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04-29-2019, 09:20 AM   #1
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Is it common for prime lenses to need adjusting for front and back focusing?

I checked out 4 prime lenses on my K5ii2 15mm limited, 21mm limited F28 2.8 and F50 1.7. All except for the 50 needed adjusted for either front of back focusing. I'm curious how commen this is?

04-29-2019, 09:33 AM   #2
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I have the DA 15, 21, 35, 40 and 70 DA Ltd and none have required adjustment for AF. However, I am mainly shooting landscapes with a big depth of field.(I Shoot with the K5iis also.)
04-29-2019, 09:34 AM   #3
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Never really paid attention until i got the DA* 55. Needed +5 on my K-1 and now I will go check my other lenses lol.

04-29-2019, 09:38 AM   #4
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Out of my 6 main lenses, 2 required adjustments. It's not a rare ocurrence, that's why Pentax built the feature in their camera.

04-29-2019, 09:41 AM   #5
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Quite common - hence why the newer cameras include a facility to set AF fine adjustment for individual lenses. Manufacturing and physical adjustment tolerances in both the camera and lens mean that some adjustment is often required. Some folks won't even notice that adjustment is needed, unless they're shooting at faster apertures and close range. At longer distances and/or smaller apertures, depth of field means any slight inaccuracy is likely to go unnoticed...
04-29-2019, 11:15 AM   #6
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QuoteOriginally posted by robert Quote
I'm curious how commen this is?
I need an average +8 on all my lenses with the K1. It is not the lens that has the issue but the camera/lens combo and/or PDAF system. But this is why the manufacturers of all DSLRs give us the option.
04-29-2019, 11:47 AM   #7
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Further to my previous comment, I keep a list of the AF fine adjustment settings for each of my lenses on each body. It's a bit out of date now and missing a few more-recently acquired lenses, but below is what I have on my K-3 and K-3II (both bodies require identical settings - I was very lucky in that respect):
HD DA15 f/4 (0)
HD DA21 f/3.2 (0)
HD DA35 f/2.8 Macro (0)
HD DA40 f/2.8 (-2)
HD DA70 /2.4 (+1)
SMC DFA100 f/2.8 (0)
SMC DA35 f/2.4 (-3)
SMC DA50 f/1.8 (0)
HD DA55-300 f/4-5.8 (0)
Sigma 17-50 f/2.8 (-4)
Tamron 28-75 f/2.8 (-4)
Sigma 18-300 (0)
SMC FA50 f/1.4 (+2)
HD DA20-40 f/2.8-4 (0)

Last edited by BigMackCam; 04-29-2019 at 05:19 PM.
04-29-2019, 12:49 PM - 1 Like   #8
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To echo comments above...it is not unusual, but more common with internal focus designs or lenses with floating elements. I don't have many AF primes, but on my K-3, I have applied to each:
Sigma 50/2.8 EX DG Macro : -3
Pentax-FA 77/1.8 Limited : +4
Pentax-FA 35/2.0 : +3
Pentax-DA 50/1.8 : +1
Of the above, both the Sigma and the FA 77 have floating elements.


Steve

04-29-2019, 12:52 PM   #9
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QuoteOriginally posted by pschlute Quote
But this is why the manufacturers of all DSLRs give us the option.
Not all manufacturers do, sadly. We're lucky in this regard.
04-29-2019, 03:31 PM   #10
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I've adjusted all but one of my AF lenses; the DA* 50-135mm. But I use the Dot Tune method, so I calibrate each lens to the range the camera thinks a known good focus is in focus. The 50-135 had a range from -7 to +6, so I set it at zero.

The first lens that I noticed might need adjustment was my DA 50mm 1.8. Using the common tedious chart photo testing method, I determined it needed an adjustment of -4. I rechecked after finding out about the dot tune method. In a fraction of the time, I determined the camera's acceptable range is -9 to 0, confirming the adjustment of -4. Now I calibrate all my lenses as acquired.
05-04-2019, 08:19 PM   #11
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QuoteOriginally posted by bdery Quote
Not all manufacturers do, sadly. We're lucky in this regard.
Just curious, which manufacturers don't provide this? I had no idea. Do those manufacturers allege they have sufficiently tight tolerances to not need adjustments? I have been critical of Pentax for providing only plus or minus 10 (since I've had lenses that needed at least that much) but had no idea there were current models without adjustment capability at all.
05-05-2019, 12:42 AM   #12
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Lenses and cameras need adjustment in the workflow. It is important that camera and lens have stable correction values for long term precision. Typically you start with a camera and fine adjust lenses if needed - the user only has one adjustment option anyways. Buying a second camera you will realize that the camera has a simple offset in fine adjustment correction.
Also be aware that fine adjustment helps the most for shallow dof applications and als changes with focus distance and apeerture setting. If you know that you use a lens only wide open at a certain distance you want to optimize for that setting. At other settings the lens may be slightly off. Same for zooms where af adjustment changes with focal length. Many reasons, many factors.
Trouble starts if your lenses do not show controlled behavior. Either your test setup is not working or something is broken.
05-05-2019, 06:21 PM   #13
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QuoteOriginally posted by robert Quote
I checked out 4 prime lenses on my K5ii2 15mm limited, 21mm limited F28 2.8 and F50 1.7. All except for the 50 needed adjusted for either front of back focusing. I'm curious how commen this is?
The system is built in to allow for the lenses or the camera's AF module not being exactly centred, since it's manufacturing tolerances we're talking about. Even the low end Pentaxes let you do a +10 to -10 adjustment.

If *all* of your lenses needed back or front adjustment, this would suggest it's the camera that's not quite aligned. But as long as it's within +10/-10, that's fine. Outside of that range, go for an exchange/refund/warranty repair.
05-06-2019, 04:59 AM   #14
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QuoteOriginally posted by tibbitts Quote
Just curious, which manufacturers don't provide this?
I haven't looked at the recent Fuji And Sony cameras (nor, in fact, to Canikon from more than two years ago). I know for a fact that Canon entry and mid levels did not offer it last I checked, and Nikon didn't either, even for cameras comparable to the K-3.

QuoteOriginally posted by tibbitts Quote
I had no idea. Do those manufacturers allege they have sufficiently tight tolerances to not need adjustments?
They don't alleg anything, they simply don't offer it. Or require the user to send the camera to their factories for adjustments.

QuoteOriginally posted by tibbitts Quote
I have been critical of Pentax for providing only plus or minus 10 (since I've had lenses that needed at least that much) but had no idea there were current models without adjustment capability at all.
I think we're pretty good to criticize Pentax, and we lose sight of everything that makes the brand unique. We take for granted everything working well, and notice only the small things that could be better. That's human nature.
05-06-2019, 08:25 AM   #15
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QuoteOriginally posted by bdery Quote
Nikon didn't either, even for cameras comparable to the K-3.
Nikon offered "AF fine tune" for the D7000 and D7100 (direct K-3 competitor) and such had been a supported feature for several years before (I don't know about their consumer line). Current model enthusiast and pro-level Nikon offer a system that is far superior to Pentax; how does full in-body automation using focus bracketing sound?

Edit: I did some research...No support for AF fine tune on the consumer-level bodies. It was available as early as 2012 on the D600.


Steve

Last edited by stevebrot; 05-06-2019 at 08:48 AM.
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