DotTune MFA question...

Zee Char said:

guy schlacter said:

Zee Char said:

This is how I see it based on doing this with rulers at one time. It is difficult to show this on a flat plane so this is a ruler on an angle.

The red lines represent the area that is was in focus originally at 0 MFA. The yellow areas are out of focus. Green is the focus point.

Column A is 0 MFA. B = 1 MFA shift. C= 2 MFA shifts. D = 3 MFA shifts.

The AF point in column D is still within the area that was in focus in column A - between the red lines.



According to Canon and the DOF chart the distance within the bracket that is in focus changes if you alter the distance to your target thus so do size of the increments.

I'm only basing this in what I think Canon is trying to tell me.

Click to expand...

I like this post to better let people understand the shift.

However,I would make these changes;

1. Label the whole chart as "overhead view of distance" .Reverse the order of the columns.

2.Label each colum after reversing as 0mfa, +2 mfa,mfa, +4mfa, and+6mfa.(remember, each mfa click is 1/8 of in focus one one side of plane.

3. Label Yellow as oof . label height of box=2mfa clicks. Label green as center of current dof when shot.

4. move the red arrow up 3 rows., and label it desired subject distance. This then with the reversed could will show how adding mfa pushes the dof back and centers around where you place the AF point on subject.

5..Remove long red lines.

6..please repost.

Click to expand...

OK I'll work on it. When you think about this when shooting BIF, at distance and happen to nail the AF point in the eye the birds body and and wings (or most if them depending on conditions) is sharp. Most of the AF points are on the body when I shoot and I get tack sharp eyes. So there is a DOF range where everything is sharp. If you do one MFA shift the plane of focus does change but it may not effect the sharpness in within that area.

A +- 1 MFA shift may show a big change to someone else because it depends on how far apart the calibration is between the lens and the camera. If you had to MFA 7, 9 to more then yes something is out and it will effect the point you are expecting to be sharp with a small move.

Click to expand...

agree on first point (hence your range of white rows in the columns / chart.



The only time a +1 will make a noticeable difference, is if the intended subject/area was right on the edge of the DOF. I believe you are saying something similar in the 2nd paragraph.

WilbaW said:

Zee Char said:

This is how I see it based on doing this with rulers at one time. It is difficult to show this on a flat plane so this is a ruler on an angle.

The red lines represent the area that is was in focus originally at 0 MFA. The yellow areas are out of focus. Green is the focus point.

Column A is 0 MFA. B = 1 MFA shift. C= 2 MFA shifts. D = 3 MFA shifts.

The AF point in column D is still within the area that was in focus in column A - between the red lines.



According to Canon and the DOF chart the distance within the bracket that is in focus changes if you alter the distance to your target thus so do size of the increments.

I'm only basing this in what I think Canon is trying to tell me.

Click to expand...

Okay, sure, fine... but what's the point of being able to depict what's happening in this way? Why is it necessary and relevant? What does it achieve? What can you do with it?

Click to expand...

It just supports what Rudy stated. The OP was wondering if one should bother with a 1 +- MFA adjustment and was told yes. I'm just saying it "may" not show any improvement. The OP or others can read this thread and find it informative or dismiss it as rubbish. Does not matter to me but I think it is fair to provide information and let people make their own decisions. It won't hurt to leave it at +- 1 but believing it solves a problem that may not exist is not really fair either.

guy schlacter said:

Zee Char said:

guy schlacter said:

Zee Char said:

This is how I see it based on doing this with rulers at one time. It is difficult to show this on a flat plane so this is a ruler on an angle.

The red lines represent the area that is was in focus originally at 0 MFA. The yellow areas are out of focus. Green is the focus point.

Column A is 0 MFA. B = 1 MFA shift. C= 2 MFA shifts. D = 3 MFA shifts.

The AF point in column D is still within the area that was in focus in column A - between the red lines.



According to Canon and the DOF chart the distance within the bracket that is in focus changes if you alter the distance to your target thus so do size of the increments.

