Why shut off IS when on tripod?

Discussion in 'Canon EOS' started by michael.gregory, Dec 25, 2008.

  1. While reading responses to another post in this forum, I came across this in one of them. "Horizontal tracking using the IS can be useful but the IS has to be turned off on a tripod."
    I use my 100-400 for nature photography and frequently have it on a tripod. So I am wondering Why this responder said this? What am I missing?
     
  2. Try it and see... Not sure of the exact technicalities, but the little gyro motors and sensors inside the lens are trying to correct for movement which isn't actually present when on a tripod. I think the effect you notice is the resisual error of the control loop (probably not a traditional closed loop system). Bottom line, do a long exposure on a tripod with IS turned on and your shots will turn out fuzzy. You must turn off the IS when on a tripod. It follows that the IS functionality actually requires a minimum amount of camera shake to take proper effect (i.e. normal hand holding), below which it starts performing negatively. My experience in this regard is with a 5D and 24-105 F4 IS.
     
  3. Yup, the gyro over compansates if there is no or very little vibration. The new lenses have an auto no-IS feture that turns off the IS of there is not enough vibration. Your 100-400 may have that auto-off function... Check the specs... If it does, that is why you don't see a difference.
     
  4. I've always made two assumptions about this, though I admit I've never verified whether either or both are true. (I guess I should put the 100-400 on a tripod some time and try it out...)
    So, my short list of completely unverified and totally speculative explanations includes:
    1. Since something moves inside the lens when IS is activated, moving "stuff" can't possibly make the IQ better but it could make it worse.
    2. The IS system could try to compensate for "something" while on the tripod and introduce its own motion into the image.
    Part of me wonders to what extent either of these might be photographic urban myths...
    Dan
     
  5. Even off a tripod, with super-steady handholding, sometimes you need to turn IS off. I've shot with the 400 just resting against something, and with the IS on, when the shutter snaps, the lens flicks off of what I was focused on. Turn the IS off and voila, no problem. By the same token there could be times when using a tripod, that you might need IS, for example in wind with no weight on the pod...
     
  6. I wonlder why you need to turn it off on the 100-400L IS, but not on the 70-200L 2.8 IS? I haven't acutaly read the manual (though I probably should), but everyone I've talked to (including the sales man at the camera store) said you don't need to turn off the IS on a 70-200L 2.8 IS when it's on a tripod.
     
  7. because IS works by counter movement with movement, if there's no movement to counter. IS becomes the primary movement and will ruin your image. The IS on the 70-200 f/2.8L IS is a newer version, it can sense when your camera is mounted on a tripod by detecting the minimal amount of movement and shuts off itself. Read your manual, they explain it better.
     
  8. The duration of your shutter speed may be a factor in the needed to turn off IS, for tripod use.
    For example, if you had a shaky set-up and used 1/60 sec @ 400mm, IS might help.
    If you had a rock solid set-up and your shutter speed was more than 1 second, I'd certainly turn IS off.
     
  9. If you're shooting on tripod, under high vibration conditions, such as strong trade winds, IS will greatly improve sharpness. I do it all the time. However, if it is calm, the images will often suffer from IS artifacts.
     
  10. J. Harrington and Puppy Face confirm what I've found to be true about tripod shooting with IS - there are times when even a tripod is not steady enough and IS helps.
    I'm thinking of a winter afternoon in gale force winds on the top of the bluff near the tip of Point Reyes. I was sitting on the ground with my camera on a tripod and braced between my legs. The wind was so strong that the vibration affected the photographs. (And, no, attaching a weighted bag to the center column hook would not have helped here at all.) In the end the only solution was to use the tripod, brace the camera and tripod, shoot with IS on, and make a lot of exposures in hopes that one would not show too much vibration.
    [​IMG]
    Dan
     
  11. Can only ditto the above, IS off normally as it does in fact tend to "hunt" , my 300/4 went down and left markedly, but in windy conditions it's useful. What you need to do is fire as soon as the IS has definitely locked.
     
  12. To echo David Bell: "try it and see"
    The reasons behind a lot of these maxims become clear when you take the time to experiment, try it out. And then you're not reliant on second hand info, you see for yourself what's going on.
    I believe it varies with IS lens, some are "tripod sensing", others persist in gamely trying to stabilize a scene that doesn't need stablizing, causing swirling. The longer the shutter speeds the worse it gets.
     
  13. The reason some lenses don't need IS to be turned off even when locked down on a tripod is because they have a built in system that senses lack of movement and turn it off automatically.
    It's not necessarily 'newer' lenses, either. My 70-200/2.8, 300/2.8 and 500/4 all automatically turn off IS when it's not needed. I use the zoom handheld mostly, but the other two lenses are most frequently on monopods or tripods with a loose, gimbal head to track moving subjects. I practically never turn off IS manually. Occasionally I'll get an 'error' like Matthew described happening with his 400mm, but not very often.
    There's a list of lenses that do and don't turn off IS themselves, which I believe is correct, at the link Yakim provided above. The 100-400 is one of the lenses that you have to turn off manually. The 24-105 and 400/2.8 or 400/4 DO should do it automatically.
    Not on the list at the link, I assume the relatively new 200/2 and 800/5.6 can self-sense and turn it off automatically, too. They darned well should, considering what Canon thinks they are worth. In fact, they should cook you breakfast and chaffuer you around.
     
  14. I have recently got 24-105 twice now I've forgotten to switch the IS off when using the tripod. Both times I've struggled to merge the bracketed images due to I assume the IS moving the image. All the images were sharp just would not line up properly.
     
  15. I have the 100-400 lens also. You can use IS with this lens on a tripod in mode 2 IF you are panning left to right or right to left. If you are simply using the lens on a tripod without any planned camera movement you need to turn IS off. Mode 1 is for up and down AND left and right movement (basically handheld shooting). It's all spelled out in the owners manual.
     

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