Stabilizing Lenses

1147 Views 4 Replies 3 Participants Last post by gordonb, Jul 12, 2010

springle

Discussion Starter · Jul 10, 2010

I've been noting the exhuberance of Yaamon with the use of his 70 mm - 200 mm F2.8 IS II lens.

Alas, I only have one stabilized lens as I purchased most of my glass in the pre-IS era and the lenses cost too much to replace. And they still are useful.

I have been using for most of this year a full-frame camera (5D Mark II) and my stabilized lens is a 120 mm - 400 mm Sigma (not a push-pull Canon).

Recently (about 9,000 photos ago), I switched to a 7D, primarily to obtain more reach. The 1.6 lens factor effectively gives this lens a reach of 640 mm at F5.6. I have a suspicion, but haven't tried to test it experimentally, that the stabilization is less effective when measured in "stops" with the 7D than with the 5D.

Virtually every review of these lenses suggests that they yield a "X" stop improvement WRT shake.

It's never clear if this metric is dependent upon the camera used. Is it the same for a 7D versus a 5D? Obviously one could pick a body, then turn the stabilizing off and on to get an idea of the gain from the stabilization. The question, though, is whether or not this metric depends upon the body chosen.

Moreover, if one adds a teleconverter to the mix, how is the stabilization affected? My intuition suggests that the stabilization is affected by the camera body and the use of teleconverters, but I have no idea by how much.

Similarly when I switched bodies, my 600 mm became effectively a 960 mm lens. My stabilization with this lens is a monopod and I have noticed that I must be more careful when steadying the gear prior to a shot. That is, I think that 960 mm is about the limit (for me) when using a monopod as a stabilizer.

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gordonb

· #2 · Jul 11, 2010

Springle,

I suspect it all comes down to the tried and true rule of thumb in the non IS/VR days of using at least 1/(effective focal length) shutter speed to ensure camera shake does not result in a blurry image.

Like binoculars when viewing through a lense with a higher magnification any shake is amplified more or less linearly (not the square of the distance as one might suppose) with the distance to the object due to the progressively more narrow field of view of Telephoto lenses as the focal length increases.

A smaller sensor results in a narrower field of view as the image sensor gets less of the image circle of the lens. Likewise a teleconverter increases the focal length.

The shake is an angular momentum perpendicular to the axis of the lens. If you draw it out this angular momentum is a right-angle triangle with the long axis along the focal point and the short axis in the plane of focus. The longer the effective distance the faster shutter speed required as the effective length along the plane of focus increases.

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gordonb

· #5 · Jul 12, 2010

springle said:
The question remains: Will, for example, the 70 mm - 200 mm F2.8 IS lens yield the same stop gain for a 5D II as it would for a 7D? Or suppose I attach a 5D II to this lens, along with a 1.4 teleconverter. Do I obtain the same stop gain with the teleconverter as I would without the teleconverter?

Yes.
As you are shooting at a longer focal length with the converter and you will have a light loss (exposure factor) with the teleconvertor you will get the same stop gain but as you lose 1 -1.5 stops with the teleconverter your effective stop gain will be less.

springle said:
WRT Rules Of Thumb, consider the following. I have an old non-IS 70 - 200 F2.8 lens. I don't recall its metrics, but suppose it weighs 20 ounces. I also have a non-IS 200 mm F1.8 which weighs around 100 ounces. Which lens do you think I'd be better able to hand hold (at 200 mm)? Or would photos shot at 1/200th second show the same sharpness, certes paribus?

You could argue that the heavier lens would make you more stable (dampening) or vice versa but those 200mm f/1.8 or f/2 lenses are, indeed, bricks and really throw the balance off as their weight is so more than the body. I guess that's why most people would use a monopod with a Wimberly gimbal mount

springle said:
And who would try to hand hold a 600 mm F4.0 at 1/600th and expect sharp photos?

An NFL linebacker who isn't using Steroids?

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