I'm only basing this in what I think Canon is trying to tell me.

Click to expand...

I like this post to better let people understand the shift.

However,I would make these changes;

1. Label the whole chart as "overhead view of distance" .Reverse the order of the columns.

2.Label each colum after reversing as 0mfa, +2 mfa,mfa, +4mfa, and+6mfa.(remember, each mfa click is 1/8 of in focus one one side of plane.

3. Label Yellow as oof . label height of box=2mfa clicks. Label green as center of current dof when shot.

4. move the red arrow up 3 rows., and label it desired subject distance. This then with the reversed could will show how adding mfa pushes the dof back and centers around where you place the AF point on subject.

5..Remove long red lines.

6..please repost.

Click to expand...

OK I'll work on it. When you think about this when shooting BIF, at distance and happen to nail the AF point in the eye the birds body and and wings (or most if them depending on conditions) is sharp. Most of the AF points are on the body when I shoot and I get tack sharp eyes. So there is a DOF range where everything is sharp. If you do one MFA shift the plane of focus does change but it may not effect the sharpness in within that area.

A +- 1 MFA shift may show a big change to someone else because it depends on how far apart the calibration is between the lens and the camera. If you had to MFA 7, 9 to more then yes something is out and it will effect the point you are expecting to be sharp with a small move.

Click to expand...

agree on first point (hence your range of white rows in the columns / chart.

The only time a +1 will make a noticeable difference, is if the intended subject/area was right on the edge of the DOF. I believe you are saying something similar in the 2nd paragraph.

Click to expand...

That is why I support anyone who says it makes a difference at +-1. There was a thread where someone said +3 made a big difference. I believe it.

Zee Char said:

It just supports what Rudy stated. The OP was wondering if one should bother with a 1 +- MFA adjustment and was told yes. I'm just saying it "may" not show any improvement.

Click to expand...

So I guess we end up with, stop when you can't achieve any more improvement.

Zeee said:

The OP or others can read this thread and find it informative or dismiss it as rubbish. Does not matter to me but I think it is fair to provide information and let people make their own decisions. It won't hurt to leave it at +- 1 but believing it solves a problem that may not exist is not really fair either.

Click to expand...

Sure, if you (anyone) don't have a problem you don't need to try for improvement, but that also means you can't tell others they don't and shouldn't.

WilbaW said:

Zee Char said:

It just supports what Rudy stated. The OP was wondering if one should bother with a 1 +- MFA adjustment and was told yes. I'm just saying it "may" not show any improvement.

Click to expand...

So I guess we end up with, stop when you can't achieve any more improvement.

Click to expand...

You got that right. Perhaps that was what the OP should have been told, not +-1 did make an improvement when it was noticed it didn't.

WilbaW said:

WilbaW said:

The OP or others can read this thread and find it informative or dismiss it as rubbish. Does not matter to me but I think it is fair to provide information and let people make their own decisions. It won't hurt to leave it at +- 1 but believing it solves a problem that may not exist is not really fair either.

Click to expand...

Click to expand...

WilbaW said:

Sure, if you (anyone) don't have a problem you don't need to try for improvement, but that also means you can't tell others they don't and shouldn't.

Click to expand...

When have I ever said that? I just explored something further and suggested people should be aware of the entire process and make their own decisions. I could not care if anyone MFA's or not. I don't care if someone gets a new lens and spends hours doing MFA before even trying it - which people have been told they "must do" here and on other sites. I'm not kidding. I have seen the word "must" and you are giving me a hard time I don't care of the OP leaves it at +-1.

You guys have my blessings to promote the "you can't shoot unless you MFA" all you like. I finally got some answers I have asked about for last 5 years.

I said at the start this is not an is MFA good or bad conversation. It was about understanding it better. Why are you are you doing this?

F3RSH said:

DOF when applied to AFMA refers to Depth of Focus, not Depth of Field - see http://en.wikipedia.org/wiki/Depth_of_focus

So, those calculations of Depth of Field are not appropriate.

