Image Stabilization Canon Lenses

I've had a question lingering in my head since I got my 70-200 F/2.8 II. My understanding is that the image stabilization uses an accelerometer to measure small movements of the camera and then uses that information to move some of the lens elements to maintain the image's position on the sensor.

With image stabilization turned on, it seems like this gets engaged any time you're pressing the focus button. Am I correct to assume it also engages any time the shutter is released and continues to work until the shutter closes? If I focus on a stationary object and take a picture it is engaged. If I take a second shot without refocusing, it must still engage the image stabilization?

s1a1om wrote in post #18546487
I've had a question lingering in my head since I got my 70-200 F/2.8 II. My understanding is that the image stabilization uses an accelerometer to measure small movements of the camera and then uses that information to move some of the lens elements to maintain the image's position on the sensor.

With image stabilization turned on, it seems like this gets engaged any time you're pressing the focus button. Am I correct to assume it also engages any time the shutter is released and continues to work until the shutter closes? If I focus on a stationary object and take a picture it is engaged. If I take a second shot without refocusing, it must still engage the image stabilization?

IS is operating while the shutter release button is half-depressed. I expect that the mechanism locks for the duration of the exposure as the shutter is completely depressed. If the shutter is released only to the half-depressed point, IS operation continues (or re-commenses)...pretty much the same way as autofocusing in AI-Servo mode.

RDKirk wrote in post #18546499
IS is operating while the shutter release button is half-depressed. I expect that the mechanism locks for the duration of the exposure as the shutter is completely depressed. If the shutter is released only to the half-depressed point, IS operation continues (or re-commenses)...pretty much the same way as autofocusing in AI-Servo mode.

I'm using back button focus, so I can release the shutter without passing through the half-depressed point. Which is what made me curious about how the IS is triggered.

s1a1om wrote in post #18546501
I'm using back button focus, so I can release the shutter without passing through the half-depressed point. Which is what made me curious about how the IS is triggered.

IS is still activated by the half-depress of the shutter release.

RDKirk wrote in post #18546507
IS is still activated by the half-depress of the shutter release.

Just pulled out my lens and sure enough, you're right. Thanks.

IS keeps running even after you have taken a shot, and released the button. IIRC it remains on while the camera still has metering active, so you get the four or five seconds that it takes for the metering to shut off. The same applies if you release the button without making an exposure.

Alan

BigAl007 wrote in post #18546829
IS keeps running even after you have taken a shot, and released the button. IIRC it remains on while the camera still has metering active, so you get the four or five seconds that it takes for the metering to shut off. The same applies if you release the button without making an exposure.

Alan

Yes, that's true. For some reason, I only see it on my 24-100. One would think I'd see it on the 70-200, but no.

You can half pres and release the shutter or bbf button while looking through the viewfinder to see how long it's active once you release.

With bbf, it is active as long as you continue to hold the bbf button, as well; regardless of what you're doing with the shutter button.

I can't look right now, but I believe the MkII also came w/ Mode 3 IS which only engages the gyro for the duration of the exposure.