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09-26-2021, 02:08 PM   #1
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Is fine tuning the focus of my lenses necessary?

I normally use Pentax lenses on my K50 and K70 and note from the user manuals that it is possible to apply "Fine Adjustments" to my cameras to get even sharper images. I have never bothered to use the complicated procedures to correct for front and back focussing since my images seem quite satisfactory for my type of photography. The fine adjustment procedure on the Pentaxes seems straight forward but II want to ask if any of you experienced Pentaxians bother to fine adjust the focus on your cameras. Is it worth the trouble for a "general photographer" like me? Of course I could give it a try but any comments would be welcome.

09-26-2021, 02:09 PM - 1 Like   #2
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are you happy with your photos?
09-26-2021, 02:12 PM   #3
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It is worth checking. I recently got a 50mm f/1.8 that was giving soft images. I check with a simple dot on paper with two rulers, and it turns out it needed a -7 autofocus adjustment. Now, I am getting sharp images when earlier I had to go to f/3.5 to achieve the same sharpness.
09-26-2021, 02:37 PM - 2 Likes   #4
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QuoteOriginally posted by psoo Quote
my images seem quite satisfactory for my type of photography.
This is the key. If you don't see a problem, most likely there isn't one. And unless done carefully, meticulously, and precisely with everything lined up perfectly during your test, you can easily make the focus worse than it was. Unless you are quite careful and use a good focusing target your margin of error in the testing can be larger than the actual error in focusing.

That said:
- I check all of the lenses I purchase, either new or used.
- I use a careful, tedious method that takes 20 to 30 minutes per lens after setup time, which can take another 10 minutes or so to align the camera to target precisely
- Most of my lenses have needed a small adjustment, one that most likely is not really noticeable in the real world
- For slow lenses such as consumer zooms, the depth of focus is usually large enough to mask any small error
- For very fast lenses such as an f/1.4 50mm, fine tuning is almost certainly needed (or at least should be checked) due to the tiny depth of focus you can achieve at that aperture

So bottom line: If your results are good, you don't likely need to mess with it. And if you do want to check, do so very carefully, keeping in mind that precise testing is needed.

09-26-2021, 02:49 PM - 1 Like   #5
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QuoteOriginally posted by pepperberry farm Quote
are you happy with your photos?
Yes, I'm happy with my photos but maybe I could even happier if I found that fine adjustments made them even sharper.
09-26-2021, 02:53 PM   #6
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As has been said, if you’re happy with results, fine. I shot for some years without bothering with checking, but didn’t know it was worth doing. After calibrating my 80-320 in particular, I get more sharply-focused keepers, but your mileage may vary.

When even the kit 18-55 improved its results I knew it was worth doing in my case.
09-26-2021, 03:21 PM - 1 Like   #7
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Just as a sanity check though, across 4 cameras, each one fine tuned with 22 lenses, in my tuning spreadsheet where I keep track of the settings, I only have 2 zeros. Almost every combination of lens and camera I have has benefited from fine tuning. My suggestion would be to go through the tuning exercise with every lens just to be sure.

09-26-2021, 03:39 PM   #8
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QuoteOriginally posted by psoo Quote
Yes, I'm happy with my photos but maybe I could even happier if I found that fine adjustments made them even sharper.
I've got a couple of lenses which I'd always regarded as possibly "not quite right" but had put up with them because the results were usually acceptable 'cos I tended to use them stopped down a bit.
Then one afternoon I had an hour spare and made up a quick test rig with a focussing target and a sloping ruler, just out of interest.
One of the lenses was "as good as it was going to get" and consigned to the back of the drawer, the other needed +10 adjustment and now performs significantly better
So I'd say, at least do a basic check. If all is well, so be it, but if adjustment appears necessary maybe a little more effort might pay dividends.
Remember, you're not actually adjusting anything mechanical, just asking the camera, through a menu setting, to act slightly differently when a particular lens is fitted.
09-26-2021, 04:19 PM - 1 Like   #9
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QuoteOriginally posted by psoo Quote
but II want to ask if any of you experienced Pentaxians bother to fine adjust the focus on your cameras.
Yes.


QuoteOriginally posted by psoo Quote
Is it worth the trouble for a "general photographer" like me?
The answer to this second question is ...it depends.

In the days of film , cameras were just as likely to suffer from FF/BF as modern DSLRs. Did we notice it ? If we mostly had our pictures printed as 6"x4" the answer would generally be no.