Click to expand...

I'm OK with that. Why doesn't Canon explain that and would some explain what the value of ⅛ relates to?

Zee,

IF someone is having FOCUS issues, most of us would recommend full stop until they MFA and then continue asking for help. Why? Remember that the AF is not perfectly consistent. Canon states that the SPEC for AF consistency / accuracy shot to shot is = Field of Focus, so 1/2 of the DOF. IF a person doesn't MFA their lens to center the focal plan onto the intended subject, then they will potentially incur much higher rates of OOF.

guy schlacter said:

Zee,

IF someone is having FOCUS issues, most of us would recommend full stop until they MFA and then continue asking for help. Why? Remember that the AF is not perfectly consistent. Canon states that the SPEC for AF consistency / accuracy shot to shot is = Field of Focus, so 1/2 of the DOF. IF a person doesn't MFA their lens to center the focal plan onto the intended subject, then they will potentially incur much higher rates of OOF.

Click to expand...

But that is exactly what I do and would suggest but apparently have been told I shouldn't be suggesting anything I shoot real world first and then if something looks off I check to see what is off. If slight or lots I decide how to proceed. Either I correct it or Canon does. Of course you go through all the other trouble shooting steps like camera settings, etc as well.

I have always said that it is a good tool to tighten things up but it can let companies get away with sloppy manufacturing. Again my example of my brand new 70-200 2.8 II.

0 @ 70mm and +15 @ 200mm.

Canon Canada told me it went to +20. Canon Newport found the lens was mis-calibrated. First lens that has happened to. I spend thousands on precision equipment and I refuse to fix someones sloppy manufacturing. Again I don't care if someone else chooses to correct it themselves. I will never tell them they "must" send it to Canon. I don't care.

What did people do before the 50D, 5D2 and 1D lines (if there were any that did not have MFA)? I have seen thousands of sharp images and I know all those bodies and lenses did not go back to Canon. Did a high percentage of the 60D's go back to Canon for recalibration? I followed those threads out of interest and people were posting all types of sharp images. People were disappointed it did not have MFA but then after shooting for a while realized they did not miss it. Not all but many did.

Just because I'm not 100% on the MFA bandwagon people think I'm telling people not to use it. and i'm branded with that. If I see something or something does not make sense I question it. I think people should see both sides of the story and make up their own minds.

Canon has decades of experience, R&D, engineers, etc. They come out with 50X "minimum" distance to target. I have nothing against 3rd party MFA software but they come out with 25X. So I asked why?

WilbaW said:

Zee Char said:

of MFA I always assumed a + or - move was a single fixed value if you did it at 2 ft or 1000 ft. Be it .0625, .125 or whatever number Canon used.

Click to expand...

"A single fixed value" of focus distance? No! If that's what this is all about, just let it go, it's simply wrong.

Click to expand...

Not the focal distance. The actual distance of the one shift of MFA regardless of distance to target.

WilbaW said:

WilbaW said:

That to me would be irrelevant.

Click to expand...

Eh? I think you mean relevant.

Click to expand...

No. I meant that if one MFA shift was always the same amount like .0625 then it would be easier to understand then less relevant to me. Based in Canon's explanation that says ⅛ of DO field the shift amount would vary based on distance to target.

WilbaW said:

WilbaW said:

It seemed logical.

Click to expand...

Sure, but AF works with DO focus AFAWCT, so it's just wrong, sorry.

Click to expand...

What does AFAWCFT mean?

WilbaW said:

WilbaW said:

I'd still like to know what Rudy means by saying ⅛ of the Depth Of Field and how this effects MFA.

Click to expand...

To the best of my understanding, what Rudy means is, a click of AF MA is applied mathematically as an increment of 1/8 of the DO focus (the context in which the AF system operates by converting focus errors at the sensor into lens drive commands), and you can see that change as a shift equivalent to 1/8 of the wide-open DO field. I also assume he's talking about focus distances up to 50f, where DOF is essentially symmetrical on both sides of the plane of focus, not further out towards hyperfocal.

