p.35 #1 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
snapsy wrote:
Many times the best inventions are those which are obvious in retrospect. If it was obvious to Nikon they would have implemented it years ago. 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).
I understand that, I was just thinking out loud because I was curious if they could also do it by comparing actual photos, necessary or not I'm sure it's faster to just do it with the hardware as it is likely done.
p.35 #2 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
woutgeo wrote:
When I did dot-tune I noticed that I had lenses with quite small ranges (6 steps) of acceptable focus and others with much larger ranges (14 steps). Does this have any meaning?
Lenses with greater DOF will be less sensitive to fine tune values, but without more info I'm not sure exactly if that applies to your situation.
p.35 #3 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
CanadaMark wrote:
Lenses with greater DOF will be less sensitive to fine tune values, but without more info I'm not sure exactly if that applies to your situation.
I should have clarified that this was happening at the same f-stop. Specifically, I noticed a big difference between my 100mm f/2.8L Macro and my 14mm f/2.8L (both set up at 50x). The only thing I could chalk this up to was user error.
p.35 #4 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
woutgeo wrote:
When I did dot-tune I noticed that I had lenses with quite small ranges (6 steps) of acceptable focus and others with much larger ranges (14 steps). Does this have any meaning?
It has meaning and relates to how the phase-differential sampling can be affected by different lenses and optics (focal length, contrast differential between focused and slightly OOF, etc...). Fortunately it doesn't have significance for DotTune because as long as the confirmed ranged fits within the full +/-20 range the midpoint of the range will still represent the optimal AF tune value irrespective of how large the range is.
p.35 #5 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
snapsy wrote:
It has meaning and relates to how the phase-differential sampling can be affected by different lenses and optics (focal length, contrast differential between focused and slightly OOF, etc...). Fortunately it doesn't have significance for DotTune because as long as the confirmed ranged fits within the full +/-20 range the midpoint of the range will still represent the optimal AF tune value irrespective of how large the range is.
Does this mean there *should* be a standard range for a specific lens/body combination? In other words, should the range of my 100mm f/2.8 on a 5D MK2 be the same as someone else's? If so, does this simplify the process even more, allowing you to just find one end of the range?
p.35 #6 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
woutgeo wrote:
Does this mean there *should* be a standard range for a specific lens/body combination? In other words, should the range of my 100mm f/2.8 on a 5D MK2 be the same as someone else's? If so, does this simplify the process even more, allowing you to just find one end of the range?
I suspect the range would be similar for a given body+lens combination but only if the focus distance and target was precisely the same, which would be hard to achieve in practice. I don't think it would help the process much since the end of the range for a specific body+lens copy would still need to be arrived at empirically.
p.35 #7 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
snapsy wrote:
I suspect the range would be similar for a given body+lens combination but only if the focus distance and target was precisely the same, which would be hard to achieve in practice. I don't think it would help the process much since the end of the range for a specific body+lens copy would still need to be arrived at empirically.
p.35 #8 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
woutgeo wrote:
And lighting, I suspect.
Definitely - lighting has a significant effect on the result, particularly the lighting temperature but also the diffuseness of the lighting as well. High-contrast lighting produces the worst result because it creates aberrations off the target.
p.35 #10 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
Can I ask a quick question about one of the steps in the dot tune method? In the step where you switch to live view, use autofocus on a target and then adjust the focus manually in live view at 10x, Would we not want to leave the autofocus as the camera determines it and then move to the step where you adjust the afma to find each end of the spectrum? It seems like if I manually adjust the focus point I am defeating the purpose of the process, though I could be wrong here just hoping for some clarification.
p.35 #11 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
Noel West wrote:
Can I ask a quick question about one of the steps in the dot tune method? In the step where you switch to live view, use autofocus on a target and then adjust the focus manually in live view at 10x, Would we not want to leave the autofocus as the camera determines it and then move to the step where you adjust the afma to find each end of the spectrum? It seems like if I manually adjust the focus point I am defeating the purpose of the process, though I could be wrong here just hoping for some clarification.
