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DotTune MFA question...

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ErikH

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Hi - I just MFA my 70D using the "DotTune" method outside on a bright day with 2 of my lenses. Here are my results and my questions below:

55-250 STM

(W)ide -8 +5 = -1 (or -2)

(T)ele -5 +3 = -1

18-135 STM

W -6 +5 = 0

T -7 + 5 = -1

1) Because my adjustments are so minimal, is it even worth making the change? The reason I'm asking, is (if I'm understanding correctly) this method balances the focal plane evenly whereas typically the focal plane is thought to be 1/3 in front & 2/3 behind (speaking generally).

Since my camera has a (slight) tendency toward the minus side, could that be part of the correction DotTune is trying to make to even "things" out? (hopefully that makes sense).

Any comments appreciated!
 
WilbaW said:
Zee Char said:
People are probably wondering why I'm obsessed by this. Too many years as a technical person in manufacturing I guess. My industry had little formal training and people ran complex equipment. It was amazing what happened when we dusted off the vendors manuals and re-trained them on how to set the equipment to manufactures specs. A difference of .030 to .020 meant a day of smooth running vs a day the where the machine kept shutting down. Combine that with their years of experience and that changed everything. There are always people who are just naturally better at things than others but now the weakest operators were doing as well as the others.

Manufacturers make mistakes but we learned to follow what they said first and then you add your experience and expand.
Click to expand...
Sure. Interested to know what you were manufacturing, what sort of machines, etc.
Click to expand...
Web offset printing where a difference of .030 to .020 would shut a machine down that was charged out at $400 an hr. That was 25 years ago. You should have seen the overtime costs for a 6 person crew when it got behind.

That was very common in the print industry just because of the way it grew from a simpler process to a much more complex one. In my early travels when I visited other plants or companies I'd ask the crews where the operator manuals were and they would have to take time to find them buried somewhere in some desk, etc. They were always as brand new as the day they got them :-) They were good people who cared about what they did but it was just part of the culture they grew up in.

10 years as an operator, 25 in technical and I facilitated quality control programs, ran workshops, implemented the Toyota manufacturing system which included statistical process control (SPC). I still have Ford's book on SPC. Fascinating stuff and you learn why Japan kicked the world in the manufacturing groin in the 80's and forced the world to get on board.
 
Last edited:
guy schlacter said:
WilbaW said:
guy schlacter said:
Hokie Jack said:
"Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus."

The first sentence is very clear. IMO the second one is vague, at best. I'm not sure what it is trying to say. I just thought it was an awkward way of saying each MFA increment moves you toward or away from the plane of focus. I don't think they intended to re-define the term DOF.
Click to expand...
I believe both sentences need to be taken together.
Click to expand...
Let's rephrase them for clarity - Each step is a very fine increment, equal to 1/8th of the total depth-of-field you'd have with the current lens wide-open. An increment moves the plane of focus forward (toward the camera) or back (toward the background).

Nothing suggests the "depth-of-field" (or focus) is intended as the single-sided depth (from the near or far limit to the plane of focus).
Member said:
We must also remember this is translated from Japanese...
Click to expand...
Rubbish. The whole paragraph is perfectly grammatical and reasonable English, using conventional terms. There is nothing to suggest that it suffers from translation errors.
Member said:
which gives some latitude of use of dof in the both sentences.
Click to expand...
DOF is always the entire depth unless specifically referred to as "near DOR" and "far DOF" or "DOF in front" and "DOF behind".
Member said:
Also, that is the reason Chuck Westfall clarifies it and calls it Depth of Focus, which aligns exactly with the 2nd definition from the earlier Wikipedia definition = ~ half of total dof in front, or behind focal plane.
Click to expand...
Yes, half of the total depth is in front of the image (or focus) plane, and the other half is behind. Both halves together make up "the depth", the total. Your assertion makes no sense and you can't explain it by reference to what you're referring to. I reject it completely. :-)
Click to expand...
Reject all you want. I have asked Chuck and Rudy to specifically clarify.
Click to expand...
Please post the questions you asked and the answers you got.
Member said:
Chuck used the term 1/8 of depth of focus, being front or back side of the dof.
Click to expand...
If "dof" is depth of focus in the above, then it doesn't make sense - the depth of focus can't also be the front or back side of itself.

If "dof" is depth of field in the above, it still doesn't make sense - the depth of focus is inside the camera while the depth of field is in the scene, so one cannot be the front or back side the other.
 
Zee Char said:
guy schlacter said:
WilbaW said:
guy schlacter said:
Hokie Jack said:
"Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus."

