Lens fine tuning
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I find once you start tinkering with MA you're never happy and are forever playing with it!
Unless you really need it (ie a prime is clearly off, in which case I'd have it looked at anyway!) avoid tinkering
I fully agree with this remark. I am not convinced that any of the methods work accurately. There are so many variables that you have to get right e.g the camera, sensor and the lens must be exactly square with the focus chart/object. How many "normal" people have the knowledge or equipment to make sure this happens.
I agree unless it is way off leave it alone and if it is way off let the professionals handle it.
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As a Nikon user, if this post is about auto focus fine tuning, no lens or body will find
its way in my bag before passing MY verifications and fine tuning. All lenses and all
bodies go through this painstaking process. One of the teachings my sons have a
hard time with is that a pro has NO EXCUSES!
As a Nikon user, if this post is about auto focus fine tuning, no lens or body will find
its way in my bag before passing MY verifications and fine tuning. All lenses and all
bodies go through this painstaking process. One of the teachings my sons have a
hard time with is that a pro has NO EXCUSES!
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If your camera has micro focus adjust so you can trim the AF for each lens, then your camera manual will contain the information on how to do it, including distances. If you want to improve your understanding by googling up answers to your questions you must be prepared to learn enough to understand, otherwise you can't tell the difference between fact and plausible fiction. The web is full of plausible fiction.
My first two DSLRs didn't have any AF adjust. I discovered that my longest lens with shallowest depth of focus back focused a bit on both of them. I tried the experiment of adjusting the position of the AF sensor plane. Owners weren't supposed to do that, but I'm a tinkerer. To my surprise once I got that lens doing AF accurately, I discovered that I'd improved focus with a few others lenses that I hadn't realised I had a problem with. That's when I decided I wouldn't buy any camera in future without AF adjustments accessible to the owner.
Of course if you're not good at learning technical stuff or find careful experimenting too tedious you should get someone else to do it. I'm good at learning technical stuff and enjoy experimenting. I'm delighted to have a camera with AF adjust for individual lenses. In that respect I'm very pleased to be abnormal. It helps me get abnormally sharp photographs
My first two DSLRs didn't have any AF adjust. I discovered that my longest lens with shallowest depth of focus back focused a bit on both of them. I tried the experiment of adjusting the position of the AF sensor plane. Owners weren't supposed to do that, but I'm a tinkerer. To my surprise once I got that lens doing AF accurately, I discovered that I'd improved focus with a few others lenses that I hadn't realised I had a problem with. That's when I decided I wouldn't buy any camera in future without AF adjustments accessible to the owner.
Of course if you're not good at learning technical stuff or find careful experimenting too tedious you should get someone else to do it. I'm good at learning technical stuff and enjoy experimenting. I'm delighted to have a camera with AF adjust for individual lenses. In that respect I'm very pleased to be abnormal. It helps me get abnormally sharp photographs
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At last I have found out distances to fine tune a lens to camera. Virtually every site says do this or do that but doesn't give the information one wants.
So here is one I did find giving mm/distance/fstop
Those distances are far too close for shorter focal lengths. 1.3ft at 16mm?! If you follow those, there's a very good chance that AF accuracy will be out at longer, normal distances.
There is no perfect distance for AF microadjustment and it's always a compromise, but something resembling real-world shooting distances is what you should be aiming for.
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Chris quote "If your camera has micro focus adjust so you can trim the AF for each lens, then your camera manual will contain the information on how to do it, including distances" unquote
i have been through all 447 pages of the user manual on the Nikons D800 and the D300 which has 421 pages and I can't find any mention of the distance fine tuning to be set at. Can you can tell me which page you saw it on?
maybe I missed it but I would have thought it would at least have taken up one page
Alex quote "What makes you think those distances are any better than others?" unquote
Could you tell me where you have found the other information on fine tuning distance given please as you presumably have found some.
What makes you think those distances are any better than others?
I use a spyderlensCal at a parallel height to the sensor lens and lined up square with the camera, so the above distance is I agree is the only variable which is why I searched for a distance chart which i quoted as above
i have been through all 447 pages of the user manual on the Nikons D800 and the D300 which has 421 pages and I can't find any mention of the distance fine tuning to be set at. Can you can tell me which page you saw it on?
maybe I missed it but I would have thought it would at least have taken up one page
Alex quote "What makes you think those distances are any better than others?" unquote
Could you tell me where you have found the other information on fine tuning distance given please as you presumably have found some.
