Why do we have autofocus?

[ancient_mariner]

D'uh - the answer's obvious, innit?

But y'know, I've been wondering.

I've just acquired a Nikon D610 body with a view to building a landscape and general purpose outfit, having no Nikon gear at all - not even a nifty fifty, and that's given me a freedom to think about how I use lenses and the focus function of a camera before I actually start to acquire them. So fast autofocus in a lens you might use in a quickly changing situation is a real bonus - shooting sports, people, animals etc - and will probably make the difference between getting or not getting the shot.

But that's not how I work most of the time.

Landscapes, flowers and plants etc. don't go belting across my field of view, so I've no need for a rapid response in that situation. In addition, I often find myself focussing on the bit I want sharp several times before I see what I want in the viewfinder: in other words I am manually focussing the camera very clumsily through the autofocus system, mostly because it breaks concentration less than trying to find the AF-M switch. So, rather than going down the 'obvious' route, I'm wondering about selecting some lenses that are just simple manual focus jobs and at the same time saving quite a bit of cash. I know technology has moved on with optics, at least at the top end, but I'm never going to spend a couple of grand on a set of lenses anyway, and really wonder if my photography might not actually improve using manual lenses for some kinds of work instead of AF.

 

[RichardTaylor]

Versatility - If a lens is only manual focus then you are restricting the camera image capturing possibilities.
Also keep in mind the DSLRs are not totally designed for manual focussing, ie no split image range finders or even a ground glass screen (although live view may help)..
I don't find it a real problem to operate the AF-M switch. I operate it when am setting the camera up for situations where I will be using manual focus (not very often).
Is it possible to buy modern manual focus only lenses nowdays (besides T/S and some macro lenses).

 

[Jayst84]

Any decent autofocus lens will have full time manual focus anyway, so no need to go hunting for switches.

If you never use autofocus though, there's a good chance you'll get more for your money by buying a manual focus only lens.

 

[woof woof]

I think that focusing manually with an optical system is difficult unless the subject is big in the frame as if it isn't how are you going to focus accurately? Zone focus and hyperfocal and other manual techniques are fine for some subjects but if you want to accurately focus on one of your subjects eyes and then look at the image at high magnification on screen these techniques aren't exactly ideal.

For macro and pseudo macro stuff I think that manual focus is ok because your subject will be big in the frame and detail and how in focus it is will be easy enough to see but for subjects other than that I struggle and I'd imagine other humans would too as how are you going to focus accurately on detail you can't see because your point of focus (for example, someone's eye) is too small to see in detail in the OVF?

You may be able to focus accurately enough for a smallish print but the chances are that if you pixel peep on screen or look very closely at a larger print you'll see focus errors in at least a percentage of your pictures. Hoping that the depth of field covers errors wont work every time... if you look closely and expect accurate focus and sharpness on one particular point.

After moving to compact system cameras I now think that focusing manually with a DSLR is primitive and inaccurate and I much prefer focusing at high magnification whilst looking at the EVF of my CSC's and if you want to use manual lenses and focus accurately with them a CSC is IMO the way to go. I can focus my Minolta 50mm f1.2 accurately at f1.2 on my CSC's, I can just about pick my point of focus along the length of an eye lash and in fact I can with some lenses. Try that on a DSLR and you'll hit problems, IMO

I suppose with a DSLR manually focusing at high magnification with live view on the back screen is an option but I'm not a fan of back screen shooting.

 

[alexkidd]

And the viewfinders these days are tiny and optimised for af, in film days the large split screens made manual focus a fast and predictable option, I'd not trust even a modded split screen through the mini view we get on modern cameras

However live view mf on mirrorless etc is definitely making it more of a thing I think

 

[Dave *]

Because manual focus is tedious. Especially if your sight is less than 20/20.

Plenty of similar questions with similar answers.

Why do we have cars? A horse and cart could do the same job but slower, but then, why a horse and cart? People on foot can walk just a bit slower, I mean people used to walk from Jarrow to London, it didn't do them any harm .

 

[chris malcolm]

I began photography before autofocus was invented, so I'm quite happy focusing manually. Except as already pointed out the old-fashioned DSLR has given up the manual focusing aids that SLRs used to have, making accurate manual focus more difficult than it used to be. Manual focusing aids are beginning to come back however, the first improvement being an instantly available magnification in live view. Focus peaking, which outlines the sharp parts of the image so you can see the depth of focus easily and accurately, and having both focus peaking and image magnification available on the LCD and in an EVF, makes manual focusing even faster and easier than it was back in the days before autofocus.

