Hyperfocal distance focusing

[merv]

Although not into landscapes yet, I have been reading in one of the mags about Hyperfocal distance focusing. I wonder how many of you landscape togs use this technique but it does appear to make sense. merv

 

[HoppyUK]

Although not into landscapes yet, I have been reading in one of the mags about Hyperfocal distance focusing. I wonder how many of you landscape togs use this technique but it does appear to make sense. merv

It does make sense. There have been a few threads about it recently, if you search hyperfocal distance against my user name.

 

[Wail]

HFD, it's what I use all the time. I don't want to go anywhere above f/11 when shooting, and with HFD I can maximise my depth of field with ease.

If only I'd known about it much earlier.

 

[aberal]

On a highly technical level HFD makes absolute sense and I'm not going to cast doubt on the technicalities of it all. Perish the thought. In reality, in the field, its way too much of a palaver for us ordinary mortals to waste time with. Focus on whatever you want to be in focus in the foreground, the rock, tree, boat, horse, whatever, set the aperture to f8 or f11 max and your landscapes will work fine.

 

[Janice]

Or just focus about 1/3rd into the landscape and that will be fine too, as it will focus a third back towards you and two thirds fowards to the distance.

Its not an exact science doing it that way, but its quick and works.

 

[HoppyUK]

Those are different ways of applying the HFD theory, except that the 'focus a third in' rule doesn't really apply to HFD and is dangerous because you need a fixed point at either end of the range to do that and one third of infinity is a bit of a moveable feast. You will likely end up with a too distant focus point doing it that way and loose out on potential foregound sharpness which is the point of HFD technique.

Another very hand bit of info is that the hyperfocal distance is always exactly double the near point of the hyperfocal range. For example, if your HFD is say 4m, then everything from 2m to infinity will be sharp. Or if the HFD is 2m, then everything from 1m to infinity, and so on.

 

[simonkit]

Read about, tried it, but very rarely use it.

It's a useful "technique" and well worth knowing about but isn't useful in all situations - it can result in important detail appearing soft as its designed to maximise DOF throughout the scene, not necessarily what you want if you have important features that need to as sharp as possible. It's also a bit more difficult now too as many modern lenses don't incorporate a DOF scale.

This article explains its potential limitations better than I can....

http://www.cambridgeincolour.com/tutorials/hyperfocal-distance.htm


By all means give it a go and its always useful to have a Hyperfocal chart with you, my guess is that you'll not use it too often though:shrug:

Simon

 

[Tyler138]

Any good links/tutorials about it, never heard of it but will have a read about it.

Tyler

 

[HoppyUK]

Read about, tried it, but very rarely use it.

It's a useful "technique" and well worth knowing about but isn't useful in all situations - it can result in important detail appearing soft as its designed to maximise DOF throughout the scene, not necessarily what you want if you have important features that need to as sharp as possible. It's also a bit more difficult now too as many modern lenses don't incorporate a DOF scale.

This article explains its potential limitations better than I can....

http://www.cambridgeincolour.com/tutorials/hyperfocal-distance.htm


By all means give it a go and its always useful to have a Hyperfocal chart with you, my guess is that you'll not use it too often though:shrug:

Simon

Sure you don't use HFD focusing all the time, but when you do want maximum sharpness all the way from distant mountains right down to those flowers in the close foreground, you need to know the hyperfocal distance.

You might then adapt it in some way, or tweak either the f/number or the distance slightly according to taste, but the HFD is still the best starting point.

And it's really easy. I have these numbers stuck inside the lens cap of my 17-40mm. It's all I ever need.

HFD f/5.6 f/11 f/22
17mm 5.6ft 2.8ft 1.4ft
24mm 11.2ft 5.7ft 2.9ft
35mm 24ft 12ft 6ft

These numbers are correct for full frame. It's easy enough (and accurate enough) to guess the inbetween settings. Make your own custom set of figures from here www.dofmaster.com

Edit: another good HFD thread here http://www.talkphotography.co.uk/forums/showthread.php?t=246922

 

[gnom]

I use it quite often for street photography. While todays auto-focus systems are more than capable, I find it quite useful to have it pre- set up like that as it allows for fast shooting and creative ways to hold the camera without worrying too much about getting the focus "right".

