When to use AF or MF?

[WayneF]

Any thread with 15 responses has already gone to pot, but I'll try one anyway.

Use AF when you want to. Use MF when AF isn't able to, but mostly when you do not want focus to change on you.

 

[dennybeall]

I also use manual focus for video. If there is something between me and my subject, such as trees, screen or other people, then I'll use manual to stay in focus on that more distant object. Also, there are times when there is not a part of the scene with enough contrast for the camera to grab focus, then it's manual also.
Other than that it's AUTO all the way.

 

[Thebigbarkhouski]

I almost read that whole response.....thanks

 

[Solarflare]

With lifeview manual focus is possible. Move the AF point to the desired location (which btw is endlessly slow, a touchscreen would really help), then press the plus magnifier until 100% or at least 50% magnification is reached. On my new D750, this is even possible in a single button press (but unfortunately losing the ability to center the AF point with the same button), but the movement of the AF point is still endlessly slow. Anyway this way one can attain critical focus.

On a full frame camera like the D600, I sorta successfully managed to manually focus my AF-S 70-200mm f4 VR. On my D5100, it was a hopeless battle. Even shooting focus series didnt guarantee me a sharp picture.

 

[Big Mike]

Another method that I recently discovered, is to use a 'hacked' firmware (Magic Lantern, on a Canon). It has several options and one of them is trap focus. In this mode, the camera is in manual focus mode and you hold down the shutter release button, and then when the AF system confirms focus, the camera snaps the picture.

Do you mean the camera will take the photo automatically once the focus is confirm by the camera and the user do not need to anything else but just keep half pressing the shutter button?

If that is the case I need to look into and see if they have a firmware for my 7D. That is going to be very useful for macro shots!!

In that mode, and with the lens in manual focus, you hold the shutter release button all the way down...and the camera only takes the photos when focus is confirmed.

I found that it worked great for close up shots, because I would hold the button down, then just move closer to whatever I was shooting until the camera takes the photo.

 

[Dao]

Great! That is really a great function for macro shots!!! Thanks Mike.

 

[beagle100]

the "trap focus" technique with Magic Lantern is good
Magic Lantern | Home

 

[snowbear]

I really like MF but my eyesight wants AF; eyesight generally wins.

 

[TCampbell]

I recently did a food shoot, but needed critical focus in specific areas. Even though my camera has 61 AF points, I found that critical area often fell outside the area where the focus points are located. Food shots are done with a camera on the tripod and the presentation table is very carefully set with particular attention to the placement of each element in the shot. This means the composition of the shot is also critical (there's nothing casual about the shoot). This means... the focus-and-recompose method would be difficult and since we're using a macro lens, those recomposed movements might knock my element out of focus anyway.

So the whole shoot is done on manual focus. I critically focus as well as possible with my eye, but since these are tethered shots I can see how well I did a moment or two after taking the shot. It worked extremely well.

AFTER the shoot, I was invited to use a program called Kuuvik Capture 2 (as far as I can tell, this is only available for the Mac). The app is written specifically for tethered shooting and with some emphasis on helping with manual focus (it's excellent for use with a tilt-shift lens). The app has a "focus peaking" mode. It does a live-view preview on your computer screen and the areas where you've achieved focus will have a bit of a sparkle-like effect. This makes it EXTREMELY easy to tell what's in focus as you do the tethered shoot.

Full disclosure: The software is not free, but the company that developed this software invited me to try it by giving me a free download code (so I did not pay for my copy). But so far, I really like it and I can see how it helps me achieve things with tethered shooting that I can't achieve if I use the tethered shooting feature of Lightroom.

 

[unpopular]

Do other cameras do that thing which Fuji has where you can auto-focus and then turn the focus ring and have it automatically go into manual? I'm guessing not, and that this is a side effect of Fuji cameras "focus-by-wire".

 

[TCampbell]

Do other cameras do that thing which Fuji has where you can auto-focus and then turn the focus ring and have it automatically go into manual? I'm guessing not, and that this is a side effect of Fuji cameras "focus-by-wire".

Full-time manual focus override available in auto-focus mode... yes. Canon has this with any lens that has either "USM" focusing motors or "STM" focusing motors (if the lens isn't one of those two then the lens doesn't have full-time manual focus.)

On a Canon "USM" lens, the focus ring is on a clutch which is allowed to slip. This means if both you and the camera are trying to change focus at the same time you cannot damage the lens focusing mechanism. If the camera focuses but you want to change focus, you can just turn the focus ring (you do not need to turn off auto-focus before doing that.)

On a Canon "STM" lens it's a bit different. The STM lens is a "focus by wire" system. There is no mechanical engagement of the focus ring to the focusing elements within the lens (on a USM lens there is mechanical engagement but it has a clutch). Instead, the camera senses your adjustments and the computer moves the focus elements. You can override focus at any time. The one "catch" with the focus-by-wire system is that since it relies on the electronics it won't work if the focus system isn't "awake". Any button no the camera that activates either the metering system or focus system (half-press of the shutter button, touching a metering button, using the back-button focus, etc.) will also activate your ability to manually focus the lens.

This is probably not an uncommon feature, so I'm guessing Nikon has lenses that support this as well.