Looks pretty good as it uses LV which is accurate and consistent as the base.
http://www.fredmiranda.com/forum/topic/1187247/0
http://www.fredmiranda.com/forum/topic/1187247/0
New MFA method
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Pure genius.
This is something so simple that even the camera manufacturers should be able to program it into their firmware.
Now wouldn't that be nice... just point the camera at a target at the distance where you wanted AF fine tune to be optimized, and press a button which would do this procedure instantly and electronically. You could even re-tune your cameras for a new distance (i.e., when shooting from the back row vs. front row) in real time on the job.
I'm definitely trying it. Why didn't we think of this before? It's so obvious.
This is something so simple that even the camera manufacturers should be able to program it into their firmware.
Now wouldn't that be nice... just point the camera at a target at the distance where you wanted AF fine tune to be optimized, and press a button which would do this procedure instantly and electronically. You could even re-tune your cameras for a new distance (i.e., when shooting from the back row vs. front row) in real time on the job.
I'm definitely trying it. Why didn't we think of this before? It's so obvious.
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Loswr
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helpful said:
Something similar has been suggested:
In theory, it should be possible to achieve an ‘accurate’ focus using contrast detection in Live View, where no alignment is needed because the image sensor is used to determine best focus, then compare that to the phase detection AF and correct accordingly. In practice, this is something that’s difficult to do (because the act of moving the focus ring to see if you were really optimally focused changes the focus, and you lose the ‘zero point’). However, this is an idea that Canon could implement as a semi-automated routine, i.e. set up and align target (Canon could sell one, and suitably overcharge for it as they do for other small pieces of plastic *cough*), then the camera automatically determines the optimal adjustment. File that one under ‘gee, wouldn’t it be nice…’
Using AF Confirmation for manual focus to avoid having to move the focus ring is a nice solution!
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That is a really interesting solution.
However...the great thing about FoCal isn't just the automation, but the fact that it's automated.
I wonder, though, if this might inspire the FoCal crew to a faster way to do their magic. Is focus confirmation without focus available through the SDK?
b&
However...the great thing about FoCal isn't just the automation, but the fact that it's automated.
I wonder, though, if this might inspire the FoCal crew to a faster way to do their magic. Is focus confirmation without focus available through the SDK?
b&
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What's even cooler about this method is that the sensor is used only once, at the very beginning. The imaging sensor isn't even used when performing the phase detection AF afterwards.
In contrast, using live view continuously as with FoCal, etc., slowly warms up the sensor and increases the noise and decreases the live view focusing accuracy.
So this method should give maximum accuracy, although it all is dependent on not bumping or vibrating the lens when flipping the switch to manual focus after the first live view photograph is taken.
In contrast, using live view continuously as with FoCal, etc., slowly warms up the sensor and increases the noise and decreases the live view focusing accuracy.
So this method should give maximum accuracy, although it all is dependent on not bumping or vibrating the lens when flipping the switch to manual focus after the first live view photograph is taken.
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TrumpetPower! said:
I use and like FoCal...but it is not fully automated with either 1DX or 5D3. "Change to -20, or +20, +10, -10, etc etc" is not exactly automation...and FoCal puts it on Cannon and I am sure Canon has no interest in making it easy for FoCal. Still, it is a great program.
But the approach in this post looks interesting.
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C'mon don't give half-hearted compliment. It's little more than similar. The crux here is to find the spread of focus distribution with MFA adjustment around the best focus achieved by live view. Its smart. Rather, what you quoted is very straightforward.neuroanatomist said:
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I dont know much about AFMA since I've never owned a body that has the feature, but after finding the acceptable range with AF confirmation wouldn't you want to set it to a value that is on the first 3rd of the lower end instead of the midpoint, since the focal plane extends 1/3 in front of the subject and 2/3 behind?
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It will be interesting to get some feedback on how it works. I have always believed that an MFA system should be based on LV. As suggested it could be incorporated in the camera system.
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Liveview AF (contrast Detect), at least on the 5D MK II and 7D has turned out to be inaccurate and inconsistent. The focus method described was one I used a couple of years back, its nothing new. Unfortunately, it is unreliable because it assumes thet Contrest Dect AF is accurate, but it has been shown to have errors, so much that FoCal had to change their software to accomodate the errors.
The most accurate methods still need about 10 shots setting the lens AF back to infinity or MFD and then throwing out obvious errors in focusing and averaging the others. Then, most shots will be in focus, but there will always be a few outliers. The 6D seem to have more accurate CD focus, the 5D MK II and 7D tends to be worse. The figures for the 5D MK III are not in yet.
http://www.reikan.co.uk/focalweb/index.php/2012/12/af-consistency-comparison-nikon-canon-phase-detect-contrast-detect/
I'd avoid this method if you have a 5D MK II or a 7D. FoCal which allows you to take a large number of shots at each AFMA setting is a great tool for ignoring obvious AF errors and picking the correct setting that gives the highest number of in focus shots.
