The "right way" to manual focus

[wolan]

Hi,
not sure, but I think I have read somewhere that the right way to focus with a MF lens and the focus indicator (available on most Nikon cameras when focusing in manual mode) is to draw the focus from infinity till to the point when the indicator is on and does not blink (so not the other way around, from the minimal focusing distance onwards).

Just a urban legend or there is something true in that?

Thanks.

[fwcetus]

[480sparky]

Depends on the model. Most lower-end bodies have a simple green dot to 'confirm' focus, while others have a triangle on either side of it. I have never heard of running the lens to infinity, then back to what the AF module says is 'in focus'. I just eyeball it myself. i think which AF points you have activated makes a difference as well. The AF module may pick out the wrong point as they all use contrast. If you use the in-cam AF module to determine focus, it may use a point that has zip to do with where YOU want the focus to be.

[bernhardas]

Edited

[tomasg]

I am a Nikon user, now D700 (owned d300, D200, D50) which has arrows to show the direction in which to turn the focusing ring to achieve focus. I relay on the green dot exclusevly to focus.

My exerience with 20+ mf lenses is that there is no rule that applies to all lenses. I tend to position the green dot on it s extreme RIGHT, or closer focusing distance. There are just to many variables to make a fixed rule on how to focus using the green, the amount of throw of the focusing ring when the dot stays on is diferent from lens to lens (my guess is becouse of different DOF), some fast lenses has focus shift when you close down the aperture so you have to keep that in mind, some of non Nikkors lenses focus in the reverse way, you move, the subject sometimes moves, then you have a lens like the Samyang 14 mm where the dot says on for a very long time and so on...

So for me the green dot is the way how i focus but it s just a guide, experence tells me how to position it on different lenses, so i focus also by feel, i tend to do a bit of focus stacking or focus bracketing when i take three shots (or more on a subjects that moves) as i slightly move the focusing ring left-right. That is my technique.

Of the five chipped Samyangs i have, only the 85 needs a full +20 adjustement, becouse the best fcous is achieved on the left side of the dot and i don t want to remember that.

With static subjects the in focus rate is good, even wide open, with moving subjects (like wie open portraits) it is of course more difficult. In short don t worry to much and adjust your technique by looking at the results
Try that: triopd, focus with a tele lens (85-135 mm) wide open on something at infinity distance (keep in mind that most lenses focus just a bit past infinity!), like a church tower bell, take a pic, turn the ring to the right until the green dot is off, then turn it back left a bit so that it comes on again, take a pic, take a pic also "in the middle" and compare. I always get the best result on the RIGHT side. Let us know your findings.

Tomas

[scsambrook]

I, too, have read that focusing back from infinity is the preferred way to focus manually - even with a coupled rangefinder camera. I've never understoof why that should be. Thinking about focusing on a reflex camera screen I alwys think the opposite should be true because there is less depth of field in front of the subject than behind it. However, ignoring the "green light" on my Pentax K30 and concentrating on the screen image, I do get more successes using the "preferred" method. If I rely on the green light, the results are all over the place. The autofocus gives me a much higher - though not 100% - hit rate, whatever lens I'm using.

Using either the Lumix or Fuji mirrorless cameras I find no difference in focusing back from infinity or out from a closer distance; the outcome is usually spot-on. But for most subjects of the subjects I phtograph, the coupled rangefinder is the quickest and surest of all (up to 90mm and f2 at any rate).

[480sparky]

[tomasg]

[mfkid]

Using an Industar 50-2 wide open on a Canon 10D with an AF confirm adapter from eBay on a tripod.

Focus on the 13.

Tried both ways turning the focus while holding the shutter until AF confirm beeped.

A little back focus in the picture when started at infinity, second picture.

[visualopsins]

Ok, there are two or three things happening here.

One has applied since film days: The focal plane has some depth (of field), so, for example, with a wide angle lens, if you want to focus from subject to infinity, you would begin focus at infinity & turn closer just until subject is in focus, thus placing the the thick dof from subject to infinity. If you had wanted everything in foreground to be in focus, you would start focusing from close, then turn farther until subject is in focus, thus placing dof from close to subject, leaving background oof.

Two applies more to focusing fast lenses with slow focus screens -- the focus screen is unable to show dof faster than f/3.5. Thus when focusing a fast aperture lens set at f/1.4, the focus screen will show what focus looks like at f/3.5, i.e., with dof of f/3.5 -- the correct f/1.4 focus is somewhere within the thicker f/3.5. Here it is recommended to "rock" focus from infinity, then from close, to find about the mid-point in the dof which can be seen, to estimate exact focus.

Three applies to cameras with "catch in focus" shutter firing feature. The focus screen is not at issue, because the AF system doesn't use it. It should work, however the habit it establishes is questionable.