The first sentence is very clear. IMO the second one is vague, at best. I'm not sure what it is trying to say. I just thought it was an awkward way of saying each MFA increment moves you toward or away from the plane of focus. I don't think they intended to re-define the term DOF.
Click to expand...
I believe both sentences need to be taken together.
Click to expand...
Let's rephrase them for clarity - Each step is a very fine increment, equal to 1/8th of the total depth-of-field you'd have with the current lens wide-open. An increment moves the plane of focus forward (toward the camera) or back (toward the background).

Nothing suggests the "depth-of-field" (or focus) is intended as the single-sided depth (from the near or far limit to the plane of focus).
Zeee said:
We must also remember this is translated from Japanese...
Click to expand...
Rubbish. The whole paragraph is perfectly grammatical and reasonable English, using conventional terms. There is nothing to suggest that it suffers from translation errors.
Zeee said:
which gives some latitude of use of dof in the both sentences.
Click to expand...
DOF is always the entire depth unless specifically referred to as "near DOR" and "far DOF" or "DOF in front" and "DOF behind".
Zeee said:
Also, that is the reason Chuck Westfall clarifies it and calls it Depth of Focus, which aligns exactly with the 2nd definition from the earlier Wikipedia definition = ~ half of total dof in front, or behind focal plane.
Click to expand...
Yes, half of the total depth is in front of the image (or focus) plane, and the other half is behind. Both halves together make up "the depth", the total. Your assertion makes no sense and you can't explain it by reference to what you're referring to. I reject it completely. :-)
Click to expand...
WilbaW,

Reject all you want. I have asked Chuck and Rudy to specifically clarify. Chuck used the term 1/8 of depth of focus, being front or back side of the dof.
Click to expand...
That is the way I read it. I don't see any reference to Depth of Focus or anything else. If they had meant something else they should have stated it more clearly or corrected it if wrong.

If nothing suggests anything then please explain what "Canon has clearly stated" 1/8 of depth of focus then means WilbaW. No references to anything that does not exist in that document unless you research it and provide evidence that it means something else - from Canon, not Wikipedia anything else. Wikipedia did not post this. Our turn :-)
Click to expand...
It's Guy who claims Chuck said something about DO focus. Are Chuck's words posted in the thread? I looked but couldn't find them. If we get that I can tell you what I think they mean. But if I can't use standard definitions of the terms used, please track down Canon's technical definitions of DO focus and field so we can use them.

Edit: I had a quick look and all we need is the diagram on this Canon DOF calculator -

http://www.usa.canon.com/cusa/profe...s/bctv_range_calculator/bctv_range_depthfield



rangecalculator2.gif
 
Last edited:
Zee Char said:
WilbaW said:
Zee Char said:
People are probably wondering why I'm obsessed by this. Too many years as a technical person in manufacturing I guess. My industry had little formal training and people ran complex equipment. It was amazing what happened when we dusted off the vendors manuals and re-trained them on how to set the equipment to manufactures specs. A difference of .030 to .020 meant a day of smooth running vs a day the where the machine kept shutting down. Combine that with their years of experience and that changed everything. There are always people who are just naturally better at things than others but now the weakest operators were doing as well as the others.

Manufacturers make mistakes but we learned to follow what they said first and then you add your experience and expand.
Click to expand...
Sure. Interested to know what you were manufacturing, what sort of machines, etc.
Click to expand...
Web offset printing where a difference of .030 to .020 would shut a machine down that was charged out at $400 an hr. That was 25 years ago. You should have seen the overtime costs for a 6 person crew when it got behind.

That was very common in the print industry just because of the way it grew from a simpler process to a much more complex one. In my early travels when I visited other plants or companies I'd ask the crews where the operator manuals were and they would have to take time to find them buried somewhere in some desk, etc. They were always as brand new as the day they got them :-) They were good people who cared about what they did but it was just part of the culture they grew up in.

10 years as an operator, 25 in technical and I facilitated quality control programs, ran workshops, implemented the Toyota manufacturing system which included statistical process control (SPC). I still have Ford's book on SPC. Fascinating stuff and you learn why Japan kicked the world in the manufacturing groin in the 80's and forced the world to get on board.
Click to expand...
I guessed it would be something like printing. I'm one of those read-the-manual-from-cover-to-cover-and-keep-going-back guys. Amazing what you can learn. :-)

Yeah, the Japanese revolutionised manufacturing, for sure.
 
WilbaW said:
guy schlacter said:
WilbaW said:
guy schlacter said:
Hokie Jack said:
"Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus."

The first sentence is very clear. IMO the second one is vague, at best. I'm not sure what it is trying to say. I just thought it was an awkward way of saying each MFA increment moves you toward or away from the plane of focus. I don't think they intended to re-define the term DOF.
Click to expand...
I believe both sentences need to be taken together.
Click to expand...
Let's rephrase them for clarity - Each step is a very fine increment, equal to 1/8th of the total depth-of-field you'd have with the current lens wide-open. An increment moves the plane of focus forward (toward the camera) or back (toward the background).