The latest AF lenses have a system which permits you to use AF and then trim it manually without having to press any switches. Some cameras offer a similar focusing mode on older lenses which normally require specific switching between AF and MF, a mode which drops into MF automatically once AF has acquired focus. Having such excellent manual focusing aids easily available means that when I have the time I usually check the accuracy of the AF on my AF lenses, and found that AF wasn't quite as good as I thought it was.

But when I took my manual 85mm to a fashion catwalk shoot I found I was really struggling to focus fast enough, or to trap prefocus accurately enough. I would have got much better results using an AF 50mm and cropping.

 

[tijuana taxi]

Presumably because autofocus is more reliable than our eyes, very true in my case.

 

[andyred]

autofocus is more reliable than our eyes, very true in my case.

Plus 1 for this

 

[Steve Smith]

However, if you are focusing manually, a manual only lens will have more control than an autofocus lens used manually and it will probably have depth of field scales marked on it which can be more useful than being able to check focus in the viewfinder for landscape use.


Steve.

 

[redsnappa]

Why do we have autofocus

For the same reason you used a computer to post on this forum, I mean you could have hand written letters to all us asking the same question.

But that's not how I work most of the time.

Maybe Nikon need to send you an apology that their camera is not perfectly customised to the way that you work. The staff an Nikon R&D should be sacked for not taking how you work into account when they designed the D610.

 

[TimmyG]

I rarely use auto-focus, partially because I don't need to use it and partially because I don't trust it. To be fair I don't use the best technology money can buy, so there may be much better autofocus systems available, but for my main subject area (macro) it's a hindrance rather than a help. For wide angle lenses it's a bit pointless too as they have such massive DoF, so I quite happily use a number of older lenses that have this feature, and I don't miss it.

Like you say though, it has a role in other types of photography, especially with moving subjects or even just hand holding certain shots. For static subjects I still prefer to manually focus (I do make use of the live view, and magnify the image as much as possible) even if using big zooms.

 

[chris malcolm]

Presumably because autofocus is more reliable than our eyes, very true in my case.

That suggests to me that your camera doesn't offer you good enough manual focusing aids. The old split image circle of many film SLRs made it very easy to see critical spot on focus. Many DSLRs are crap at manual focus simply because the cameras have thrown away the necessary visual aids, and modern lenses often don't have such good well geared smooth manual focusing rings. One could argue that they've made AF better than MF by making MF too difficult When I got my first DSLR that offered easily accessible image magnification on the live view LCD and started checking my AF when I had the time to do so, I was surprised to discover that AF wasn't as good as I'd thought. In fact some of my lenses were sharper than I (and apparently some reviewers) had thought. We'd blamed poor AF on the glass.

I have a 500mm lens without image stabilisation which is damn near impossible to focus manually. The problem is that it has a very shallow depth of focus requiring critical spot on focus. That critical focus can only properly be judged in a magnified view, and when the image is magnified the slightest touch of a finger causes the lens, firmly secured on a tripod, to wobble so much I can no longer see to judge the focus properly. It takes me around 20 seconds o do my best at manual focusing, and my best isn't as consistent as AF. In five tries I'll get it spot on about once, whereas AF -- when it has been carefully calibrated -- gets it spot on at least 4 out of 5 times. So before I upgraded to a camera with individual lens focus adjusting I used to set up my cameras to focus that lens perfectly. Luckily that AF calibration improved the AF on most of my other lenses too.

Now that I have a camera with focus peaking, I can focus some lenses accurately in a couple of seconds, not as fast as AF, but there are things AF can never get right, such as focusing on something partly obscured by foliage.

At the other end of the scale, very wide angle lenses have always been an AF problem. AF is inconsistent and sometimes pretty badly wrong, although the very wide DoF often conceals this from a casual inspection. I actually get better focus by doing manual zone focusing with these lenses. I've memorised the positions on the focus scale corresponding to a few yards, across the street, and infinity, and with their wide DoF that's better than AF. For critical work on a tripod when I'm going for maximum detail at lowest ISO I'll carefully manually focus each shot individually, carefully checking out depth of focus, and edge as well as centre sharpness.

If you can't see enough detail to do good manual focus I'd blame the camera for not offering you good enough manual focusing aids.

 

[Nostromo]

You could ask, "why did I buy a digital camera", you could have bought a film camera.
Convenience I guess is the answer, having AF makes your lens more adaptable for different situations. You may go out shooting flowers but find something else interesting while out and about that requires AF. You may not have time to change to a lens that has AF if you've brought one with you at all.

