Optical Quality: AF vs MF

Generally speaking which category has better optics:
Auto-Focus or Manual Focus?
Thanks,
Mike.

 

In 35mm camera lenses, neither is a reliable indication of quality,
and junk comes in both types.

 

The difference is not in the lens optics it is in the focusing/viewing
screen. In most autofocus cameras the viewing screen is very difficult to
use for critical manual focusing.

 

IMO, manual focus lenses give you the best quality for the money, simply
because they have been made for many years, and the used market is flooded
with them. Bear in mind however, that optical design has improved over the
years, and the newest glass is probably the best, although it will also be
the most expensive. But the real bargains are in the pre-AF lenses that are
ten years old or older.....

 

Yes.

 

Good and bad examples of both abound - you can certainly get first rate
optics in either.

However, AF is not as accurate as _careful_ manual focus, so manually
focussing will give you better results, other things being equal (ie., we
aren't talking about you shooting a subject that is fast moving and really
benefits from AF, and you don't have fading eyesight.)

The issue then is that _some_ AF lenses are harder to focus precisely
manually than MF ones, just because of the 'looser' focus mechanism that is
designed to reduce the load on the AF focus motor. There are also lots of
better AF lenses where this isn't the case, notably those with a focus
clutch or similar mechanism - though this isn't a requirment for good MF
feel, as the Pentax FA-Limited lenses show.

The focusing screens in AF bodies also don't help. They are designed
assuming that focusing isn't their prime job, and so are optimised for
brightness and 'smoothness' which can make precise manual focus (and
especially fast and precise manual focus) harder to achieve.

So the best lens optics exist in both. The best results from those optics
are usually from manual focus or 'top end' AF lenses on manual focus
bodies - or AF bodies with their focusing screens replaced with ones more
suited to the task of focusing.

All the same, if your body has a good AF system, the differences in final
sharpness will often be less than the difference that is made by using a
tripod - ie., this is the way to get 'the best' results, but you'll see a
bigger differnece by using good technique first, and only then looking to
squeeze out the last ounce of performance.



Peter

 

Manual-focus gives sharper pictures. Before Spazado explodes in front of
his monitor, maybe he should read this:

http://medfmt.8k.com/third/af.html

 

Geez, what a quickly thrown-together document! ;-)

 

For the lens, the only difference is the drive to move the focus,
the optics otherwise can be the same.

The focusing screens in AF cameras make critical manual focusing
more difficult than with a MF system... this does not reflect on
the lens quality.

Final point, AF systems cannot focus as accurately as the human
eye can focus (with a MF viewfinder), so with AF there is a
certain probability that the focus is a tad off from 'best'.
Selecting higher DOF helps alleviate this where possible...

Cheers,
Alan

 

Monagan is anti AF and tends to load his "facts" to benefit his opinion. He
also thinks Vivitar and Phoenix lenses are as good as Canon and Nikon -
which leads one to wonder --- does it matter whether one uses MF, AF or NoF.
If you are dumb enough to believe the crap on his site -- it does not bother
me -- I'm not the one basing expensive decisions on crap, so I have no
concern at all. Goodbye, troll.

 

Well, I read some of it - the author seems to have a bad case of verbal
diarrhoea - the article is HUGE. But huge doesn't mean correct. And
it's largely the opinion of one man. Further, the article was written
more than four years ago, using cameras extant at the time. The last
four years haven't been wasted as far as camera development goes, so he
is plain out of date.

I can pick holes in his approach and conclusions in numbers of
instances. He carries on about AF 'focusing on an eye and getting the
chin', and other critical focus situations - but these are usually
portrait or even studio shots, where AF is inappropriate. Nobody who
knows what they are doing would use AF in that scenario.

He prattles on about sensors that are only able to resolve about 25
lpmm, let alone 50 lpmm. Here's something you might like to think
about. Since the screen in an slr is the same size as the film frame,
greater than 50 lines per mm on the film is also greater than 50 lpmm on
the viewing screen. Given that the viewfinder optics provide some
magnification, you are asking the screen to be able to show such fine
detail, and your eye to resolve it. I think the truth is that one
*can't* see such detail, and the act of focusing consists of adjusting
the focus both ways until one *can* see the image is just out-of-focus,
then guessing the midway position where hopefully it will be sharp.

Conversely, he totally ignores the situations where AF is useful -
'grab' shots, sports, fast-moving subjects, even ordinary general
photography where, because there is no absolute pinpoint that *needs* to
be in focus (a group shot - whose eye are you going to focus on?). And,
many modern AF cameras, certainly my Canons, have a 'dep' setting, where
the camera figures out the required depth of field and sets the
resulting aperture and focus point, far faster than any human could do
it. Not used often, but it's there if you want it.

Lastly, a very valid point that has been made many times, and I make no
excuses for making it again. Manual focus, especially on 35mm cameras,
is good only *IF* the user has very good eyesight. There are many
camera users, like me, who are not 21 anymore, and whose sight is simply
not good enough to focus the damned camera manually. It's also slower -
there aren't many who can snap the image into focus without some racking
back and forth to ascertain the focal point. Remember seeing those MF
users screwing the focus ring backwards and forwards a dozen times
before taking the shot? Then, a moment later, because someone moved,
doing it all again? Subjects calling out 'Hurry up, take the shot'?

