Lens VR unit IR leakage affects long exposures - cont'd.

Started Feb 17, 2008 | Discussions thread
SteveL54 Senior Member • Posts: 2,709
Re: Yes, you can turn it off

Marianne Oelund wrote:

Well, this is certainly embarrassing - I shouldn't believe every
claim made in posts, without verifying them first. Max insisted that
there was no combination of switch settings that would clear the
problem. See

http://forums.dpreview.com/forums/read.asp?forum=1039&message=26784890 , where he claimed to have been using the M/A switch "M" position.
Clearly, he wasn't, as this will turn off the IR source on both the
18-200 VR and 70-200 VR.

Talk about much ado about nothing, though . . .

LOL... I think you and I were more 'focused' on the nature and source of the image contamination rather than how to configure the camera/lens to simply avoid it.

It's good to know that VR lenses have sources in them that actively radiate IR. It's a new source to add to things such as amp glow and thermal noise as long term exposure image spoilers.

Looking back through that thread it's apparent that Max initially assumed or expected the body's AF switch -- along with the lens VR switch -- should be sufficient to deactivate any lens electronics causing the problem. I don't think Max initially claimed to have explored every switch combination that could have impacted the result. Max just claimed to have disabled AF and VR. He just didn't specify how he disabled AF.

Later Max mentioned that he would check into the lens M/A-M switch setting impact.

http://forums.dpreview.com/forums/read.asp?forum=1039&message=26807156

To be fair to Max, why would it be necessary to turn off the lens focus switch to disable something associated with VR? After all, non-VR AF-S lenses have an M/A-M switch, but one doesn't have to set them into the M position to avoid IR contamination. (I checked this with three of my non-VR AF-S lenses.) It looks like the designers coupled the lens AF with VR in some way -- possibly to save a few pennies.

I did check the operation of the 18-200 on the D3, though, and the IR
pattern is very interesting. No smooth gradients in the "bigger
picture;" there are clear light and shadow areas on the sensor. If
anyone's interested, I can post a sample.

Yes, I'd be interested in seeing such an image. It's useful to be able to identify the signature of such issues.

Thanks again for the excellent investigative work.

Steve

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