Hyperfocal distance - tutorial misleading?

[Downrigger]

Been reading on this principle trying to figure out how to use the concept of hyperfocal distance practically in the field.

The CIC tutorial makes a statement the following statement: "The fraction of the depth of field which is in front of the focal plane approaches 1/2 for the closest focus distances, and decreases all the way to zero by the time the focus distance reaches the hyperfocal distance."

This conflicts with my other readings, and really doesn't read to make sense - there has to be some field of focus in front of the focus point.

Generally my reading has indicated that the depth of field extends from half the hyperfocal distance to infinity when the lens is focused on the hyperfocal distance.

Does the tutorial need correction? Or am I missing a semantic? Not meaning to be a nerd, but wondering, and also wondering if anyone uses this concept in a practical way in the field, or if it's mainly a book thing.

[HaseebM]

I have read all tutorials though yet to come to grips with them. I find them informative with good illustrations and in-depth. Isn't there always an exception? Would be interesting what your other readings and why you feel they conflict with this.

[Donald]

Mark - Your understanding from other readings is quite correct. But I don't think the CiC tutorial needs correcting. What you've isolated in terms of your quote is the technical stuff. And in technical terms it's correct. For us non-techie type people, I tend to ignore the technical stuff and look at the rest. And if you do that with this tutorial, you'll find that what it says is exactly as you understand it.

Does anyone use it in a practical way? Yes. I do, however, think that I'm in a minority with that. Most people understand the concept, but don't apply it on a day-to-day basis. I tend not to apply it rigidly if I'm shooting with one of the longer lenses. By the time I paced out 200 yards to identify the hyperfocal spot on which to focus, the light would be gone and I'd have lost the shot.

[Downrigger]

It is a bit semantic - the CiC tutorial is mathematically correct. But it's clear from all sources that when focused at the hyperfocal distance the depth of field extends half the distance from that point towards the camera, and that's a critical point in applying the concept of hyperfocal distance.

Although the tutorials statement is mathematically true that the fraction of the total in-focus depth of field comprised by the field in focus on the near side of the hyperfocal point is "zero" (since the denominator is infinity), it is still often a substantial and useful distance.

Thus, I think the tutorial should emphasize the amount of depth of field which is in front of the focal plane (which is useful to know), not the fraction that distance makes when divided by the total distance in the depth of field.

I guess my other question was more important - how to some of the excellent photographers here manage depth of field in landscape shooting?

[Downrigger]

Mark - Your understanding from other readings is quite correct. But I don't think the CiC tutorial needs correcting. What you've isolated in terms of your quote is the technical stuff. And in technical terms it's correct. For us non-techie type people, I tend to ignore the technical stuff and look at the rest. And if you do that with this tutorial, you'll find that what it says is exactly as you understand it.

Does anyone use it in a practical way? Yes. I do, however, think that I'm in a minority with that. Most people understand the concept, but don't apply it on a day-to-day basis. I tend not to apply it rigidly if I'm shooting with one of the longer lenses. By the time I paced out 200 yards to identify the hyperfocal spot on which to focus, the light would be gone and I'd have lost the shot.

Thanks Donald... I was responding as your post went up. You said what I thought I might hear. It seems to me the concept as a qualitative sense is practically useful but not practical as a quantitative tool.

[dje]

It is a bit semantic - the CiC tutorial is mathematically correct. But it's clear from all sources that when focused at the hyperfocal distance the depth of field extends half the distance from that point towards the camera, and that's a critical point in applying the concept of hyperfocal distance.

Although the tutorials statement is mathematically true that the fraction of the total in-focus depth of field comprised by the field in focus on the near side of the hyperfocal point is "zero" (since the denominator is infinity), it is still often a substantial and useful distance.

Thus, I think the tutorial should emphasize the amount of depth of field which is in front of the focal plane (which is useful to know), not the fraction that distance makes when divided by the total distance in the depth of field.

I guess my other question was more important - how to some of the excellent photographers here manage depth of field in landscape shooting?

Mark I think your reasoning is correct. My guess is that Sean included this statement to provide context to the one that follows it in the tutorial regarding focussing 1/3 into the scene. Selecting a distance one third into an infinite distance is not possible !