Nothing suggests the "depth-of-field" (or focus) is intended as the single-sided depth (from the near or far limit to the plane of focus).
WilbaW said:
We must also remember this is translated from Japanese...
Click to expand...
Rubbish. The whole paragraph is perfectly grammatical and reasonable English, using conventional terms. There is nothing to suggest that it suffers from translation errors.
WilbaW said:
which gives some latitude of use of dof in the both sentences.
Click to expand...
DOF is always the entire depth unless specifically referred to as "near DOR" and "far DOF" or "DOF in front" and "DOF behind".
WilbaW said:
Also, that is the reason Chuck Westfall clarifies it and calls it Depth of Focus, which aligns exactly with the 2nd definition from the earlier Wikipedia definition = ~ half of total dof in front, or behind focal plane.
Click to expand...
Yes, half of the total depth is in front of the image (or focus) plane, and the other half is behind. Both halves together make up "the depth", the total. Your assertion makes no sense and you can't explain it by reference to what you're referring to. I reject it completely. :-)
Click to expand...
Reject all you want. I have asked Chuck and Rudy to specifically clarify.
Click to expand...
Please post the questions you asked and the answers you got.
WilbaW said:
Chuck used the term 1/8 of depth of focus, being front or back side of the dof.
Click to expand...
If "dof" is depth of focus in the above, then it doesn't make sense - the depth of focus can't also be the front or back side of itself.

If "dof" is depth of field in the above, it still doesn't make sense - the depth of focus is inside the camera while the depth of field is in the scene, so one cannot be the front or back side the other.
Click to expand...
Thanks, you said it better than I did.

Also, I do not see this distinction in the Wikipedia article. The first definition is the pure 50:50 one. The second definition, the conjugate of Depth of Field, accounts for the fact that far DOF is larger than near DOF (the alleged "1/3 : 2/3 rule").
 
Hokie Jack said:
WilbaW said:
guy schlacter said:
WilbaW said:
guy schlacter said:
Hokie Jack said:
"Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus."

The first sentence is very clear. IMO the second one is vague, at best. I'm not sure what it is trying to say. I just thought it was an awkward way of saying each MFA increment moves you toward or away from the plane of focus. I don't think they intended to re-define the term DOF.
Click to expand...
I believe both sentences need to be taken together.
Click to expand...
Let's rephrase them for clarity - Each step is a very fine increment, equal to 1/8th of the total depth-of-field you'd have with the current lens wide-open. An increment moves the plane of focus forward (toward the camera) or back (toward the background).

Nothing suggests the "depth-of-field" (or focus) is intended as the single-sided depth (from the near or far limit to the plane of focus).
Hokie Jack said:
We must also remember this is translated from Japanese...
Click to expand...
Rubbish. The whole paragraph is perfectly grammatical and reasonable English, using conventional terms. There is nothing to suggest that it suffers from translation errors.
Hokie Jack said:
which gives some latitude of use of dof in the both sentences.
Click to expand...
DOF is always the entire depth unless specifically referred to as "near DOR" and "far DOF" or "DOF in front" and "DOF behind".
Hokie Jack said:
Also, that is the reason Chuck Westfall clarifies it and calls it Depth of Focus, which aligns exactly with the 2nd definition from the earlier Wikipedia definition = ~ half of total dof in front, or behind focal plane.
Click to expand...
Yes, half of the total depth is in front of the image (or focus) plane, and the other half is behind. Both halves together make up "the depth", the total. Your assertion makes no sense and you can't explain it by reference to what you're referring to. I reject it completely. :-)
Click to expand...
Reject all you want. I have asked Chuck and Rudy to specifically clarify.
Click to expand...
Please post the questions you asked and the answers you got.
Hokie Jack said:
Chuck used the term 1/8 of depth of focus, being front or back side of the dof.
Click to expand...
If "dof" is depth of focus in the above, then it doesn't make sense - the depth of focus can't also be the front or back side of itself.

If "dof" is depth of field in the above, it still doesn't make sense - the depth of focus is inside the camera while the depth of field is in the scene, so one cannot be the front or back side the other.
Click to expand...
Thanks, you said it better than I did.

Also, I do not see this distinction in the Wikipedia article. The first definition is the pure 50:50 one. The second definition, the conjugate of Depth of Field, accounts for the fact that far DOF is larger than near DOF (the alleged "1/3 : 2/3 rule").
Click to expand...
Yeah, it's roughly 1/3:2/3 at hyperfocal, but around 50f it's close enough to 50:50 that it doesn't matter to a photographer.
 
