70D: MFA with dottune, amount question

[walkaround]

I just finished a round of using "dottune" to MFA my lenses with my 70D. I am consistently getting +3 and +4 with wide angle focal lengths 28mm and less. With telephotos 50mm and up, 0 or -1. In both primes and zooms.

Changing the distance to the target does not change the correction amount, although I started in all cases at 50x focal length printed on lens.

Photos seems to be accurate. I just took 30 frames of my kids scootering around me yesterday, using the 28/1.8, at f/2.8, auto ISO, center AF point, and I deleted only 2 frames for being out of focus.

Does this mean my particular 70D body is a "-3", and it's not really the lenses?

 

[Jerry-astro]

I just finished a round of using "dottune" to MFA my lenses with my 70D. I am consistently getting +3 and +4 with wide angle focal lengths 28mm and less. With telephotos 50mm and up, 0 or -1. In both primes and zooms.

Changing the distance to the target does not change the correction amount, although I started in all cases at 50x focal length printed on lens.

Photos seems to be accurate. I just took 30 frames of my kids scootering around me yesterday, using the 28/1.8, at f/2.8, auto ISO, center AF point, and I deleted only 2 frames for being out of focus.

Does this mean my particular 70D body is a "-3", and it's not really the lenses?

Glad you're getting consistent results, and they might suggest that the camera is what requires a little bit of calibration more so than the lenses. However, given the fact that it's correctible and that the amount is very small, I wouldn't worry about it. Great article a while back from Lensrentals on the factors that can contribute to need for MFA both in the lens and the camera:

http://www.lensrentals.com/blog/2008/12/this-lens-is-soft-and-other-myths

You used a good, solid process for checking this out, including some pretty fast lenses, so my guess is that you're good to go. MFA was a lifesaver for me with my old 100-400L, which required just under +10 when used with my 7D, but was dead accurate once that was dialed in. Congrats and good shooting.

 

[Bret L.]

Which end of the 100-400 did you Dot Tune to? The 100 mm end or the 400 mm end or somewhere in the middle?

 

[BirdShooter7]

Doesn't the 70D allow you to MFA both ends of the zoom range? I seem to remember doing that when I did MFA on my 70-300L.

Greg

 

[walkaround]

Doesn't the 70D allow you to MFA both ends of the zoom range?

Yes, it does. And the points in between are automatically averaged between the two settings, based on focal length.

 

[RogerZoul]

Doesn't the 70D allow you to MFA both ends of the zoom range?

Yes, it does. And the points in between are automatically averaged between the two settings, based on focal length.

How do you know what happens between the two focal length settings? Is this published some where?

 

[walkaround]

Doesn't the 70D allow you to MFA both ends of the zoom range?

Yes, it does. And the points in between are automatically averaged between the two settings, based on focal length.

How do you know what happens between the two focal length settings? Is this published some where?

Yes, pg 382 of the manual.

 

[Jerry-astro]

Which end of the 100-400 did you Dot Tune to? The 100 mm end or the 400 mm end or somewhere in the middle?

In my case, I was determining MFA settings for a 7D, not 70D, so you only get a single value to set. I separately tested both ends and found there to be only a small difference between them (fortunately), so the single value of +8 was good enough to calibrate all ranges of the lens. With the 70D, as others have mentioned, you can enter a value for both ends of the zoom range. I believe the camera will extrapolate between the ends as you zoom through its range, but you'll need to confirm that in your manual.

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

 

[elfroggio]

Does this mean my particular 70D body is a "-3", and it's not really the lenses?

No, it's the combination of the camera and the lens.

FYI, each +1 or each -1 in the MFA is 1/8 of the DOF for the lens at that setting (short end/long end of the zoom). This means that a -1 at the wide end will have a greater correction than at the tele end.

 

[skanter]

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

What is the Bird Photographer's procedure?

 

[Jerry-astro]

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

What is the Bird Photographer's procedure?

Thanks for asking, Sam... should have posted a link.

http://www.birdphotographers.net/forums/showthread.php/58042-AF-microadjustment-tricks

This procedure basically uses a highly magnified view while tethered to assess and fine tune focus. I used this for years and tested all of my lenses. Most required very little if any adjustment... the 100-400L was the big exception. I'm not the only one who's reported the need for larger adjustments with that lens as well. The good news is that once adjusted, focus was spot on.