 

[Kev.s]

If you have an ipod touch or iphone the dofmaster app in a must have

 

[aberal]

All this is well and good and in the days of film, possibly essential for an amateur landscape photographer when they didn't have the luxury of firing of several shots and reviewing the results. Nowadays we use digital. Use your depth of field preview before you even take the shot, if you camera has got one. If it doesn't, fire off a shot anyway, and review the shot, zoom in and peer at your screen if you have to - if the tree in the foreground isn't sharp enough - refocus/adjust the aperture, do whatever and try again.

Because the fundamental trouble with HFD is that it invariably relies on estimating the distance, by eye to any given object, which instantly renders any supposed accuracy of using it to maximise dof useless. Unless you want to carry a tape measure with you and physically measure if it really is 25 ft to that tree.

 

[merv]

Thanks folks. Will have a look at dofmaster.com. merv

 

[Forbiddenbiker]

As a hobbyist that doesn’t do much landscapes and in a general use way with a well used lens.

I think if you can visualise the angles of focused rays of light falling onto your sensor and understand that the filtering effect of a variable aperture changes the tightness or looseness of millions of tiny clusters of focused light that make uip an image, then you can guess at both dof and hyper focal in the same way you guess how to catch a ball thrown at you.

I'll visualise the size of the aperture, I know the size of my sensor behind it and I can see my subjects in front of me.. kinda see it all as balls being thrown at you in straight lines, visualise the angles of focused light hitting the sensor and you may get my point...or you may not, It is a bit of an odd description I know.

I also know that my 28mm is going to be well sharp on most subjects at whatever distance over say F8 at a max,. actual sharpness is all gonna come down to how large I bow it up anyway.. ...so unless Im really going for it guessing works well for me.

 

[HoppyUK]

I use it quite often for street photography. While todays auto-focus systems are more than capable, I find it quite useful to have it pre- set up like that as it allows for fast shooting and creative ways to hold the camera without worrying too much about getting the focus "right".

That's a good point. On a crop format camera, if you set the lens to 24mm for example, at f/8 the HFD is 12.5ft. Pre-focus at that distance and you know that everything from half that distance, ie 6.25ft, to infinity will be sharp.

All this is well and good and in the days of film, possibly essential for an amateur landscape photographer when they didn't have the luxury of firing of several shots and reviewing the results. Nowadays we use digital. Use your depth of field preview before you even take the shot, if you camera has got one. If it doesn't, fire off a shot anyway, and review the shot, zoom in and peer at your screen if you have to - if the tree in the foreground isn't sharp enough - refocus/adjust the aperture, do whatever and try again.

Because the fundamental trouble with HFD is that it invariably relies on estimating the distance, by eye to any given object, which instantly renders any supposed accuracy of using it to maximise dof useless. Unless you want to carry a tape measure with you and physically measure if it really is 25 ft to that tree.

Fair comment, and if you have a decent LCD it is always a good idea to check that everything is sharp. But what do you use as your starting point for setting the focusing distance? You need to have a idea of the HFD to at least get you close.

The reality of HFD work does not usually mean having to measure long distances accurately. The most common application is landscape with a wide-ish angle lens, and quite close distances, which are quite easy to judge by eye. Furthermore, DoF is not nearly such an exact business as those detailed tables of numbers on a DoF calculator might suggest. Depth of field fades gradually and the point at which sharp becomes unsharp is both subjective and dependant on quite a few individual variables, so you need to make a personal assessment.

This is how I do it. Frame up the shot and note the focal length, then decide what is the important bit of foreground detail that I want sharp. Let's say it is a stately home with some nice flowerbeds close by. If the flowers are a little way away, like 20ft or so, you probably don't need to worry about HFD anyway but let's say they're quite close. It's easy to estimate those kind of distances.

So, I have framed up the shot with the lens at 35mm (I'm on full frame) and I reckon they are 6ft away, and from that figure I also know that the hyperfocal distance I need will be exactly double that, so the lens should be focused at 12ft. Don't try and set that from the lens scale, as they usually only have about three numbers written on them which isn't very helpful. Look for a subject that is 12ft away, estimated by eye, and simply AF on that using the centre focus point. That's the focus set.

Now you need to know the f/number relating to a hyperfocal distance of 12ft at 35mm focal length, and I know from looking at the simple little table written in my lens cap (as above post #11) that it's f/11.

Now I'm set, and I might shoot at those settings or make a small adjustment in line with the comments above. But either way, I know what the optimum starting point is.

 

[Arkady]

You don't have to estimate distances by eye - you already have a range-finder with you:
use the lens.