WilbaW said:
around 50f it's close enough to 50:50 that it doesn't matter to a photographer.
Click to expand...
Yes. By the way, my opinion on the "why 50f" recommendation question is that it performs the MFA at an assumed "typical" shooting distance for the focal length, making the adjustment more directly applicable to most shooting situations. It's just a rule-of-thumb.
 
Hokie Jack said:
WilbaW said:
around 50f it's close enough to 50:50 that it doesn't matter to a photographer.
Click to expand...
Yes. By the way, my opinion on the "why 50f" recommendation question is that it performs the MFA at an assumed "typical" shooting distance for the focal length, making the adjustment more directly applicable to most shooting situations. It's just a rule-of-thumb.
Click to expand...
I've never seen a credible technical reason for it, and Canon don't calibrate your gear at 50f, so I don't think it's anywhere near as important as the "Oh My God, Canon said you have to!" crowd believe it is. :-)
 
WilbaW said:
Zee Char said:
guy schlacter said:
WilbaW said:
guy schlacter said:
Hokie Jack said:
"Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus."

The first sentence is very clear. IMO the second one is vague, at best. I'm not sure what it is trying to say. I just thought it was an awkward way of saying each MFA increment moves you toward or away from the plane of focus. I don't think they intended to re-define the term DOF.
Click to expand...
I believe both sentences need to be taken together.
Click to expand...
Let's rephrase them for clarity - Each step is a very fine increment, equal to 1/8th of the total depth-of-field you'd have with the current lens wide-open. An increment moves the plane of focus forward (toward the camera) or back (toward the background).

Nothing suggests the "depth-of-field" (or focus) is intended as the single-sided depth (from the near or far limit to the plane of focus).
WilbaW said:
We must also remember this is translated from Japanese...
Click to expand...
Rubbish. The whole paragraph is perfectly grammatical and reasonable English, using conventional terms. There is nothing to suggest that it suffers from translation errors.
WilbaW said:
which gives some latitude of use of dof in the both sentences.
Click to expand...
DOF is always the entire depth unless specifically referred to as "near DOR" and "far DOF" or "DOF in front" and "DOF behind".
WilbaW said:
Also, that is the reason Chuck Westfall clarifies it and calls it Depth of Focus, which aligns exactly with the 2nd definition from the earlier Wikipedia definition = ~ half of total dof in front, or behind focal plane.
Click to expand...
Yes, half of the total depth is in front of the image (or focus) plane, and the other half is behind. Both halves together make up "the depth", the total. Your assertion makes no sense and you can't explain it by reference to what you're referring to. I reject it completely. :-)
Click to expand...
WilbaW,

Reject all you want. I have asked Chuck and Rudy to specifically clarify. Chuck used the term 1/8 of depth of focus, being front or back side of the dof.
Click to expand...
That is the way I read it. I don't see any reference to Depth of Focus or anything else. If they had meant something else they should have stated it more clearly or corrected it if wrong.

If nothing suggests anything then please explain what "Canon has clearly stated" 1/8 of depth of focus then means WilbaW. No references to anything that does not exist in that document unless you research it and provide evidence that it means something else - from Canon, not Wikipedia anything else. Wikipedia did not post this. Our turn :-)
Click to expand...
It's Guy who claims Chuck said something about DO focus. Are Chuck's words posted in the thread? I looked but couldn't find them. If we get that I can tell you what I think they mean. But if I can't use standard definitions of the terms used, please track down Canon's technical definitions of DO focus and field so we can use them.

Edit: I had a quick look and all we need is the diagram on this Canon DOF calculator -

http://www.usa.canon.com/cusa/profe...s/bctv_range_calculator/bctv_range_depthfield

rangecalculator2.gif
Click to expand...
So now with this diagram, the labeling of from depth of field and back depth of field, doesn't that align with what I have been saying all along, AND with what is in the Canon text in the 2nd sentence? It is 1/8 of the dof in front of the subject Plane of focus. Hence 1/16 of total dof.
 
WilbaW said:
Zee Char said:
guy schlacter said:
WilbaW said:
guy schlacter said:
Hokie Jack said:
"Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus."

The first sentence is very clear. IMO the second one is vague, at best. I'm not sure what it is trying to say. I just thought it was an awkward way of saying each MFA increment moves you toward or away from the plane of focus. I don't think they intended to re-define the term DOF.
Click to expand...
I believe both sentences need to be taken together.
Click to expand...
Let's rephrase them for clarity - Each step is a very fine increment, equal to 1/8th of the total depth-of-field you'd have with the current lens wide-open. An increment moves the plane of focus forward (toward the camera) or back (toward the background).