 

[walkaround]

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

What is the Bird Photographer's procedure?

Thanks for asking, Sam... should have posted a link.

http://www.birdphotographers.net/forums/showthread.php/58042-AF-microadjustment-tricks

This procedure basically uses a highly magnified view while tethered to assess and fine tune focus. I used this for years and tested all of my lenses. Most required very little if any adjustment... the 100-400L was the big exception. I'm not the only one who's reported the need for larger adjustments with that lens as well. The good news is that once adjusted, focus was spot on.

But like any other method that uses visual sharpness of the whole PD+lens circuit, this introduces the random variations of the mechanical system? Or at least that's what the guy who came up with dot-tune says.

 

[skanter]

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

What is the Bird Photographer's procedure?

Thanks for asking, Sam... should have posted a link.

http://www.birdphotographers.net/forums/showthread.php/58042-AF-microadjustment-tricks

This procedure basically uses a highly magnified view while tethered to assess and fine tune focus. I used this for years and tested all of my lenses. Most required very little if any adjustment... the 100-400L was the big exception. I'm not the only one who's reported the need for larger adjustments with that lens as well. The good news is that once adjusted, focus was spot on.

That's the method I use! (didn't know it was called Bird method). My lenses usually plus or minus 2 or 1. Never tried dot tune, but this method seems good to me.

 

[losifanatic]

Dottune works great. Can't believe how well it actually worked, just wish I would have done it sooner.

--
Loving this hobby

 

[Jerry-astro]

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

What is the Bird Photographer's procedure?

Thanks for asking, Sam... should have posted a link.

http://www.birdphotographers.net/forums/showthread.php/58042-AF-microadjustment-tricks

This procedure basically uses a highly magnified view while tethered to assess and fine tune focus. I used this for years and tested all of my lenses. Most required very little if any adjustment... the 100-400L was the big exception. I'm not the only one who's reported the need for larger adjustments with that lens as well. The good news is that once adjusted, focus was spot on.

But like any other method that uses visual sharpness of the whole PD+lens circuit, this introduces the random variations of the mechanical system? Or at least that's what the guy who came up with dot-tune says.

Does he explain how Dottune gets around that? It would seem that any method would be subject to similar variations, which is why you typically shoot multiple samples at various distances after MFA adjustment just to make sure that you got it right. This method has never let me down with multiple lenses I calibrated with my 7D. I did try Dottune once and honestly didn't see any advantages and in fact, for me at least, didn't seem quite as reliable. I do realize that MANY folks here swear by it, so this could well have been some sort of an issue on my side. Best advice is to use whatever works best for you.

 

[Jerry-astro]

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

What is the Bird Photographer's procedure?

Thanks for asking, Sam... should have posted a link.

http://www.birdphotographers.net/forums/showthread.php/58042-AF-microadjustment-tricks

This procedure basically uses a highly magnified view while tethered to assess and fine tune focus. I used this for years and tested all of my lenses. Most required very little if any adjustment... the 100-400L was the big exception. I'm not the only one who's reported the need for larger adjustments with that lens as well. The good news is that once adjusted, focus was spot on.

That's the method I use! (didn't know it was called Bird method). My lenses usually plus or minus 2 or 1. Never tried dot tune, but this method seems good to me.

The "aha" in this method for me was the idea of using tethering and a highly magnified shot to do the adjustment in realtime. What I did before was definitely the hard way, which was to shoot a series of shots a -6, -4, -2, 0, +2, +4, and +6 MFA and review/pixel peep them to see which one yielded the best result. If none were sharp, then I went outside that range. Once I found the sharpest of the bunch, I would then bracket the setting by + and -1 to fine tune. Overall, it works, but it's time consuming. Either this method or Dottune would likely be easier and better IMHO.

Either way, I'm glad I don't have to deal with this stuff any more. Pain in the tush.

 

[walkaround]

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

What is the Bird Photographer's procedure?

Thanks for asking, Sam... should have posted a link.

http://www.birdphotographers.net/forums/showthread.php/58042-AF-microadjustment-tricks

This procedure basically uses a highly magnified view while tethered to assess and fine tune focus. I used this for years and tested all of my lenses. Most required very little if any adjustment... the 100-400L was the big exception. I'm not the only one who's reported the need for larger adjustments with that lens as well. The good news is that once adjusted, focus was spot on.

