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IS lenses


DAVID LYDIATE 18 305
17 Jan 2007 8:55PM
Are IS lenses really that good? Somehow the idea of having your lens set at 300mm with a shutter speed of 30secs or over on a night shoot, sounds far fetched?

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keithh 16 25.6k 33 Wallis And Futuna
17 Jan 2007 8:57PM
well.......THEY'RE NOT THAT GOOD!!!
Boyd 16 11.2k 11 Wales
17 Jan 2007 8:59PM
Sounds a bit far fetched to me too. I might be able to hand hold for thirty seconds when I'm dead or frozen but no sooner than that.
csurry 18 9.2k 92
17 Jan 2007 9:00PM
30 secs, I don't think so. 1/30 sec maybe!
DAVID LYDIATE 18 305
17 Jan 2007 10:02PM
I thought as much, just thought I would find out for sure thanks
rbm105 15 22 United Kingdom
18 Jan 2007 5:35PM
Yep, i think thats a bit much.... found something in a book about the IS lenses, says that you can hand hold at a length of 125mm @ 1/30 sec, but in my eyes thats a lot better than 1/125 sec Smile oh how i wish my lenses had them two little letters..........
Brownie127 14 61 United Kingdom
26 Jan 2007 6:12PM
The way Canon put it for their IS system is as follows:

Recommended minimum shutter speed for non IS lenses would be 1/lens focal length (mm). "/" = divided by.

So for non IS example with 125 mm lens 1/125th sec could be your slowest speed. Canon state their IS systems allow speed reductions of 3 (or some 4) stops. So in the above example 3 stops improvement = shooting at 1/20th second.

Now these statements are valid for 35mm format systems only. So, if you use a 125mm lens on say the EOS 350D, that lens has an effective focal length of 1.6 times (125 x 1.6 = 200 mm focal length).

So the truth is that you could hand hold your 350d with 125 mm lens at 1/200th second on a non IS system. Or, 1/25th on a 3-stop IS system.

Barry
Snapper Plus
15 4.5k 3 United States Outlying Islands
26 Jan 2007 6:43PM
One other thing (and I could be wrong!) is that I think some of them only work in one plane (ie landscape format) and don't work when you turn the camera on its side.
nikon5700ite 16 1.8k
26 Jan 2007 9:28PM
I would have thought that if the OIS is working on horizontal information in landscape mode then when you use portrait mode it would work on vertical info?

I have fluked a reasonably sharp [hand-held but elbows on windowsill of car] shot using OIS with a 950mm angle of view at 1/20. It is not what a DSLR user would call sharp but I was quite pleased with it at the time.

To believe in the original supposition one needs to know how the camera was supported.

Another angle to this ... Larry Bolch has written that he handholds, without OIS, better at say 1/4 than at 1/20 ... it must be a mental thing I guess, you take greater care at 1/4 than at 1/20 perhaps.

If it is 1/4 f/5.6 instead of 1/20 f/2.8 the greater DoF gives a better result despite some camera shake ... not sure I believe that supposition Smile
Snapper Plus
15 4.5k 3 United States Outlying Islands
26 Jan 2007 9:50PM
You may well be right. The Canon website says that some lenses have a second mode of IS that allows you to use it when panning, so this is probably where I was getting confused.
barnowl 14 697
26 Jan 2007 10:00PM
Position 1 on the lens activates the IS in both horizontal and vertical planes. Position 2 activates the IS in the vertical plane so that when you are panning the lens does not try to compensate for the movement.

On a tripod the IS should be switched off although apparently later versions of IS lenses are able to sense when the camera is mounted on a tripod. It still uses battery power though and I always turn mine off.

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