Click to expand...

I don't get this. "you can see that change as a shift equivalent ⅛ of the wide open DO field." So aren't we back to taking the area in focus within the DO field and diving that by 8? The DO field still varies in size based on distance to target. So will the amount of shift of the AF point not also vary in amount based on distance to target?

walkaround said:

Zee Char said:

Unless there is another answer to the DOF value the calculations based on a perfectly calibrated lens and body, no deviation from perfect 0, which is impossible, you would need to shift + or - 4 to see any difference.

Click to expand...

The entire depth of field is not in equally sharp focus. There is still a focus point within the DOF.

Click to expand...

Yes there is but when I'm out doing BIF and my focus point lands on the body of the bird why do I get a tack sharp eye?

guy schlacter said:

F3RSH said:

DOF when applied to AFMA refers to Depth of Focus, not Depth of Field - see http://en.wikipedia.org/wiki/Depth_of_focus

So, those calculations of Depth of Field are not appropriate.

Click to expand...

correct, hence the need to fix it to 2 mfa steps per row (block).

Per the second definition found using your link, of the near-symmetrical Depth of Focus around the plane of focus, there are 8 mfa clicks to Depth of Focus, so hence, each MFA click is 1/16 of the total Depth of Field.

Click to expand...

Where is it stated that it's 1/8 of the single-sided DO focus, not 1/8 of the total DO focus?

F3RSH said:

DOF when applied to AFMA refers to Depth of Focus, not Depth of Field - see http://en.wikipedia.org/wiki/Depth_of_focus

So, those calculations of Depth of Field are not appropriate.

Click to expand...

I'm trying to understand this. First it says DO focus is used to mean DO Field.

We know this

Depth of field is the range of distances in object space for which object points are imaged with acceptable sharpness with a fixed position of the image plane (the plane of the film or electronic sensor).

Depth of focus can have two slightly different meanings.

Is the next sentence basically not the same thing as DO field?

The first is the distance over which the image plane can be displaced while a single object plane remains in acceptably sharp focus;

I think this just says it divides the object plane that remains sharp in half does it not? The front part and the back from the focus point. ⅓ - ⅔ or ½ - ½

The second is the image-side conjugate of depth of field. With the first meaning, the depth of focus is symmetrical about the image plane; with the second, the depth of focus is greater on the far side of the image plane, though in most cases the distances are approximately equal.

Zee Char said:

I foresee if I use your method @ a distance of 5 ft it may not even react with the defocusing step. If I do it at 50 it will be easier to do.

Click to expand...

I guess you're talking about "my method" of using the EOS Utility to compare defocused images. Using that method near MFD I can see front-focus at one setting and back-focus a single click away. IOW, I can see the effect of a single click of microadjustment, and that's not micro enough sometimes.

You won't get anywhere with foresight - just try it!

Zeee said:

Zeee said:

Zeee said:

If this is not correct please explain what Canon means by ⅛ of depth of focus...

Click to expand...

I think it is as simple as that - they claim 1 click is a 1/8 shift. If you want it shifted, shift it. What's the problem?

Click to expand...

There isn't one. You said it was all about depth of focus and I was questioning why Canon says depth of field.

Click to expand...

'Cos DO focus is how engineers make AF work, but DO field is what photographers can see. DO focus and DO field are geared together so they effectively mean the same thing in this context. If Canon said an MA click shifts focus by 1/8 of the DO focus, lots of people would be running around pulling the hair out going, "Eh? What? DO focus? What the heck is that? Do they mean DOF?"

Zeee said:

I'm curios how the ⅛ increments are effected by distance to target.

Click to expand...

The same way DOF is affected by distance to target, since an increment is always 1/8 of that whatever it is (according to Canon).