Nothing suggests the "depth-of-field" (or focus) is intended as the single-sided depth (from the near or far limit to the plane of focus).
WilbaW said:
We must also remember this is translated from Japanese...
Click to expand...
Rubbish. The whole paragraph is perfectly grammatical and reasonable English, using conventional terms. There is nothing to suggest that it suffers from translation errors.
WilbaW said:
which gives some latitude of use of dof in the both sentences.
Click to expand...
DOF is always the entire depth unless specifically referred to as "near DOR" and "far DOF" or "DOF in front" and "DOF behind".
WilbaW said:
Also, that is the reason Chuck Westfall clarifies it and calls it Depth of Focus, which aligns exactly with the 2nd definition from the earlier Wikipedia definition = ~ half of total dof in front, or behind focal plane.
Click to expand...
Yes, half of the total depth is in front of the image (or focus) plane, and the other half is behind. Both halves together make up "the depth", the total. Your assertion makes no sense and you can't explain it by reference to what you're referring to. I reject it completely. :-)
Click to expand...
WilbaW,

Reject all you want. I have asked Chuck and Rudy to specifically clarify. Chuck used the term 1/8 of depth of focus, being front or back side of the dof.
Click to expand...
That is the way I read it. I don't see any reference to Depth of Focus or anything else. If they had meant something else they should have stated it more clearly or corrected it if wrong.

If nothing suggests anything then please explain what "Canon has clearly stated" 1/8 of depth of focus then means WilbaW. No references to anything that does not exist in that document unless you research it and provide evidence that it means something else - from Canon, not Wikipedia anything else. Wikipedia did not post this. Our turn :-)
Click to expand...
It's Guy who claims Chuck said something about DO focus. Are Chuck's words posted in the thread? I looked but couldn't find them. If we get that I can tell you what I think they mean. But if I can't use standard definitions of the terms used, please track down Canon's technical definitions of DO focus and field so we can use them.

Edit: I had a quick look and all we need is the diagram on this Canon DOF calculator -

http://www.usa.canon.com/cusa/profe...s/bctv_range_calculator/bctv_range_depthfield

rangecalculator2.gif
Click to expand...
OK then. My apologies. Like I said before when I thought I figured it out. There is DO Field and DO Focus. DO Field is what is going through the lens and what we see in images. DO Focus is at the sensor. If the DO Field changes which we control then the DO Focus follows respectively. It must.

I'm sure you could do the math for a ⅛ of DO Focus. I say that because if Canon claims ⅛ DO Field then there must be a corresponding value for DO Focus but there would be so many zeros (fine increments) most people would say "what"?

Values for 1/8 DO Focus would be more accurate to what is really going on in during an MFA shift but the general public does not deal with that so using DO Field helps people understand what is going on. Until someone else can prove otherwise then I still think the values (both) are equally variable depending in DO Field.

I keep trying to find a the word for the relationship between Field and Focus. They both have different values because Field is much larger but they are both relative to each other and the values change in equally when the Field is change by the user.
 
WilbaW said:
Zee Char said:
WilbaW said:
Zee Char said:
People are probably wondering why I'm obsessed by this. Too many years as a technical person in manufacturing I guess. My industry had little formal training and people ran complex equipment. It was amazing what happened when we dusted off the vendors manuals and re-trained them on how to set the equipment to manufactures specs. A difference of .030 to .020 meant a day of smooth running vs a day the where the machine kept shutting down. Combine that with their years of experience and that changed everything. There are always people who are just naturally better at things than others but now the weakest operators were doing as well as the others.

Manufacturers make mistakes but we learned to follow what they said first and then you add your experience and expand.
Click to expand...
Sure. Interested to know what you were manufacturing, what sort of machines, etc.
Click to expand...
Web offset printing where a difference of .030 to .020 would shut a machine down that was charged out at $400 an hr. That was 25 years ago. You should have seen the overtime costs for a 6 person crew when it got behind.

That was very common in the print industry just because of the way it grew from a simpler process to a much more complex one. In my early travels when I visited other plants or companies I'd ask the crews where the operator manuals were and they would have to take time to find them buried somewhere in some desk, etc. They were always as brand new as the day they got them :-) They were good people who cared about what they did but it was just part of the culture they grew up in.

10 years as an operator, 25 in technical and I facilitated quality control programs, ran workshops, implemented the Toyota manufacturing system which included statistical process control (SPC). I still have Ford's book on SPC. Fascinating stuff and you learn why Japan kicked the world in the manufacturing groin in the 80's and forced the world to get on board.
Click to expand...
I guessed it would be something like printing. I'm one of those read-the-manual-from-cover-to-cover-and-keep-going-back guys. Amazing what you can learn. :-)
Click to expand...
There are so many variables in printing. Mechanical, chemistry, paper and the list goes on. I have a good example. There is a V shaped board which the paper ran down and folded it in half. If not set correctly could cause the paper to crease, wrinkle, or tear and stop the machine. Sometimes creased product got out the door. The operator would just adjust, sometimes for hours and the when they got it stepped back said don't touch anything.

