Autofocus. Am I missing something

i recently started back into photography after being busy with young children. I did not want to spend too much so picked up a used 5d which goes wonderfully with the 24-105.

Many years ago I was in the military as a photographer and used 4 x 5 220 and 35 mm. As I have been reading these message boards I noticed many people complain about the inadequacy of the auto focus systems on their cameras. I use mainly manual focus because I get to decide the focus point. I know you can focus by selecting focus point and then recompose while holding button half day down.

So do people totally rely on the autofocus and if it is bad why not try manual focus then they can only blame themselves?
Just curious
Allan

The 5D and the 24-105 is a great combo. There are many situations where AF is needed over MF. Action shots is one example where AF works best. Like me, my eyes will not allow MF, so I rely on AF. A lot of people complain about AF but most are using Multi AF points. Better to use center only or one of the selectable points. I have a 5D and have never found any problem with the AF, after using it for almost five years. Forums are full of complainers.

Steve

I think that those of us who started years ago before auto-focus existed are impressed that it works at all, and grateful for those situations where it performs well. To those of a generation where A/F has always existed perhaps expectations are different.

Kevin

Think of it this way.

Most of the people buying DSLRs are consumers, not photographers - not even enthusiasts.

They buy a DSLR because, typically, they want to capture great shots of the kids, etc. and do it easily.

Canon, Nikon and the rest tell them loudly and frequently that they can do that.

As you know, but consumers don't, autofocus is limited and simply a convenience - albeit getting more sophisticated.

Consumers don't care. In the instant they point the camera vaguely in the direction of the subject they expect it to autofocus precisely, mind read what effect they're after and choose a suitable shutter speed and aperture to do that. And from the ads and the morons in the shops selling to them that's what they've been told to expect.

They're unhappy because they're lied to. Pure and simple.

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StephenG

Pentax K100D
Fuji S3 Pro
Fuji S9600

Can I confess my ignorance on a related subject. Perhaps someone can explain the significance of the increasing number of AF points on the latest cameras. We seem to have moved from 3 point all the way up to 19 point and more. As another who grew up with manual focus but does find AF convenient at times, can someone explain why we need so many AF points? Are they designed to put the whole frame in focus if possible and when this is not possible how does the software decide? I usually use the centre point only with entirely acceptable results. Thanks John

pakiwi said:

i recently started back into photography after being busy with young children. I did not want to spend too much so picked up a used 5d which goes wonderfully with the 24-105.

Many years ago I was in the military as a photographer and used 4 x 5 220 and 35 mm. As I have been reading these message boards I noticed many people complain about the inadequacy of the auto focus systems on their cameras. I use mainly manual focus because I get to decide the focus point. I know you can focus by selecting focus point and then recompose while holding button half day down.

So do people totally rely on the autofocus and if it is bad why not try manual focus then they can only blame themselves?
Just curious

Click to expand...

I assume you are talking about DSLR and not P&S.

You had much better manual focus aids with those cameras. Good pentaprisms, split screens, lenses designed for sensitive touch etc. I am quite disappointed with the less efficient pentamirror arrangement and my kit lens is so coarse that fine focussing is difficult with little to tell me whether or not I have clear focus. And as it is an autofocus lens I have to remember to take it out of autofocus before I try to rotate the ring. The autofocus is very quick and very accurate once you realise what the pitfalls might be.

And you didn't pixel peep, equivalent to printing to some unreasonable size and complain that the whole picture isn't clearly defined, where some of that could be camera movement, subject movement, sharpness setting and normal OOF due to insufficient DOF.

A number of years ago, while I was still using film and a Nikon F3hp, a professional sports photographer friend of mine switched from Nikon to Canon. It was an expensive switch and I asked him why.

He told me to use his new camera while he ran towards me from about 50 yards away. He told me to keep gunning and try to keep the focus on him. I did and quickly learned how multiple ponts and a quality tracking algorithm works.

A couple of years ago, Mark switched back to Nikon totally. I again asked him why. He said, "do you want to do that running test again?" I understood. The new Nikon D3 had 51 focus points and tracked slightly better. As Mark said, the cost is trivial when it's your living at stake. That one or two extra keeper might be one Getty uses.

If your subject is stationary, fine. Use one, but if it's moving and hard to track, sometimes more is better. Sometimes, I also might want my focus on one thing in a landscape shot. I might focus on it, keep the shutter button down and recompose. I lke to see that focus point stay fixed over there on the correct item. I love 51 focus points, sometimes. I sometimes use less on birds in flight. I sometimes use only one, like you, but they all have their place. The more experienced with AF you get and the more varied your photography becomes, the more you'll learn to use the many different tools in your camera.