You can use LV AF or LV manual focus or a combination of the two. Whatever you feel is the best method to get precise focus before starting the AF tune scaling steps.
p.35 #12 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
woutgeo wrote:
I should have clarified that this was happening at the same f-stop. Specifically, I noticed a big difference between my 100mm f/2.8L Macro and my 14mm f/2.8L (both set up at 50x). The only thing I could chalk this up to was user error.
At 14mm ( 50x ) you need to be at 0.7m or 2.29 feet from your target.
At 100mm ( 40x ) you need to be at 4m or 13.12 feet from your target.
p.35 #13 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
I just installed magic lantern on my 6d but dot tune is not in the menu. Do I maybe have the wrong version of ML? Can anyone point me in the right direction?
p.35 #17 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
It's there, I just used it on my 6D. You have to enable it in the setup menu, then go to the control menu to use it. It works quite well.
kkroeker wrote:
I just installed magic lantern on my 6d but dot tune is not in the menu. Do I maybe have the wrong version of ML? Can anyone point me in the right direction?
p.35 #18 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
Snapsy,
IMHO, one of the novel, yet obvious after the fact parts of your dottune method, was the concept of identifying the Range for PD AF confirmation. I would guess that AF confirmation is a threshold, hence no true peak created by pd AF screen signal(imho). If true, then any automation using PD AF signal with 'walking' mfa values would need to also ideal tiny the range.
Now, a more perfect way IS possible in current processor right cameras. Two digital images can be digitally compared through a correlation algorithm of the image by taking the known shape image and comparing it to the walking 1s images. Through correlation, a true peak MFA value can be identified for that FL and distance.
Now that I mention this correlation method, It would be interesting to do this off line (using a PC) to see if the mathematical correlation Peak really does correspond to the center of the range. (it might be more related to the true ratio of front and back dof from Live View optics dof.
snapsy wrote:
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.
p.35 #19 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
Noel West wrote:
Thanks for the reply Schlotz, I have been following those instructions. It is interesting that on my 1D Mk IV body where I am getting images quite out of focus at 400-600mm and at great distances that the camera focuses incorrectly in quick mode but gets much closer (if not perfect) using the live view focus mode. Must be as it is using contrast detection for focus as opposed to the af chip in quick mode.
It is difficult to fine tune focus using live view outdoors and at long distances as you get a lot of camera movement, I may try using my laptop using eos utility to see the image on a larger screen. I may also have to try doing the testing indoors as I haven't been able to find a day without wind which makes it much more difficult as well. As long as I am lighting the target (using a 12" x 18" pattern that is the updated version on the dot tune website) well I am assuming I should get as good results as if I was outdoors but I can see the live view image much better and not have to deal with wind.
I am testing at those 4 different AFMA distances as shown in the two charts below. I want to redo the infinity testing as I wasn't getting reliable data:
Noel,
(I haven't finished reading the thread but thought it would be worth mentioning in case it hasn't.)
Live view, when zoomed in to 10x, can still do Contrast AF so you know exactly where it is AF'ing. You don't want to do Quick Mode in live view as it does phase detect which you are adjusting. Mfa has no affect on Live View Contrast Detect.
For your specific focal lengths, why are you using multiple distances? Distance is known to affect focus, most people choose their most common distance for each FL.
Definitely get the new firmware for your Sigma. The amount of time you have spent is mind boggling. This Dottune method can usually be done in about 5 to 10 minutes using a stationary object with good contrast. You don't need fancy targets, just am object with reliable edges for the PD to work and contrast for the CDAF to work. Snaps's alias is very apprapo!
p.35 #20 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes
snapsy wrote:
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.
It sounds like the two of you might bereferring to two different things back in 2007. Sands, I Think CanadaMark was referring to just MFA capabilities on cameras back in 2007, not the dottune method.
I'm sure it's faster to just do it with the hardware as it is likely done.