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Thread started 05 Feb 2017 (Sunday) 14:55
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Problems with FoCal. looks like its still unreliable after all these years.

 
Wilt
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Post edited over 2 years ago by Wilt. (9 edits in all)
     
Apr 25, 2017 18:11 |  #46

digital paradise wrote in post #18337053 (external link)
At first Canon recommend 50X. Then the manual and other documents said best at the location you are shooting. Lens Align and others said 25X. I may even have a Canon document that says 25X but I can't back it. I'll have to look in the vault. I know I have other documents (besides the manual) that say best at the location and 50X.

If you read the entire article you find this. That is what originally tuned me off to MFA. "If you think you can do better". I hope the person servicing the engine of the jet I will fly does not come up with a better method that Boing's service manual :-) Canon - you engineered it - you tell me how to do it correctly ;-)a

http://digitaljournali​st.org/issue0812/tech-tips.html (external link)

I, too, have 50X burned into memory as the recommended distance by Canon. Furthermore, it IS POSSIBLE to find substiation of this distance in Canon publications, such as the one at the end of this reply.

In this POTN discussion about MFA and FoCal, one of the things I also recall about camera focus was (stated by Canon, paraphrased: ) 'to within one DOF zone' or something to that effect. Still trying to find that. But... (a light bulb turns on faintly...)

  • So if Tom Reichner has issues with 800mm at 250 yards (BTW, Tom, just how do you know you are at 250yards for your testing?!)

    800 * 50 = 40000mm, or 1575 inches. For 800mm f/5.6, the 20/20 vision DOF is 11.5" so accuracy of AF is achieved when it is within 11.5", if my interpretation of the Canon statement (which I cannot find at the moment) is a correct one.

  • Or for Larry20d and his lens at 400mm, your 30' basement is not going to 'cut it', as 50x is 66' away, so you need to buy a new home to conduct your test, or go to a high school gym that you can get into, as the basketball courts are supposed to be 74' long. And 400mm f/5.6 at 66' has a 20/20 DOF zone of 11.5", so that is the best you should expect to achieve.

  • Or for Digital Paradise and his 100-400 II and 1.4 III, for 92' of indoor space (plus a bit more to stand behind your camera) you need to get into an NBA or NCAA 94' basketball court. And And 560mm f/5.6 at 92' has a 20/20 DOF zone of 11.5" as well, so that is the best you should expect to achieve, also!



One Canon 'paper' on the topic of MFA is at https://learn.usa.cano​n.com …ate_EOS_AF_Quic​kGuide.pdf (external link)

"There is no one “right” way to perform a microfocus
adjustment; however, the following method has
the benefit of being accurate and easy to perform...

1. Mount the camera and lens on a tripod. If the lens has
IS, shut it off.
2. Use Live View to manually focus on a stationary,
flat, high-contrast object that is at the center of the
viewfinder and parallel to the plane of focus. The
camera-to-subject distance should be no less than 50
times the focal length of the lens.
For a 50mm lens this
would be at least 2.5 meters, or approximately 8.2 feet.
3. Focus the lens at its maximum aperture. Use Live View
magnification if necessary to assure that the image is
as sharp as possible.
4. Without touching the focusing ring or moving the tripod,
turn off Live View, and return the camera to One-Shot
AF, using only the center AF point.
5. Gently press the shutter button down halfway (or the
AF button if using back-button AF) while observing the
focusing ring or scale on the lens. It should not move.
If it does, take note of whether AF moves the plane of
focus closer (front-focus) or further away (back-focus).
If there is no shift in focus your lens is well-calibrated
and requires no adjustment.
6. To determine the correct amount of adjustment
necessary, take three sets of images at microadjustment
settings of -10 , 0 and +10; in other words,
three consecutive images at -10, three consecutive
images at 0, and three consecutive images at +10.
7. Examine the resulting images on your computer
monitor at 100% pixel magnification.
8. Take additional sets of test images at different
microadjustment settings if necessary until you can
determine which setting produces the sharpest image.
9. Register the corresponding microadjustment setting in
the camera

[edit] Oh, I just read that Tom is using 800mm on a 1.3 crop body! In that case, DOF at 800mm f/5.6 is a zone of 9.2" depth, so you can achieve a tighter criteria of AF accuracy!


