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11-11-2016, 04:29 AM   #1
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Do all lenses need fine tuning?

I am very new to photography and have recently recieved a k1 with a 55mm 1.4 lense. I am trying to figure out if all lenses need fine tuning?

The shots i have attached were a typical result from shooting over 100 pics. I wasn't able to get the eyes in focus or get a sharp shot of the face at least. I don't know if this is has to do with when shooting in afs and single spot focus, that i couldn't move the focus point around (can this be done) or do i need to fine tune? I know typical rookie but any advice would be great.


Last edited by yozza; 11-13-2016 at 01:28 AM.
11-11-2016, 04:42 AM   #2
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Yep, we move the single point around with the four buttons around the central OK one.

You can fine tune for individual lenses if they front or back focus.

That's unlike low end Nikons. I had a very annoyed work colleague today who says he needs to do that with a 105mm macro on his 3200 but it's not possible!

Last edited by clackers; 11-11-2016 at 05:01 AM.
11-11-2016, 04:51 AM - 1 Like   #3
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I'm afraid so, Speaking of 105mm Nikkor lenses. I have to do AF adjustment on my new Nikkor 105mm f/1.4G, calibrating focus at f/1.4 is not going to be fun.
11-11-2016, 05:06 AM   #4
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Oh ok thankyou, better learn how to do that

11-11-2016, 05:20 AM - 1 Like   #5
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Injecting two questions, which have probably been asked and answered long since: 1) is there a best distance for calibrating focus, and is it different for each FL? 2) is there a best zoom setting for calibrating (long end, intermediate, short end), or should/can it be done for different FLs on a zoom?
11-11-2016, 05:40 AM   #6
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Just saw your plea on Gumtree. I am too far to help in person, but, may I suggest you start by reading the manual. Asking here will help tremendously too. It is not that hard to do and it can be done quite quickly.

Yes, the lens tuning charts are very good and give excellent results. But, perhaps, you could try a ruler on a 45 degree slant, good lighting and a tripod for your camera.

Place camera on the tripod and turn Shake Reduction OFF. Place ruler on 45 degree incline in front of the camera at the shortest focal distance possible (getting razor thin Depth of Field). Set autofocus point to single point (middle).

Focus wide open (f1.4) at centimetre mark using autoconfirmation. Take a shot and review in live view magnified in. Is the focus mark in focus? If not, which side of the focus mark is in focus?

Go to the Menu settings and find AF Adjustment. Adjust + or - and retest as above.

Ultimately it is a little bit of playing around and you eventually settle on a satisfying adustment.

Play with your camera - don't be afraid of it
11-11-2016, 05:46 AM   #7
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QuoteOriginally posted by WPRESTO Quote
Injecting two questions, which have probably been asked and answered long since: 1) is there a best distance for calibrating focus, and is it different for each FL? 2) is there a best zoom setting for calibrating (long end, intermediate, short end), or should/can it be done for different FLs on a zoom?
1. I've seen five to fifty times the focal length, Wpresto.

2. You're going to have to pick a focal length. Naturally, if you measure for long, intermediate and short, you hope they need the same adjustment. But Sigma recognize this isn't always true and their own utility for their Contemporary and Art series lenses lets you do different FLs for zooms.

11-11-2016, 05:49 AM - 1 Like   #8
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QuoteOriginally posted by yozza Quote
Oh ok thankyou, better learn how to do that
Yes, of course, read the manual.

BTW, there's an old PentaxForums article on the topic:

Fixing Front and Back Focus - Introduction - In-Depth Articles
11-11-2016, 06:06 AM   #9
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QuoteOriginally posted by Wild Mark Quote
Just saw your plea on Gumtree. I am too far to help in person, but, may I suggest you start by reading the manual. Asking here will help tremendously too. It is not that hard to do and it can be done quite quickly.

Yes, the lens tuning charts are very good and give excellent results. But, perhaps, you could try a ruler on a 45 degree slant, good lighting and a tripod for your camera.

Place camera on the tripod and turn Shake Reduction OFF. Place ruler on 45 degree incline in front of the camera at the shortest focal distance possible (getting razor thin Depth of Field). Set autofocus point to single point (middle).