 

[ianp5a]

Maybe back button focussing is a solution here?

I use AF for speed. But sometimes I'd like to be able to tell the camera the closest and furthest points to be sharp and it would set the appropriate focus and aperture. Like spot exposure modes where you pick the highlight and shadow points.

 

[SFTPhotography]

After moving to compact system cameras I now think that focusing manually with a DSLR is primitive and inaccurate and I much prefer focusing at high magnification whilst looking at the EVF of my CSC's and if you want to use manual lenses and focus accurately with them a CSC is IMO the way to go. I can focus my Minolta 50mm f1.2 accurately at f1.2 on my CSC's, I can just about pick my point of focus along the length of an eye lash and in fact I can with some lenses. Try that on a DSLR and you'll hit problems, IMO

I suppose with a DSLR manually focusing at high magnification with live view on the back screen is an option but I'm not a fan of back screen shooting.

It is easy with the SLR. Compose using the OVF then use the live view to focus critically and use the histogram preview mode. Works everytime

 

[Steve Smith]

You could ask, "why did I buy a digital camera", you could have bought a film camera.

He could have done, but having made the mistake of buying one of those new fangled electric cameras, he's stuck with it!!

but find something else interesting while out and about that requires AF.

People managed to photograph all sorts of things with manual focus before autofocus existed... and still manage to do so!


Steve.

 

[itsdavedotnet]

Maybe back button focussing is a solution here?

I use AF for speed. But sometimes I'd like to be able to tell the camera the closest and furthest points to be sharp and it would set the appropriate focus and aperture. Like spot exposure modes where you pick the highlight and shadow points.

^ this.

Cameras and especially top end nikons have incredible autofocus that's generally better than what your eyes can do - works great. Fiddle with some of the settings, and tweak it to how you like, it's incredibly powerful. I take hundreds of thousands of photos a year and use autofocus for every single one of them

 

[Nostromo]

He could have done, but having made the mistake of buying one of those new fangled electric cameras, he's stuck with it!!

But as I said, "convenience and adaptability"


People managed to photograph all sorts of things with manual focus before autofocus existed... and still manage to do so!


Steve.

 

[ancient_mariner]

Maybe Nikon need to send you an apology that their camera is not perfectly customised to the way that you work. The staff an Nikon R&D should be sacked for not taking how you work into account when they designed the D610.

Why the aggression?

I'm trying to suggest that for some purposes it may be useful to work manually, and that for those purposes manual lenses - which Nikon still make - might offer a benefit over AF. There's a financial incentive, with older manual lenses looking like real bargains.

More generally, I'm not suggesting AF is *wrong* in any sense, and in my OP gave some examples of where it is extremely useful. My current kit is all Sony/Minolta, all lenses have the focus ring mechanically coupled to the AF system, and to switch between manual and AF breaks flow. The idea of working with a manual lens seems rather freeing - assuming the 610 screen is clear enough to actually see when part of the image is in focus or not. For situations where I need shallow DoF I'll still happily use AF with a suitable lens.

 

[Jayst84]

Why the aggression?

Because it's the Internet. And people would rather read one sentence, and then show how clever they are, than read a whole paragraph and respond to the actual questions.

 

[ancient_mariner]

Because it's the Internet. And people would rather read one sentence, and then show how clever they are, than read a whole paragraph and respond to the actual questions.

I didn't think Redsnappa was another 'angry internet guy', or I'd just have ignored him.

 

[tijuana taxi]

If you can't see enough detail to do good manual focus I'd blame the camera for not offering you good enough manual focusing aids.

More like my eyesight is crap, can just about get away without wearing glasses if I turn the diopter right up. Definitely not good
enough for manual even with focusing aids which my camera does have.

Perhaps the answer should be "so we can use it if we so wish" each to their own, no right or wrong method

 

[ancient_mariner]

That suggests to me that your camera doesn't offer you good enough manual focusing aids. The old split image circle of many film SLRs made it very easy to see critical spot on focus. Many DSLRs are crap at manual focus simply because the cameras have thrown away the necessary visual aids, and modern lenses often don't have such good well geared smooth manual focusing rings. One could argue that they've made AF better than MF by making MF too difficult When I got my first DSLR that offered easily accessible image magnification on the live view LCD and started checking my AF when I had the time to do so, I was surprised to discover that AF wasn't as good as I'd thought. In fact some of my lenses were sharper than I (and apparently some reviewers) had thought. We'd blamed poor AF on the glass.

