The order in which a TC is attached to a lens question...

I was reading a review of the 400 DO II by Bryan at the-digital-picture. When he discussed using the lens with a TC, he said this...

Note that Canon Europe CPN has stated "To get the best out of the new lenses and the Mark III extenders photographers must ensure they attach the extender to the lens first, before attaching the whole unit to the camera. This ensures that the combined lens information is transmitted correctly to provide the optimum image quality and focus performance.

Now Canon's manuals tell users to change lenses with power off. If so, why would the order that a TC is attach matter? Power is off.

I own the 300 f2.8 IS II and 1.4xIII, 2xIII. I always power off before inserting or removing TCs. A few times I have done so with power on, by mistake.
Nothing bad happened, and I did not notice a performance decline.

I can think of two reasons why the order of TC attachment is important. The first one is a wild guess on my part...

Some electronic circuits contain a capacitor to hold a small charge. Perhaps the lens or TC also has one. If so, the order may matter, even if camera power is off.
Sports or action photographers my want to attach a TC without turning off the camera. In this case, the order may matter also.

What's your take on this?

I never turn the camera off when changing lenses.

But I do observe the instructions about attaching the TC to the lens first. Plus, you are supposed to remove the TC in the reverse order. Not sure how that would affect the camera's ability to transmit information.

Another thread recently regarding the same topic. I often power off camera before changing lenses, but not always. I totally ignore the recommendation to attach TC to lens first. I do what is easiest. It's much easier to attach body and TC to a larger lens where you are attaching body to lens. ie when the lens is much bigger and heavier than the body, I consider it mounting body to lens.

Define 'power off'. It's not a light switch. Turn power off when camera is writing to card and it will finish writing to card. Then remove card then put it back in. Little red light comes on. Remove lens then remount. Little red light comes on. In modern Canon bodies if the battery is in it will supply power to the clock. (Older bodies had a clock battery). With power switched off, no button on the camera will result in the camera doing anything. The card door has a micro switch and will result in the camera doing something if the battery is in and has some charge. There is no switch for the lens so it's the lens contacts and the body contacts that do the job of a switch and cause the camera to do something.

Searching problems for Canon camera gear, or any manufacturer, will uncover every problem imaginable and some unimaginable, eg brand new camera unboxed and found to smell like human body odour. You won't find any problems attributed to mounting TC to lens instead of body or changing lens with camera power on. It is possible there have been problems, eg lens fault develops and only reveals itself sometime after one of those actions but EF system is decades old and logically it would have been realised by now.

The power is never really off as long as the battery is installed. You can use a volt meter on the camera’s lens mount contacts if you want to confirm it.

msowsun wrote in post #18863332
The power is never really off as long as the battery is installed. You can use a volt meter on the camera’s lens mount contacts if you want to confirm it.

Yup. A much easier test is to remove and replace the SD card. You will notice the camera shows read/write activity when the door is opened or shut.

yeah I figured turning off the camera was BS thought up by the lawyers. and the order of tc attachment wafts of bull dung too

I don't worry about the order or turning off the camera. Never had a problem.

Practical experience tells us that the order of attachment does not matter. I agree with that.

But it still makes me wonder why Canon would say the order is important for optimum image quality and focus performance.
I would like for Canon to provide a technical reason for saying this. When time permits I'll search Canon's site for an explanation.
I have a feeling I won't find it.

Perfectly Frank wrote in post #18863972
Practical experience tells us that the order of attachment does not matter. I agree with that.

But it still makes me wonder why Canon would say the order is important for optimum image quality and focus performance.
I would like for Canon to provide a technical reason for saying this. When time permits I'll search Canon's site for an explanation.
I have a feeling I won't find it.

They have already provided the explanation. It's just that many don't see issues (usually!) when we ignore the advice.

Archibald wrote in post #18863988
They have already provided the explanation. It's just that many don't see issues (usually!) when we ignore the advice.

Where? Have a link?

Perfectly Frank wrote in post #18864191
Where? Have a link?

Post number 1 in this thread.

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Perfectly Frank wrote in post #18862979
What's your take on this?

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That none of this matters at all.

That you can switch lenses with the power on and you can put stuff on in any order you feel like, and it will never - no not once - ever have any affect on anything.


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Archibald wrote in post #18864227
Post number 1 in this thread.

Nope, not a technical explanation, just a procedure.

Perfectly Frank wrote in post #18864553
Nope, not a technical explanation, just a procedure.

In your earlier post you said Canon Europe explained that it is a data transmission issue. That is not a procedure, it is a technical explanation.

From Canon Europe:

Perfectly Frank wrote in post #18862979
... This ensures that the combined lens information is transmitted correctly to provide the optimum image quality and focus performance.

Fortunately, it doesn't matter to anything.

I wanted some thing in more depth. But I agree with you, it doesn't matter.