Focus wide open (f1.4) at centimetre mark using autoconfirmation. Take a shot and review in live view magnified in. Is the focus mark in focus? If not, which side of the focus mark is in focus?

Go to the Menu settings and find AF Adjustment. Adjust + or - and retest as above.

Ultimately it is a little bit of playing around and you eventually settle on a satisfying adustment.

Play with your camera - don't be afraid of it
Thankyou Mark that's very helpful i will give that a go. What is autoconfirmation?

---------- Post added 11-11-16 at 06:11 AM ----------

QuoteOriginally posted by yozza Quote
Thankyou Mark that's very helpful i will give that a go. What is autoconfirmation?
I guess the difference with a chart is that i have something to aim for, where as a ruler i don't really
11-11-2016, 06:49 AM - 1 Like   #10
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QuoteQuote:
I am trying to figure out if all lenses need fine tuning?
They all need to be checked, although adjustments might not be required for all.

QuoteQuote:
The shots i have attached were a typical result from shooting over 100 pics. I wasn't able to get the eyes in focus or get a sharp shot of the face at least.
On the specific examples you posted, note that the AF system will more than probably lock on the black edges of the glasses, which are slightly in front of the face and eyes. Not by much, but certainly enough to cause problems if you shoot at 1.4 with a 55mm lens, or give the illusion of a front focusing problem. The solutions here are to either use a smaller aperture to still have the eyes sharp even if the focus is done on the glasses, or manually correct the focus with the focus ring after AF is locked (or just switch to manual focus). Or you can let the camera lock focus on the glasses and then move yourself slightly toward the subject to move focus on the eye...

Also, you said that you used AF-S. Are you sure you haven't move yourself or teh camera between the time AF locked and you pressed the shutter ? At f/1.4 , even moving a inch or two might be enough to put the focus point in front or back of where you actually wanted to focus...

Last edited by CarlJF; 11-11-2016 at 07:04 AM.
11-11-2016, 07:19 AM   #11
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30 to 50 times focal length is the general recommendation for the distance for calibration. A few do it using an object at infinity. Most zooms are a compromise pick a focal length you use most and adjust for that or test several focal lengths. and average it.
11-11-2016, 09:39 AM   #12
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I'm learning about digital imaging a lot later than many of you started so most of my approach still gets filtered through many years of film shooting experience. Something I have been curious about for a while is why we are expected to accept having to make adjustments to our auto focus systems at all. When we all used strictly manual focus lenses on our film cameras and encountered a lens that was not sharply focused on an object the same distance away as the distance scale (remember those?) on the lens was set, then we knew it was built faulty and returned it because of the obvious DEFECT.
Now, are we experiencing faulty builds or poor quality optics? Perhaps the auto focus systems are inherently unreliable or not made with enough precision?
Fill me in if I am missing something please but in the meantime I don't see a reason not to continue using mostly manual focus lenses I already own since I know I can trust my eyes. From the already mentioned method of correction process, apparently I would have to trust my eyes to determined proper settings anyway, right?
Does anybody know if a better auto focus technology is coming any time soon that will not require corrections? Or at the least require a one time automatically calibrated set up step?
11-11-2016, 10:40 AM - 2 Likes   #13
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QuoteOriginally posted by From1980 Quote
I'm learning about digital imaging a lot later than many of you started so most of my approach still gets filtered through many years of film shooting experience. Something I have been curious about for a while is why we are expected to accept having to make adjustments to our auto focus systems at all. When we all used strictly manual focus lenses on our film cameras and encountered a lens that was not sharply focused on an object the same distance away as the distance scale (remember those?) on the lens was set, then we knew it was built faulty and returned it because of the obvious DEFECT.
Now, are we experiencing faulty builds or poor quality optics? Perhaps the auto focus systems are inherently unreliable or not made with enough precision?
The front/back focus issue was always present. But since people couldn't do anything about it anyway, they didn't care much unless the problem was severe enough that one would consider the lens defective. And in the film era, people were not expecting much from AF and the word was to switch to manual focus as soon as you need precise focusing. Nobody at the time would have expected a camera to autofocus perfectly, with 100% accuracy, on an eye with a f1.4 lens.