Focus on the nearest point you want in focus - read off the distance on the lens.
Then focus on the furthest point you want in focus (assuming it's not at infinity) - read off the distance on the lens.

No guesswork required.

 

[dcash29]

I wonder how many of you landscape togs use this technique but it does appear to make sense.

Depends which mag you read and in another case which page.

WARNING: HFD can seriously damage youre health

Dont lose sleep over it try HFD/thirds and infinity focusing for a couple of shots which has near and far detail.
Review at home, choose the one you prefer and stick with it.

I'm with Alan, focus on whats important/detail regardless of where it is.

 

[CaptainPenguin]

I use manual primes on my DSLR a lot and alwys always use hyperfocal distance focusing

 

[HoppyUK]

You don't have to estimate distances by eye - you already have a range-finder with you:
use the lens.

Focus on the nearest point you want in focus - read off the distance on the lens.
Then focus on the furthest point you want in focus (assuming it's not at infinity) - read off the distance on the lens.

No guesswork required.

You can't do that with most lenses - they just don't have the markings on the focusing scale to read off.

My 17-40L has just three distances marked to infinity - 1m, 1.5m and 3m. 24-105L is similar. I think most people can guesstimate at close range by eye more accurately than that.

I use manual primes on my DSLR a lot and alwys always use hyperfocal distance focusing

With primes, marked with a depth of field scale, things are much easier. But note that they are calibrated to full frame sensors and will be just over a stop out for crop format.

It's impractical to put a DoF scale on a zoom as it varies with focal length setting, and also as mentioned the DoF differs between formats by approx 1.25 stops.

Edit: you can make your own DoF and HFD calculator - a really good rotary one, real easy to use, basically the same as those engraved scales on prime lenses but much more comprehensive and also customised to exactly how you want them. It's all free here http://www.dofmaster.com/custom.html - input the numbers, configure it how you want, print it and cut out

 

[MScotts]

..............
Edit: you can make your own DoF and HFD calculator - a really good rotary one, real easy to use, basically the same as those engraved scales on prime lenses but much more comprehensive and also customised to exactly how you want them. It's all free here http://www.dofmaster.com/custom.html - input the numbers, configure it how you want, print it and cut out

There's also a myriad of Apps out there for the iPhone and Android driven phones.
The majority cost a couple of quid or less, with some free ones available too!.
http://www.talkphotography.co.uk/forums/showthread.php?t=255735 to DOF calculators for iPhone, hopefully at some point ther'll be DOF calculator links for Android apps in there too

 

[mrtoad]

i dont...i shoot to a feature and not a distance...i choose my 'actually in focus' point relative to the other elements of the scene...far off things i class as way past infinity...i set infinity's range at 30-40 metres
if i want to take in as much as possible with a foreground feature i focus around 1/4-1/3 past it and let the devil take the hindmost...there is only so much a lens will do at any aperture...
obviously with digital i can take a few at differing focus points
job done

 

[merv]

Both my lenses, the 14-24 and 24-70 have distance scales. I suppose therefore that I switch to manual focus, turn the scale to the hyperfocal distance, compose the picture and trust the camera to do the rest. I don't need even to look through the viewfinder isn't that correct. If I left the camera in autofocus and focused at the hyperfocal distance, when I fire the shutter after composing the shot, it would autofocus again which I dont want. Have I got that right?

 

[HoppyUK]

Both my lenses, the 14-24 and 24-70 have distance scales.

All lenses have a distance scale, some with more detail than others. Most primes also have a depth of field scale. See what one of those looks like in the pics posted on the other HFD thread I linked to in post #9

I suppose therefore that I switch to manual focus, turn the scale to the hyperfocal distance, compose the picture and trust the camera to do the rest. I don't need even to look through the viewfinder isn't that correct.

Yes.

If I left the camera in autofocus and focused at the hyperfocal distance, when I fire the shutter after composing the shot, it would autofocus again which I dont want. Have I got that right?

Well yes, possibly. You obviously have to stop the camera refocusing after you've set it. So either switch to manual, or hold the focus position with first pressure on the shutter release, or maybe assign AF to another button if your camera allows it - the so-called 'back-button AF' configuration.

 

[merv]

Have been working out the HFD's for the 14-24 and 24-70 lenses and notice at the upper focal lengths, ie 24 and 70 the distance scale on the lenses is very vague and cannot be set accurately. The lower ends are fine. I take it that it is a matter of the best guess as to where the scale should be set.