That did not help anyone down the road. We dug out the manuals (or other vendor info if required), found the correct angles and got them protractors. Now they had a base setting and they could fine tune as required. It blew them away but at first many were sceptical but now the weakest operator could quickly set it up and at least get going as he had 50 other problems to deal with. You would not believe what an impact something so simple can make.
WilbaW said:
Yeah, the Japanese revolutionised manufacturing, for sure.
Click to expand...
Yes it did. Fascinating stuff when you get into it and learn how they did it and the most interesting part is it came from the US. A statistician from the US proposed this stuff and they basically ignored him. Japan and Europe were devastated by the war so when you are the only one producing anything and making 40% profit who cares about anything expect martinis at lunch and the 2:00 golf game. So they shipped him to Japan. Perfect choice because the Japanese culture was just perfect for this. Bet they did not know that back then. Figured his ideas would just fade away.
 
you know what you are talking about. You authored this so this has not been easy to explain myself at times. Perhaps if we were talking about printing presses :-)

Loading…

www.dpreview.com
 
guy schlacter said:
WilbaW said:
Zee Char said:
guy schlacter said:
WilbaW said:
guy schlacter said:
Hokie Jack said:
"Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus."

The first sentence is very clear. IMO the second one is vague, at best. I'm not sure what it is trying to say. I just thought it was an awkward way of saying each MFA increment moves you toward or away from the plane of focus. I don't think they intended to re-define the term DOF.
Click to expand...
I believe both sentences need to be taken together.
Click to expand...
Let's rephrase them for clarity - Each step is a very fine increment, equal to 1/8th of the total depth-of-field you'd have with the current lens wide-open. An increment moves the plane of focus forward (toward the camera) or back (toward the background).

Nothing suggests the "depth-of-field" (or focus) is intended as the single-sided depth (from the near or far limit to the plane of focus).
Member said:
We must also remember this is translated from Japanese...
Click to expand...
Rubbish. The whole paragraph is perfectly grammatical and reasonable English, using conventional terms. There is nothing to suggest that it suffers from translation errors.
Member said:
which gives some latitude of use of dof in the both sentences.
Click to expand...
DOF is always the entire depth unless specifically referred to as "near DOR" and "far DOF" or "DOF in front" and "DOF behind".
Member said:
Also, that is the reason Chuck Westfall clarifies it and calls it Depth of Focus, which aligns exactly with the 2nd definition from the earlier Wikipedia definition = ~ half of total dof in front, or behind focal plane.
Click to expand...
Yes, half of the total depth is in front of the image (or focus) plane, and the other half is behind. Both halves together make up "the depth", the total. Your assertion makes no sense and you can't explain it by reference to what you're referring to. I reject it completely. :-)
Click to expand...
WilbaW,

Reject all you want. I have asked Chuck and Rudy to specifically clarify. Chuck used the term 1/8 of depth of focus, being front or back side of the dof.
Click to expand...
That is the way I read it. I don't see any reference to Depth of Focus or anything else. If they had meant something else they should have stated it more clearly or corrected it if wrong.

If nothing suggests anything then please explain what "Canon has clearly stated" 1/8 of depth of focus then means WilbaW. No references to anything that does not exist in that document unless you research it and provide evidence that it means something else - from Canon, not Wikipedia anything else. Wikipedia did not post this. Our turn :-)
Click to expand...
It's Guy who claims Chuck said something about DO focus. Are Chuck's words posted in the thread? I looked but couldn't find them. If we get that I can tell you what I think they mean. But if I can't use standard definitions of the terms used, please track down Canon's technical definitions of DO focus and field so we can use them.

Edit: I had a quick look and all we need is the diagram on this Canon DOF calculator -

http://www.usa.canon.com/cusa/profe...s/bctv_range_calculator/bctv_range_depthfield

rangecalculator2.gif
Click to expand...
So now with this diagram, the labeling of from depth of field and back depth of field, doesn't that align with what I have been saying all along, AND with what is in the Canon text in the 2nd sentence? It is 1/8 of the dof in front of the subject Plane of focus. Hence 1/16 of total dof.
Click to expand...
Wilba,

THIS should make you happier. It says what I have been trying to write (based on field being 50/50 depth of field when not at hyperfocal distance. I think you will be much happier with Chuck's wording I dug up from some recent correspondence with him, and included below. This also corroborates the 1/16 calculation (1/8 single sided) when DOField is close to 50/50

Thanks again for posting the diagram. Makes it very clear how the two sides of the field focus plan get compressed into their respective side of the depth of focus at the image plane. When field is 50/50 (most often for non-landscape work), compression is about the same into the depth of total focus spanning from front to back sides from image, but hyperfocal would get much more compressed behind the field plane of focus.