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Apr 25, 2017 19:08 |  #47

Larry20d wrote in post #18338342 (external link)
Okay. Bear with with me. I'm a little slow.

My basement is 30 feet from wall to wall. Will I have enough distance to provide satisfactory calibration on my 100-400 lens?

Yes 26 ft minimum at 400mm. Just so you now I did it at about 30 ft at my cottage in March with my 5D4 and 100-400 II. I got +2 at 400mm. Today I decided to revisit it at home and I have about 22 ft to work with. I got +2 at 400mm again.


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Apr 25, 2017 19:15 |  #48

Wilt wrote in post #18338416 (external link)
I, too, have 50X burned into memory as the recommended distance by Canon. Furthermore, it IS POSSIBLE to find substiation of this distance in Canon publications, such as the one at the end of this reply.

In this POTN discussion about MFA and FoCal, one of the things I also recall about camera focus was (stated by Canon, paraphrased: ) 'to within one DOF zone' or something to that effect. Still trying to find that. But... (a light bulb turns on faintly...)

  • So if Tom Reichner has issues with 800mm at 250 yards (BTW, Tom, just how do you know you are at 250yards for your testing?!)

    800 * 50 = 40000mm, or 1575 inches. For 800mm f/5.6, the 20/20 vision DOF is 11.5" so accuracy of AF is achieved when it is within 11.5", if my interpretation of the Canon statement (which I cannot find at the moment) is a correct one.

  • Or for Larry20d and his lens at 400mm, your 30' basement is not going to 'cut it', as 50x is 66' away, so you need to buy a new home to conduct your test, or go to a high school gym that you can get into, as the basketball courts are supposed to be 74' long. And 400mm f/5.6 at 66' has a 20/20 DOF zone of 11.5", so that is the best you should expect to achieve.

  • Or for Digital Paradise and his 100-400 II and 1.4 III, for 92' of indoor space (plus a bit more to stand behind your camera) you need to get into an NBA or NCAA 94' basketball court. And And 560mm f/5.6 at 92' has a 20/20 DOF zone of 11.5" as well, so that is the best you should expect to achieve, also!


One Canon 'paper' on the topic of MFA is at https://learn.usa.cano​n.com …ate_EOS_AF_Quic​kGuide.pdf (external link)

"There is no one “right” way to perform a microfocus
adjustment; however, the following method has
the benefit of being accurate and easy to perform...

1. Mount the camera and lens on a tripod. If the lens has
IS, shut it off.
2. Use Live View to manually focus on a stationary,
flat, high-contrast object that is at the center of the
viewfinder and parallel to the plane of focus. The
camera-to-subject distance should be no less than 50
times the focal length of the lens.
For a 50mm lens this
would be at least 2.5 meters, or approximately 8.2 feet.
3. Focus the lens at its maximum aperture. Use Live View
magnification if necessary to assure that the image is
as sharp as possible.
4. Without touching the focusing ring or moving the tripod,
turn off Live View, and return the camera to One-Shot
AF, using only the center AF point.
5. Gently press the shutter button down halfway (or the
AF button if using back-button AF) while observing the
focusing ring or scale on the lens. It should not move.
If it does, take note of whether AF moves the plane of
focus closer (front-focus) or further away (back-focus).
If there is no shift in focus your lens is well-calibrated
and requires no adjustment.
6. To determine the correct amount of adjustment
necessary, take three sets of images at microadjustment
settings of -10 , 0 and +10; in other words,
three consecutive images at -10, three consecutive
images at 0, and three consecutive images at +10.
7. Examine the resulting images on your computer
monitor at 100% pixel magnification.
8. Take additional sets of test images at different
microadjustment settings if necessary until you can
determine which setting produces the sharpest image.
9. Register the corresponding microadjustment setting in
the camera

[edit] Oh, I just read that Tom is using 800mm on a 1.3 crop body! In that case, DOF at 800mm f/5.6 is a zone of 9.2" depth, so you can achieve a tighter criteria of AF accuracy!