 

[merv]

Hi Richard, no, I know what the depth of field scale looks like and these definitely do not have one. As I said in my following post, the distance scale is not too detailed, particularly at higher focal lengths.

 

[HoppyUK]

Have been working out the HFD's for the 14-24 and 24-70 lenses and notice at the upper focal lengths, ie 24 and 70 the distance scale on the lenses is very vague and cannot be set accurately. The lower ends are fine. I take it that it is a matter of the best guess as to where the scale should be set.

Which is the reason why I said above that the focsuing scale is often not very helpful.

So don't use it. If your HFD is say 12ft, then estimate 12ft by eye and using centre point AF, focus on something at that distance. Hold that focus with first pressure on the shutter release, recompose, and take the picture. It's standard focus-recompose technique.

The distances usually invloved in HFD setting are generally pretty close and easy to estimate well enough.

 

[merv]

Thanks Richard, well explained. merv

 

[Arkady]

You can't do that with most lenses - they just don't have the markings on the focusing scale to read off.

My 17-40L has just three distances marked to infinity - 1m, 1.5m and 3m. 24-105L is similar. I think most people can guesstimate at close range by eye more accurately than that.

Best swap to Nikon then - all my lenses, new and old, have full distance scales, marked in feet and metres...
Use that to guage the distances then use your DoF calculator as described above.


None of my lenses apart from an old MF 35mm f/2 has a DoF scale any more, which you used to be able to use to calculate DoF reasonable accurately.

 

[HoppyUK]

Best swap to Nikon then - all my lenses, new and old, have full distance scales, marked in feet and metres...
Use that to guage the distances then use your DoF calculator as described above.


None of my lenses apart from an old MF 35mm f/2 has a DoF scale any more, which you used to be able to use to calculate DoF reasonable accurately.

You have "full distance scales"? Err, no. With wide and super-wide zooms, even Nikon ones, of the kind that most folks use for HFD setting in landscape photography, the last increment on the scale is around 5ft or 1.5m. There is nothing else all the way to infinity.

So, if you think you can set say 8ft, 10ft or 12ft HFD more accurately by nudging the focusing ring a fraction of a mm, than you can estimate that distance by eye and then AF on it spot on, then by all means do it your way.

 

[Arkady]

You have "full distance scales"? Err, no. With wide and super-wide zooms, even Nikon ones, of the kind that most folks use for HFD setting in landscape photography, the last increment on the scale is around 5ft or 1.5m. There is nothing else all the way to infinity.

So, if you think you can set say 8ft, 10ft or 12ft HFD more accurately by nudging the focusing ring a fraction of a mm, than you can estimate that distance by eye and then AF on it spot on, then by all means do it your way.

err... yes... that is a full distance scale as far as lenses go...stop being such a ******* pedant for once in your life will you?

Maybe if you'd try to make a point instead of scoring points maybe people wouldn't think you were such a prat.

Hyperfocal distance isn't the exact science you seem to think it is - even at optimum aperture the only part of the scene actually in-focus is the bit where the lens is focussed at - everything else is merely in 'acceptable-focus' according to the aperture set - the circles of confusion are merely so small as to go unnoticed. Also the area of acceptable focus decreases as you get further away from the actual focus-poiunt within the scene.

The reason that there are more values closer than 5m is that beyond that distance pretty much everything is within acceptable focus at most apertures that you'd be using where this was an issue. No-one's going to be that concerned about HFD when shooting wide-open at close subjects, are they?
The amount of lens movement between 5m and infinity isn't enough space to engrave those values anyway...

Therefore the lens' distance scale is accurate enough to use as a DoF guide for hyperfocal distance purposes...

 

[HoppyUK]

err... yes... that is a full distance scale as far as lenses go...stop being such a ******* pedant for once in your life will you?

Maybe if you'd try to make a point instead of scoring points maybe people wouldn't think you were such a prat.

Hyperfocal distance isn't the exact science you seem to think it is...

<snip>

I don't think those comments are either helpful or true.

You cannot have understood what I am saying here, or in the other HFD thread I linked to.

I have not dismissed your method of doing things, but offered what I think is a helpful alternative for those occasions when, by your own admission, the markings on the lens scale simply don't exist (ie what you said earlier about Nikon lenses is untrue).

