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05-20-2010, 12:00 PM   #16
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QuoteOriginally posted by junyo Quote
Don't usually bother to shut off, haven't had an issue through a couple of DSLR bodies, but maybe I'm just lucky.
+1....but, due to this behavior I try to avoid SDM lenses like a plague.


Last edited by pcarfan; 05-20-2010 at 07:27 PM.
05-20-2010, 02:01 PM   #17
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I rarely turn my K10 off, it's set to shut down after a few minutes so that's how I leave it.
I certainly don't bother to switch off to change lenses.

Never had a problem.
05-20-2010, 02:10 PM   #18
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I agree the warning in the manual probably has to do with the possibility of AF engaging while you are trying to remove the lens. Not that it would all by itself, but it could if you accidentally hit the shutter/AF button. That doesn't concern me, but the *possibility* that there is something to the oft-reported claim about static is all the reason I need to do the shutoff anyhow. Plus it gives the camera an excuse to run the dust removal when I turn it back on - lens changes are basically the *only* time my camera ever gets turned off. And by being in the habit of always turning the camera off for lens changes, I never forget to update the SR focal length when mounting a manual lens.

So, I'd say there is not likely to be any real *harm* in not turning the camera off, but there are enough small reasons to turn it off that I really don't see any reason not to just go ahead and turn it off.

Last edited by Marc Sabatella; 05-21-2010 at 09:37 AM.
05-20-2010, 06:43 PM   #19
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Could the reason for powering off the camera also be related to charges passing to the wrong contacts in the lens?

From my understanding, the lens has a chip & electronics to transmit lens info (including model, aperture, distance) to the camera. Sufficient charge in the wrong direction could potentially do damage - to either device.

Although to be fair, over the years I've handled enough CMOS devices without earthing and not fried one.

Cheers

05-20-2010, 09:26 PM   #20
hcc
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QuoteOriginally posted by MoiVous Quote
Could the reason for powering off the camera also be related to charges passing to the wrong contacts in the lens?

From my understanding, the lens has a chip & electronics to transmit lens info (including model, aperture, distance) to the camera. Sufficient charge in the wrong direction could potentially do damage - to either device.

Although to be fair, over the years I've handled enough CMOS devices without earthing and not fried one.

Cheers
Chris,
I am glad that you re-direct the discussion in the right direction. I would be most concerned about the contacts and any damage that could occur during the switch.

I initiated the thread because I am puzzled by the limited 'warning' in the Pentax instruction manual. The outcomes of the thread suggest, to date, that there is no agreement/consensus among Pentaxians. I am puzzled by this lack of consensus...
05-20-2010, 09:48 PM   #21
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If you are waiting for consensus on this issue, don't hold your breath. You aren't going to find consensus for anything.

As for shorting things out with the contact pins...

(1) Features and Operation of the Ka Mount
The pins are not active (well, I guess the * pin activates, but it isn't powered or anything). They won't short anything.

(2) The interior pins for power zoom or SDM are probably safe. If I were designing the lens, I'd shut them off until * connects. Or something else that is safe.

Anyway, you aren't going to short much by goofing with the contacts. Worst case is your camera thinks a different lens is attached.
05-20-2010, 10:52 PM   #22
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QuoteOriginally posted by hcc Quote
Chris,
I am glad that you re-direct the discussion in the right direction. I would be most concerned about the contacts and any damage that could occur during the switch.

I initiated the thread because I am puzzled by the limited 'warning' in the Pentax instruction manual. The outcomes of the thread suggest, to date, that there is no agreement/consensus among Pentaxians. I am puzzled by this lack of consensus...
Consensus is a rare thing indeed - particularly when we don't have all the facts... - but I think your original question still needs resolution.

QuoteOriginally posted by Aegon Quote
If you are waiting for consensus on this issue, don't hold your breath. You aren't going to find consensus for anything.

As for shorting things out with the contact pins...

(1) Features and Operation of the Ka Mount
The pins are not active (well, I guess the * pin activates, but it isn't powered or anything). They won't short anything.

(2) The interior pins for power zoom or SDM are probably safe. If I were designing the lens, I'd shut them off until * connects. Or something else that is safe.
The KA mount is the original basic AE mount, however, the KAF mount (see Features and Operation of the Kaf Mount) added electronics in a 7th pin providing serial communication with links to a ROM chip in the lens (by implication).

