Forget about aperture. A better way to think about image stabilization is that it gives you something like the equivalent of bumping the ISO up without incurring any noise penalty (for static subjects).

If you need, say, f/8 to make the picture you want to make (in order to get the right depth of field), then you need f/8. It doesn't matter what the maximum aperture of the lens is if it has to be set to f/8 to get the shot. In order to get the correct exposure, your remaining two variables are the sensitivity of the recording medium (the ISO) and the shutter speed.

As you increase the sensitivity (ISO), you will, of necessity, be reducing the dynamic range of the sensor and increasing the noise. Current-generation digital cameras are bloody amazing in terms of what they can do at high ISOs, but they will create better images at lower ISOs (provided, of course, that the image has been properly exposed). So cranking the ISO up is not always an option.

No matter how steadily you can hold a camera, you aren't perfect. You're not even as good as a tripod. In the 35mm film days, we used 1/(focal length in mm) as a rule of thumb for the slowest shutter speed you could use hand-held with ordinary films. (With high-acutance films like Kodachrome 25, Ektar 25 and Kodak Technical Pan, that would often be too slow.) That assumes full-frame 35mm film images and image enlargements that rarely went beyond 11 by 14 inches. These days, you're as likely to use a crop-sensor camera as full-frame, your sensor can record as much detail as the sharpest films, and if you print, your prints are likely to be larger. So the rule of thumb goes up to 1/(some multiple of the focal length in mm). If your lens is set to a 50mm focal length, then the slowest shutter speed you'd want to use hand-held would probably be in the neighbourhood of 1/125s (unless you are very practiced and steady). Any longer than that and the angular displacement of the image on the film/sensor caused by camera motion would be visible in the image.

Image stabilization means that as long as you are not trying to freeze subject motion, you can use a slower shutter speed at a given focal length. The IS/VR will compensate for camera movement. Somewhat. That means that you can use smaller apertures and/or lower ISOs than you would be able to use if you had nothing but the shutter speed to restrict the effects of camera movement.

If, on the other hand, narrowing the depth of field or freezing action with a high shutter speed is your aim, IS/VR won't help at all. You need a wider maximum aperture, either to reduce the DoF or to let enough light into the camera that you can use a higher shutter speed.

Faster aperture and image stabilization both reduce the effects of camera shake, but in very different ways. A faster aperture lets you use a shorter shutter speed for the same exposure. Image stabilization lets you keep the slower aperture and longer shutter speed and tries to actively counteract the movements of the camera. For completeness, a tripod also lets you use a longer shutter speed by passively counteracting movement.

Because of this, image stabilization is more like a tripod in its effect. Modern systems work reasonably well, and in some situations live up to the claims of 2-4 (or even 5 stops). But I don't think that's exactly what you're asking. The key to your puzzle is in understanding what a stop is, exactly. Reading What does f-stop mean? and What is one "stop"? should help clear this up, but in short, it means doubling or halving the amount of light. For shutter speed, that means doubling or halving the time. In the context of image stabilization, it simply means that you can double your shutter speed by that much under roughly the same conditions and expect the same amount of blur due to camera shake. In fact, What does "N stops" mean when describing an image stabilizer? is 90% of the way to answering your question. For aperture, it means doubling or halving the area of the aperture diaphram, which (for simple mathematical reasons) happens every time you change the aperture stop by a factor of the square root of 2. (That is, the familiar sequence of 1.4, 2, 2.8, 4, 5.6, 8, etc. — it's sqrt(2) each step, rounded for convenience.)

So once you understand all that, the last bit is simple: the difference between f/2.8 and f/3.5 is two-thirds of one stop. Most modern IS systems will provide that amount of benefit easily, even if we assume the 2-4 stop claim to be inflated, and even in non-ideal situations or if you have extra-jittery hands. But, it's not necessarily the same, because you will still need that longer shutter speed, and that might not be the best given subject motion.

Impossible to answer. There are no absolute for any of the elements involved.

Let me elaborate:

• Every lens varies in sharpness as aperture changes. Lenses are sharper a little stopped down from the maximum. This can be anywhere between 1/2 to 3 F-stops, and there are the few exceptional lenses which are sharpest at their widest aperture.
• You will get maximum sharpness at the lenses sharpest aperture. You have to know your lens and select that aperture yourself. No matter how effective is your IS, it cannot make the sharpness better than what the aperture allows.
• The quoted stabilization improvement is an ideal-condition figure. The stabilization you will get from the mechanism will vary from nothing to the maximum quoted depending on how tired you are, the wind, your hand-holding technique and your breathing.
• Different stabilization systems work differently. Having used hundreds of lenses and cameras with built-in stabilization, I can say that some are more effective at higher shutter-speeds and some at lower ones. They also vary with angle-of-view, so as you zoom in or out, the system can become more or less effective.

