"Turn off camera when changing lenses"

> When I got my first, second-hand, Pentax film autofocus camera (MZ5n - still going strong), the dealer advised me to turn it off when changing lenses, as he said it might cause problems with the screwdrive autofocus in the lens.

 

Out of academic interest... is there any good logic in this? Does an electromagnet hold the screw drive in place, or something? Just curious - I don't know my Pentax bodies very well. I've turned the AF motor on a D700 by cranking the lens (in my defence, it was a clutch-drive Sigma, and I failed to distinguish "a bit stiff" from "using the AF motor as a dynamo" when I had it in the wrong position - though it would be cool if you could recharge a battery like that). But it wouldn't have made much difference whether the camera was on at the time, as far as I know.

> When I got my first, second-hand, Pentax film autofocus camera (MZ5n - still going strong), the dealer advised me to turn it off when changing lenses, as he said it might cause problems with the screwdrive autofocus in the lens.

 

Out of academic interest... is there any good logic in this? Does an electromagnet hold the screw drive in place, or something? Just curious - I don't know my Pentax bodies very well. I've turned the AF motor on a D700 by cranking the lens (in my defence, it was a clutch-drive Sigma, and I failed to distinguish "a bit stiff" from "using the AF motor as a dynamo" when I had it in the wrong position - though it would be cool if you could recharge a battery like that). But it wouldn't have made much difference whether the camera was on at the time, as far as I know.

 

At least on Nikons, one could simply flip the A/M switch next to the mount, which retracts the screwdriver.

 

Also, I've noticed that there's almost always a bit of "slop" in the AF when a lens is first mounted. If you CAREFULLY turn the focus ring on a screwdriver lens after mounting it, you usually will feel no resistance until the screwdriver slots into place(if you listen, you can hear it also).

 

There again, with Nikons the F4 carries no such warning about turning it off whether or not you're mounting an AF lens. Then again, you won't FIND an "off" switch on an F4-like its predecessor mechanical SLRs, it has a "lock" position. I'm not sure if the lock position does anything more than physically lock the shutter button from being pressed.

> At least on Nikons, one could simply flip the A/M switch next to the mount, which retracts the screwdriver.

 

Indeed. It's actually a slightly annoying feature - in the interests of reducing my odds of scratching the rear element, I'd prefer the lens mount to be as flat as possible, and since most of my lenses are AF-S I'd quite like the screwdriver retraction to be separate from whether AF is on.

 

This might be a moment when I say something stupid, since I don't have my camera with me to check. I believe the AF switch (which is in an awkward place to reach partly because it has to be mechanically linked to the screwdriver) can't be overridden by a separate "I'd still like AF-S autofocus". Maybe it should go on my feature request list. (I really am going to post that soon, although at this point I realise it's mostly going to tell us what we wish Nikon had delivered instead of what they actually give us...)

I always turn the camera to OFF when changing lenses. And the same applies to VR on VR lenses. I believe that Nikon says VR should be turned to OFF too.

Read somewhere that leaving the power on is more likely to attract dust. Whether this is true or not, it is not hard to just do it - i.e., if I remember to do so.

Read somewhere that leaving the power on is more likely to attract dust. Whether this is true or not, it is not hard to just do it - i.e., if I remember to do so.

 

I couldn't see the argument on that for any DSLR, but it certainly wouldn't be the case for the camera that prompted me to start the thread. As I said, both the F100 and F5 carry the warning.

On Nikon VR lenses, you are supposed to park the VR motors before turning off the camera. That is why I turn VR to OFF before changing lenses and before turning off the camera.

As I said, both the F100 and F5 carry the warning.

Maybe it's just happy-go-lucky me, I hadn't worried too much about this. I had used the F100 for years and never really paid any particular attention to it, nor about VR being on or off. If I happened to remember or noticed it, I would turn the camera or VR off before disengaging a lens. Nonetheless it's a good practice to do it, though it is probably not that critical.

Edited July 1, 2017 by Mary Doo

> When I got my first, second-hand, Pentax film autofocus camera (MZ5n - still going strong), the dealer advised me to turn it off when changing lenses, as he said it might cause problems with the screwdrive autofocus in the lens.

 

Out of academic interest... is there any good logic in this? Does an electromagnet hold the screw drive in place, or something? Just curious - I don't know my Pentax bodies very well. I've turned the AF motor on a D700 by cranking the lens (in my defence, it was a clutch-drive Sigma, and I failed to distinguish "a bit stiff" from "using the AF motor as a dynamo" when I had it in the wrong position - though it would be cool if you could recharge a battery like that). But it wouldn't have made much difference whether the camera was on at the time, as far as I know.

The screw driver is attached to a servo motor I would think. This type of motor can be free or holding in place.

The "screwdriver" is coupled by a spring-loaded mechanism and can be easily pushed back into the lens mount without damage. It's automatically retracted by both use of the lens-release button, and by switching the camera to manual focus.

 

So Nikon pretty much have any situation foolproofed as far as the mechanical AF coupling is concerned.

It might be a "good idea", but I've never done it.

> So Nikon pretty much have any situation foolproofed as far as the mechanical AF coupling is concerned.

 

Well, except the "anything sticking out of the mount makes it more likely you'll scratch a rear element" argument (although yes, I know, the screwdriver is slightly rounded), and the "turn AF off without doing weird contortions to reach a button that's in a weird place because of the mechanical coupling" thing. Though that one could have been fixed by putting a second switch under the little finger, at the bottom of the grip. Fortunately I don't hugely mind, because I usually use AF-On back-button-focus anyway, but it still doesn't seem the best bit of ergonomics. No complaint about the mechanics.

 

> It's automatically retracted by both use of the lens-release button, and by switching the camera to manual focus.

 

I actually never noticed the lens release button retracting it. I'll have another look - if it really does that, I'll get into the habit of holding down the lens release when mounting (which would also remove another scratchy protrusion from the mount).

I actually never noticed the lens release button retracting it. I'll have another look - if it really does that, I'll get into the habit of holding down the lens release when mounting (which would also remove another scratchy protrusion from the mount).

It sure does. I have noticed that years ago, and I bought my first AF body in 1989 in the N8008 (F801). Therefore, I have been using Nikon AF SLRs almost from the very beginning of their existence.

I generally do it, but sometimes forget, and it's never caused a problem. Somehow, I never forget to turn the camera off when removing or inserting memory cards.

While it may or may not make a difference in real life, I figure powering down any electronic device before making electrical connections or disconnects makes sense. I don't pull thumb drives or SD cards our of the reader without first "ejecting" them, either. While I sometimes forget, and have not seen any obvious problems, I still think it's a good idea, and cheap insurance against Mr. Murphy.