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Lens Auto Focus Tuning

Lens Auto Focus Tuning

Lens Auto Focus Tuning

Lens Auto Focus Tuning

Often we find when I want to play bokeh with f large openings for example f1.8, the lens is very soft. After being reduced by 1 f-stop to f2.5 – f2.8 it usually returns sharply. 
Lens Auto Focus Tuning

Lens Auto Focus Tuning (https://i.ytimg.com/)

So you bought f1.8 lens yesterday or f2.8 huh? Well, I believe the desire to get sharp images in the DOF area according to the specifications of the lens you have purchased is a dream … that hasn’t even been realized? Let’s continue with the discussion about sharp or not sharp, focused or not focused, missed? shake? 

In general, the essence of this article is Lens Calibration or lens calibration. If you find that the case of soft lesions is very far compared to when the stop down to 1 f-stop, then the AF calibration should be done. If you currently have very sharp results in the largest openings, then this article can be scanned.

Miss Focus Factor
From a number of experiences that have been, the factors that are often the cause of the auto-focus misses are the following:
  1. These affordable lenses are produced thousands of times, in addition to saving costs, it is targeting prosumer or non-pro photographers, all of them definitely like 50mm f1.8, right? … right. This is what makes quality control, especially mechanical focus on lenses of this type not as tight as Canon L or Nikon Gold Ring lenses.
  2. AF mechanical system on the body, so it’s not just the lens that makes the focus miss, it could be your body that actually makes the X miss focus lens. For crossing factors no. 1 and 2 it is a good idea to exchange lenses and cameras with each other and test them with friends, if necessary and if there is time.
  3. A used lens, which we don’t know has ever fallen to the floor, hit a wall? or have been washed because of fungus
  4. Too late pressing the shutter when the subject turns out to be moving / moving in a coordinate z axis (depth, back and forth), understand, even the subject retreating just 1cm of natural movement is already out of sharp space when you use a very large f with close subject distance.
What we will discuss next is only factors number 1, 2 and 3, because number 4 is too personal. 

AF Tune / AF Micro adjustment
In the example in this article, I used the Nikon D700 body. This focus tuning feature is basically the same in function, only the names that sound different. 
At Nikon, it’s called  AF Fine Tune , Canon and Sony:  AF Microadjustment , Pentax:  AF Adjustment , Olympus:  AF Focus Adjust . But unfortunately this lens tuning feature apparently can not be found in the body of the entry camera, so please note the following Nikon and Canon cameras that have this feature to immediately save the disease of your lens miss focus:
  • Nikon D7000 / 7100, D300, D600, D700, D3, D4
  • Canon 50D, 7D, 6D, 5D, 1D
* sorry for other brands I am not familiar with, please be advised 

Lens Calibration
It should be noted earlier, that both modern AF lenses and modern DSLR bodies have CPUs that interact with each other. So every time we do a calibration on lens A, it will automatically save presets for lens A.
When we replace lens B, the additional tuning focus is automatically off for lens B. The body activates lens tuning A only for lens A. Here what is read is ID lens, not the type of lens. So don’t worry to change the lens between the yellow and the yellow ones. 

What is needed is Lens Align as shown below

The way this tool works is very simple, with us aiming for one of the points in the biggest f opening, if it’s not sharp, it means a miss focus lens. Then tune slowly + or – from the camera body to get the sharpest. I don’t really understand in Indonesia where to go and the price could be millions. To be practical we use other methods that are more economical, but you are required to be very sensitive and patient. 

The following is a very short tutorial in point flow:
  • Our D700 camera is set on a tripod (yes, it must be a tripod because we are going to do an image comparison)
  • Setting (conditioning) ISO 3200, 1/25
  • The coincidence lens is a 24mm f / 2.8 old school AF lens, buy 2nd hand how many times this is a clear miss focus on the biggest aperture, so our lens is set f2.8
  • Make the subject pattern lined up at least 2 positions front and back, it’s good to be closer together, imagine you put the property like the Lens Align image above
  • Aim for consistent focus on the most contrasting subjects
  • The default AF Tune is 0, if you don’t feel it sharp, do an extreme tune to +10 or -10, to determine whether this is  front focusing  or  back focusing
  • Snap, zoom 100%, observe and feel … or if you want to definitely check on a computer with a bigger screen, do it again
  • If you have found the character missed, do precision tune slowly until it can be the sharpest, the body gives room tuning -20 to +20
  • Already sharp ? Enjoy, your lens seems to be reborn

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