Even today precise an accurate focusing with a f1.4 lens used at full aperture are pushing the system to the limit. The best Af system are calibrated for a 2.8 aperture, and not on all focus points. On the K-1, only 3 center points are high precision 2.8 points, all the others being the standard f5.6... So, basically, if you want precise focusing with a wide open f1.4 lens, you will still have to use your eyes and correct the focus if needed because there's no guarantee that the AF system will nail it perfectly all the time.

So, it's not a question of bad optics or general quality. This is mostly a mix of people having much higher expection for AF performance now than in the '80, that modern digital sensor are much less forgiving of misfocus than were films, and now that people can calibrate their lenses, it just makes sense to do it. People in the '80 had no reason to care for a feature that didn't existed at the time...


QuoteOriginally posted by From1980 Quote
Does anybody know if a better auto focus technology is coming any time soon that will not require corrections? Or at the least require a one time automatically calibrated set up step?
On sensor focus, as used on mirrorless camera and liveview for DSLR, gives you perfect focus without the need for correction or calibration. Until recently, this on sensor focus also had its own drawbacks. But the most recent iterations are now quite good. IMHO, the precision of this on sensor focus is probably the biggest advantage of mirrorless camera.

Last edited by CarlJF; 11-11-2016 at 10:45 AM.
11-11-2016, 12:33 PM   #14
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QuoteOriginally posted by From1980 Quote
Now, are we experiencing faulty builds or poor quality optics?
It's build quality, From1980. Sample variation.

The light from the focus point is split into two paths and must be combined to coincide at two places in the AF module, which has to be perfectly seated and aligned.

As I understand it, in the AF film era, you could get a camera repair guy to globally adjust its position.

These days - and all Pentax models have this, not just the high end ones like Nikon - we can do this ourselves, and for individual lenses, too, meaning we can try to do something about *their* manufacturing variation.
11-11-2016, 12:45 PM - 1 Like   #15
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QuoteOriginally posted by Wild Mark Quote
But, perhaps, you could try a ruler on a 45 degree slant, good lighting and a tripod for your camera.
Unless one is providing a good size, high contrast target (parallel to sensor plane) for the camera to actually focus on, the ruler approach is an exercise in futility. The AF system will lock focus to the point on the ruler with the best contrast, which may or may not be the point one intends as a reference.

The intent is to make it easy for the system to attain accurate focus. My suggestion has been and continues to be to use a flat, high contrast target and compare against CDAF or magnified manual focus in live view as a "gold standard". The direction to correct is the indication of whether to apply +/- adjustment. It is also good to do multiple attempts (10 or more) before setting a correction. If half the attempts indicate "+" and half indicate "-", no correction is needed.

As for distance, conventional wisdom is 20x - 50x the focal length. If one wants more specific guidance, LensAlign provides an online calculator for their system that should help.

LensAlign Web Site (click "Distance Tool" tab)

Attempting calibration at infinity distance is not a good idea. There are multiple threads on this site where a user post complaints of their inability to attain sharp focus at distance despite exhaustive attempts to calibrate. Blame is usually placed on the camera or lens with the usual outcome being multiple trips for camera/lens repair and eventual sale of both. Truth is that the focus mechanism (poor precision at distance) and the atmosphere (poor contrast and distortion at distance) work against one's best efforts.

As for all lenses needing adjustment...that has not been my experience. At the very least, I suggest checking focus (10 - 20 attempts) as described above before messing with fine adjustment.

One final observation...with zooms different adjustment may be needed at different focal lengths. Similarly, internal focus lenses adjustment may shift calibration by focus distance.*

FWIW: If I were inclined to systematically adjust my camera to the lenses on my shelf, I would strongly lean towards the current version LensAlign tool in conjunction with their software. The system design is sound and uses computer image assessment in a statistical approach to assist in adjustment. OTOH, I am happy with my PDAF results and switch to manual focus in live view or my well-calibrated split-image optical focus screen when critical focus is needed.


Steve

* For example, recent model Sigma zoom calibration using their USB Dock appliance requires adjustment at multiple focal lengths and distances. Not fun or easy.

Last edited by stevebrot; 11-11-2016 at 12:58 PM.
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