Please help me understand image stabilisation

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Wdiane

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Name
Diane
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Hello
I have a Canon 7D and I am currently using the Tamron 70-300mm VC lens.
With the days still not getting any brighter so that fast shutter speeds can be used please help me with a question I have on Image stabilisation.
Which out of the following would be the best method, I would appreciate others members observations please.
I have found that with the IS switched off in the daytime I do get get more keepers, but which is the best way out of the following given that IS gives 2-3 stops advantage:-

1-Lens used at its widest F stop with IS off
2-Lens stopped down by 2-3 stops (I understand that lenses are at their sharpest this way) and IS on?

By the way I am shooting hand held.
 
I guess this depends on what you are photographing. Shooting wide open limits your comntrol over depth of field. Stopping down 2 stops will certainly let your lens work at ts best, but may reduce the shutter speed resulting in image blur - IS cannot improve blur caused by subject movement. I would recommend that you use IS all the time when hand holding. The only time you may have issues is if you are panning a moving subject, where you may have to change IS mode or switch it off. I am wondering why you get more keepers with IS off, I think almost everyone would say the opposite.
 
I have no idea why I get more keepers with IS off, all I can say is the images are definately sharper when not using it.
 
What are you shooting?

IS can slow down focussing and so if you're shooting fast moving action then you may get more keepers with IS because its slowing down the auto focus.

I shoot a lot of football and never have IS on for this reason and the fact that it won't make any difference as I'm keeping a fast shutter speed
 
IS is useful if *you* are moving not the subject.

With a lot of IS systems if you're trying to track a moving subject it'll make the image less sharp as its trying to "correct" your tracking which is why mine is always off for birds and sport.

One way to see if you do get more keepers with IS vs no IS would be to take an identical scene at a fast shutter speed (over the 1/focal length) with each setting and compare.

The 1-2 stops IS boost you see wont come into play if the subject isnt stationary.
 
Wdiane said:
I have no idea why I get more keepers with IS off, all I can say is the images are definately sharper when not using it.
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This can only be true if you are using it wrongly, such as not engaging Mode 2 when panning, or sometimes it doesn't work well when trying to track diagonally moving or erratic subjects like birds in flight. In situations like that the IS system can attempt to correct deliberate movement and fight against it, making things worse, but otherwise image stabilisation is very reliable and effective.

IS is completely unrelated to lens aperture, other than when using a high or low f/number results in a change in shutter speed. IS is most effective when you're at the margins of hand-holdability, such as longer shutter speeds than perhaps 1/250-1/500sec with a 300mm lens. In that case, it will be very beneficial but becomes increasingly less useful at faster speeds, like 1/1000sec, that are fast enough to freeze camera-shake movement without any help.

Of course, IS has no effect on subject movement - only shutter speed alone can freeze that.

tophatter said:
What are you shooting?

IS can slow down focussing and so if you're shooting fast moving action then you may get more keepers with IS because its slowing down the auto focus.

I shoot a lot of football and never have IS on for this reason and the fact that it won't make any difference as I'm keeping a fast shutter speed
Click to expand...

IS doesn't slow down focusing, and arguably makes AF more accurate by holding the image more steady. However, the system needs to be up and running (by holding half-pressure on the release) before the shutter release is pressed fully as it take a fraction of a second to activate.

At high shutter speeds IS has no benefit, but some action photographers leave IS on anyway as it also stabilises the viewfinder image for easier framing. Others turn it off, if only to reduce battery consumption.
 
#1 Are you happy with the IQ results with the lens used wide openj or nearly wide open?
I am, for my final publishing needs (web or prints up to A4).

#2 What are your consistent (good) hand holding shutter speeds?
If below that I will definately have IS on.

For myself most of the time it is off.
 
I leave IS on unless I am

a) using a tripod

b) panning

or c) shooting something moving fast e.g birds, dogs running etc.

With heavy cameras and lens combinations I suspect only a few people (especially those of my generation) can hand hold without any lens movement. IS helps by compensating for this shaking.
 
Thanks every one for your replies. The IS on the Tamron makes the image rock solid through the viewfinder but when the shutter button is pressed the recorded image is quite often blurred. I try to keep the shutter speed above a 300th when at 300mm and I am always in AV mode. My subject matter is mainly birds and wildlife and maybe 300th is not fast enough to freeze subject movement as pointed out above?
I do miss the sensor shift IS of the Sony Alpha A500 I used to have but when I get it right with the Canon the images ar far superior so its worth persevering for the final result.
I still really cannot understand why having IS on makes things worse, for me, than having it off. I could have saved some money and bought a lens with no IS. Maybe I would be better to buy the Canon 70-200mm F4 non IS lens and cropping the image?
 
Wdiane said:
Thanks every one for your replies. The IS on the Tamron makes the image rock solid through the viewfinder but when the shutter button is pressed the recorded image is quite often blurred. I try to keep the shutter speed above a 300th when at 300mm and I am always in AV mode. My subject matter is mainly birds and wildlife and maybe 300th is not fast enough to freeze subject movement as pointed out above?
I do miss the sensor shift IS of the Sony Alpha A500 I used to have but when I get it right with the Canon the images ar far superior so its worth persevering for the final result.
I still really cannot understand why having IS on makes things worse, for me, than having it off. I could have saved some money and bought a lens with no IS. Maybe I would be better to buy the Canon 70-200mm F4 non IS lens and cropping the image?
Click to expand...