THIS WAS CHUCK'S WESTFALL'S DIRECT RESPONSE:

In answer to the AF Microadjustment question, the focus shift amount per step is calculated by multiplying the maximum aperture's single-side depth of focus by 1/8. The key phrase is "single-side depth of focus." It equates to half of the total depth of focus, which of course extends equally both in front of and behind the focal plane. Note also that the calculation is based on depth of focus, which is measured at the focal plane and is always equally distributed in front of an behind it, and not depth of field, which is measured at the subject and does not always extend equally in front of or behind it. Note further that the depth of focus is proportional to the focal length and the maximum aperture of the lens; therefore, the larger the maximum aperture and the longer the focal length, the smaller each individual AF Microadjustment step becomes.



-Guy
 
guy schlacter said:
guy schlacter said:
WilbaW said:
Zee Char said:
guy schlacter said:
WilbaW said:
guy schlacter said:
Hokie Jack said:
"Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus."

The first sentence is very clear. IMO the second one is vague, at best. I'm not sure what it is trying to say. I just thought it was an awkward way of saying each MFA increment moves you toward or away from the plane of focus. I don't think they intended to re-define the term DOF.
Click to expand...
I believe both sentences need to be taken together.
Click to expand...
Let's rephrase them for clarity - Each step is a very fine increment, equal to 1/8th of the total depth-of-field you'd have with the current lens wide-open. An increment moves the plane of focus forward (toward the camera) or back (toward the background).

Nothing suggests the "depth-of-field" (or focus) is intended as the single-sided depth (from the near or far limit to the plane of focus).
Member said:
We must also remember this is translated from Japanese...
Click to expand...
Rubbish. The whole paragraph is perfectly grammatical and reasonable English, using conventional terms. There is nothing to suggest that it suffers from translation errors.
Member said:
which gives some latitude of use of dof in the both sentences.
Click to expand...
DOF is always the entire depth unless specifically referred to as "near DOR" and "far DOF" or "DOF in front" and "DOF behind".
Member said:
Also, that is the reason Chuck Westfall clarifies it and calls it Depth of Focus, which aligns exactly with the 2nd definition from the earlier Wikipedia definition = ~ half of total dof in front, or behind focal plane.
Click to expand...
Yes, half of the total depth is in front of the image (or focus) plane, and the other half is behind. Both halves together make up "the depth", the total. Your assertion makes no sense and you can't explain it by reference to what you're referring to. I reject it completely. :-)
Click to expand...
WilbaW,

Reject all you want. I have asked Chuck and Rudy to specifically clarify. Chuck used the term 1/8 of depth of focus, being front or back side of the dof.
Click to expand...
That is the way I read it. I don't see any reference to Depth of Focus or anything else. If they had meant something else they should have stated it more clearly or corrected it if wrong.

If nothing suggests anything then please explain what "Canon has clearly stated" 1/8 of depth of focus then means WilbaW. No references to anything that does not exist in that document unless you research it and provide evidence that it means something else - from Canon, not Wikipedia anything else. Wikipedia did not post this. Our turn :-)
Click to expand...
It's Guy who claims Chuck said something about DO focus. Are Chuck's words posted in the thread? I looked but couldn't find them. If we get that I can tell you what I think they mean. But if I can't use standard definitions of the terms used, please track down Canon's technical definitions of DO focus and field so we can use them.

Edit: I had a quick look and all we need is the diagram on this Canon DOF calculator -

http://www.usa.canon.com/cusa/profe...s/bctv_range_calculator/bctv_range_depthfield

rangecalculator2.gif
Click to expand...
So now with this diagram, the labeling of from depth of field and back depth of field, doesn't that align with what I have been saying all along, AND with what is in the Canon text in the 2nd sentence? It is 1/8 of the dof in front of the subject Plane of focus. Hence 1/16 of total dof.
Click to expand...
Wilba,

THIS should make you happier. It says what I have been trying to write (based on field being 50/50 depth of field when not at hyperfocal distance. I think you will be much happier with Chuck's wording I dug up from some recent correspondence with him, and included below. This also corroborates the 1/16 calculation (1/8 single sided) when DOField is close to 50/50

Thanks again for posting the diagram. Makes it very clear how the two sides of the field focus plan get compressed into their respective side of the depth of focus at the image plane. When field is 50/50 (most often for non-landscape work), compression is about the same into the depth of total focus spanning from front to back sides from image, but hyperfocal would get much more compressed behind the field plane of focus.