I know when I moved from manual to AF and digital, I couldn't understand the need for more than one, but now use more of the vast array of tools my Nikon's offer. I'm happy to have them and am still learning. Those tools are there for a reason.
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Cheers, Craig

Equipment in Plan via Profile

Modern AF digital DSLRs have a bright matt focusing screen with no micro collar or split image aid. The modern AF lens is not nearly dampened as well to allow as accurate or as fast manual focusing even if these old eyes could do better with these new screens, and I have a D300 and D700 with big bright optical glass pentaprisms like my old Nikon F3hp had.

Times change and AF today is generally faster and more accurate under most conditions when you learn how to properly use them. It can be a Godsend for action photography.

If you'd rather manually focus, Katzeye makes the older focusing screens available for most modern digital cameras. The problem is that the metering isn't as happy with the dimmer view. That microprizm collar can dim things in spot meter mode. You have to be careful. AF can also be affected. I've thought about putting one in my backup camera, for using all my old glass, but keep putting it off. It might be nice for macro.

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Cheers, Craig

Equipment in Plan via Profile

so does this mean having more af points is not a direct indication of af acquisition speed?

If so, what determines af speed? Just the usm motor speed?

If a lens hunts for af lock in low light, is this lens related or sensor related?

Thanks,
Tom

Although some modern AF systems are terrific it's worth remembering that the best AF systems are on the best ( i.e. most expensive ) cameras need to use the more expensive professional lenses to get the best from the AF system.

For the humble masses AF does get better and better, but it doesn't always cut the mustard and for some situations AF won't reliably and/or quickly pick what you want. For these situations manual is indispensable IMO.

It's also worth knowing that the type of AF areas is just as important as the number. Some cameras use a lot more cross-type AF areas which are more useful.

Also bare in mind that if you use Live View you'll typically be using a contrast based AF system, ( as a P&S would ), rather than the faster and more accurate phase detection systems used by SLRs and DSLRs when not in Live View. All the mirrorless large sensor cameras also use contrast based AF.

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StephenG

Pentax K100D
Fuji S3 Pro
Fuji S9600

Phase detection AF is faster then contrast AF but not more accurate. In some DSLRs which have contrast AF in Live View, it is the contrast AF which is more accurate.

sjgcit said:

Although some modern AF systems are terrific it's worth remembering that the best AF systems are on the best ( i.e. most expensive ) cameras need to use the more expensive professional lenses to get the best from the AF system.

For the humble masses AF does get better and better, but it doesn't always cut the mustard and for some situations AF won't reliably and/or quickly pick what you want. For these situations manual is indispensable IMO.

It's also worth knowing that the type of AF areas is just as important as the number. Some cameras use a lot more cross-type AF areas which are more useful.

Also bare in mind that if you use Live View you'll typically be using a contrast based AF system, ( as a P&S would ), rather than the faster and more accurate phase detection systems used by SLRs and DSLRs when not in Live View. All the mirrorless large sensor cameras also use contrast based AF.

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StephenG

Pentax K100D
Fuji S3 Pro
Fuji S9600

Click to expand...

Steven,

I never said that manual focusing wasn't useful in many situations. It certainly is and that's why a quick manual override can be important. Macro is one such time where it's mainly a manual focus game and a reason I've thought about installing a Katzeye screen.

Liveview has it's uses, but again, it's not a mainstream way of focusing on most SLRs. It's going to be slow.

I'm not sure that cross type points are that much more effective than non types. I think, at least to me, the jury is still out. I don't know that horizontal points are that much less efficient than both. I've read some that suggests it's not that much less. I know in my case, the peripheral points that aren't cross type seem as effective when I'm tracking.

As far as the humble masses, you get what you pay for to a degree. It's another reason to buy the best you can afford. It's also another reason that old film cliche where people suggest the body isn't important, just concentrate of the glass doesn't hold true anymore. It all depends on what you want your camera to be capable of. If one needs to be able to track well in sports, a superior AF system is extremely important. The same might hold true with tracking fast animals or birds. I've certainly found it to be extremely useful over time.

This morning, I just finished a shoot for the local Little League Baseball association at a local park, covering the opening of the fall season. An entry level AF system and kit lenses would have had a hard time getting a high keeper count. If you're being paid or if it's very important, you have to make that investment. If they want me full time, I'm thinking about getting a 200 f/2 VR to backup my 300 f/2.8. It would pay for itself, or maybe. That would be my rational, and I'd stick to it.

That all said, there are many times manual focus comes in handy. It's just not designed to be as easy as it once was because of the lack of focusing aides in the focusing screen. For example, this morning. I turned off AF entirely and manually focused on the home plate for some shots. Home plate wasn't going to move.



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Cheers, Craig

Equipment in Plan via Profile

Where I find AF inadequate is when taking portraits with long lens wide open at 2.8. In these cases you want to focus on the nearer eye or on another specific spot on the face since the DOF does not cover the whole face. AF does makes it diffcult not because it is inaccurate but because AF point is not really a point but a much bigger area and it is difficult to predict which part of the face will be in focus. I am not able to manually focus on plain APS-C sized screen.

pakiwi said:

i recently started back into photography after being busy with young children. I did not want to spend too much so picked up a used 5d which goes wonderfully with the 24-105.