1/300sec is not fast enough to hand-hold a 300mm lens on a crop format camera like your 7D. The 'rule' is shutter speed should at least equal the 'effective' focal length on full frame, ie 300 x 1.6 crop factor = 1/480sec. Some people can beat the rule, others are less steady, and a lot depends on technique, ie leaning against a wall helps, while bending down and strecthing out makes things worse. The camera/lens should always be held with your left hand cupped underneath taking all the weight while you right hand does nothing but steady the camera and operate the controls. Your left elbow should be braced against the side of your chest to form a supporting triangle.

The rule is also a minimum as it does not eliminate shake, but merely reduces the visible effect to acceptable levels. Ideally, shutter speeds should be much higher than the rule, though IS will help considerably and you should be able to get acceptable sharpness at 300mm with maybe 1/100sec. However, 1/100sec is not enough to freeze much in the way of subject movement at all.
 
HoppyUK said:
1/300sec is not fast enough to hand-hold a 300mm lens on a crop format camera like your 7D. The 'rule' is shutter speed should at least equal the 'effective' focal length on full frame, ie 300 x 1.6 crop factor = 1/480sec. Some people can beat the rule, others are less steady, and a lot depends on technique, ie leaning against a wall helps, while bending down and strecthing out makes things worse. The camera/lens should always be held with your left hand cupped underneath taking all the weight while you right hand does nothing but steady the camera and operate the controls. Your left elbow should be braced against the side of your chest to form a supporting triangle.

The rule is also a minimum as it does not eliminate shake, but merely reduces the visible effect to acceptable levels. Ideally, shutter speeds should be much higher than the rule, though IS will help considerably and you should be able to get acceptable sharpness at 300mm with maybe 1/100sec. However, 1/100sec is not enough to freeze much in the way of subject movement at all.
Click to expand...

Thank you but I am even more confused now. I thought the whole point of spending the extra money for an IS lens was so that I could shoot at slower shutter speeds (I know that I cant shoot at slow speeds just slower than without IS). If I still have to shoot at a minimum 480th then surely the Image Stabilistion is not needed which is exactly what I am finding? :bonk:
 
shufflemoomin said:
I've shot concerts at 1/125 for years and suffer from no problems with freezing movement. 1/100 isn't that far off.
Click to expand...

Well that depends on the movement of the subject. The OP is shooting birds and wildlife, and they often move fast. Small garden birds move very fast indeed and are constantly twitching in quick jerky movements. 1/125sec will be no use at all for that.
 
Wdiane said:
Thank you but I am even more confused now. I thought the whole point of spending the extra money for an IS lens was so that I could shoot at slower shutter speeds (I know that I cant shoot at slow speeds just slower than without IS). If I still have to shoot at a minimum 480th then surely the Image Stabilistion is not needed which is exactly what I am finding? :bonk:
Click to expand...

Maybe you're misunderstanding. Image stabilisation reduces the effect of camera movement, camera-shake. And it is very good at that, but has no effect on subject movement.

So if you use 1/480sec as a starting point for successfully hand-holding a 300mm lens without IS, then a two-stops reduction with IS (realistic estimate, could be a bit more) will allow you to shoot at 1/125sec or so.

However, if you also need maybe 1/1000sec to freeze subject movement anyway, then the IS will be no help with that.
 
HoppyUK said:
Well that depends on the movement of the subject. The OP is shooting birds and wildlife, and they often move fast. Small garden birds move very fast indeed and are constantly twitching in quick jerky movements. 1/125sec will be no use at all for that.
Click to expand...

Ah I see and that would maybe explain some of my problem but can I try and clarify my question, I dont think I put it quite right.
At around 500th sec or above IS on or IS off makes very litlle difference the recorded image.
At around 100th, IS is definately better because without it the images are of no use whatsoever but I wouldnt really ever shoot 100th at 300mm focal length as the images are still not what I would call brilliant.
At around 300th sec I consistantly, by a big margin, get better images with IS off than with it on and that is where I am lost as to why? What am I doing wrong where IS causes softer/blurier shots. I dont mean by a massive amount but it is still very noticeable?
 
Wdiane said:
Ah I see and that would maybe explain some of my problem but can I try and clarify my question, I dont think I put it quite right.
At around 500th sec or above IS on or IS off makes very litlle difference the recorded image.
At around 100th, IS is definately better because without it the images are of no use whatsoever but I wouldnt really ever shoot 100th at 300mm focal length as the images are still not what I would call brilliant.
At around 300th sec I consistantly, by a big margin, get better images with IS off than with it on and that is where I am lost as to why? What am I doing wrong where IS causes softer/blurier shots. I dont mean by a massive amount but it is still very noticeable?
Click to expand...

That sounds unlikely Diane, unless it's in panning and similar situations I mentioned above that can confuse IS, or you are not allowing the IS system to engage fully by holding half-pressure on the shutter release, before shooting.

When you're on the margins like that though, you have to play the percentage game. Using IS or fast shutter speeds is no guarantee of 100% sharp pictures, but if you shoot say six frames with IS and and other six without (with a static subject) you'll find that your hit rate goes up with IS on.

Edit: put up an example image. It's usually quite easy to tell if blurring is camera-shake or subject movement.
 
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