But like any other method that uses visual sharpness of the whole PD+lens circuit, this introduces the random variations of the mechanical system? Or at least that's what the guy who came up with dot-tune says.

Does he explain how Dottune gets around that? It would seem that any method would be subject to similar variations, which is why you typically shoot multiple samples at various distances after MFA adjustment just to make sure that you got it right. This method has never let me down with multiple lenses I calibrated with my 7D. I did try Dottune once and honestly didn't see any advantages and in fact, for me at least, didn't seem quite as reliable. I do realize that MANY folks here swear by it, so this could well have been some sort of an issue on my side. Best advice is to use whatever works best for you.

Here’s the original (very long) thread at fredmiranda where “Snapsy” discusses the method. Not sure which page goes into that particular issue.

Loading…

www.fredmiranda.com

But basically, since dot-tune only uses one manual focus point at the initial setting, it never engages the mechanical AF system, avoiding variations seen in other methods. It's not a calibration based on sharpness of photos, it's a calibration based on the feedback loop of the phase detection AF system (the green dot in your viewfinder). But I’m no expert, and I’m probably doing a poor job explaining it.

 

[Jerry-astro]

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

What is the Bird Photographer's procedure?

Thanks for asking, Sam... should have posted a link.

http://www.birdphotographers.net/forums/showthread.php/58042-AF-microadjustment-tricks

This procedure basically uses a highly magnified view while tethered to assess and fine tune focus. I used this for years and tested all of my lenses. Most required very little if any adjustment... the 100-400L was the big exception. I'm not the only one who's reported the need for larger adjustments with that lens as well. The good news is that once adjusted, focus was spot on.

But like any other method that uses visual sharpness of the whole PD+lens circuit, this introduces the random variations of the mechanical system? Or at least that's what the guy who came up with dot-tune says.

Does he explain how Dottune gets around that? It would seem that any method would be subject to similar variations, which is why you typically shoot multiple samples at various distances after MFA adjustment just to make sure that you got it right. This method has never let me down with multiple lenses I calibrated with my 7D. I did try Dottune once and honestly didn't see any advantages and in fact, for me at least, didn't seem quite as reliable. I do realize that MANY folks here swear by it, so this could well have been some sort of an issue on my side. Best advice is to use whatever works best for you.

Here’s the original (very long) thread at fredmiranda where “Snapsy” discusses the method. Not sure which page goes into that particular issue.

http://www.fredmiranda.com/forum/topic/1187247

But basically, since dot-tune only uses one manual focus point at the initial setting, it never engages the mechanical AF system, avoiding variations seen in other methods. It's not a calibration based on sharpness of photos, it's a calibration based on the feedback loop of the phase detection AF system (the green dot in your viewfinder). But I’m no expert, and I’m probably doing a poor job explaining it.

Nope, good explanation, and pretty well as I remember it. For whatever reason, I had some difficulty with it, but by that time, my MFA had pretty well been dialed in, so I didn't have a strong motivation to give it another go. Given its popularity, it's likely an excellent method for people to use.

 

[skanter]

I was pretty convinced that the tether method worked, but I wouldn't mind trying dotune to see if results are the same. I think Magic Lantern had an auto dotune method, I may wait till I get ML on 70D.

 

[Bret L.]

Which end of the 100-400 did you Dot Tune to? The 100 mm end or the 400 mm end or somewhere in the middle?

In my case, I was determining MFA settings for a 7D, not 70D, so you only get a single value to set. I separately tested both ends and found there to be only a small difference between them (fortunately), so the single value of +8 was good enough to calibrate all ranges of the lens. With the 70D, as others have mentioned, you can enter a value for both ends of the zoom range. I believe the camera will extrapolate between the ends as you zoom through its range, but you'll need to confirm that in your manual.

Also, I didn't use Dottune. I prefer the Bird Photographer's procedure and had better luck with it. Once I acquired FoCal software, I ended up using that instead, but the MFA values for that lens ended up being pretty well the same.

Thank you very much. I have both a 7D and a few weeks old 7D MK II. I understand how to do MFA on a zoom lens with the 7D MK II, but was wondering how you determined the MFA setting for your 7D and the 100-400. Your response was very helpful.