Zee Char said:

WilbaW said:

Sure, if you (anyone) don't have a problem you don't need to try for improvement, but that also means you [any random reader, not Zee Char in particular] can't tell others they don't and shouldn't.

Click to expand...

When have I ever said that?

Click to expand...

I don't know whether you ever have, but that's irrelevant because I was addressing the entire forum, which is sure to include someone who thinks that AF MA is unnecessary and therefore pooh-poohs its use.

Zeee said:

I finally got some answers I have asked about for last 5 years.

Click to expand...

I'm interested to know what you've learned.

Zee Char said:

WilbaW said:

Zee Char said:

I always assumed a + or - move was a single fixed value if you did it at 2 ft or 1000 ft. Be it .0625, .125 or whatever number Canon used.

Click to expand...

"A single fixed value" of focus distance? No! If that's what this is all about, just let it go, it's simply wrong.

Click to expand...

Not the focal distance. The actual distance of the one shift of MFA regardless of distance to target.

Click to expand...

Let's spell it out so we don't get caught up in "focus distance" versus "focal distance" versus "actual distance" misunderstandings.

Do you mean that a click of MA will shift the focus the same distance in object space regardless of how far away the focus target is? For example, if we say "a single fixed value" is 1 inch, and we focus on a target 2 ft away, then a -1 adjustment will shift the focus 1 inch closer to the camera? And if we focus on a target at 1,000 ft, a +1 adjustment will also shift the focus just 1 inch further away from the camera? If that's what you mean, it's simply wrong. According to Canon, a click is 1/8 of the DOF (focus or field, doesn't matter, it's the same effect). Full stop. End of story.

Zeee said:

Based in Canon's explanation that says ⅛ of DO field the shift amount would vary based on distance to target.

Click to expand...

You understand, now just accept.

Zeee said:

Zeee said:

Zeee said:

It seemed logical.

Click to expand...

Sure, but AF works with DO focus AFAWCT, so it's just wrong, sorry.

Click to expand...

What does AFAWCT mean?

Click to expand...

As far as we can tell.

Zeee said:

Zeee said:

Zeee said:

I'd still like to know what Rudy means by saying ⅛ of the Depth Of Field and how this effects MFA.

Click to expand...

To the best of my understanding, what Rudy means is, a click of AF MA is applied mathematically as an increment of 1/8 of the DO focus (the context in which the AF system operates by converting focus errors at the sensor into lens drive commands), and you can see that change as a shift equivalent to 1/8 of the wide-open DO field. I also assume he's talking about focus distances up to 50f, where DOF is essentially symmetrical on both sides of the plane of focus, not further out towards hyperfocal.

Click to expand...

I don't get this. "you can see that change as a shift equivalent ⅛ of the wide open DO field." So aren't we back to taking the area in focus within the DO field and diving that by 8?

Click to expand...

Yes, that's exactly what "1/8 of the DOF" means, whatever the wide-open DOF at the current focus distance is.

Zeee said:

The DO field still varies in size based on distance to target.

Click to expand...

Correct.

Zeee said:

So will the amount of shift of the AF point not also vary in amount based on distance to target?

Click to expand...

Yes, it must vary in that way. The idea that it won't is the problem. You understand, now the challenge is to accept.

WilbaW said:

Zee Char said:

WilbaW said:

Sure, if you (anyone) don't have a problem you don't need to try for improvement, but that also means you [any random reader, not Zee Char in particular] can't tell others they don't and shouldn't.

Click to expand...

When have I ever said that?

Click to expand...

I don't know whether you ever have, but that's irrelevant because I was addressing the entire forum, which is sure to include someone who thinks that AF MA is unnecessary and therefore pooh-poohs its use.

WilbaW said:

I finally got some answers I have asked about for last 5 years.

Click to expand...

I'm interested to know what you've learned.

Click to expand...

I believe I figured it out. DO Field and DO Focus are the exact same thing.

DO Field is based on distance to target, fstop and focal length. This is the real world being projected through the lens and what we see in our final image.

DO Focus is at the sensor level.

