Re: Dot-Tune: Autofocus Fine Tuning in under 5 minutes
CanadaMark wrote: snapsy wrote: CanadaMark wrote: snapsy wrote: CanadaMark wrote: thepiecesfit wrote:
Ive found dot tune to be a bit inconsistent, even the automated version in Magic Lantern. The easiest way is to send your gear to the manufacturer sadly. My 5d3 85 1.2 and 135 brought into Canon and all came back perfect at 0 AMFA.
I would agree and I find it\'s a band-aid solution at best. People have been using this method since ~2007 albeit not with the same catchy name. If the gear cannot be calibrated perfectly at all combinations of focal length and subject distance (extremely rare for a zoom), it should be exchanged or sent along with the body for factory calibration in my opinion.
Can you share a reference from 2007 of this method being used? Nikon\'s implementation of their automated tuning method in the D5/D500 appears to function in the same manner as DotTune (based on the description provided in their tech sheet), so apparently Nikon finds value in it even if some don\'t share that opinion.
I don\'t have the time to dig around for 8-9 year old forums posts with no easily searchable key word, sorry An employee at a local camera store was talking about this general method way back in the day when the D3 was still new and everyone was excited about AF fine tune, that\'s where I very first heard of it myself.
Nikon\'s automated implementation on the D5/D500 just compares CDAF to PDAF as far as I can tell, which has been the most basic way to do it since the beginning - there is no mention of viewfinder focus indicator unless perhaps I missed something. With the D5 apparently already out in some parts of the world, we should see the finer details on the process revealed soon enough. Automating the AFFT process and making it quick & easy will primarily be useful for quickly determining if you need to exchange a lens or not, and may be quick enough to be done in a camera store, which I think could be very useful.
I think lens returns & exchanges are going to go way up after the D5/D500 because customers are going to now have a numerical value generated by the camera itself to \'prove\' a lens is out of calibration using an easily understandable quantitative scale. How I see this happening is they will run the calibration at a few combinations, and if the values are different across the range, it probably can\'t be reliably tuned and people will exchange it. As far as I know it still only stores a value for a single combination of focal length and distance which is again at best a band-aid solution for most people, especially if you\'re picky.
Nikon\'s D5/D500 mechanism uses CDAF to focus and then likely cycles through all the PDAF AF tune values to find the one with the strongest PDAF focus confirmation. It\'s the same method used by DotTune but automated - the feedback from the focus confirmation is sampled directly by firmware from the same mechanism that drives the VF rangefinder display. It\'s how the automated version of DotTune in Magic Lantern works on Canon bodies - the ML firmware samples a firmware PDAF confirmation flag in memory, the same flag that is used to drive the VF confirmation dot.
If it ends up working exactly like that, it sounds like they just automated the most obvious way to do it using a guess & check algorithm that people have been doing manually for years. Definitely still a time saver, and I am curious to read about it in detail. I wonder if it could also be done by taking pictures and comparing edge contrast, but I imagine that would be far more complex. Regardless, like I was saying, I think they are going to see lens returns & exchanges go way up! I can see it now... \"The camera says the lens is out by -15, I need to exchange please.\"
Many times the best inventions are those which are obvious in retrospect. Btw Canon has a patent on a similar technique. There\'s no need to take pictures because the PDAF differential can be sampled from the AF sensor once perfect focus has been established (either via CDAF or manual focus).
Mar 17, 2016 at 03:06 PM
Previous versions of snapsy's message #13468590 « Dot-Tune: Autofocus Fine Tuning in under 5 minutes »
An employee at a local camera store was talking about this general method way back in the day when the D3 was still new and everyone was excited about AF fine tune, that\'s where I very first heard of it myself.