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02-06-2012, 01:46 PM   #1
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Inputting focal length?

Bought a used K-x on ebay. Did not get a book with it. When I put on a manual fisheye from my K1000 the K-x said to input focal lenght. What is this for? If you skip this step will pictures suffer any?

Thanks

02-06-2012, 01:49 PM   #2
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It's for the shake reduction to function.
I'm not sure but i assume shake reduction will not work if you skip this step because it needs it to function.
02-06-2012, 01:58 PM   #3
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QuoteOriginally posted by slackercruster Quote
Bought a used K-x on ebay. Did not get a book with it. When I put on a manual fisheye from my K1000 the K-x said to input focal lenght. What is this for? If you skip this step will pictures suffer any?

Thanks
It's for Shake Reduction. The camera has to know focal length to know how much and how fast the sensor has to move for reducing shake blur.
If setting much longer focal length than lens is, SR will add blur instead of reducing it.
The camera will also add focal length chosen in image exif.

If you do not want to input focal length I would recommend turning off SR. For a fish-eye lens SR will not make much difference anyway.
02-06-2012, 03:17 PM   #4
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Oh, I've got a follow-up question if there's room for it..?
My DA17-70mm SDM have by (de)fault a focal length at 43mm not depending on what focal length the lens is ACTUALLY set to.
Will this in other words actually cause the pictures taken at <43 mm to be blurrier than expected if using the SR?
I actually do think that I've seen this happen; was surprised that I vouldn't achieve a stabilized image in a wide angle shot some time ago...

One extra question; Is the faulty SDM expensive to get fixed if there's no guarantee left on the lens?

Tommy

02-06-2012, 03:23 PM   #5
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QuoteOriginally posted by Anvh Quote
I'm not sure but i assume shake reduction will not work if you skip this step because it needs it to function.
Shake reduction will use whatever value was input last. If no focal length was ever input it will use the default. I can't remember what FL that would be. As mentioned by Fogel70, the wrong SR setting can mess up your photo, so best to enter the correct value. The other reason to enter FL is so you will know which lens you used when reviewing the photos later. Whichever value was entered last shows up as the stated focal length when using a manual lens.
02-06-2012, 03:33 PM   #6
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QuoteOriginally posted by Larsenio Quote
Oh, I've got a follow-up question if there's room for it..?
My DA17-70mm SDM have by (de)fault a focal length at 43mm not depending on what focal length the lens is ACTUALLY set to.
Will this in other words actually cause the pictures taken at <43 mm to be blurrier than expected if using the SR?
I actually do think that I've seen this happen; was surprised that I vouldn't achieve a stabilized image in a wide angle shot some time ago...

One extra question; Is the faulty SDM expensive to get fixed if there's no guarantee left on the lens?

Tommy
The camera does not appear to communicate with your 17-70. The focal length should change as you rotate the zoom. This has nothing to do with SDM. Is exposure working properly? Do you have other DA lenses? Do they work well? Have the lens or camera been dropped?

Incorrect focal length and SDM could be due tp fouled contacts. I'd clean them with alcohol as a first step. If that doesn't work you probably need a repair.
02-06-2012, 03:41 PM   #7
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To the OP...

I would get in touch with Pentax in your country (or put a 'wanted' advert up in the buy/sell section of this site) and see if you can get hold of your camera's manual... I've only just (after 2 years) stopped carrying my manual with me... Useful? Yes.
02-06-2012, 03:57 PM - 1 Like   #8
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QuoteOriginally posted by DaveHolmes Quote
To the OP...

I would get in touch with Pentax in your country (or put a 'wanted' advert up in the buy/sell section of this site) and see if you can get hold of your camera's manual... I've only just (after 2 years) stopped carrying my manual with me... Useful? Yes.
In the meantime, it's available for download.
http://www.pentax.jp/english/support/man-pdf/k-x.pdf

The digital version is good enough for me. I've never taken my manuals out of the house.