You are also mistaken about HFD not being an "exact science". It is a very exact science, and that is why there's a problem because the practical application of it is so prone to error, which is what I'm trying to reduce. With this technique, if you don't get the HFD setting as exact as you possibly can, the whole thing goes out of the window. By definition, infinity sits right at the edge of acceptable sharpness and if you underestimate the HFD by just a fraction then the far distance will not be sharp.

If that makes me a pedant, then I plead guilty. But pointing out that you are wrong has nothing to do with scoring points. I can't help it if you keep making mistakes.

And by the way, you petulant imbecile, I think the score is about ten-nil

 

[Richard King]

the point being made is that...

HFD is not liniar, and only becomes more and more of an issue, the closer the closest object needed to be in focus is to you. The further away that object, the less impact it has on focus

without throwing real numbers in the pot

if you want something in focus at 30m and at infinity, and you are shooting with a smallish focal length lens then the movement on the focussing ring is negligible to non existent, which is why large measurements are not on the scale. if you want to be in focus at 3M and infinity, that's a bigger deal, and getting it wrong could mean the front and back of the subject wont be in focus (even if we are in focus at infinity). That's why on the lenses with markings to indicate distance, the detail is at the near end

Rob raises a good point about circles of least confusion. CoC does not mean "in focus", it is just where the image is deemed to be "visually acceptable for the size of the film/sensor". We also need to remember that 30m away isn't a straight line drawn 30M away, it is a circle drawn 30m away. This means if you are not careful if the aim is to get a straight flat building sharp at 30M and a child sharp at 3M and you go down HFD route, you also need to account for the fact the edges of the building are further away from you. A CoC is a 2 dimensional thing drawn as a line diagram on paper, the world is a three-dimensional place, and in fact, a CoC in three dimensions becomes elliptical off axis

The crunch comes in comparing CoC vs Resoloution. The CoC formula were drawn up when film was the target for light. Clearly 1 square MM of a 10MP sensor on a 3/4 format camera has more receptor sites than a 1mm square patch on a 10MP non-crop sensor. however a 24MP full frame sensor will have more sensor sites per square mm. Assuming the antialiasing/aliasing filters are not screwing things about the size of the "aceptable size of CoC" needs to vary with the pixel density too . What becomes vitally important in all this is the ultimate resolving power of the camera, without knowing that an assumed OK CoC diameter from film may be way off the mark

 

[HoppyUK]

the point being made is that...

HFD is not liniar, and only becomes more and more of an issue, the closer the closest object needed to be in focus is to you. The further away that object, the less impact it has on focus

without throwing real numbers in the pot

if you want something in focus at 30m and at infinity, and you are shooting with a smallish focal length lens then the movement on the focussing ring is negligible to non existent, which is why large measurements are not on the scale. if you want to be in focus at 3M and infinity, that's a bigger deal, and getting it wrong could mean the front and back of the subject wont be in focus (even if we are in focus at infinity). That's why on the lenses with markings to indicate distance, the detail is at the near end

Rob raises a good point about circles of least confusion. CoC does not mean "in focus", it is just where the image is deemed to be "visually acceptable for the size of the film/sensor". We also need to remember that 30m away isn't a straight line drawn 30M away, it is a circle drawn 30m away. This means if you are not careful if the aim is to get a straight flat building sharp at 30M and a child sharp at 3M and you go down HFD route, you also need to account for the fact the edges of the building are further away from you. A CoC is a 2 dimensional thing drawn as a line diagram on paper, the world is a three-dimensional place, and in fact, a CoC in three dimensions becomes elliptical off axis

The crunch comes in comparing CoC vs Resoloution. The CoC formula were drawn up when film was the target for light. Clearly 1 square MM of a 10MP sensor on a 3/4 format camera has more receptor sites than a 1mm square patch on a 10MP non-crop sensor. however a 24MP full frame sensor will have more sensor sites per square mm. Assuming the antialiasing/aliasing filters are not screwing things about the size of the "aceptable size of CoC" needs to vary with the pixel density too . What becomes vitally important in all this is the ultimate resolving power of the camera, without knowing that an assumed OK CoC diameter from film may be way off the mark

At the risk of straying even further into pedant territory that's not all quite right Richard.

