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06-12-2012, 12:12 PM   #1
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How much BF/FF adjustment is too much?

I just got a Sigma 50 F1.4, and on my k-x in debug mode, it appears that an adjustment of about 120 micrometers makes it focus quite perfectly. However, seeing the AF adjustment statements regarding the k-5, people say that you can go "+10 or -10", and I do not know if that refers to micrometers in intervals of 10, or some other value.

Is a lens that requires +120 micrometers of adjustment too back focused?

06-12-2012, 12:45 PM   #2
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+10 and -10 is the adjustments made using IN CAMERA custom FINE AF Adjustment for higher end cameras that offer that feature.
On my K-5, you can either adjust autofocus for ALL lenses or individual lenses.

are you getting 120micrometers from a chart or from debug mode?

Last edited by usmcxm35; 06-12-2012 at 12:52 PM. Reason: more information
06-12-2012, 12:50 PM   #3
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QuoteOriginally posted by usmcxm35 Quote
+10 and -10 is the adjustments made using IN CAMERA custom FINE AF Adjustment. are you getting 120micrometers from a chart or from debug mode?
The k-x can only make focus adjustment in debug mode, yes.

In looking online, it seems that the k-5 (and subsequently the k-30) makes adjustment in steps of 10micrometers. I assume that I cannot exceed those adjustments on the k-5 (and the k-30) as there is no debug mode available for them?
06-12-2012, 12:57 PM   #4
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There is a "debug" mode through third party software on the computer, but would shift ALL lenses to the corresponding adjustment. BTW, where are you in NYC? in manhattan?


Last edited by usmcxm35; 06-12-2012 at 12:58 PM. Reason: typo
06-12-2012, 01:06 PM   #5
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I live in Queens, but work in Manhattan. Picked up the Sigma yesterday at B&H.

If there's a third party adjustment, I could make that work. Currently I have the Tamron 70-200 (+30 or 40 micrometers) and a DA 35 F2.4 (no adjustment, AFAIK). So I can shift everything to get my 0 where I need it to be.. or I can send it to Sigma for adjustment.
06-12-2012, 01:20 PM   #6
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1 step in that mode is the same as 10 micrometers


if your value is too much.
Well there is variation in the camera and in the lens, so if your camera needs +60 micrometers and the lens as well you get your value but if for example the camera needs -60 then the total of adjustment needed will be 0 micrometers.

I would say try to match your lenses if you can all my lenses fall inside 80 micrometers of adjustment and i hope that's enough to make sure if i buy a new camera that i can adjust the focus enough as well.
06-12-2012, 01:20 PM   #7
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I would just take it back to B&H tomorrow and get an exchange.
I have been a forum lurker for a long time, and Sigma always gets singled out for having QC issues.
"Sigma is way better than Tamron, (fine print: IF/WHEN you have a good copy)"
I sent my K-5 to Pentax for adjustment, but I may have screwed myself.
Before it left, I had FA50 1.4 needing +8, FA*28-20 needing +10, DA 12-24 needing +10
After it came back I have a DA35 2.4 that needs -9, FA50 1.4 that needs -9, FA50 1.7 that needs -9, DA70 that needs -4, a DA12-24 that needs 0, and a FA*28-70 that needs +1
If your K-x is adjusted properly to factory specs, I would get another copy of the lens, B&H will send it back to Sigma.
If you end up looking for a FA 50 1.4, let me know, I just got the 1.7 and most likely not be shooting the 1.4 too much.
06-12-2012, 01:25 PM   #8
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Thanks for the advice - I'll drop by B&H on thursday or something. I'll test the lens again - to be sure, but it was definitely in the 100-120 micrometer range.

I do like the Sigma though, it's focus speed and lack of sound is just lovely.

I wouldn't get my k-x calibrated, I bought it refurbed, and I'll be getting a K-30 towards the end of the year. If I can run the Sigma at +10 adjustment and still be fine, I'm willing to live with that.

06-12-2012, 04:37 PM   #9
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Unfortunately with third party lenses, the AF adjustment can not be made on per lens basis.... (true)?
06-12-2012, 04:45 PM   #10
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QuoteOriginally posted by aleonx3 Quote
Unfortunately with third party lenses, the AF adjustment can not be made on per lens basis.... (true)?
Not so, but because there's a lot of sharing of lens identifier ID's between various lenses if you are unlucky enough to have 2 lenses with the same id, any adjustment will affect both (as the camera thinks it's the same lens).
06-12-2012, 06:22 PM   #11
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QuoteOriginally posted by twitch Quote
Not so, but because there's a lot of sharing of lens identifier ID's between various lenses if you are unlucky enough to have 2 lenses with the same id, any adjustment will affect both (as the camera thinks it's the same lens).
Fortunately my Tamron and my DA 35 have both their own IDs, according to the exif files. That means the Sigma will be the odd man out, at worst.
06-12-2012, 07:35 PM   #12
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My Sigma 30mm was also out a lot compared to other lenses so i traded it the next day for another one at the store and that one is much better on my camera.
06-29-2012, 11:42 AM   #13
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A) I also have a K-x. Using the debug mode as you do, you can only set the adjustment to a specified level. On higher level cameras, you can set the adjustment to match more than one lens.
B) I have a DA 18-135 which I really like, but my best results are at +150micrometers. (I don't have official testing equipment. This was the result of a lot of fixed setup testing as well as real world testing.)
C) All my autofocus lens needed at least +80 adjustment. I use my 18-135 most, but taking into account the other lens I use most which was a +100 adjustment, I set my adjustment to +130micrometers as an acceptable compromise.
06-29-2012, 03:31 PM   #14
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QuoteOriginally posted by JinDesu Quote
I just got a Sigma 50 F1.4, and on my k-x in debug mode, it appears that an adjustment of about 120 micrometers makes it focus quite perfectly. However, seeing the AF adjustment statements regarding the k-5, people say that you can go "+10 or -10", and I do not know if that refers to micrometers in intervals of 10, or some other value.

Is a lens that requires +120 micrometers of adjustment too back focused?
I'm relatively new to digital photography and have read the comments in this thread with puzzlement. I thought that after you stick a lens on your camera the auto, or manual, focus procedure will give you the sharpest picture. Are you folks saying that I have to calibrate each lens I use to the camera to get the sharpest picture?
06-29-2012, 03:35 PM   #15
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QuoteOriginally posted by P. Soo Quote
I'm relatively new to digital photography and have read the comments in this thread with puzzlement. I thought that after you stick a lens on your camera the auto, or manual, focus procedure will give you the sharpest picture. Are you folks saying that I have to calibrate each lens I use to the camera to get the sharpest picture?
Some lenses are pretty spot on with focus without adjustment. Some lenses need minor adjustment, and may not matter. Some lenses may need large adjustments. Some lenses are so fast (F1.8 and faster) that even small adjustments means you may miss-focus when shooting wide open.

The Pentax k-x has only a universal focus adjustment application. The Pentax k-5 (and the k-30) has a feature that allows it to adjust the focus for each lens.
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