Suggestion to Nikon regarding AF fine tuning.

[chuck]

Having found my sample of 70-200 VR required large amount of AF fine tunning on the D810, I decided to calibrate the focus of every

AF lens I have using the D810's focus fine tunning feature.

 

Having spent a whole day doing this, I have several suggestions for Nikon:

 

1. Record the amount of AF fine tunning used with the lens in shooting data.

 

2. Instead of having the user dial in different amount of AF fine tuning via trial and error, The camera should allow the user to focus

manually with live view, and then record the focus position the user entered, and when the user switch the camera back to phase

detection AF, the camera should automatically determine the difference between the manual focus distance and what the phase detection

AF thinks ought to be the focus distance, and calculate the equivalent amount of AF fine tuning to go from what the phase detection AF

thinks is the right focus, and what the manual focus position actually is. In fact, it should allow the user to repeat this procedure several

times, and the camera should then average these to AUTOMATICALLY arrive at a best average AF fine tunning value.

[Ian Rance]

<p>I think that the problem is that the accuracy of the distance (D) register on the lens is not accurate enough to work with the fine tune. So what you are saying would work well IF the distance register on the lens was accurate enough to apply the various offsets. As it is the focus in live view is completely separate from that in normal phase detect and if you then get perfect focus in live view the camera still does not know what the offset is compared to what the camera thinks is correct due to the technology not being enough to make this happen. Perhaps if Nikon were to massively up the distance technology then it could happen.</p>

[rodeo_joe1]

<p>+1 to Ian's reply. There just isn't enough accuracy in the data delivered from the lens to the camera body, since we're looking at millimetres (or less) DoF in metres of subject distance when wide-aperture lenses are used - especially if you're pixel peeping on the likes of a D810. Other issues are that zoom lenses don't keep the same focus error throughout their zooming range, and wide-aperture lenses often shift focus as they're stopped down. I'm pretty sure that pointing a lens up or down might affect its AF accuracy too.</p>

<p>My own suggestion to Nikon would be to drastically widen the range of AF "fine" tune available. I've had lenses that needed more adjustment than was possible. Admittedly they were mostly 3rd party lenses, and quite old ones at that. I've also noticed that new lenses need a running-in period, and that their focussing becomes more, or less, accurate over the first few days or weeks of use.</p>

<p>Basically camera-body sensor based AF isn't perfect, and I don't foresee it getting much more perfect in the near future. Anything that moves is subject to tolerances and backlash or wear in the mechanical parts. The only thing that would really work is a complete real-time servo loop between sensor and lens motor to keep the desired area in focus, but even that could be fooled by lack of subject texture. Live View is nearly there, but Nikon's implementation of it on DSLRs leaves quite a bit to be desired. Mirrorless is probably the future. Short of Laser Interferometer range-finding.</p>

[dmanthree]

<p>Better idea: eliminate the mirror and put the PDAF senors on the imaging sensor itself. Then there's no need for AF adjustment. Hopefully, we'll get there soon.</p>

[Ian Rance]

<p>Surely that would be CDAF David - like normal live view? What would the mirror do during the AF operation - it would be in the way surely?</p>

[joseph_smith3]

<p>Chuck, like you I have spent hours trying to properly calculate and then set the AF fine tune adjustment needed for each of my Nikon lenses on my D 800E and D 810.<br>

One step that eased the process was to view all of the images taken with Nikon View NX2 in that this software does show each unique AF fine tune setting made for each individual image taken during the testing process. This is free Nikon software. Just download it from Nikonusa. It saves you from having to record the data as you take the test images. <br>

I could not believe the amounts of adjustments required across the different lenses on my two bodies. Adjustments ranging from minus 12 to plus 12-15 were needed. I am going to redo some of the tests to make sure I did not introduce any errors in the AF settings through poor testing techniques. I do agree with the recommendation that greater ranges ought to be built into the camera menu software. <br>

I believe that you can view the AF adjustment setting you have made for a particular lens only when that lens is mounted to the camera body. If this is true, I would like to view this information for a particular lens without having to mount that lens. This way I could double check the setting made against what I am viewing with Nikon View NX2.<br>

The biggest change needed is to allow for multiple AF fine tuning settings for your zoom lenses like a 70-200mm.<br>

I would also like to see Nikon use tighter tighter tolerances during the manufacturing stage for its cameras and lenses. Given what we are paying for these items, there ought to be more effective ways to correct/prevent these out of spec AF fine tune adjustments. That being said at least we have a way of making them when needed. <br>

Joe Smith</p>

 

[dmanthree]

<p>Ian: no, I mean PDAF. Sony and Canon already do this. The latest A7, the A7r II has PDAF sensors on the imaging sensor. And "mirrorless" means that there isn't a mirror. Full time live view, electronic first curtain or global shutter, and no need for AF adjustments.</p>

[bob_h]

<p>In a perfect world we should not have to make AF fine tuning adjustments. If we could send astronauts to the moon 46 years ago, one would think that AF adjustments should be a piece of cake and completely not necessary now. Still waiting for that perfect world.....</p>

[dmanthree]

<p>Bob, that "perfect" world exists in any CDAF camera or one with PDAF sensors on the imaging sensor. No microfocus adjustments needed there. Not to worry, our SLRs will get it some day.</p>

[pete_s.]

<p>Some adjustments should be made in the camera while others should actually be made on the lens itself.</p>

<p>The camera has an electronic adjustments for AF fine tuning that is adjustable by service technicians only. This is for the entire camera and not on a per lens basis. The mount is mechanically adjustable with shims, the mirrors with mirror stops and both affects the AF. The actual distance between the bayonet mount and the sensor is also adjustable but only when the camera is almost disassembled. The nominal value is 46.50mm.</p>

<p>The lens (AF-S lenses) has aberration correction values inside the lens as well as focus fine tuning, at least max and min focal length for zoom lenses. There are also fine tuning of the focus motor inside the lens that adjust the speed and the precision. These can be changed by a service technician. The back focus (distance from the mount on the lens to where the lens projects the image on the sensor) is also adjustable on the mount mechanically.</p>

<p>The AF fine tune in the camera is just a compromise. In real life the sensor to mount should be adjusted mechanically first, then the mirror and the viewfinder and finally the AF adjusted in the camera to align with the sensor to mount distance. Now the camera is as perfect as it can be.</p>

<p>Now if you put on a lens that isn't good it should have it's back focus adjusted mechanically, then the AF adjustments in the lens fine tuned. Now the lens is as perfect as it can be.</p>

<p>When the camera is as perfect as it can be and the lenses are as perfect as they can be then the system is as good as it can be. No AF fine tuning needed by the photographer really. Nikon service can do this, they have the tools and they have the knowledge. They just don't have as many that are willing to pay them. They could do it at the factory too but then there would not be as many willing to pay the price of the camera. And most people wont notice or care anyway.</p>

<p>Most of the real adjustments that should be made are actually the mechanical ones. But it's faster to have them slightly off and just adjust electronically. Unfortunately the error piles up then as you add more bodies and lenses. For instacne what should you do when you have two identical lenses? You can only AF fine tune for one lens type, not an individual lens.</p>

<p>At least in the past, a lot of pros sent in their cameras and lenses to Canon CPS and had them all checked and adjusted on a yearly basis. Since there is a lot of plastic in the lenses and cameras and things get bumped around adjustments will need to be checked regularly.</p>

<p>If the AF fine tune in the camera is not enough to adjust the AF or if you need highly different AF fine tune values for different focal lengths, it's a sign that you should send both the camera and lens to Nikon for adjustment. I used to live 5 minutes from Nikon - life was good then :-)</p>