New MFA method

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#21
neuroanatomist said:
If LV is inconsistent, as the data indicate(....)
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Is it actual live view that you've found to be inconsistent (that is, not an accurate representation of what the sensor captures), or is it live view slow mode autofocus that's inconsistent?

If it's the latter, I can easily believe that...on more than one occasion when doing tripod work, I've improved upon the autofocus. For most stuff it's "good enough," but it's not the gold standard.

If it's the former, though...well, that'd be a huge problem, actually....

b&
 
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#22
CD focus using liveview is what is inconsistent (on some bodies, but not all). That green dot is part of the CD focus system, so it is suspect as well.
The liveview image you see is right off the sensor, and is the image you are getting, so you can use 10X and focus fairly well using the rear LCD. Its better if you tether to a large monitor though.
 
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#23
But I think what he refers to is the green dot in PD mode not in CD mode. I agree LV does not always give you critical focus but it's a starting point and you can tweak manually from there. Here the use of a lenscal target, newsprint, or something like that would help get that LV 10X shot in perfect focus. So the question is the AF Detect system consistently flakey or just plain flakey? I tend to think it's consistently flakey and should work well in this case since you just trying to get the range and not an absolute.

We'll see, once I get over this flu I plan to try it out on my 300 2.8L and 600 F4L. It cant be any worse than focal in it's current state and if I dont have to carry my test setup out to a football field then it's worth it.

Mt Spokane Photography said:
CD focus using liveview is what is inconsistent (on some bodies, but not all). That green dot is part of the CD focus system, so it is suspect as well.
The liveview image you see is right off the sensor, and is the image you are getting, so you can use 10X and focus fairly well using the rear LCD. Its better if you tether to a large monitor though.
Click to expand...
 
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#29
Btw I've decided to put a name to the technique so that everyone has an easy way to refer to it and to make it web searchable as it evolves with any improvements. I'm calling it "DotTune", since the focus confirmation dot is central to the technique. I'm also working on a youtube video to bring it to a wider audience.
 
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#30
Tried this yesterday evening, and except for being a bit shocked for how much adjustment my shiny new 1DX needed (only the 24-70@24 came out at 0) it actually worked pretty well, that is when I double-checked some of the obtained values they were spot on...
 
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#32
horshack said:
Btw I've decided to put a name to the technique so that everyone has an easy way to refer to it and to make it web searchable as it evolves with any improvements. I'm calling it "DotTune", since the focus confirmation dot is central to the technique. I'm also working on a youtube video to bring it to a wider audience.
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Excellent job and a neat name ... what I like about this technique is that it is simple, pretty much anyone can do it without having to break their head. AWESOME! ... keep up the good work!
 
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#33
Tried this this morning on two lenses - my 85 1.4 Siggy and my 35L. -1 and +1 respectively, which correlates very closely with what I knew. My ranges of AF cut out for both were in the order of +9 and -9 (or thereabouts) - so a range of about 18. This seems like a pretty logical and effective method to me.
 
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#34
Well, this makes FoCal and LensAlign obsolete... or does it? Could there still be any advantage to a FoCal type method and, if so, how much better might it be?

The points made about being able to achieve critical/perfect/best (or whatever you might call it) focus using CD are valid, but I think it's a reasonable assumption that manual focus at 10x live view can get real darn close to perfect focus... anyone have any experience with that?

But, maybe perfect focus or repeatability don't matter so much... even using a theoretically "perfect" method only gets a theoretically "perfect AMFA setting" at one distance. If we accept that the AFMA setting can not be perfect anyway for all subject distances and focal lengths (for a zoom lens) and all we are trying to do is identify substantial systematic PD focus error and adjust to get closer to the centre of the focus variability then this method may do the job quite well.

Are we sure the focus confirmation dot in the viewfinder works exactly how we think it does? Does testing for the range of focus confirmation while in MF mode actually give us the centre of the focus variability when PDAF is functioning normally?

Hmmmm.... I suspect we'll see an official word from FoCal why this method doesn't work so good and we will all read it and collectively say "nice try, bye bye".
 
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#35
Meh said:
Hmmmm.... I suspect we'll see an official word from FoCal why this method doesn't work so good and we will all read it and collectively say "nice try, bye bye".
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Sorry to be cynical, but we live in a day and age where people and companies with any kind of commercial interest are known to tell a lot of lies and even defend them in court if it means that they can, well, maximise profit. They might of course really have something, but anything they say will have to be double checked. And although I'll have to do some more tests, as I wrote above, double checking this new method the other day indicated that it was spot on for me.
 
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#38
Even accounting for a margin of error of say 1-2 on the AFMA scale, I think this is a perfectly valid approach. I don't believe 1-2 (for example) would be noticeable in real life shooting. Essentially I think this method would satisfy 80-90% of AFMA users, even considering AFMA users are a pretty anal bunch :)
 
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#39
caruser said:
Meh said:
Hmmmm.... I suspect we'll see an official word from FoCal why this method doesn't work so good and we will all read it and collectively say "nice try, bye bye".
Click to expand...
Sorry to be cynical, but we live in a day and age where people and companies with any kind of commercial interest are known to tell a lot of lies and even defend them in court if it means that they can, well, maximise profit. They might of course really have something, but anything they say will have to be double checked. And although I'll have to do some more tests, as I wrote above, double checking this new method the other day indicated that it was spot on for me.
Click to expand...

That was in fact my point... that Focal will issue a explanation of why this DotTune doesn't work but we will say "nice try" to them. You hit the nail on the head... in order to protect their business they will come up with a reason even if it isn't quite true or if it overstates the advantage of their method.
 
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#40
Focal has the advantage of doing everything automatically (when it works as I've had the odd crash plus 5D3 is semi-auto) plus providing some data analysis and documentation that you can refer to later.

The question is whether that is of any tangible $ value to you if the end result is the same. I like automation (not having to touch the camera once the test is set up) and documentation so it would probably be worth it for me.
 
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