I have a 500mm lens without image stabilisation which is damn near impossible to focus manually. The problem is that it has a very shallow depth of focus requiring critical spot on focus. That critical focus can only properly be judged in a magnified view, and when the image is magnified the slightest touch of a finger causes the lens, firmly secured on a tripod, to wobble so much I can no longer see to judge the focus properly. It takes me around 20 seconds o do my best at manual focusing, and my best isn't as consistent as AF. In five tries I'll get it spot on about once, whereas AF -- when it has been carefully calibrated -- gets it spot on at least 4 out of 5 times. So before I upgraded to a camera with individual lens focus adjusting I used to set up my cameras to focus that lens perfectly. Luckily that AF calibration improved the AF on most of my other lenses too.

Now that I have a camera with focus peaking, I can focus some lenses accurately in a couple of seconds, not as fast as AF, but there are things AF can never get right, such as focusing on something partly obscured by foliage.

At the other end of the scale, very wide angle lenses have always been an AF problem. AF is inconsistent and sometimes pretty badly wrong, although the very wide DoF often conceals this from a casual inspection. I actually get better focus by doing manual zone focusing with these lenses. I've memorised the positions on the focus scale corresponding to a few yards, across the street, and infinity, and with their wide DoF that's better than AF. For critical work on a tripod when I'm going for maximum detail at lowest ISO I'll carefully manually focus each shot individually, carefully checking out depth of focus, and edge as well as centre sharpness.

If you can't see enough detail to do good manual focus I'd blame the camera for not offering you good enough manual focusing aids.

I really appreciate this, Chris, and your point about focussing rings is spot on. I'm looking at an old-school Nikon manual zoom where the barrel controls both zoom and focus, so there's no moving the hand back and forth between controls - just compose and focus at the same time.

 

[Swanseajack]

If budget is coming into play, I have had some excellent results from some of the older Nikon D lenses, these can be auto focus or manual and as they have aperture rings they can be used on film camera if desired.. As a starting point you can get the 50mm 1.8d new for around £80.00, then you have lenses like the 24-50, 28-70, 28-85, 28-105, 70-210 etc....all these lenses should cost less than £100 (maybe not the 28-105mm). My favourites have been the 24-50, 28-85mm and 75-300mm lenses in these ranges.

This time of year you can get some good bargains if you hunt around. The above are all Nikon lenses, you then have the choice of Sigma, Tamron etc......I bought a Sigma 75-300mm APO,DG, Macro lens from Wex a few months ago for £44 and it was an excellent lens, and I'm sorry I sold it now. IMHO it was optically good as the Nikon 70-300mm VR I have owned and the Tamron 70-300mm VC I have now.

 

[Steve Smith]

More like my eyesight is crap, can just about get away without wearing glasses if I turn the diopter right up.

I wish my sight was that good so that all I needed was the fairly minimal Dioptre adjustment on a camera!


Steve.

 

[tijuana taxi]

I wish my sight was that good so that all I needed was the fairly minimal Dioptre adjustment on a camera!

That's only my right eye, left one is next to useless and needs a lot more correction than the plus or minus 2 that a diopter gives

 

[Terrywoodenpic]

Even my little Fuji X30 has cracking manual focus ability and even a mix of both manual and auto.

with the selector set to manual you can set focus by pressing the AFL button which it will then hold.
You can also manual focus by turning the ring around the base of the lens and engage maximum magnification by pressing in the control wheel.

These days it is not a case of either manual or Auto but either, and each of them.

Auto focus is by its nature less precise, especially in the choice of the exact point of focus.
But it is incredibly fast and in most instances accurate enough at normal distances.

 

[droj]

Versatility - If a lens is only manual focus then you are restricting the camera image capturing possibilities.

Doesn't sound like Toni minds ...

Also keep in mind the DSLRs are not totally designed for manual focussing, ie no split image range finders or even a ground glass screen (although live view may help).

No screen? What the [PLEASE DON'T TRY TO BYPASS THE SWEAR FILTER] am I focussing on, then? And for the wimps, there's a green focus confirmation dot ...

I don't find it a real problem to operate the AF-M switch. I operate it when am setting the camera up for situations where I will be using manual focus (not very often).

So?

Is it possible to buy modern manual focus only lenses nowdays (besides T/S and some macro lenses).

A wide range of legacy Nikkors is available, then there's Zeiss, Samyang, Voigtlander .... if you haven't experienced the sweet focussing action of such a lens, you haven't lived.