In this Canon document it says

http://www.learn.usa.c​anon.com …oadjustment_art​icle.shtml (external link)

• Shoot test pictures using the lens(es) you normally use, and at the distances you typically use them. In other words, if you're seeing a consistent focus shift when you shoot group pictures at weddings, don't take test shots of a ruler on your desk with a macro lens.


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Apr 25, 2017 19:17 |  #49

If you read the PDF this one says 50X.

http://www.learn.usa.c​anon.com …oadjustment-landing.shtml (external link)


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Apr 25, 2017 19:19 |  #50

I thought I would provide some AF Setup Guide books by Canon, for those who had not previously discovered this information

http://www.learn.usa.c​anon.com …os7dmk2_afGuide​book.shtml (external link)

http://cpn.canon-europe.com …_AF_setting_gui​debook.pdf (external link)


While it does not cover MFA, they are nice 'pockatable' guides, in PDF form, which can easily be stored on a smartphone for field consultation.


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Apr 25, 2017 19:22 |  #51

This one says 50X as well.

http://learn.usa.canon​.com …ate_EOS_AF_Quic​kGuide.pdf (external link)

So we have two (one is the manual) saying at the location or were you shoot most and two saying 50X.


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Post edited over 2 years ago by Wilt. (4 edits in all)
     
Apr 25, 2017 19:25 |  #52

digital paradise wrote in post #18338491 (external link)
In this Canon document it says

http://www.learn.usa.c​anon.com …oadjustment_art​icle.shtml (external link)

• Shoot test pictures using the lens(es) you normally use, and at the distances you typically use them. In other words, if you're seeing a consistent focus shift when you shoot group pictures at weddings, don't take test shots of a ruler on your desk with a macro lens.


digital paradise wrote in post #18338492 (external link)
If you read the PDF this one says 50X.

http://www.learn.usa.c​anon.com …oadjustment-landing.shtml (external link)

Well, Canon DID say, ""There is no one “right” way to perform a microfocus adjustment..."  :p
so they gave us two of them in three references (we linked to the same Digital learning guide!


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Apr 25, 2017 19:31 |  #53

Wilt wrote in post #18338416 (external link)
  • So if Tom Reichner has issues with 800mm at 250 yards.
  • It's around 250 feet, not yards, where the AF troubles begin.

    Wilt wrote in post #18338416 (external link)
    BTW, Tom, just how do you know you are at 250yards for your testing?!

    How do I know it's around 250 feet? Well, I have spent my entire life guessing distances, and then checking them to see how close my guess was. I'm pretty darn good at it, if I must say so myself!

    Guys at my old job had a rangefinder, and they would challenge me to estimate distances, then check my estimate against the rangefinder. There is a reason why I was the one that everybody would try to get to guess distances.

    Wilt wrote in post #18338416 (external link)
    Oh, I just read that Tom is using 800mm on a 1.3 crop body! In that case, DOF at 800mm f/5.6 is a zone of 9.2" depth, so you can achieve a tighter criteria of AF accuracy!

    Just imagine that - at a whopping 250 feet away - almost the length of a football field - my DOF is only 9 inches. That means that if I get the tip of a deer's nose in focus, his ears won't be in focus (if he's facing towards me).

    Few people realize just how insanely critical focus accuracy needs to be when shooting wildlife.

    .


    "Your" and "you're" are different words with completely different meanings - please use the correct one.
    "They're", "their", and "there" are different words with completely different meanings - please use the correct one.
    "Fare" and "fair" are different words with completely different meanings - please use the correct one. The proper expression is "moot point", NOT "mute point".

      
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    Apr 25, 2017 19:35 |  #54

    Wilt wrote in post #18338502 (external link)
    Well, Canon DID say, ""There is no one “right” way to perform a microfocus adjustment..."  :p
    so they gave us two of them!