Your point about DoF being becoming shallower at closer distances is actually what's behind my previous posts. Hyperfocal distance is just not necessary at longer range - you can focus on pretty much anything you like and all will be well. HFD is not a method for obtaining maximum sharpness, it is a technique for achieving maximum distance of acceptable sharpness - that is, a compromise setting that spreads optimum sharpness between everything from infinity to close up objects. If those subjects are 30m away, it's not relevant, but it most certainly is when those subjects are 1m, 2m or 3m away. For example, a person in front of a great landscape, or maybe a flower bed in front of a stately home - that kind of thing. And when you need maximum depth of field, pushing both close subjects and distant ones right to the edge of acceptable sharpness, you need to know both where your hyperfocal distance point is, and also how to set it accurately.

If you are just a fraction out on the rather coarse adjustments available when manually focusing a lens, then either the foreground or background will not be as sharp as it could be. And with that thought in mind, you just cannot set the HFD accurately when the last mark on the lens before infinity is 1m, which it is on most super-wide lenses like my 17-40L that I and many others use for landscape (and Nikon super-wides are just the same). Which is why I've suggested a way of getting around that. If on the other hand you are using a longer lens with more distant settings marked, then obviously you can use that.

Field flatness - lenses are corrected to focus a flat plane parallel to the sensor. It is not a curve as you suggest. Some lenses are better corrected than others, which is why shooting flat test charts at close distance is sometimes a problem, but it is not a relevant issue here.

Circles of confusion. Depth of field as a concept, and with it HFD theory, is independent of format, or pixels, or lens resolution. The CoC is defined as the smallest detail the human eye can differentiate when a print is viewed from a normal distance, and that distance is taken as the diagonal of the print. For example, a 10x7in print viewed from 12in.

Therefore your comments about pixel density do not apply, but as an aside it's not quite clear what you are comparing when you say 3/4 format vs a non-crop sensor and full frame. Generally speaking the smaller the format the greater the pixel density and therefore compacts cram in far more per square mm than 4/3rds and Nikon/Canon crop format sensors. Full frame tends to have the lowest pixel density even though the total number may be higher, due to the substantially larger format area.

 

[Richard King]

Your point about DoF being becoming shallower at closer distances is actually what's behind my previous posts. Hyperfocal distance is just not necessary at longer range - you can focus on pretty much anything you like and all will be well. HFD is not a method for obtaining maximum sharpness, it is a technique for achieving maximum distance of acceptable sharpness - that is, a compromise setting that spreads optimum sharpness between everything from infinity to close up objects. If those subjects are 30m away, it's not relevant, but it most certainly is when those subjects are 1m, 2m or 3m away. For example, a person in front of a great landscape, or maybe a flower bed in front of a stately home - that kind of thing. And when you need maximum depth of field, pushing both close subjects and distant ones right to the edge of acceptable sharpness, you need to know both where your hyperfocal distance point is, and also how to set it accurately.
Agree, i was illustrating why the lens markings are apparently poor/non existant at that end of the scale

If you are just a fraction out on the rather coarse adjustments available when manually focusing a lens, then either the foreground or background will not be as sharp as it could be. And with that thought in mind, you just cannot set the HFD accurately when the last mark on the lens before infinity is 1m, which it is on most super-wide lenses like my 17-40L that I and many others use for landscape (and Nikon super-wides are just the same). Which is why I've suggested a way of getting around that. If on the other hand you are using a longer lens with more distant settings marked, then obviously you can use that.
Agree - see point 1 - also - knowing how to do the maths is always useful

Field flatness - lenses are corrected to focus a flat plane parallel to the sensor. It is not a curve as you suggest. Some lenses are better corrected than others, which is why shooting flat test charts at close distance is sometimes a problem, but it is not a relevant issue here.
Yes and no - it is something you need to know when pushing a limit. Clearly proportionatally the closer the brick wall, the more the lens is effected. As mentioned in my previous post, the issues are not liniar, if you are shootig a group of 10 people that are quite close, and you then push the focussing boundaries a bit to het the building that is further away in focus, check the chaps and chapesses on the end of the line for focus

Circles of confusion. Depth of field as a concept, and with it HFD theory, is independent of format, or pixels, or lens resolution. The CoC is defined as the smallest detail the human eye can differentiate when a print is viewed from a normal distance, and that distance is taken as the diagonal of the print. For example, a 10x7in print viewed from 12in.

Therefore your comments about pixel density do not apply, but as an aside it's not quite clear what you are comparing when you say 3/4 format vs a non-crop sensor and full frame. Generally speaking the smaller the format the greater the pixel density and therefore compacts cram in far more per square mm than 4/3rds and Nikon/Canon crop format sensors. Full frame tends to have the lowest pixel density even though the total number may be higher, due to the substantially larger format area.