Last edited by audiobomber; 02-06-2012 at 04:10 PM.
02-06-2012, 03:59 PM   #9
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QuoteOriginally posted by audiobomber Quote
The camera does not appear to communicate with your 17-70. The focal length should change as you rotate the zoom. This has nothing to do with SDM. Is exposure working properly? Do you have other DA lenses? Do they work well? Have the lens or camera been dropped?

Incorrect focal length and SDM could be due tp fouled contacts. I'd clean them with alcohol as a first step. If that doesn't work you probably need a repair.
Hi Dave and thank you for answering my rather bad-formulated questions.

I know the wrong focal length isn't a SDM-problem, it just happens the lens has got a SDM-failure as well as the mentioned mm-failure...
I should have informed you that I've got several DA & FA-lenses and this lens is the only one sith that exact problem.

The SDM-problem is consequently @50-70mm's, the camera don't find a focusing point; just goes back and forth.
At <50mm it's better but has it's querks here too.

About the suggested solving of the focal length problem; I will try that.

About the un-answered SDM-problem; is it going to be costly?

Br,

Tommy.
02-06-2012, 04:17 PM   #10
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QuoteOriginally posted by Larsenio Quote

About the un-answered SDM-problem; is it going to be costly?
I don't have any SDM lenses, but from talking to someone who did, I believe the repair will be $200+.
02-07-2012, 02:21 AM   #11
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QuoteOriginally posted by Larsenio Quote
Oh, I've got a follow-up question if there's room for it..?
My DA17-70mm SDM have by (de)fault a focal length at 43mm not depending on what focal length the lens is ACTUALLY set to.
Will this in other words actually cause the pictures taken at <43 mm to be blurrier than expected if using the SR?
I actually do think that I've seen this happen; was surprised that I vouldn't achieve a stabilized image in a wide angle shot some time ago...
You get reduced SR as you change the actual focal length away from the figure being used by the camera. For actual-FLs greater than the working value, the effect of the SR is reduced as the actual-FL is increased, until virtually no SR is being achieved (so it's similar to turning SR off).

The dangerous situation is where the actual-FL is less than the working value. The effect of SR will be reduced as you reduce the actual-FL, until it reaches zero SR when the actual-FL is half the working value. Further reduction of actual-FL beyond this point will result in magnification of any shake you apply to the camera.
02-07-2012, 05:43 AM   #12
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QuoteOriginally posted by Larsenio Quote
Hi Dave and thank you for answering my rather bad-formulated questions.

I know the wrong focal length isn't a SDM-problem, it just happens the lens has got a SDM-failure as well as the mentioned mm-failure...
I should have informed you that I've got several DA & FA-lenses and this lens is the only one sith that exact problem.

The SDM-problem is consequently @50-70mm's, the camera don't find a focusing point; just goes back and forth.
At <50mm it's better but has it's querks here too.

About the suggested solving of the focal length problem; I will try that.

About the un-answered SDM-problem; is it going to be costly?

Br,

Tommy.
You might want to read this thread:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/130429-diy-sdm...us-repair.html
02-08-2012, 01:09 AM   #13
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QuoteOriginally posted by Docrwm Quote
That won't work most of the time and here there is a lot more going on then just SDM problem, half off the electrics doesn't function as it should.
So send it in for repairs i would say.
02-08-2012, 01:57 AM   #14
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QuoteOriginally posted by Larsenio Quote
The SDM-problem is consequently @50-70mm's, the camera don't find a focusing point; just goes back and forth.
At <50mm it's better but has it's querks here too.
The 50-70mm range seems to be a known problem with the DA17-70; you can search the forum for it.

Send it in for repairs if it's worth it to you; alternatively get another one and buy extended warranty.
02-08-2012, 02:26 AM   #15
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Thanks for your replies, guys
I checked norwegian prices for repairing of this problem-lens and can easily say I jumped to the conclusion of keeping it as is...
Most likely the costs will be close up to the price of a new lens here.
That is approx. 4000NOK~ 694US $.

:/
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