I believe Canon (Rudy) uses DO Field because this is what we work with every day and understand it. We can use the on line calculator to figure out total DO Field, divide by 8 and get a sense of how large the MFA moves are.

DO Focus at the sensor level is but is relative to the DO Field, the dimensions are just different. Perhaps correlates instead of relative is a better word. The will be an area that will be in focus and an area that will be out of focus on the sensor, just like an image. I don't know the dimensions as they are very small compared to the DO Field. As you can see 300mm @ 50ft has a total DO Field of 15.12 inches, divided by 8 = 1.89. The sensor is far smaller than 15.12 inches but there will be an in focus area on the sensor that will correlate to the 15.12 inches.



Now we look at 300mm @ ft. The total DO Field has now dropped to a sliver of 0.12 inches. There will be a slit of a area in focus in your image and the area that is focus at the sensor level will be much smaller but again they correlate.

So is the math correct? Yes it is for DO field. If anyone wants to know what it is for DO Focus at the sensor level I'm sure there is a formula but to me it is unnecessary. Knowing they are as Canon states "fine increments" is good enough. I do know that the fine increments dimensions vary at the sensor level as they do going in real world images when distance to target, fstop and focal length changes.

So do I need to know the dimensions at the sensor level (DO focus) so I can divide by 8? No. The DO Field values are all that is necessary because I can relate to them.

So what have I learned?

1. I once thought that a single MFA move was a fixed value regardless of distance to target, fstop and focal length. Now I know it is variable. How does this help me? Read on.

2. I now understand Canons explanation of ⅛ of DO Field means and how it relates to DO Focus. That never made any sense to me. Canon may have as well asked me to explain how long is a piece of string.

3. I know believe I understand why Canon suggests 50X and others 25X distance to target. If you look at the table doing MFA at 50X is much more forgiving than at MFD or 5 ft. I compare it to using a ruler and drawing a line at every inch. Pretty easy. Now draw a line at each 1/64 of an inch. You need a finer pen, maybe a magnifying glass and it is not as easy.

50X reduces the chances of error. Many people just don't have the facilities for 50X with long lenses so 25X is suggested. It works the same way but the MFA shifts are smaller thus more prone to error. Some methods may not even work at MFD.

4. I have two Canon documents now that tell me it is best to MFA at the location or the distance you normally shoot at. If you can't 50X is Canom's lab number.

5. I have learned that Canon supports what I have thought all along. +- 3 or so MFA moves may not show any significant difference. Does anyone else believe this. I don't know and I don't care. This is not what this is about.

Like I said I have been asking for 5 years why does Canon suggest 50X and others 25X and how does this impact MFA? No one could answer that. I have seen that ⅛ of DOF before, I decided to explore it and now I know what it means.

Will this help me when MFA in the future? Yes. Very much so. Distance to target has been my #1 question and now it has been answered.

F3RSH said:

DOF when applied to AFMA refers to Depth of Focus, not Depth of Field - see http://en.wikipedia.org/wiki/Depth_of_focus

So, those calculations of Depth of Field are not appropriate.

Click to expand...

The math is correct.

WilbaW said:

Zee Char said:

WilbaW said:

Zee Char said:

I always assumed a + or - move was a single fixed value if you did it at 2 ft or 1000 ft. Be it .0625, .125 or whatever number Canon used.

Click to expand...

"A single fixed value" of focus distance? No! If that's what this is all about, just let it go, it's simply wrong.

Click to expand...

Not the focal distance. The actual distance of the one shift of MFA regardless of distance to target.

Click to expand...

Let's spell it out so we don't get caught up in "focus distance" versus "focal distance" versus "actual distance" misunderstandings.

Do you mean that a click of MA will shift the focus the same distance in object space regardless of how far away the focus target is? For example, if we say "a single fixed value" is 1 inch, and we focus on a target 2 ft away, then a -1 adjustment will shift the focus 1 inch closer to the camera? And if we focus on a target at 1,000 ft, a +1 adjustment will also shift the focus just 1 inch further away from the camera? If that's what you mean, it's simply wrong. According to Canon, a click is 1/8 of the DOF (focus or field, doesn't matter, it's the same effect). Full stop. End of story.