This is a simple one. There is a triad - the optical resolving power of the lens, the optical resolving power of the camera and the CoC. Whats the point in a 20MP sensor, if you only ever shoot for web...? If you have invested ina 20mp sensor, then when viewd in 1:1 pixels, the equivelent CoC will look awful when compared to a 6mp sensor... If you have a 20MP sensor, you would hope the resolving power of the lens optics was good enough to exploit it, otherwise you may as well have a 6mp sensor, and interpolate up. If we choose to skim over this and refer back to a arbitary print sixe, then you are almost saying there is no point to higher pixel count cameras

If you check out this: http://en.wikipedia.org/wiki/Circle_of_confusion they rightly make reference to the frame size, for all the obvious reasons

I love that maths

 

[HoppyUK]

Thanks for you reply Richard, but I beg to differ on a couple of points.

On field flatness, there is no need to check the ends of a line of people as you suggest, not for reasons of field flatness. Any half decent lens today will have a very flat field of sharpness at that kind of distance. It might need looking at because the lens maybe has poor edge definition or perhaps the corners of a very wide angle shot are a little distorted due to rectilinear correction, but not field flatness.

In the Wiki link, I can't find any reference to frame size (or anything else) except in relation to the calculation of the circle of confusion. There is no 'triad' as you say, and if there was then you would have to include the output medium as well - enlarging lens, print emulsion, screen resolution, printer jets - the entire imaging chain all contributes to ultimate sharpness.

To repeat, for the purposes of depth of field calculation and HFD, lenses and pixels and whatever else have no bearing - it's just down to your eyes and the finest level of detail we can detect from a given distance. That's it. You could well argue, and you'd be absolutely right, that current practise puts a different emphasis on the acceptable size of the CoC. We tend not to look at 'standard size' prints quite so much, and to view images on big TVs and computer screens, often pixel peeping at high magnifications. In which case, this changes all CoC dimensions substantially.

However, whatever size CoC you come up with, the process and calculation by which it's arrived at will be the same. And since there will never be total agreement on that, we might as well stick with what we've got which is not a bad starting point and is at least an accepted standard that has been universally used since the year dot (haha!).

Furthermore, no matter what standards or changes you want to make, the hyperfocal distance will remain in exactly the same place, and the methods for setting it will apply just the same.

 

[mrtoad]

dear fellows...what do you need hyperfocal distance settings for outside of the classroom
what if your subject is a smaller compass than the hpd will cater for...change the f no..??
what if it is larger...buy a slower lens??
what do you do if the point of minimum confusion is not where your anchor element is??
with the aperture ring/focussing method...do you set infinity at your aperture or your nearest element...which you want in focus...or set the focus on your anchor element and then pick an aperture which will reach infinity and leave the nearest dof setting to chance...or...set the closest focus and let infinity take care of itself...
finally ...i dont know this...when a lens is set at infinity...what exactly is the distance where the optics are concentrated on

sorry to sound a prat but i am one and like to prattle

cheers
geof

 

[HoppyUK]

dear fellows...what do you need hyperfocal distance settings for outside of the classroom
what if your subject is a smaller compass than the hpd will cater for...change the f no..??
what if it is larger...buy a slower lens??
what do you do if the point of minimum confusion is not where your anchor element is??
with the aperture ring/focussing method...do you set infinity at your aperture or your nearest element...which you want in focus...or set the focus on your anchor element and then pick an aperture which will reach infinity and leave the nearest dof setting to chance...or...set the closest focus and let infinity take care of itself...
finally ...i dont know this...when a lens is set at infinity...what exactly is the distance where the optics are concentrated on

sorry to sound a prat but i am one and like to prattle

cheers
geof

Geof, hyperfocal distance is not really needed in the classroom. Not unless it is a very long classroom

HFD technique is only necessary when you need the maximum distance of acceptable sharpness, from far distance to close up. If you don't need that, then there are other options, but if you do, the HFD is the only way.*

I think you use a compact camera, which has a very small sensor, and with it great depth of field - whether you want it or not. So HFD is not likely to be necessary.

The distance to infinity varies with focal length. With a wide angle it is quite close, like a few tens of yards, but with a long tele it is very distant, like hundreds of yards. It is for this reason - the greater distance to infinity with longer lenses - which makes it impossible to use HFD technique with anything longer than a standarish focal length lens, as you would need something like f/64 to get any near foregound sharp at the same time.

