad or something. It's aggravating

[TCampbell · Accepted solution]

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@Tsleel2811 wrote:
I'm having a pretty hard day with this lens. I can't use auto focus at f8. And I definitely can't auto focus on the sun. But I appreciate the input. I just thought there's a way to loosen and tighten without going out of focus. It's kinda pissing me off. Sorry if I seem mad or something. It's aggravating

---

It sounds like you might be trying to use the camera to photograph the eclipse.

I'm hoping you have a solar filter for you lens (ND 5.0 is the most common but there are ND 4.0 and even some "18 stop" (which works out to ND 6.3).  You'll need one of those.

Also, exposures on the sun are _always_ done with manual focus and manual exposure (don't use automatic anything).  This is normal -- it wouldn't matter what camera you owned.

As for the lens, the tension ring is for the zoom... not the focus.  But if you change the zoom you will ALSO change the focus because the lens is not 'parfocal' (extremely few DSLR lenses are... 'parfocal' means that once you focus on a subject, you can zoom to another focal length and that original subject will still be focused. ). This is normal and nothing to worry about (it's not a defect.)

If you want to avoid bumping the focus ring.. a few rubber bands usually do the trick.  You can buy commercially made rubber bands designed just for this job... but any wide rubber band of appropriate size will work.  Put the rubber band on the lens so that part of it is on the focus ring and part on the non-moving part of the lens barrel.  This will make it harder (but not impossible) to shift focus... but each time you add another rubber band, you'll increase the tension.  Usually two rubber bands is enough... but you could do three.

[Tsleel2811]

The functionality is not the problem. It's a great lens. Just going out of focus is a sensitive issue this close to the eclipse. I cant refocus easily if it goes out of focus all the time.

[Waddizzle]

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@Tsleel2811 wrote:
The functionality is not the problem. It's a great lens. Just going out of focus is a sensitive issue this close to the eclipse. I cant refocus easily if it goes out of focus all the time.

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It is probably to too late to order one, but they sell rubber sleeves that go over lenses to minimize lens creep.  Maybe you could improvise something.  It may not necessarily need to made out of rubber

[Tsleel2811]

I appreciate it alot but none of those are my problem. My problem is as follows: when the lens it at 100mm it's when I'm carrying it in my bag. I'm going to focus on the moon a few days prior to the eclipse. So when I focus on the moon the lens is at 400. I have to tighten and loosen the tension ring accordingly. And that in turn takes me in and out of focus. I'm not saying it's a defect I'm just trying to find a way to able to keep the focus. I think I'll just mark it with a marker. Because none of the tips seem to be good ones for my need. Especially the rubber band. But I appreciate the input. And yes I'm using a solar filter and manual everything

[Tsleel2811]

I appreciate it alot but none of those are my problem. My problem is as follows: when the lens it at 100mm it's when I'm carrying it in my bag. I'm going to focus on the moon a few days prior to the eclipse. So when I focus on the moon the lens is at 400. I have to tighten and loosen the tension ring accordingly. And that in turn takes me in and out of focus. I'm not saying it's a defect I'm just trying to find a way to able to keep the focus. I think I'll just mark it with a marker. Because none of the tips seem to be good ones for my need. Especially the rubber band. But I appreciate the input. And yes I'm using a solar filter and manual everything

[kvbarkley]

I am not sure if you can. Do you have it in manual focus mode?

I for one, would not trust a lens to stay in focus under those circumstances. AT the very least you have a problem with the temperture of the lens changing the infinity focus point, which is why Canon has a "bar" for infinity focus and not a point.

It might be best to just use the distance scale to set a hyperfocal point.