Today we can pixel-peek at 100% view and see the slightest misfocus. If we usually view our images on screen and don't crop much, again any FF/BF will not be noticed much in a general scene. But if we crop and if we print our images, then the misfocus will be much more apparent.

I do crop and I do print regularly at 24"x16". I therefore always calibrate my lenses.
09-26-2021, 06:49 PM   #10
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I'm not a big 'super sharpness' kinda guy but my AF lens are plenty sharp for me. My most used AF lens are F32-70 F-50 DA70 DA16. The DA70 is almost too sharp. I just don't see 'things' with those kinda edges.
09-26-2021, 06:57 PM   #11
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QuoteOriginally posted by jatrax Quote
If you don't see a problem, most likely there isn't one
This ^ ^ ^

Unless you are seeing a clear pattern of front focus or back focus with a particular lens, there is no sense going through the chore of doing AF fine adjust. By clear pattern, I mean obvious evidence from the field where PDAF (viewfinder) focus consistently places focus behind or forward of the subject at the selected* AF point.

Note this has nothing to do with ultimate sharpness. Note too that testing with a slant ruler or anything other than a flat target parallel to the camera sensor is an exercise in futility.


Steve

(...currently has AF fine adjust in play with zero lenses, but will caution that AF is not used for fine focus by this photog...)

* Unless you selected the know for a fact that the subject was unambiguously covered by the AF point, there is no reason to assume front or back focus.
09-26-2021, 08:31 PM - 1 Like   #12
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My own relationship to this topic is complex. I have tried and NEVER gotten the same results from fine focus testing even with a costly test target system. I havenít tried DOT TUNE methods yet but they look promising.Sometimes if critical focus is needed I resort to CDAF live view or magnified live view and manual focus.
09-26-2021, 10:47 PM - 2 Likes   #13
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QuoteOriginally posted by psoo Quote
I normally use Pentax lenses on my K50 and K70 and note from the user manuals that it is possible to apply "Fine Adjustments" to my cameras to get even sharper images. I have never bothered to use the complicated procedures to correct for front and back focussing since my images seem quite satisfactory for my type of photography. The fine adjustment procedure on the Pentaxes seems straight forward but II want to ask if any of you experienced Pentaxians bother to fine adjust the focus on your cameras. Is it worth the trouble for a "general photographer" like me? Of course I could give it a try but any comments would be welcome.
I calibrate all my lenses Psoo, and I think everyone should calibrate a new purchase and also check it for decentreing during the return period. I will not buy a lens from a vendor who doesn't accept returns. We pay a lot of money for these things, we're entitled to one that's up to spec.

I think Digitalis went through three copies of the Sigma 100-300mm f4 (a good design) to get a keeper.
09-27-2021, 04:25 AM   #14
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QuoteOriginally posted by DeepThrob Quote
I'm not a big 'super sharpness' kinda guy but my AF lens are plenty sharp for me. My most used AF lens are F32-70 F-50 DA70 DA16. The DA70 is almost too sharp. I just don't see 'things' with those kinda edges.
Fine Adjustment of the PDAF autofocus system is not about "sharpness". Even a camera/lens combo with severe FF or BF will have maximum sharpness somewhere in the picture.... just not where the photographer wants it

---------- Post added 09-27-21 at 12:35 PM ----------

QuoteOriginally posted by UncleVanya Quote
My own relationship to this topic is complex. I have tried and NEVER gotten the same results from fine focus testing even with a costly test target system. I havenít tried DOT TUNE methods yet but they look promising.Sometimes if critical focus is needed I resort to CDAF live view or magnified live view and manual focus.
My K1 back-focusses with every lens unless calibrated. I need +7 to +10 with lenses to get spot-on focus.

I have used the test-chart technique, but now my quick and dirty method is to use a wine bottle that has clear lettering running a long way around the label. With an uncalibrated lens the BF is clearly evident, and I just adjust it until it is gone.
09-27-2021, 05:05 AM - 4 Likes   #15
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QuoteOriginally posted by pschlute Quote

I have used the test-chart technique, but now my quick and dirty method is to use a wine bottle that has clear lettering running a long way around the label. With an uncalibrated lens the BF is clearly evident, and I just adjust it until it is gone.
Many thanks for this suggestion - I look forward to trying it. BTW, how long after drinking the wine does it take for your eyes to return to their own preferred 'zone of sharpness' ?
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