[agp1337]

This is probably a very basic question. I read recently that when you change lenses the camera should be turned off. I've been taking pictures for over half a century, but I've never even thought about it, and it seems to have caused no harm. Does it actually matter?

[Ole]

Same here. I have never turned my cameras off when changing lenses and I have never had any issues with that approach.

[agp1337]

I've remembered where I read it. Page 32 of the K1 manual:

Attaching a lens

In bold: "Make sure the camera is turned off."

[RoccoStiglitz]

I'm not sure of if it's bad or not but it is weird having the lens off, mirror up, camera on and being able to see the sensor float around.

[Adam]

It doesn't hurt to turn the camera off, so I would recommend doing it, especially if you are using older lenses. But no, I don't think it's strictly necessary in practice.

[jatrax]

I have always turned off the camera, just a habit I got into. But I have forgotten and changed lenses with the camera on with no harm.

Personally I feel it probably is not an issue but I feel better turning the camera off so that is what I do.

[pschlute]

The theory is that if you change lenses with the camera on the charge in the camera/sensor area is likely to attract dust into the mirror box/sensor area.

I have no idea if this is valid or not. But it would make sense at least to switch off the camera if you are using LV where the sensor is exposed.

I always switch the camera off. Why take the risk?

[DeadJohn]

Manufacturer says turn it off, I see no risk in complying, so I follow the direction.

Potential risks swapping lenses while on:
- Electrical spark at lens contacts. Low voltage so I'm not especially worried but why risk it.
- Lens ID gets read at startup. EXIF will have incorrect lens info.
- Shake reduction might not detect focal length correctly, leading to blur.

[gatorguy]

It doesn't hurt to turn the camera off, so I would recommend doing it, especially if you are using older lenses. But no, I don't think it's strictly necessary in practice.

I have an inkling that powered components in the camera may tend to create a dust attracting static charge with the lens removed, at least under certain conditions. I've noticed I tend to pick up "stuff" even on a relatively calm day if I do a lens change while forgetting to turn the camera off, more often than when turning the camera OFF. I really try to make it a point to check now.

Even if the dust I see in the viewfinder isn't on-sensor and appearing in the shots it's still a major irritation to me just seeing it, particularly when it's managed to get on the backside of the focusing screen!!

[Fogel70]

If it where a great risk of damage while changing lenses with power on, manufacturers would make sure the lens release button was also a power switch.

I never turn off the camera if I need to switch lens. I have never heard of failures caused by this.
Why risk wearing out the power switch?

[jddwoods]

Somewhere I remember a recommendation that the camera be turned off when changing lenses. So, I turn off the camera and its a habit now. Occasionally I forget and change lenses powered on. I never had an issue with those power on lenses changes.

[stevebrot]

I first read the advice in 2007 in the K10D manual. There was also the explanation...

Turn camera off before attaching or removing the lens to prevent unexpected lens movement.

When the camera detects lenses having contacts on the mount, it may initiate initial "homing" of the AF mechanism and/or diaphragm. This may not be a good thing if the lens barrel or focus ring is being firmly grasped at the time.

Turning the camera off before swapping lenses help ensure an ordered sequence of lens recognition and initialization.


Steve

[E-man]

I've never read that but I've always intuitively turned the camera off when changing lenses. It just seemed to make sense. That said, Steve's explanation above also makes good sense and to my mind lends credence to what I was doing already.

[SpecialK]

The theory is that if you change lenses with the camera on the charge in the camera/sensor area is likely to attract dust into the mirror box/sensor area.

I have no idea if this is valid or not. But it would make sense at least to switch off the camera if you are using LV where the sensor is exposed.

I always switch the camera off. Why take the risk?

In my K100D days, I got in the habit of turning off the camera for lens changes and it really cut down the sensor dust problem.

[micl161]

My camera is 50% on and 50% off.

I will turn the camera off before change the lens if I remember to do so, but half of the time is other things like finding the lens caps, hood...will make you forget the power on / off, but so far nothing bad happen.