Dave

[jcuknz]

I agree with Mark that it doesn't read to make sense to me either. The first part of the sentance makes sense and I worked it out for myself from Hyperfocal Tables a long time ago but the second phrase seems completely wrong. But I guess it depends on one's interpretation of words used.
'closer distances' to me means 25ft or less ... then there is "1/2" .... half of what? remembering at distances half is a third but at closer distances the third becomes a half.

I would put it as .... At distances the 'normal' lens [ 50mm on full frame ] has perceived sharpness from one third in front and two thirds behind the focus point. However as the focus point comes closer to the camera that 1/3-2/3 balance changes to a 50/50 balance.... which is the practical angle I need to know.

I suspect that the oft regurguitated 1/3-2/3 balance started when most photographers took photos with distance and coming close was a rare event so it was correct. Most people spent their time taking landscapes. But since today coming in close is available to almost every camera it is worth appreciating that the balance changes as one comes closer. The effect is different with different lenses.

Like a lot of technical aspects hyperfocal distances play no part in my photography.They used to but not today.

In practical terms sharpness beyond perhaps fifty feet is academic and infinity could be there with a 'normal' angle of view lens and viewed on a monitor.

[inkista]

Mark, I think I found what the issue is....(bold mine)

The CIC tutorial makes a statement the following statement: "The fraction of the depth of field which is in front of the focal plane approaches 1/2 for the closest focus distances, and decreases all the way to zero by the time the focus distance reaches the hyperfocal distance."

This conflicts with my other readings, and really doesn't read to make sense - there has to be some field of focus in front of the focus point.

They're not saying the DoF in front of the focus distances goes to zero, although it's easy to read it that way. They're saying the FRACTION (i.e., ratio) approaches zero at hyperfocal.

In other words,

Call the distance range that's in focus in front of the focus point front.
And the distance range that's in focus behind the focus point back.

What that sentence is describing is how much of the full DoF distance range front is.

When you're at macro focus distance, the front:back ratio is 1:1 (1/2 of the DoF is in front of the focus point, 1/2 is behind it). When you hit hyperfocal, the ratio is 1:infinity (i.e., zero).

Basically, this is just a way to say that the 1/3 in front and 2/3 behind rule-of-thumb doesn't always hold true, depending on your subject distance.

Generally my reading has indicated that the depth of field extends from half the hyperfocal distance to infinity when the lens is focused on the hyperfocal distance.

This is about the actual distances at which stuff starts to be in/out of focus. Not the ratio of how much of your depth of field is in front of or behind the focus point. Of course, all this is also arguable depending on your definition of "acceptable sharpness" and "in focus".

Personally, the only way I use hyperfocal distance is to pull out one of my manual adapted lenses, stick it on my 5DMkII, set the aperture, and then use the DoF scale to put my f-number next to the infinity mark (yay slide-rule technology!).

[Downrigger]

Right Kathy. Thank you.

You have the issue that was on my mind, but you may have found a way of expressing it more clearly than I did. The problem IS the emphasis, in the tutorial, on fraction of what you call "front" to what you call "back", which has to go to zero as the back approaches infinity. This is not useful to think about when setting up to achieve depth of field the includes near objects and infinity.

It is very different from saying that the distance in focus on the near side of the point of focus is half of the distance from the focal point to the camera when focused on the hyperfocal distance. Or, equivalently, when focused at the hyperfocal point, everything from halfway to that point to infinity is in focus. That is useful to think about when setting up to achieve depth of field that include near objects and infinity and kind of a pretty thing to know, I think.

[Colin Southern]

I guess my other question was more important - how to some of the excellent photographers here manage depth of field in landscape shooting?

Generally, it's a non-issue because often we're desiring long exposures (anywhere from 30 seconds to 30 minutes or more) to achieve desirable effects with water and clouds -- and so the aperture is generally stopped right down anyway (and often with additional ND filtering attached). Add to that the fact that landscape often involves wide-angle lenses and it becomes even less of an issue.