From Boris' KAF page:
QuoteQuote:
Digital Communication

The KAF mount features the same six electric contacts as the KA, and thus remains fully compatible with the older mounts. However, in addition to those (electric) contacts, it features a seventh electronic one. Using a yet-unknown serial protocol, the body uses this contact to communicate with a digital chip contained inside the lens housing. The chip provides at least the following information:
  • Focal length of the lens. This allows more efficient flash operation as well as calculating the longest hand-holdable shutter speed. In addition, it is also one of the parameters taken into account when the body is in one of the "smart" picture modes and has to choose a program curve. Prime lenses provide one fixed value, while zooms provide an approximate value that changes as the focal length changes. The focal length information is precise enough to distinguish between 35, 28 and 24 mm lenses, as evidenced by F-flashes that trigger a warning when they cannot cover the field of view of the lens.
  • Lens-to-subject distance. This is used by the more advanced bodies for calculating if the flash is powerful enough to illuminate the subject that is in focus. In addition, this is one of the parameters taken into account when the body is in one of the "smart" picture modes and has to choose a program curve.
  • Exact selected aperture. The KA mount supports displaying the picture-taking aperture when the "A" aperture setting is engaged. The KAF mount supports displaying the aperture even when a numeric f-stop is selected. The displayed value is quantized by half-stops, but is correct even when a variable-aperture zoom lens is used.
  • Lens dimensions. The lens also gives the body enough information for determining if the lens is going to cast a shadow on the subject when the camera's built-in flash is used. This parameter takes into account the size changes due to zooming and focusing too.
The lenses contain a ROM chip that holds the program curve (brightness/shutter speed/aperture) for prime lenses or up to three program curves for zooms at their different focal length settings. The distance information is hardwired on the lens barrel. A number of tiny parallel conducting/non-conducting strips are glued to the rotating part of the lens. The same number of contacts are attached to the fixed part of the lens. As the lens barrel turns during focusing, different combinations of the strips are detected by the contacts. There are four parallel strips in the F 50/1.7, resulting in at most 16 different distance settings. But for that particular lens not all combinations are used.

A similar technique must be used for the focal length.
QuoteOriginally posted by Aegon Quote
Anyway, you aren't going to short much by goofing with the contacts. Worst case is your camera thinks a different lens is attached.
So it wouldn't just be a different lens that appears to be attached if the chip was damaged. It might affect exposure as well.

I would assume the ROM uses standard TTL voltages (+5V?) for its function. Has anyone measured the voltages off of the pins?

Therefore, I think the question is how this pin is grounded during mount/dismount on both the body and the lens?

I agree that good design would ensure this is not affected - but why do Pentax suggest turning the camera off during mount/dismount?

So many questions, so little information......

Cheers
05-20-2010, 11:15 PM   #23
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In 2 decades of using Pentax/Nikon/Canon, I have switched lenses whenever I wanted. Never had a single problem because the cameras were on. If any camera must be turned off b4 switching lenses, it is a fail in design imho. Just imagine, would all the working pros have time to switch them off for every lens switch? Even amateurs baby their gears would forget sometimes.

05-20-2010, 11:47 PM   #24
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I'm another one who doesn't power off when changing lenses. 5 years, 5 Pentax DSLR bodies, probably something like 1,000 lens changes, and no problems with any of the bodies or lenses. . . of course this means that the next time I do it, the whole bunch will probably explode. . .

Scott
05-21-2010, 04:46 AM   #25
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I power off just to get the sensor shake at start up after swapping lenses. I wish Pentax would simply allow for the higher frequency shake automatically after a lens change. The camera does have enough information to be able to determine that a lens has changed so it is just programming the functionality.

I imagine that the contact between lens ROM and camera is only active while metering is active. Why drain the battery, even if the draw is tiny? Why this isn't cut when the lens lock is pressed leaves me scratching my head, but I'm not complaining as I use the lens lock as a quick shift for all my lenses that don't have sure a feature.

Thank you
Russell
05-21-2010, 05:15 AM   #26
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In Scott Kelby's latest book, Digital Photography Vol 3, he specifically states that it is not necessary to turn the camera off before chaning lenses. He also states that of all the pros he knows and works with (which would be many, many, top names) NONE of them turn the camera off to change lenses.

Having said that, I do turn it off myself, BUT only so that I get that turn-on shake of the sensor after changing lenses - just in case...
05-21-2010, 07:39 AM   #27
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Original Poster
Thanks all for your feedback and inputs.

If I recap:

- there is no consensus among Pentaxians about turning off (or not) the camera before switching lenses;

- a number of Pentaxians have switched lenses with their dSLR left on without any record of damage;

- many prefer to turn off the camera before switching lenses; I would fall in that category but I sometimes forget in the heat of the action when in rush;

- the Pentax instructions 'caution' to turn off before switching lenses; note that the wording is a caution, not a 'warning' nor 'requirement'.


I would add to the above that:

- there is some function(s) that may require to turn off the camera before switching lenses: e.g., catch in focus; alternately the camera must be turn off after switching lenses to enable the function.

Thanks again for feedback and advice....

Last edited by hcc; 05-21-2010 at 07:41 AM. Reason: Typos
05-21-2010, 08:15 AM   #28
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Sigma advise to shut the camera off when changing a Sigma IS lens.
05-21-2010, 10:12 AM   #29
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QuoteOriginally posted by hcc Quote
Thanks all for your feedback and inputs.

If I recap:
You forgot:

-The one time I've ever done this, I got dust goobers on my sensor. So at least one person says "don't do this".
05-21-2010, 10:19 AM   #30
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I'm sure Penatx and all other major camera brands have thought of this topic when designing their cameras. They have to know that not everyone will always turn off their camera before a lens switch so it would be very irresponsible of Pentax/Canon/Nikon to not put in a fail-safe for either shorting out pins and sensor attracting dust (via static charge or whatnot) when the camera is on and a lens is being swithced.

I turn off my camera by the way but have certainly forgotten a hand full of times with no problems.
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