What makes you think those distances are any better than others?
I use a spyderlensCal at a parallel height to the sensor lens and lined up square with the camera, so the above distance is I agree is the only variable which is why I searched for a distance chart which i quoted as above
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Kodiak Qc
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That would make two of us!!!
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How many times have I seen Posts about lenses being out of focus and sent back for recalibration? too many times is the answer. So in reality there has to be a starting point before deciding if a lens needs calibration or not . Hence I posted to help in making that decision
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Not having a Nikon I didn't see it in a Nikon D800 manual. Sorry your Nikon manual has no distance suggestions for AF adjust. The usual recommendation is 50X the focal length, in the case of zooms the focal length(s) you prefer to optimise.
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•Why do some of your posts start with a dot?
Well observed! …but you just caught me with my pants down!
I think… (no, I'm sure) it is my way to take a deep breath as I try to put my
ideas together and translate them in english the best I can. This translation
effort plus the fact that I am a very bad typist (I hate typing) is an exercise
that will demand all my attention.
The dot may very well mean: "Ok, let's do this!"
For more, I would have to see a psychiatrist…
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Over the last several years, with every new body or lens, I've packed the kit off for calibration.
I'm asked what distance I shoot at for each lens and they calibrate it for that.
I had a canon 100mm macro lens that was once perfectly calibrated for close up macro work - except I used it for outdoor portraits taken 3-5 meters from the subject. AF was 50cm out in this case and had to be returned for recalibration.
So work out what distance you are most often going to be shooting at and use that as your basis.
I'm asked what distance I shoot at for each lens and they calibrate it for that.
I had a canon 100mm macro lens that was once perfectly calibrated for close up macro work - except I used it for outdoor portraits taken 3-5 meters from the subject. AF was 50cm out in this case and had to be returned for recalibration.
So work out what distance you are most often going to be shooting at and use that as your basis.
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Reikan, say in their "Testing Manual" for Focal...
"The distance to the target will usually affect the AF microadjustment value by a small amount. As you approach minimum focus distance (MFD), the values can sometimes become quite different to the rest of the range.
What does this mean? Well, in reality, it means that you can either calibrate your lens to work as well as possible very close and not very good far away, or go for the opposite way round.
In one of their MA calibration documents, Canon recommends calibrating at 50x the focal length of the lens. This generally keeps well away from MFD and is not such a bad “standard” for all lenses."
They go on to say...
"In practice, the distance you calibrate at is the distance that the selected AF microadjustment value will be correct for. So you should try to pick a distance that is around the “most used” distance for your particular shooting style."
*** Obviously, if Reikan object to me quoting this, I'll delete it. ***
"The distance to the target will usually affect the AF microadjustment value by a small amount. As you approach minimum focus distance (MFD), the values can sometimes become quite different to the rest of the range.
What does this mean? Well, in reality, it means that you can either calibrate your lens to work as well as possible very close and not very good far away, or go for the opposite way round.
In one of their MA calibration documents, Canon recommends calibrating at 50x the focal length of the lens. This generally keeps well away from MFD and is not such a bad “standard” for all lenses."
They go on to say...
"In practice, the distance you calibrate at is the distance that the selected AF microadjustment value will be correct for. So you should try to pick a distance that is around the “most used” distance for your particular shooting style."
*** Obviously, if Reikan object to me quoting this, I'll delete it. ***
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Me too either I'm not fussy enough or I've been very lucky with my lenses! Ad adjust just seems to be a black hole of tinkering!
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If you shoot fast glass wide open very often it's much more crucial to have lenses accurately calibrated. It's the first thing I do when I buy them, but I use a row of batteries staggered at 45*.
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Test target should be flat, square to the camera, and at a realistic distance. A line of batteries at 45 degrees fails on all three points
AF points are usually sensitive to a larger area than shown in the viewfinder, so with anything but a flat target, positioned square to the camera, you can never be certain what distance the AF system has chosen to lock on to.
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Test target should be flat, square to the camera, and at a realistic distance. A line of batteries at 45 degrees fails on all three points
AF points are usually sensitive to a larger area than shown in the viewfinder, so with anything but a flat target, positioned square to the camera, you can never be certain what distance the AF system has chosen to lock on to.