The most accurate methods still need about 10 shots setting the lens AF back to infinity or MFD and then throwing out obvious errors in focusing and averaging the others. Then, most shots will be in focus, but there will always be a few outliers. The 6D seem to have more accurate CD focus, the 5D MK II and 7D tends to be worse. The figures for the 5D MK III are not in yet.
http://www.reikan.co.uk/focalweb/index.php/2012/12/af-consistency-comparison-nikon-canon-phase-detect-contrast-detect/
I'd avoid this method if you have a 5D MK II or a 7D. FoCal which allows you to take a large number of shots at each AFMA setting is a great tool for ignoring obvious AF errors and picking the correct setting that gives the highest number of in focus shots.
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Hi everyone,
This is horshack (dpreview) / snapsy (FM), the guy who developed this AF tune technique. Don't get hung up on Live View - the fact that LV is used to establish critical focus (step 1) is only incidental to the process. You can use whatever focus method you want, including viewfinder AF or MF, LV contrast AF or MF...doesn't matter, as long as you establish and verify critical focus prior to starting the other steps.
What's unique about this technique is that you're using the confirmation dot and scaling the AF tune values to find the range and ultimate midpoint (final) AF tune value, all while keeping the same critical focus you established in step #1 (never refocusing). This avoids the mechanical AF variability that you get with all other MFA methods, since those involve reacquiring PDAF to verify focus, which in turn require multiple PDAF acquisitions/check cycles to normalize the PDAF variability out of the process.
This is horshack (dpreview) / snapsy (FM), the guy who developed this AF tune technique. Don't get hung up on Live View - the fact that LV is used to establish critical focus (step 1) is only incidental to the process. You can use whatever focus method you want, including viewfinder AF or MF, LV contrast AF or MF...doesn't matter, as long as you establish and verify critical focus prior to starting the other steps.
What's unique about this technique is that you're using the confirmation dot and scaling the AF tune values to find the range and ultimate midpoint (final) AF tune value, all while keeping the same critical focus you established in step #1 (never refocusing). This avoids the mechanical AF variability that you get with all other MFA methods, since those involve reacquiring PDAF to verify focus, which in turn require multiple PDAF acquisitions/check cycles to normalize the PDAF variability out of the process.
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Loswr
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Thanks, Mt. Spokane - I had read those data, and forgotten about them.
I wouldn't call it incidental. As you point out, establishing 'critical focus' is, well...critical. If LV is inconsistent, as the data indicate, there's no simple way to establish that baseline, certainly not with a single shot. Have you tested repeatability - several rounds of a single LV focus, resulting in the same selected AFMA value every time?
Have you, for example, used your method and selected an AFMA value 'on the edge' (one that gives confirmation where the next value out does not) then re-checked that value multiple times and seen confirmation every time, then the next value out and observed a lack of confirmation every time?
Thanks!
horshack said:
I wouldn't call it incidental. As you point out, establishing 'critical focus' is, well...critical. If LV is inconsistent, as the data indicate, there's no simple way to establish that baseline, certainly not with a single shot. Have you tested repeatability - several rounds of a single LV focus, resulting in the same selected AFMA value every time?
Have you, for example, used your method and selected an AFMA value 'on the edge' (one that gives confirmation where the next value out does not) then re-checked that value multiple times and seen confirmation every time, then the next value out and observed a lack of confirmation every time?
Thanks!
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Mt Spokane Photography said:
The accuracy of LV depends hugely on the light level. Without knowing that, I would take those tests with a grain of salt.
My own experience with the 5D2 and the 100L, LV, is as perfect focus as it gets, even in artificial but not too low light. In low light, it is unreliable or it just cannot focus when PD has no problems.
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neuroanatomist said:
If by LV being inconsistent you mean its CDAF then sure it's by no means infallible, although it is rather precise, both in my experience and in Roger's LensRental tests. But again you don't have to rely on its consistency because you can verify critical focus visually at 10x and adjust manually if necessary before proceeding with my method. Or focus entirely manually if you prefer. If by inconsistent you mean that LV @ 10x isn't sufficient for visually confirming critical focus, then that I would disagree with that. But you can always take a photo to confirm focus if you don't feel LV can be trusted.
As for the repeatability of my technique, so far it's been very consistent in my tests, to within one or two AF tune units across iterations, when using the same target, focus distance, and lighting conditions between iterations. If you change any of these factors then you may certainly get different results, but those differences will arise from the sensitivity of the PD phase sensing mechanism itself rather than from this specific technique (ie, you'd get the same AF tune deltas using other MFA techniques in those situations).
As for the accuracy of the technique, I developed and tested it first on a D800 with 5 different lenses, all of which produced AF tune values equal or better than what I achieved via LensAlign. I have also tested it on a 5DM3 with two lenses so far, with the same level of accuracy. On my original dpreview for the Nikon version of the technique (link: http://forums.dpreview.com/forums/post/50774257), everyone who has tried it so far has achieved similar levels of accuracy. I think a few have compared it to Focal as well.
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