In such - and indeed nearly all - situations, AF works better. It might
not be perfect, but it's better. A good analogy is the auto box in your
car. Sometimes it doesn't do what you want, and you select manual
second, or whatever. But do you say 'I hate my gearbox. I'm gonna get
a stick shift'? No, you learn to use the auto properly, and so it is
with AF cameras.

Colin D.

Beware the Pontificators. They are rarely Performers.

 

You mean that the Nikon F5, the Minolta Maxxum 9, and the Canon EOS1v
cameras are out of date?

What about the discussion on focusing screens? Or how AF lenses are
looser?

AF is absolutely useful for sports, wildlife, and other
fast-moving subjects. For everything else, it is not useful and possibly
even detrimental.

Valid point.

You are talking to the wrong guy here. My 2000 Maxima has a 5-speed
manual transmission. I love it. Even my 60-year old mother drives a
manual in her Mazda Miata. I guess it runs in the blood.

AF is great for most people. The article I posted may be biased, but
I think there is some merit in it.

 

He may be biased, but I don't think you can dismiss his data so quickly.
In fact he has data and you don't. So am I dumb or are you just an old,
ignorant man?

 

When percise focus matters (micro and portrait work comes to mind) I
always use MF. If you are using a AF screen, it is hard to tell exactly
where the focus point is. But by setting the focus half way between
when you detect out of focus at the near and far, you can get really
good results. With a MF screen, the split really helps if the image is
bright enough. As far as the design goes. The older MF lenses were
marketed towards the professional and so most all were good. There was
no consumer grade then. If you wanted cheep you did not buy from the big
5 (Nikon, Canon, Minolta, Pentax or Olympus) New glass clearly is
divided into pro and consumer grade and most or all are AF. There are
some really excellent lens designs now which were not possiable to make
20 years ago. Or even 2. Especially in the Zoom lenses. And there are
some, shall I say, compromised designs. You just have to do some
research to figure out what is what and what is important to you.
However the old axiom of you get what you pay for helps. Don't expect a
$99 zoom lens to give pro quality results. It is not going to happen.

 

This is not always true.....The 75-150 mm "E" type Nikkor zoom, used in the
80's by professional fashion photographers in New York, can be had used
today for $99. (approximately) If you are willing to do some research, and
look for what you want with some patience, you can get really good buys, but
it helps to have a camera that can work with old glass.......

 

Yeah, automatic transmission is for sissies!

Every car I have ever owned has been manual. I don't think I would know
what to do with my left foot if I ever drove an auto.

 

When I travel to Europe, I can rent a manual. When I travel to
the US (or elsewhere in Canada) renting a manual is pretty much
impossible.

 

It is *always* true... of *new* lenses. And assuming the pro in "pro
quality" is a pro involved in photography that, for whatever reason, demands
high resolution low distortion low falloff imagery. And assuming you didn't
just get incredibly good discount on a Leica 35-70 f2.8 R lens.

 

I can pick holes in his approach and conclusions in numbers of

As a 62 yr. old guy whose eyesight is about as good as can be expected, I
find it much, much easier to focus an MF camera, w/ the correct diopter than
an AF. By the time I get done argueing with the stupid thing, it's all over.
I will agree that the finders are much brighter than a fresnel screen, but
the fresnels "snap in". No doubt about in or out. The AF mirrors just slowly
get better. Plus, of course, they tend to look for something vertical and
contrasty, which may be great for football, but not so good for scenery. As
far as racking the focus back and forth on a med. format, that becomes a
habit. No matter what you tell them, people move. They just do. And the
closer you stand, the faster they go. Between the blinkers, the spinners,
and the guy who had a couple for breakfast, racking becomes more of an art
form than the shot. And you can't teach an AF to get a bigger lite and focus
in front of the shot. As far as lenses go, I just don't see plastic being
as good as glass, period. Bob
Hickey www.pbase.com/bobhickey/galleries

 

OK, Bob, I guess you're somewhat better off with your sight than
others. If a correction lens (diopter) fixes it for you, that's great.
The great majority of people who need correction lenses also suffer from
some degree of astigmatism, and no simple 'diopter' can correct for
that. They need a prescription lens from their optician, and that
raises problems when rotating the camera from landscape to portrait. Or,
they just wear their glasses with the camera, which can be a damned
nuisance.

Due to early cataract formation (too much RF from my ham radio days?) I
have had the lenses replaced in both my eyeballs, so now they are 'fixed
focus' eyeballs. With the proper correction at the proper distance, I
can see better than most - but if things are out of focus, then that's
it. AF is my saviour. Having said that, though, it doesn't often miss,
and the camera (300D) will focus well down to about EV 0.5 without
supplementary light.

Colin D.
Beware the Pontificators. They are rarely Performers.