Even this shot - taken at F4 - has sold several 22 x 44" canvases (and is currently hanging on the bedroom wall of one of our national celebrities)



Once you get into the smaller apertures than it becomes a complete non-issue, eg this shot at F22

[Downrigger]

That’s really helpful, real world advice and they are nice photos with impressive resumes. That's really the helpful sort of response I was seeking - stop down and fugedaboudit. For the novice though, the reason for what you say is so true is interesting and worth grasping.
For instance: For your second photo (assuming full frame/circle of confusion = 0.03) the hyperfocal distance is about .9M which means that if you had focused on something roughly a meter away you’d have everything from half a meter to infinity sharp. (theoretically, and for 8x10's not bedroom walls). Of course one wouldn’t do that, but the point is, you can pull your focus point well back from the infinite horizon at f22 and 23mm, to bring focus to nearly your feet while keeping the horizon sharp (on an 8x10). Most beginners wouldn't do that for a shot like your #2 – they’d focus on the horizon. Focusing on the infinite horizon loses lots of foreground focus when shooting wide and stopped down. At f22 and 23mm as in your shot you can theoretically bring focus all the way back to a meter and have everything from a foot and a half to forever sharp. That’s sort of amazing to a
beginner like me - and worth keeping in mind when shooting big distances.

[jcuknz]

I baulk at the suggestion that infinity is zero ... infinity is infinity ... obviously we had different maths teachers

[Downrigger]

I baulk at the suggestion that infinity is zero ... infinity is infinity ... obviously we had different maths teachers

The CIC tutorial makes the following statement: "The fraction of the depth of field which is in front of the focal plane approaches 1/2 for the closest focus distances, and decreases all the way to zero by the time the focus distance reaches the hyperfocal distance." I do not think they are confusing infinity and zero, rather they point out that the value of a fraction approaches zero as the denominator approaches infinity, provided the numerator is a finite number.

[revi]

Different students...:
what approaches zero isn't the infinity (which is behind the focal plane anyway), but the ratio

(sharp range in front of focal plane)/(sharp range behind focal plane).

When you focus (or beyond) the hyperfocal distance, this becomes:

(sharp range in front of focal plane)/infinity ≈ 0

[Colin Southern]

That’s really helpful, real world advice and they are nice photos with impressive resumes. That's really the helpful sort of response I was seeking - stop down and fugedaboudit. For the novice though, the reason for what you say is so true is interesting and worth grasping.
For instance: For your second photo (assuming full frame/circle of confusion = 0.03) the hyperfocal distance is about .9M which means that if you had focused on something roughly a meter away you’d have everything from half a meter to infinity sharp. (theoretically, and for 8x10's not bedroom walls). Of course one wouldn’t do that, but the point is, you can pull your focus point well back from the infinite horizon at f22 and 23mm, to bring focus to nearly your feet while keeping the horizon sharp (on an 8x10). Most beginners wouldn't do that for a shot like your #2 – they’d focus on the horizon. Focusing on the infinite horizon loses lots of foreground focus when shooting wide and stopped down. At f22 and 23mm as in your shot you can theoretically bring focus all the way back to a meter and have everything from a foot and a half to forever sharp. That’s sort of amazing to a
beginner like me - and worth keeping in mind when shooting big distances.

Normally I'll just focus on something about 1/3 of the way into the scene; it's not best practice in theory, but in practice, it's worked fine for me. Occasionally I'll whip out a dof calculator if I'm forced to shoot at a wide aperture, but it's not usually needed.

[ajohnw]

Been reading on this principle trying to figure out how to use the concept of hyperfocal distance practically in the field.

The CIC tutorial makes a statement the following statement: "The fraction of the depth of field which is in front of the focal plane approaches 1/2 for the closest focus distances, and decreases all the way to zero by the time the focus distance reaches the hyperfocal distance."

This conflicts with my other readings, and really doesn't read to make sense - there has to be some field of focus in front of the focus point.

Generally my reading has indicated that the depth of field extends from half the hyperfocal distance to infinity when the lens is focused on the hyperfocal distance.