* There is another way of getting very deep depth of field, without using HFD technique. And that is a tilt & shift lens - the shift bit is for correcting perspective effects, and the tilt element for realigning the focus plane with the subject plane. While it doesn't increase DoF by itself, it puts the DoF where you need it most, so 'effective' DoF is increased. They're very specialist lenses though, and cost a rocket.

 

[mrtoad]

Geof, hyperfocal distance is not really needed in the classroom. Not unless it is a very long classroom

HFD technique is only necessary when you need the maximum distance of acceptable sharpness, from far distance to close up. If you don't need that, then there are other options, but if you do, the HFD is the only way.*

I think you use a compact camera, which has a very small sensor, and with it great depth of field - whether you want it or not. So HFD is not likely to be necessary.

The distance to infinity varies with focal length. With a wide angle it is quite close, like a few tens of yards, but with a long tele it is very distant, like hundreds of yards. It is for this reason - the greater distance to infinity with longer lenses - which makes it impossible to use HFD technique with anything longer than a standarish focal length lens, as you would need something like f/64 to get any near foregound sharp at the same time.

* There is another way of getting very deep depth of field, without using HFD technique. And that is a tilt & shift lens - the shift bit is for correcting perspective effects, and the tilt element for realigning the focus plane with the subject plane. While it doesn't increase DoF by itself, it puts the DoF where you need it most, so 'effective' DoF is increased. They're very specialist lenses though, and cost a rocket.

what you say is clear...when one takes a photograph...isnt there something in it which one focusses on...irrespective of all other aspects...which take second place...but included as best as possible
my point is that the hyperfocal distance may not co-incide with the point of interest
the front to back landscape sounds like the only place an arbitrary focal point is required...so the subject here is sharpness of the whole scene..
considering landscapes...for me the 28-35mm wide angle should have more than enough dof even at low f no's for most views
it seems to hinge on the daisy to mountain viewpoint..which i like but tend to concentrate on the daisy..so to speak.
now you have mentioned longer lenses...does one really pay attention to hfd when using these...i have found i am focussing on discrete elements and to hell with oof parts..as in a portrait on a 105 or 200
if i ever get a camera with the engravings on the lens aperture ring i will see if i really need to use them..and i guess from the input here i will...
thanks for the lesson
cheers
geof

 

[HoppyUK]

what you say is clear...when one takes a photograph...isnt there something in it which one focusses on...irrespective of all other aspects...which take second place...but included as best as possible
my point is that the hyperfocal distance may not co-incide with the point of interest
the front to back landscape sounds like the only place an arbitrary focal point is required...so the subject here is sharpness of the whole scene..
considering landscapes...for me the 28-35mm wide angle should have more than enough dof even at low f no's for most views
it seems to hinge on the daisy to mountain viewpoint..which i like but tend to concentrate on the daisy..so to speak.
now you have mentioned longer lenses...does one really pay attention to hfd when using these...i have found i am focussing on discrete elements and to hell with oof parts..as in a portrait on a 105 or 200
if i ever get a camera with the engravings on the lens aperture ring i will see if i really need to use them..and i guess from the input here i will...
thanks for the lesson
cheers
geof

You're welcome Geof

And you're quite right when you say that HFD is not needed for a lot of landscape. However, I find it is very often quite handy to know where the HFD point is, even if you perhaps don't use it directly.

And the way to do that, without any tables, and this works with absolutely any camera and lens, is to know that the hyperfocal distance is always exactly double the near point of the hyperfocal range.

That is, if you want that daisy in the foregound to be sharp, as well as the distant mountains, then you know that if the daisy is say 4ft away (by your best estimation) then the HFD is 8ft.

Unfortunately, without the tables you don't know what f/number to use to deliver enough DoF to get both extremes of distance sharp, but if you just focus on 8ft and use the highest f/number that you dare, there's a pretty good chance that all will be well.

It's about having the knowledge, and then applying the most appropriate technique.

 

[jerry12953]

. Focus on whatever you want to be in focus in the foreground, the rock, tree, boat, horse, whatever, set the aperture to f8 or f11 max and your landscapes will work fine.

....or not, it all depends......

I see a little bit of heat has been generated here, and much as I would like to contribute to the debate, I think I'll just leave it at that.