manual focus vs auto focus

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Hi all

I'm a beginner and I've just got my new EOS 300. There's one thing I want to know: it seems to me that most lenses now can auto-focus, is there a reason to use manual focus? or is it just for backward compatibility? I understand that under some situations auto-focus wouldn't work. But is there a reason for manual focus to be used in normal situation? Thanks.

-Jon

-- Jon (jonhui@hotmail.com), April 23, 2002

Answers

Manual focus on an AF Canon is virtually impossible--there is no split-image or microprism focus aid, so you're left guessing as to whether or not you've got the focus right. Of course, some cameras offer focus confirmation. Hold the shutter button down halfway, focus manually, and the familiar green light will come on, indicating you have achieved focus--but why not just use autofocus at that point if you are relying on the computer anyway?

In a normal situation, you may be focusing on some small element that confuses your autofocus point (like trying to focus on something in the distance between the narrow planks of a fence, and the AF always grabs the fence). You might then focus manually to give the camera a hint, and then let AF take over.

Maybe other people can, but I simply can't manually focus an AF Canon lens. My eyes can't beat the computer and sensors, which are extremely accurate.

Manual focus cameras are a different story . . .

-- Preston Merchant (merchant@speakeasy.org), April 23, 2002.


Often you have to manually focus in the dark, or change the focus from a person's nose to his/her eye. Or switch it to MF when you want to lock the focus at a certain point and not have the camera override your decision. Or there isn't enough contrast for AF. There are a lot of times people want MF.

FYI I've found it easier to manual focus with the Elan 7 than any of the Rebels, it seems like the focus screen is a bit better -- but cameras designed for manual focus are still 10x easier. Some of the higher end Canons let you put in different focus screens that can make MF easier (there are even a few third party screens I think).

-- Steven Fisher (steven_fisher@hotmail.com), April 23, 2002.


For entertainment, you could read the Autofocus Problems page.

-- Julian Loke (elan7e-owner@yahoogroups.com), April 23, 2002.

I used MF for 25 years before buying an ElanIIe and 28-105USM, and have never had to use MF thereafter because AF on that rig is just so reliable (I use MF only for shooting landscapes on tripod).

I have 2 simple rules: (a) never use automatic focus point selection, and (b) in low light, just use the center focus point.

-- kenneth katz (socks@bestweb.net), April 23, 2002.


I've used an Elan IIe for years and I have found autofocus faster and more accurate in just about every situation I've been in. It's not hard to prove to yourself. Just try focusing on various scenes manually, then try it with autofocus. If I concentrate really hard, sometimes I may just barely me able to manually focus more accurately than the autofocus, but it also takes me twenty times as long to do it, and it's no where near 100%. The autofocus on my Elan IIe, on the other hand, does it in a fraction of the time and gets it just about every time. Plus, it can do things that I could never do, even if I had a split-screen viewfinder to help me. For example, with the infrared focus assist beam on my camera, the autofocus can lock onto a blank white wall in a dark room. And it can you it fast. Try that with manual focus. Plus, in very low light, split screen viewfinders black out anyway.

Even though it is better to use autofocus most of the time, it is still useful to be able to manually focus. These times occur when you have plenty of time to focus. If you're in a hurry, forget it. More likely than not, you aren't focusing as sharply as the autofocus sensor can.

I actually have two manual focus Canon EOS lenses. How can that be, you say? Because they are the 24mm and 45mm tilt-shift lenses. I can tell you that manually focusing theses lenses can be a pain in the butt. It's a slow and deliberate labor of love manually focusing these lenses, considering that the Elan IIe's viewfinder isn't as bright as the high-end viewfinders of the EOS 3 or 1v. Would I prefer that they be autofocus? You bet, at least as an option. But I don't think that's possible with current technology.

-- Peter Phan (pphan01@hotmail.com), April 23, 2002.