Does the tutorial need correction? Or am I missing a semantic? Not meaning to be a nerd, but wondering, and also wondering if anyone uses this concept in a practical way in the field, or if it's mainly a book thing.

The problem with all tutorials is that they tend to "focus" on field of focus and terms like that. The main point really is that there is only one focus point and the focus deteriorates each side of it at different rates past and before that point.

Easier to talk about if considered in another way.

Imagine focusing on an infinitely small point that is so small the lens can't reproduce it so produces a circle of confusion of a size determined by it's optical accuracy and F stop. This circle of confusion will get bigger each side of the actual focus point. Images are considered to be built up of circles of confusion. The smallest detail a lens can reproduce is determined by it's circle of confusion.

The tutorial seems to be stating that the circle of confusion is at it's minimum at the hyperfocal distance - fact.

It's a wonderful area to fill up web pages with but there are some catches. One for instance is do you carry a laser range finder about with you? The other is more serious. You have this image made up of circles of confusion that vary with distance. When you come to view the image these will have been enlarged by an amount dependent on the size of the final image be it on a print or a screen. At some enlargement from sensor size they will become evident or even objectionable so without considering that the whole thing is a bit pointless really. Where it can be used with a tape measure is to introduce just enough blur into the back ground of things like portrait and whole figure shots,

So put it all together and Colin's 1/3 way into a shot makes some sense plus learning what F stops are needed for what is in front of you and what you want to achieve. As far as landscapes go the distance is usually misty anyway, In practice 1/2 way into the shot might work out as I doubt if any one would take the trouble to note the distances reliably by eye and then set an exact F stop accordingly. The important thing about the tutorials is to note the effects and why.

One other aspect that relates is AF. The camera has some metric it uses to decide that something is in focus. As I grew up with manual lenses I notice that this is often the front of the subject when the depth of field is shallow. Really it should focus 1/3 of the way into the subject. On manual lenses the saying was always focus into subjects not on them. No mention of a 1/3. In some cases it's possible to focus on the far side of something and then the near side and set in between. Lenses had a nice little scale allowing appropriate apertures to be set based on distance. Most would add a stop just to be sure or know from experience what would be needed. More usually the latter and some more just in case. No one wants to risk a shot coming out that is unusable. When you think about how AF works that is likely to need more as well. Otherwise out comes the tape measure or you gauge by eye through the viewfinder.

John
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[Black Pearl]

AAAARRRRHHHHHGGGGG!!!!!!!!!!!!!

Go out and take some pictures.

I love a bit of Tech Talk as much as the next (wo)man but sometimes I just want to grab people and shout at them. Surely getting out a bit more and trying techniques by taking photographs - kind of the whole point of a camera - will produce more real world knowledge than frantically Googling it.

Please don't take this the wrong way - I'm just sitting here (not taking my advise by the way) and screaming at the iMac in exasperation and had to post something

[Andrew76]

I'm at work - so I'm allowed to be wasting time!!!

For instance: For your second photo (assuming full frame/circle of confusion = 0.03) the hyperfocal distance is about .9M which means that if you had focused on something roughly a meter away you’d have everything from half a meter to infinity sharp. (theoretically, and for 8x10's not bedroom walls).

Just a quick question, from someone who still doesn't fully understand. How can you calculate this circle of confusion, if you don't have all the information? I think I might be missing something - I got f22, I got 23mm, and I got FF camera. But we're still missing one variable, aren't we?

[Andrew76]

Nope, we're not - just answered my own question. Thanks!

[ajohnw]

AAAARRRRHHHHHGGGGG!!!!!!!!!!!!!

Go out and take some pictures.

I love a bit of Tech Talk as much as the next (wo)man but sometimes I just want to grab people and shout at them. Surely getting out a bit more and trying techniques by taking photographs - kind of the whole point of a camera - will produce more real world knowledge than frantically Googling it.

The real problem is that plenty of books and web pages encourage people to try and do otherwise. I watched a video on 1/3 and leading lines recently. The guy forgot all about them when taking shots shortly after the starts and remembered what it was about again near the end.

I mostly feel there is no point on posting on these subject really. Eventually people find out for themselves but these days that can take a long long time and might not even happen.

John
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