D90: Why "off" when changing lenses?

[doug grosjean]

<p>Hi all,<br>

<br />New to digital SLRs, but old in photography.</p>

<p>In a hurry while photographing my son and other kids unicycling, I accidentally left the camera on when I changed lenses. The owner's manual cautions agains this, implying disaster.</p>

<p>It doesn't seem to have hurt anything... But I'm curious, why the warning?</p>

[chris_autio]

<p>I have heard of this with Canon, but haven't followed the rules myself with my D200Nikon. Everything seems ok after two years! However a new lens of mine, the Sigma 18-200, is supposed to have the OS optical stabilizer turned off while changing lenses.</p>

[JosvanEekelen]

<p>One of the reasons is that the sensor is statically charged when power is "on", resulting in dust on the sensor. This is denied by Canon's Chuck Westphall but you never know. In addition to this it may have to do with the electronics. Personally I don't mind the power switch when changing lenses but YMMV.</p>

[g._v.]

<p>The only reason that I have heard for turning the camera off while changing lenses is that it reduces the dust that is attracted to the sensor. Otherwise I haven't experienced any problems associated with leaving a DSLR on while changing lenses...</p>

[peter_k4]

<p>I think the main concern is that while the lens is off, if the camera is on it's conceivable that you COULD accidentally release the shutter, and something could get in there and scratch the sensor.</p>

<p>I turn mine off out of habit and nothing more. Every once in a while I forget and nothing bad has happened *knock on wood*</p>

[doug grosjean]

<p>Thanks...!!!!!!! I'm very much relieved. Whew!</p>

[neil_califano]

<p>IMHO, I always tilt the camera downward when changing lenses to keep dust out no matter what.</p>

[lex_jenkins]

<p>Gremlins. They're attracted to the ectoplasm vortex emitted by the sensor when the lens is removed.</p>

<p>Semi-seriously, about half the time I forget to turn off my D2H when changing lenses, and the other half the time I'm in too big a rush. Same with my N6006. So far, so good.</p>

[victor_ho2]

<p>The manual somewhere does state to turn off the camera when changing lenses. That said, I have mostly done so. As any habit, turning the camera off has become a natural motion as I switch glass. And when I forget which is not infrequent, the sky does not fall. In fact there are no consequences I've noted. Somewhere I believe it may also say that there is an affect on VR setting of the lens. I assume this is fixed with a quick off and then on of the camera again. In any case it has not affected my shooting.</p>

[MichaelChang]

<p>Camera makers are pretty careful about these things, and in order to remove the warning, they would have to test every possible permutation of lens and state of camera controls and at every increment of lens barrel rotation to see if damage occurred - they can't, and won't, hence the warning. <br /> <br /> There are obvious not-to situations such as a stabilized lens, but even with "normal" lenses, it is conceivable that you can find just the right combination of circumstances that can cause failure, for example, by engaging misaligned contacts under power thus shorting the power supply, or by accidentally engaging a camera control button during a lens change - you'll never know until it happens. <br /> <br /> To be absolutely safe, I would always heed the warning of powering the camera down for a lens change.</p>

[andrew_wales]

<p>My old D70 froze when I popped a lens off while it was switched on, and it wouldn't respond to anything at all. It needed a two week return to Nikon to fix it by swapping out the main board. With every camera since then I've turned the body off every time when changing lenses.</p>

[Matt Laur]

<p>Yeah, well, I <em>try</em> to remember. But I'm sure that I've swapped out lenses on a hot camera - including VR lenses, with the lens's VR set to "on" - at least several hundred actual, real times. Multiple lenses, multiple bodies. So far, I can comfortably say that when my photographs are crappy, it's still because I'm not paying attention to what I'm doing when shooting, not because I've hosed something up while swapping lenses around. It's simply never been an issue. Obviously, it's a good habit to turn off the body while you're messing with it. But I tend to swap lenses in the heat of battle, and am, so far, no worse for the wear. <br /> <br /> <em>Official MythBusters Disclaimer:</em> Do not try this at home, you might die, photos of cats may no longer be in focus, etc.</p>

[emiliogtz]

<p>Back in my college days, had this hardware course, and among many other things we had a talk whether something could be damaged by plugging/unplugging electronic devices while they are tuned ON, like computers, peripherals and the like. Mostly it depends on the device, but the logic goes sort of like this.</p>

<p>A camera nowadays is mostly a computer. Computers communicates with peripherals usually via a bus. Data is exchanged bewtween camera and lens by the means of a bus: the pins in the lens connect to the terminals in the camera body and thus the data exchange becomes possible. Most of this buses, like USB for example, are designed to be hot-swappable, that is, you can connect and disconnect devices while turned on.</p>

<p>As far as I can tell, cameras and their lenses aren't being designed to be hot-swappable. Still, you can change lenses, with the camera turned on, and nothing happens, the lens is recognized and everything goes on as usual. This is mostly due to the fact that the lens is not a self-powered device, the lens gets powered by the camera body. This doesn't mean nohting can happen. Static electricity can build up on the lens and produce a discharge when entering contact with the camera. Static electricity kills intergated circuits. Static electricity alone is a good enough reason to always turn off your camera while changing lenses.</p>

[tri-x1]

<p>My question is, since these DSLRs are pretty much "instant on" why not turn them off to change lenses? If the instructions say you should turn it off, there probably is a good reason.</p>

[james_symington1]

<p>I don't think I ever turn my cameras off when changing lenses - or if I do it is kind of unconsciously. I don't think it makes the slightest bit of difference.</p>

[JAPster]

<p>Because both the camera body and the lens (if its a modern CPU lens) have sensitive built-in IC's (intergated circuits) and electronic circuits that can get zapped by things like sudden unexpected voltage and current surges and spikes, not to mention ESD (electro-static-discharge) from your hands. When the camera is ON, all these circuits and IC's are 'live' and 'active', so disconnecting and reconnecting lenses and such could indeed cause disruptions to the types of signals that are expected on the various contact points, and introduce abnormal voltage or current levels or extreme noise that might damage the internal circuits. It's the same principle as being told to turn off everything on the computer before you hook up and install a new peripheral.</p>

[carl_becker2]

<p>I have forgotten to turn off the camera for the evening let alone turn it off for a lens change. So far three different bodies and no problems, knock on wood. I also do alot of changing as I mostly use primes.</p>

[rob_c3]

<p>Had I not read this thread, I probably wouldn't even know to turn off my camera during lens change. I think its better to just err on the safe side and turn of camera during the transformation.</p>

[david_c.1]

<p>I had a friend once who I showed my new DSL camera to. For God knows what reason, he removed the lens before turning off the power on the camera. It wasn't like he had another lens he could have tried on or anything. I was infuriated by this, not knowing of the hidden the damages his action had brought onto both my new camera and lens. I came to the likely conclusion that his utter disregard for the valuable possessions of others came from pure spite and malice intent. Needless to say, I've not spoken to that person since. </p>