I always had great trouble manually focusing wider angle lenses on my EOS 5. The EOS 3 is much easier to use in this respect. Also, swapping out the focusing screen can help. I use Ec-N and Ec-CIII screens in my EOS 3. Ec-N is brighter, Ec-CIII is grainier and has more focus "snap".

-- Isaac Sibson (isibson@hotmail.com), April 24, 2002.

I often read of people lamenting difficulty using manual focus on a modern EOS camera body. Learning to focus properly is just as important as learning to meter correctly. This makes me wonder if they are aware of the many focussing aids that are part of the EOS system.

Built-in

Optional Accessories

There is no single method that can be used in all situations. For instance, when it is too dark (e.g. astrophotography, macro) a reticle focussing technique can be used. The best part is that my Elan 7E standard focussing screen has marks etched on the screen that lets me do this without having to buy another accessory (althought the Magnifier S does help). If you like, consider this "Thinking inside, outside, and on the box."

-- Julian Loke (elan7e-owner@yahoogroups.com), April 24, 2002.


Julian, can you explain what reticle focussing is all about? The only reference I found op photo.net is a reply from you to a question. Since you seem to be the expert on this topic: please explain.

Regards,

Jos

-- Jos van Eekelen (jos@compuserve.com), April 24, 2002.


Reasons to manual focus with EOS cameras?

1--I always manually focus when doing close ups with supplementary diopters or extension tubes. It's more precise than autofocus and I can choose the area of the image I want to be the sharpest without having to place an autofocus sensor over it. 2--When using Canon extenders, I often manually focus because the autofocus can be sluggish, depending on the lens. 3--I manually focus when shooting scenics and landscape photos 100% of the time. I set the hyperfocal distance based on the aperture being used. That's actually scale focusing. 4--When shooting photos of people or animals, the eye needs to be in sharpest focus and sometimes the autofocus is not able to maintain that fine a point. 5--Finally, no matter how many autofocus sensors there are in the viewfinder, I always come upon a subject which will not frame the way I want it with a sensor covering the point I want in sharpest focus. It's sometimes faster to just manually focus rather than move the camera, autofocus and then recompose.

EF lenses with USM are a great assest, allowing full time manual focusing as well as autofocusing.

-- Lee (Leemarthakiri@sport.rr.com), April 24, 2002.


Julian, can you explain what reticle focussing is all about? The only reference I found op photo.net is a reply from you to a question. Since you seem to be the expert on this topic: please explain.
Regards,
Jos

Hi Jos,

I presume that you are familiar with the phenomenon of PARALLAX. If you look at the same scene from different directions, the relationship of objects in the scene will change if the objects are not in the same place.

When you focus a lens, you move the aerial image projected by that lens until it appears "sharp" on a ground glass/plastic. If the aerial image is in front of, or behind the plane of the ground glass, the image will be out-of-focus.

Reticle focussing uses parallax to determine if the aerial image is in the same plane as some feature on the ground glass (such as a millimeter reticle mark, or AF rectangular mark, or a metering circle, or a grid, or even some dirt on the screen).

Shift your head so that you look in from the left edge, then move again to look in from from the right edge of the viewfinder. The image of the detail you want to be in focus should not shift relative to the reticle mark / AF mark / whatever.

This method works best if the camera is on a tripod, and at high magnifications (especially with viewfinder Magnifier S). It can be used equally for central and off-centre subjects.

I do not claim to be any expert about the lost art of reticle focussing. See these other links:



-- Julian Loke (elan7e-owner@yahoogroups.com), April 25, 2002.


Thanks Julian, seems to work well, but as you described: using a tripod and using a magnifier.

Regards,

Jos.

-- Jos van Eekelen (jos@compuserve.com), April 25, 2002.


Hi Jos,

But it still works even without a magnifier. It is like using a split-image screen without a split image screen.

-- Julian Loke (elan7e-owner@yahoogroups.com), April 25, 2002.


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