簡短：

• 如果您使用其他相同的70-200mm f / 2.8非IS鏡頭或70-200mm f / 4 IS鏡頭（請參閱下文）， ，如果您很重視在邊緣照明情況下拍攝手持設備的能力，基於我對這兩種選擇的等效功能的紮實的個人經驗，那麼使用IS鏡頭的整體效果會好得多。這似乎有悖於此處給出的一般建議。鑑於我的回答是基於IS與非IS系統之間特定的實際直接比較，因此我不確定為什麼其他人會說它們在做什麼。

• IS使您能夠以**大量**較低的快門速度補償相機的移動。然後，您可以拍攝一些與給定目標類型配合使用的幸運/靈巧鏡頭。沒有IS，這些聰明/幸運的鏡頭就不可能成功。

• 一站式的改善總是很高興，但它本身並沒有太大用處。如果一站式增益使&閃閃發光的成功與模糊的令人沮喪的失敗之間有所區別，並且/或者取景器的亮度差異令人震驚，則說明您是在其他宇宙中拍照，這裡的答案不適用。

f/2.8和f / 4之間的差異很小，其他所有條件都相同。在許多情況下，一站式差異（2倍光度變化）相對不可見-ISO的40％變化和快門速度的40％降低將恢復相同的照明情況，然後為您提供3或4個IS停止。如果您可以在給定的情況下以1 / 200s的速度手持，則可以嘗試更大一點並管理1/150 s。如果ISO 800正常，則ISO 1200不太差-這兩個給了您1個停止更改的位置-現在您可以使用3個以上的IS停止-參見下文。

問題更重要的是f-stop還是IS。不帶IS的佳能70-200 f2.8與帶IS的f4之間幾乎沒有價格差異。由於該問題已經結束，因此我在這裡發布了我的答案，並附有少量mod以反映這一舉措。

鑑於直接選擇為f / 2.8，沒有IS或f / 4和IS在這裡，我會反對大多數觀點，選擇IS鏡頭。這是基於（對我而言）非常令人信服的個人經驗。

直到最近 ALL ，我的鏡頭一直有效，因為我先是通過美能達產品線升級，然後是索尼DSLr產品線-均具有機內防抖功能，基本上不論價格或年齡如何，都與在任何鏡頭上使用IS一樣。雖然可以關閉防抖功能（主要用於使用三腳架的情況下），但幾乎在所有情況下都啟用了防抖功能，並且對其效果沒有給予太大的關注。我有Minolta 7D和Alpha 5D（內部部件相同），Sony A700和Sony A77 SLT。

然後，我購買了除了A77之外的尼康D700，並將它們一起使用。我期望D700在光線不足的情況下表現出色，（當然）可以。如預期的那樣，當使用三腳架或穩定的拍攝位置時，D700遠遠優於A77。但是在現實世界中的手持低光環境下，當使用非IS鏡頭時，由於A77的體內防抖功能，在許多情況下A77可能會比D700更好。在給定的情況下，如果兩個攝像機的最大光圈均為f / 3.5，則A77可以在ISO 800下運行，而D700在ISO 3200下運行。在這種情況下，D700的快門速度為4倍-例如：1/120 D700僅次於A77的1/30。到現在為止還挺好。但是A77的防抖功能使其具有3到4個檔位的性能優勢。多少取決於感知和情況，但是對我來說最終結果是兩個相機都使用相同的最大光圈鏡頭，並且在兩種情況下都沒有鏡頭內防抖，因此帶有機身防抖功能的A77將在相同的條件下提供出色的清晰度在低照度情況下，噪聲含量相似。這不是世界傾向於告訴你的。

更糟糕的是，如果您不是在比較低噪點和高噪點相機，而是同一相機上只有f / 4與f / 2.8鏡頭，則IS將為您在相同的ISO和燈光水平。可以大大改進大幅降低的能力。

非固定目標怎麼樣？人們總是指出
IS，它僅有助於相機運動而不是主體運動。
這在基本層面上是正確的，但忽略了非常重要的一點。
對於給定的光照水平，在某些情況下，與IS鏡頭或機身配合使用的1/30秒可能太慢，無法容納運動目標。但是，並非在所有情況下都如此。最大可能的照顧，平移，等待運動暫停或方向改變等類似操作“有時” [tm]允許1/30的人工作。如果速度不因“ IS”引起的相機震動而引起問題，則可以嘗試這些小心/運氣/微弱的拍攝，並且有些可以使用。沒有IS，相同的情況幾乎可以肯定會帶來近100％的糊糊。

穩定是有益的，因為它不會在光線不足的情況下移動，即當您的快門速度小於鏡頭焦距時（通常，不同的人有不同的主張），在快門速度下，IS沒什麼區別。

如果您的主題正在移動，則更多地取決於您想要實現什麼創造性。要凍結運動，您需要較高的快門速度，或者您要顯示運動模糊並設置較慢的快門速度。

所有這些情況下，光圈的影響。對於弱光，暗度越大，光圈越大，光的放大率越低，即ISO設置越低。

但是，代價是，光圈越大，焦平面越小。

當您查看鏡頭表時，您會發現最大的圖像清晰度不是光圈全開而是停了2或3檔。因此，對清晰度的最大影響是鏡頭的設計和質量，然後要有可以充分利用它的膠片或傳感器。

如果要使用鏡頭，請問我要去哪裡。 IS則可以在較低的快門速度下減輕相機震動的影響。當然，它有幫助嗎，但這只是系統的一部分。

最後，回答您的問題；

“但是，對於銳利圖像，更好的效果是：更大的光圈或是系統嗎？”

快門速度。如果您的快門速度較慢，無論是否使用IS，如果被攝對象正在移動或手握，都將產生模糊。

使用三腳架：o）