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10-27-2011, 07:26 AM   #1
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Join Date: Jul 2011
Posts: 24
"input focal length" on af lens...yeah.

Okay, so here´s a question.

I have the k-7 with the 18-55 wr and the 50-200 wr... and i love it a alot.
I also have several manual lenses that i love, that when attached makes the camera promt me for focal length.
But the deal is, i have a 0.70 screw on "lens/filter", VLC-MHG07, and when i attatch it to my 18-55wr lens, i would LOVE to be able to ajust the focal length to lets say 12.. or 13 (or something around that area)

But of course when the 18-55 wr is attached the "change focal length" is greyed out in the menu. is there anyone out there in pentax-land how know of a hack or similar that would make this work for me.

Sorry if this is a bit vague, english is my second language.

Best wishes.
a pentaxian in love with his camera.

10-27-2011, 07:56 AM   #2
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Location: Finland
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You could probably fool the camera into thinking your lens is 'A' type with the trick mentioned here: This would mean using manual focus though. If there is enough light so that you don't have to depend on SR you might just turn that off: the camera needs to know the focal length for its SR calculations (and to use as EXIF info).
10-27-2011, 08:05 AM   #3
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So, you want your photos to show 12mm in the EXIF data for image stabilization and such? To remove the focal length information from the shot (to be replaced with your input value), the data pin (the contact closest to the autofocus shaft) would have to be isolated. You would also lose the distance to the subject, exact absolute f-stop value, and (pretty sure) distortion correction ability.

Now, what to isolate it with? To test, scotch tape would probably work, but it might leave a residue. Anyone else have any ideas that are long lasting but non-permanent?
10-27-2011, 08:16 AM   #4
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Join Date: Jan 2007
Location: Toronto
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Sadly there is no correction for this in the present software, apparently because pentax does not seem to be willing to support add-on or accessories that are manufactured by thrid parties.

The same issue has been present from the onset with respect to shake reduction and exposure issues when using a teleconverter. Most teleconverters simply pass through the lens data, and as a result, all automatic functions use the wrong aperture and focal length in the calculation.

this impacts not only SR, but also P-TTL flash, Program exposure lines, shutter speeds in Av mode when using flash, etc.....

It would be nice if there was an entry, just like focal length for manual lenses, at start up for "Using TC Y/N" with several options

Input / select multiplication factor
Correct for Focal length y/n
correct for aperture y/n
correct for both y/n

Are you listening pentax?


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