THIS WAS CHUCK'S WESTFALL'S DIRECT RESPONSE:

In answer to the AF Microadjustment question, the focus shift amount per step is calculated by multiplying the maximum aperture's single-side depth of focus by 1/8. The key phrase is "single-side depth of focus." It equates to half of the total depth of focus, which of course extends equally both in front of and behind the focal plane. Note also that the calculation is based on depth of focus, which is measured at the focal plane and is always equally distributed in front of an behind it, and not depth of field, which is measured at the subject and does not always extend equally in front of or behind it. Note further that the depth of focus is proportional to the focal length and the maximum aperture of the lens; therefore, the larger the maximum aperture and the longer the focal length, the smaller each individual AF Microadjustment step becomes.

-Guy
Click to expand...
So hopefully this supports what I have been saying. Rudy Winston uses DO Field as an example because that is what the general public can relate to. They both work together. If the DO Field changes then the DO Field does as well. The DO Focus math would produce a lot of zeros and not mean much to most people. Fine increments is something I can relate to even if I don't know what they are.

Even if I'm off with that interpretation and we stick with DO Focus the ⅛ measurement would still be variable based on DO Field changes. The DO Focus dimension would change on the plane of the sensor.

Knowing that it is variable is more important to me than an actual value. That is just a guideline. It tells me MFA may react differently at different distances to target, f stops and focal lengths.
 
Zee,

THe only thing it doesn't agree with you on is that it is 1/16 total DOField. This is from 1/8 factor of the corresponding single sided Depth of Focus (at image) using 50/50 approximation.
 
guy schlacter said:
Zee,

THe only thing it doesn't agree with you on is that it is 1/16 total DOField. This is from 1/8 factor of the corresponding single sided Depth of Focus (at image) using 50/50 approximation.
Click to expand...
I see. I stayed out of the 1/16 part of the conversation because I did not really understand it. I just watched to see how that has or will conclude. I always used ⅛ in my conversations. I was more interested in the entire area of DO Field or Focus rather than what was happening on the front and back sides. Not that it isn't interesting.
 
Bottom line is that DotTune will allow you to MFA your lenses without knowing all the things discussed in this thread.
 
"Each step is a very fine increment, equal to 1/8th of the depth-of-field you'd have with the current lens wide-open. And that 1/8th of the depth of field is only moving forward (toward the camera) or back (toward the background) from the sharpest plane of focus."

rangecalculator2.gif

guy schlacter said:
So now with this diagram, the labeling of from Front depth of field and back Rear depth of field, doesn't that align with what I have been saying all along, AND with what is in the Canon text in the 2nd sentence? It is 1/8 of the dof in front of the subject Plane of focus. Hence 1/16 of total dof.
Click to expand...
No. "1/8th of the depth-of-field" in the text is 1/8 of the "Depth of field" in the diagram, which is the sum of the "Rear depth of field" and the "Front depth of field".

The second sentence just says that each such 1/8 total DOF increment moves the plane of focus (which is at the "Subject distance" in the diagram), either towards the camera or away from it. That sentence doesn't magically change the increment to half of "1/8th of the depth-of-field", or 1/8 of the rear or front DOF. That's perverse.

So here's how you can find out what's actually happening:
  1. Set up an object at the 50f "Subject distance" of your lens.
  2. Microadjust for accurate focus.
  3. Do a standard DOF calculation for that scene.
  4. Set up objects at the "Near point" and the "Far point" of the DOF.
  5. Focus on the object at the Subject distance and verify that the objects at the Near point and Far point are on the limits of DOF under standard viewing conditions.
  6. Focus on the object at the Near point.
  7. See how many clicks of MA you need to shift focus to the object at the Subject distance.
  8. See how many more clicks of MA you need to shift focus to the object at the Far point.
  9. When you're finished, don't forget to reset MA to what it was in step 1. :-)
If the answer is 8 clicks in steps 7 and 8, you win.

Please include all inputs to and outputs of the DOF calculation, and images from steps 2, 5, 6, 7, and 8 in your report so that we can verify them and duplicate the result.
 
Last edited:
Zee Char said:
Zeee said:
rangecalculator2.gif
Click to expand...
OK then. My apologies.
Click to expand...
No worries.
Zeee said:
I keep trying to find a the word for the relationship between Field and Focus. They both have different values because Field is much larger but they are both relative to each other and the values change in equally when the Field is change by the user.
Click to expand...
Like I said way back, and you can see from the above diagram, it's just similar triangles. You choose an acceptable circle of confusion, and everything else follows. If you shift the image plane by 1/8 of the depth of focus (which is what MA does, as far as I know), then you shift the subject plane (at the "Subject distance) by 1/8 of the depth of field, 'cos it's all proportional.

Is that the word you're looking for? :-)
 
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