Well, it's what I do and it works. I'm as anal as they come when it comes to exacting AF performance and this test is closer to real world use than any other I've used.
Actually, that's not true. I've also tried the cornflake box with a ruler laid at 45* next to it to determine front or back focussing issues and have honestly not found it to be any more accurate.
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Zooms are the most frustrating lenses imaginable. If I buy a lens and it can only be adjusted well at one end I send it back.
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So true, but it amazes me how many people do it..
The chart at the top of this thread is rendered almost useless because of the decimalised distance measurements. E.g does 16.4 feet mean 16 feet 4 inches or does it mean 16 feet plus 4/10 of a foot?
Test target should be flat, square to the camera, and at a realistic distance. A line of batteries at 45 degrees fails on all three points
AF points are usually sensitive to a larger area than shown in the viewfinder, so with anything but a flat target, positioned square to the camera, you can never be certain what distance the AF system has chosen to lock on to.
Richard, I'm familiar with this testing methodology and tried it amongst others. However, I would say i'm with Dean on this when it comes to real world approximations. I make my living shooting portraits and I want the eye I focus on to be in focus and not as was recently case on my subjects nipple, several inches in front of her eye due to severe front focus issues! Sure, any method could have picked up something this severe (apart from the facilities at the canon authorised service centre apparently), but say I take a few bottles of whisky and line them up at 35 degrees. I'll then take one with the bland skin coloured label that doesn't offer much contrast akin to a womans delicate complexion. Then I'll focus from a typical shooting distance on to a line of text that curves around the bottle, simulating her eyelashes that I wanted sharply in focus.
I'll take a series of shots, manually adjusting focus one way and then the other for it to reacquire focus lock.
My canons were useless at this. The Nikons flawless.
So basically, if I'm going to be taking test shots, I want them to be as representative of real shots that I'm making a living off as possible.
Once I've figured out if theres an issue however, its a ruler at 45 degrees, typical shooting distance, tripod, timer and af micro adjust or back to the service centre.
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If I buy a lens or body that needs micro adjusting, it gets sent back. Damned if i`m doing Nikons QC for them.
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I've only ever had one decent Nikon body that worked perfectly with every lens. I'm with you on that from now on.
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They bl00dy well should be, especially for the price of much of the kit!
Let's just have a think about `production lines`.
Cars, computers............
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Quite, cornflakes just won't do - nothing but Optivita for me. Or you can pay £50 for a Spyder Lenscal, that does exactly the same thing http://www.amazon.co.uk/datacolor-S...3001107&sr=1-3&keywords=lens+calibration+tool
The DIY route can also be scaled up, using a bigger box and a longer ruler or similar for checking wide-angles. Also, once you've got the hang of the basic principle of AF micro-adjustment, you can improvise with real world subjects, eg a fence or wall at an angle with a suitable target positioned against it - good for checking longer distances with telephotos. Or a car number plate, where you can see the actual focused point on the tarmac* or a road sign where the actual focused point can be seen on the road/grass below. I do this a lot with my lens testing work for magazines, when out and about and need to give the AF a tweak
*Edit: For this method, I get a small stone or scrap of something and put it on the road, positioned exactly in line with the number plate. When shooting from some distance, this reference easily shows exactly which point on the tarmac should be accurately focused. Slight changes in distance, ie when your standing hand-held, don't matter as the AF system automatically adjusts for this - so long as you refocus every shot, and make sure you don't move between focusing and tripping the shutter.
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AFAIC, the method is less important than the results. After I fine tune do I hit focus +90% of the time on the eye I'm aiming for whilst shooting wide open? If the answer is yes then I'm happy, and whether that causes a face palm from anyone is irrelevant to me.
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There's obviously nothing wrong with your method, and the way you're assessing it - using bottles is a far larger and more realistic target than a line of AA batteries. You also appear to be doing more than an straightforward AF calibration, and assessing how your particular AF system selects the exact focus point. For a basic AF micro-adjustment there is some risk in doing that, but you seem to know what you're doing
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Very diplomatic, Richard.There's obviously nothing wrong with your method, and the way you're assessing it - using bottles is a far larger and more realistic target than a line of AA batteries. You also appear to be doing more than an straightforward AF calibration, and assessing how your particular AF system selects the exact focus point. For a basic AF micro-adjustment there is some risk in doing that, but you seem to know what you're doing