    LOL. I figure they are just covering their tails at 50X to be sure that the user is far past the curve FoCal talks about. At location or distance you normally shoot just makes the most sense except I'll shoot from 10 to 100 ft :-)

    There was a member here that posted some country in the , Sweden I think MFA's the super telephotos at 21 ft. I asked for more info but never got a response. Liquidstone does it at MFD and you can't argue with results. That was his reply the last time I asked.

    http://www.romyocon.ne​t (external link)

    This all gave me a headache and I gave up until I really need to do it. My 1.4 III throws off my 100-400 quite a bit. Since I purchased FoCal I did all my lenses which needed little sans the TC.


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    Apr 25, 2017 19:54 |  #55

    Tom Reichner wrote in post #18338513 (external link)
    It's around 250 feet, not yards, where the AF troubles begin.

    How do I know it's around 250 feet? Well, I have spent my entire life guessing distances, and then checking them to see how close my guess was. I'm pretty darn good at it, if I must say so myself!

    Guys at my old job had a rangefinder, and they would challenge me to estimate distances, then check my estimate against the rangefinder. There is a reason why I was the one that everybody would try to get to guess distances.

    Just imagine that - at a whopping 250 feet away - almost the length of a football field - my DOF is only 9 inches. That means that if I get the tip of a deer's nose in focus, his ears won't be in focus (if he's facing towards me).

    Few people realize just how insanely critical focus accuracy needs to be when shooting wildlife.

    .

    Yeah, I mis-spoke, I did DOF calculation for 250 FEET


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    Apr 25, 2017 20:00 |  #56

    digital paradise wrote in post #18338519 (external link)
    LOL.
    This all gave me a headache and I gave up until I really need to do it. My 1.4 III throws off my 100-400 quite a bit. Since I purchased FoCal I did all my lenses which needed little sans the TC.

    Frankly I have never found a real NEED for MFA in my shooting. so I have nothing to avoid, I just don't think I need it! Ostrich?!
    I even have managed to largely avoid the dreaded focus-recompose issues of digital SLR legend.


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    Apr 25, 2017 20:01 |  #57

    I must be missing something. With crop - 800mm, 5.6 at 250 ft I get 6.33 ft. With a FF I get 10 ft.

    http://www.dofmaster.c​om/dofjs.html (external link)


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    Apr 25, 2017 21:41 as a reply to  @ digital paradise's post |  #58

    Thanks !!!

    How do we know if you would have had a different adjustment if you were able to calibrate at 66 feet? Do you find the lens sharp with the +2?


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    Post edited over 2 years ago by Wilt. (4 edits in all)
         
    Apr 25, 2017 21:56 |  #59

    digital paradise wrote in post #18338539 (external link)
    I must be missing something. With crop - 800mm, 5.6 at 250 ft I get 6.33 ft. With a FF I get 10 ft.

    http://www.dofmaster.c​om/dofjs.html (external link)

    That program does not state its assumed level of visual acuity, which determines the Circle of Confusion size (that dimension at which the eye can perceive 'blur' rather than 'point').
    It is most certainly using 'manufacturer standard' bad vision assumption (rather than what our optometrists strive to achieve in correcting vision), which is same as the DOF scale assumptions engraved on 135 format lenses.

    The Cambridge Color DOF calculator says

    • FF with 800mm at f/5.6 focused at 250' has DOF zone of 10.56' for 'manufacturer standard' DOF
    • FF with 800mm at f/5.6 focused at 250' has DOF zone of 3.51' for '20/20 vision' DOF
    • APS-C with 800mm at f/5.6 focused at 250' has DOF zone of 6.6' for 'manufacturer standard' DOF
    • APS-C with 800mm at f/5.6 focused at 250' has DOF zone of 2.1' for '20/20 vision' DOF

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    Apr 26, 2017 08:14 |  #60

    Larry20d wrote in post #18338606 (external link)
    Thanks !!!

    How do we know if you would have had a different adjustment if you were able to calibrate at 66 feet? Do you find the lens sharp with the +2?

    I normally never bothered with a small adjustment like +-2 but since I calibrated with paid software I entered it. Read the last sentence of the last paragraph on page 1.

    http://www.learn.usa.c​anon.com …oadjustment_art​icle.shtml (external link)


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