Many years ago I was in the military as a photographer and used 4 x 5 220 and 35 mm. As I have been reading these message boards I noticed many people complain about the inadequacy of the auto focus systems on their cameras. I use mainly manual focus because I get to decide the focus point. I know you can focus by selecting focus point and then recompose while holding button half day down.

So do people totally rely on the autofocus and if it is bad why not try manual focus then they can only blame themselves?
Just curious

Click to expand...

99%+ of photographers use autofocus. Only 10% of the cameras sold even have a realistic manual focus capability (DSLR's). Of that 10%, probably a tiny percentage use manual focus all the time. Those that do have a reason, they do macro photography, or just prefer manual focus.

I use manual focus for product shots in my studio, for example. i'm tethered to a pc with 24 inch monitor, and focus precisely on the features of the product that I want emphasied and select the aperture to get the depth of field I want. All this can be previewed live, along with the lighting, of course.

I use autofocus for most of my day to day images unless there is a good reason to manually focus.

Professional PJ's almost always use AF. Certainly, MF of a fast moving object is possible, but you must pre-focus and take many images hoping that you got one that shows the action well, and is also in focus. A rare talent is required to get a high keeper rate.

sjgcit said:

... rather than the faster and more accurate phase detection systems used by SLRs and DSLRs

Click to expand...

Faster at the moment, using current technology.
More accurate? Maybe not.

In fairness I can't say I've any current evidence that phase detection is more accurate than state of the art contrast detection. However given the nature of the technologies I don't see any way for contrast detection to be more accurate. Something to check into in the coming wet and windy months I suppose.

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StephenG

Pentax K100D
Fuji S3 Pro
Fuji S9600

sjgcit said:

In fairness I can't say I've any current evidence that phase detection is more accurate than state of the art contrast detection. However given the nature of the technologies I don't see any way for contrast detection to be more accurate. Something to check into in the coming wet and windy months I suppose.

Click to expand...

Fundamentally, phase detection is indirect (like a coupled rangefinder) while contrast is direct (even more direct than a ground glass).

Phase autofocus is done by an optomechanical assembly that's somewhere in the camera and tells the lens to move. If you're lucky, the phase sensor is set to the same plane as the imaging sensor, the focus at f/5.6 is the best focus for for your actual taking aperture and the lens moves the way the sensor told it (I have to admit that my D300 does a pretty good job of all this).

Contrast autofocus reads pixels on the actual imaging sensor and commands the lens to move, then iterates that process to maximize the difference signal between adjacent pixels. You have fewer opportunities for error with contrast detection, although it does take longer to do.

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Leonard Migliore

For portraits done with a fast lens, I always switch to a single AF point. I sometimes move to a single point that's not in the center, but on the same side as the near eye. It's quick and easy regardless. I also find it more accurate than manual focus, especially when the model is moving about.

--
Cheers, Craig

Equipment in Plan via Profile

Scales USA said:

pakiwi said:

i recently started back into photography after being busy with young children. I did not want to spend too much so picked up a used 5d which goes wonderfully with the 24-105.

Many years ago I was in the military as a photographer and used 4 x 5 220 and 35 mm. As I have been reading these message boards I noticed many people complain about the inadequacy of the auto focus systems on their cameras. I use mainly manual focus because I get to decide the focus point. I know you can focus by selecting focus point and then recompose while holding button half day down.

So do people totally rely on the autofocus and if it is bad why not try manual focus then they can only blame themselves?
Just curious

Click to expand...

99%+ of photographers use autofocus. Only 10% of the cameras sold even have a realistic manual focus capability (DSLR's). Of that 10%, probably a tiny percentage use manual focus all the time. Those that do have a reason, they do macro photography, or just prefer manual focus.

I use manual focus for product shots in my studio, for example. i'm tethered to a pc with 24 inch monitor, and focus precisely on the features of the product that I want emphasied and select the aperture to get the depth of field I want. All this can be previewed live, along with the lighting, of course.

I use autofocus for most of my day to day images unless there is a good reason to manually focus.

Professional PJ's almost always use AF. Certainly, MF of a fast moving object is possible, but you must pre-focus and take many images hoping that you got one that shows the action well, and is also in focus. A rare talent is required to get a high keeper rate.

Click to expand...

It's an absolute indispensible tool. While you can reset the AF when it locks onto a branch near the subject, you cannot reset the subject, and often enough they don't hang around while you get the AF to work.

Dave

Another point when using the 24-105 lens. If you don't have the manual for the lens, it tells you to turn off the IS if you mount it on a cam stand. Just thought I would mention that as it does make a difference.

Steve