WilbaW said:

Based in Canon's explanation that says ⅛ of DO field the shift amount would vary based on distance to target.

Click to expand...

You understand, now just accept.

Click to expand...

I do. When did I say I didn't. The moment I started to explore ⅛ of DO field it was clear. The conversation then included DO Focus.

WilbaW said:

WilbaW said:

WilbaW said:

WilbaW said:

It seemed logical.

Click to expand...

Sure, but AF works with DO focus AFAWCT, so it's just wrong, sorry.

Click to expand...

What does AFAWCT mean?

Click to expand...

As far as we can tell.

Click to expand...

Thanks. I was getting a headache

WilbaW said:

WilbaW said:

WilbaW said:

WilbaW said:

I'd still like to know what Rudy means by saying ⅛ of the Depth Of Field and how this effects MFA.

Click to expand...

To the best of my understanding, what Rudy means is, a click of AF MA is applied mathematically as an increment of 1/8 of the DO focus (the context in which the AF system operates by converting focus errors at the sensor into lens drive commands), and you can see that change as a shift equivalent to 1/8 of the wide-open DO field. I also assume he's talking about focus distances up to 50f, where DOF is essentially symmetrical on both sides of the plane of focus, not further out towards hyperfocal.

Click to expand...

I don't get this. "you can see that change as a shift equivalent ⅛ of the wide open DO field." So aren't we back to taking the area in focus within the DO field and diving that by 8?

Click to expand...

Yes, that's exactly what "1/8 of the DOF" means, whatever the wide-open DOF at the current focus distance is.

WilbaW said:

The DO field still varies in size based on distance to target.

Click to expand...

Correct.

WilbaW said:

So will the amount of shift of the AF point not also vary in amount based on distance to target?

Click to expand...

Yes, it must vary in that way. The idea that it won't is the problem. You understand, now the challenge is to accept.

Click to expand...

Read this.

WilbaW said:

guy schlacter said:

F3RSH said:

DOF when applied to AFMA refers to Depth of Focus, not Depth of Field - see http://en.wikipedia.org/wiki/Depth_of_focus

So, those calculations of Depth of Field are not appropriate.

Click to expand...

correct, hence the need to fix it to 2 mfa steps per row (block).

Per the second definition found using your link, of the near-symmetrical Depth of Focus around the plane of focus, there are 8 mfa clicks to Depth of Focus, so hence, each MFA click is 1/16 of the total Depth of Field.

Click to expand...

Where is it stated that it's 1/8 of the single-sided DO focus, not 1/8 of the total DO focus?

Click to expand...

The link to the Canon site stating this has been included a couple of times in this thread, and the text included as well.

Zee Char said:

F3RSH said:

DOF when applied to AFMA refers to Depth of Focus, not Depth of Field - see http://en.wikipedia.org/wiki/Depth_of_focus

So, those calculations of Depth of Field are not appropriate.

Click to expand...

I'm trying to understand this. First it says DO focus is used to mean DO Field.

We know this

Depth of field is the range of distances in object space for which object points are imaged with acceptable sharpness with a fixed position of the image plane (the plane of the film or electronic sensor).

Depth of focus can have two slightly different meanings.

Is the next sentence basically not the same thing as DO field?

The first is the distance over which the image plane can be displaced while a single object plane remains in acceptably sharp focus;

I think this just says it divides the object plane that remains sharp in half does it not? The front part and the back from the focus point. ⅓ - ⅔ or ½ - ½

The second is the image-side conjugate of depth of field. With the first meaning, the depth of focus is symmetrical about the image plane; with the second, the depth of focus is greater on the far side of the image plane, though in most cases the distances are approximately equal.

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Yes

And

yes.