 

[Terrywoodenpic]

Maybe back button focussing is a solution here?

I use AF for speed. But sometimes I'd like to be able to tell the camera the closest and furthest points to be sharp and it would set the appropriate focus and aperture. Like spot exposure modes where you pick the highlight and shadow points.

That would make an interesting Auto alternative. However it is easy to forget Depth of field is always a compromise, and that Critical focus is only at a single point what ever the aperture.

 

[mortimerhill]

But sometimes I'd like to be able to tell the camera the closest and furthest points to be sharp and it would set the appropriate focus and aperture. Like spot exposure modes where you pick the highlight and shadow points.

Canon EOS SLR cameras used to have this facility, certainly on the EOS5 and the EOS3. They refered to it as Depth of Field AE. The camera determined the aperture needed and then set the correct shutter speed. I guess that Canon's research showed it wasn't used very much and not valued by customers, and so it has been dropped from the current range of DSLR cameras.

 

[woof woof]

No screen? What the f*** am I focussing on, then? And for the wimps, there's a green focus confirmation dot ...

What the f*** are you reading? He didn't say there was no screen. What he said was... well, read it for yourself.
Green confirmation dot isn't going to give you the accuracy that MF with a magnified view would.

 

[boliston]

in my dslr days i tended to prefer legacy manual ai/ais nikkors as the build quality just seemed so much nicer compared with modern nikkors - no longer have a dslr as sold it to get a rangefinder and i can say that rangefinder focussing is far easier than manually focussing a dslr!

 

[ianp5a]

Canon EOS SLR cameras used to have this facility, certainly on the EOS5 and the EOS3. They refered to it as Depth of Field AE. The camera determined the aperture needed and then set the correct shutter speed. I guess that Canon's research showed it wasn't used very much and not valued by customers, and so it has been dropped from the current range of DSLR cameras.

Yes. Many would never bother with it. And I'd only need it occasionally. And if they made it difficult to use, perhaps not even then.

 

[dizidav]

I have to agree with the OP, as I usually use MF for Landscapes, AF never seems to work for me, also use MF for Macro shots, it would be nice if the Camera manufacturers offered a split Prism screen as an alternative.

 

[ancient_mariner]

First 2 lenses on the way, and as it turns out, they're both autofocus. Found a mint 50mm for £10 less than new grey, and a well-used 35-105 AF for only £40. I will likely add some manual lenses, probably wide primes that will be for landscape use, maybe a 24-50 too. IIRC I also have an ancient 18mm lens with T2 mount, though IIRC image quality was weak at 12X16 from film, so it may not be worth resurrecting unless Ilike 'special effects'.

 

[redsnappa]

I know the OP wants to us manual focus but the likes of Nikon Canon Pentax don't care. Their research departments tell them say everyone wants autofocus. The camera manufacturers want to sell as may new AF lenses as they can.
The fact that some users use old MF lenses on new cameras must only serve to annoy camera manufacturers.
I do my self prefer a combination of AF,MF, BBF and TSF all dependant on the subject.

 

[boliston]

I know the OP wants to us manual focus but the likes of Nikon Canon Pentax don't care. Their research departments tell them say everyone wants autofocus. The camera manufacturers want to sell as may new AF lenses as they can.
The fact that some users use old MF lenses on new cameras must only serve to annoy camera manufacturers.
I do my self prefer a combination of AF,MF, BBF and TSF all dependant on the subject.

It looks like fuji are actually embracing the concept by offering their own m mount adaptor
http://www.fujifilm.com/products/di...ens/mount/fujifilm_m_mount_adapter/index.html

 

[domart]

Better to have something and not need/use it, than to need something and not have it

People always say shooting manual focus slows you down so you concentrate more on composition, but I actually find that af allows me to concentrate more on composition, as I just let the camera do the work it can do better than I can

 

[ancient_mariner]

Better to have something and not need/use it, than to need something and not have it

People always say shooting manual focus slows you down so you concentrate more on composition, but I actually find that af allows me to concentrate more on composition, as I just let the camera do the work it can do better than I can

I would be interested to know if you learned photography on manual or AF cameras? I ask because with AF gear, designs have made the manual focussing option much less convenient and a choice of last resort, rather than a fully valid way of working. This can be seen in the way focussing rings have stopped being the main part of the lens that you grip, and instead are often a narrow band at the end of the lens, in many cases requiring you to move your hand to focus, then shift it back to steady the camera.