manual focus

Discussion in 'Beginner Questions' started by gwenyth_m, Oct 4, 2012.

  1. I am just curious more than anything, and I am not sure where to post this. Today a LOT of people rely on autofocus to focus their images. BUT most lenses still come with the option to manual focus. So which one is better? Do they both serve a purpose? Are you considered to be shooting in full manual if you are still allowing the camera to autofocus on your set points for you? I shoot in manual mode now, but I am wondering if I am missing something by not also manually focusing and then using BBF to lock in the focus. Thoughts?
     
  2. Do whichever you want or need. If I'm using an AF lens I almost always use AF, although usually in continuous, single-point mode, much of the time but not always on the center sensor, and using the lock button in order to recompose as necessary.
    I find it more reliable and faster than manually focusing, although that comparison is obviously a personal one. I've shot a lot of basketball and while I know people used MF for everything in the past it would have been very difficult for me to get many of the shots.
    I occasionally use MF for situations where I'm shooting through chain link fence, or there's a bit of foliage in front of the actual target and the AF system doesn't do what I want. I have a couple of MF lenses and I have a doubler which is MF so when using those I have no choice and it forces me to slow down a bit.
    I think it's a good skill to be able to quickly focus manually, but I'm not so skilled. Also, DSLRs don't have the focus aids that film cameras used to have and on small-sensor cameras the viewfinders are smaller. Manually focusing on my D90 is harder than it was on a Pentax K1000.
    So while I usually shoot in M, and set ISO and WB manually per the situation, I usually do use AF.
    I'm not sure what you mean by "manually focusing and then using BBF to lock".
     
  3. I don't know if how you can use the back button focus option for AF, if you can also manually focus and then lock the focus using the back button option? but then the more I think about it, I suppose because the focus was done manually, it would be locked in anyway.
     
  4. It would, Gwenyth. The rear button normally tells the camera to focus while you're pressing it (assuming you've turned off focus on shutter release).

    The advantage to manual focus (on an autofocus lens - there are obvious advantages for a manual focus lens...) is that you can tell what you're focussing on - especially in live view - whereas you're always trusting that the camera has picked up the edge you really wanted - much as spot metering ensures that you know what the camera is doing. The focus confirmation/digital rangefinder is only as accurate as the autofocus, so there's no advantage there (you may or may not do any better with a split screen finder, but live view is generally a better choice when available). The advantage to autofocus is that the camera is much faster at this than you are, but it may sometimes be confused (you could make the same argument about a matrix meter).

    Generally, unless experience has taught you otherwise, I'd start with autofocus and only go manual if you think the camera might not be getting it right. Don't be afraid of manual focus (with the digital rangefinder or live view), it's not as painful as it sounds, and manual focus lenses can be bargains (or not, in the case of high-end Zeiss lenses). Don't try to trust the viewfinder screen for manual focus, though.
     
  5. Merely to add to what Andrew says:
    Also, don't be misled into some act of ritual purity in which you feel you HAVE to manually focus to be a "real photographer".
    Always watch what is being focused on, and "touch up" the focus manually when it is needed - that's why lenses that will allow manual adjustment even when set to AF are so useful.
     
  6. With my Olympus digital SLRs it is possible to manually over-ride auto-focus once that has been achieved. I found this invaluable when taking close-ups of botanical subjects without a tripod. Re-composing after auto-focus was ruled out as even the act of breathing could change subject distance enough to affect focus. Of course, as David and Andrew have said, the view-finder is not terribly helpful.
     
  7. As to if AF is going to give you the focus you want I believe depends on the size of the focusing or target area. Here we are using a 'spot focusing' area rather than hoping that the camera will read our mind and focus where we want it to.
    As David wrote 'single point mode', though the size of the single point will affect how good this works for us.
     
  8. Hi again Gwyneth,
    Are there specific situations in which auto focus isn't working for you?
     
  9. After growing up on manual focus, I now use AF most of the time. But I'm not entirely happy with it. Even though I generally use the focus-and-recompose technique there are some times when AF misses. There have even been times when I think the camera is autofocusing and I find out the switch has slipped from AF to MF. There have definintely been more times when AF has missed than when I missed while manually focusing. Particularly at times when the focus is off just enough to cross the line from soft to out of focus. With MF, it generally was either in focus or it wasn't, not these shots where I'm having to pixel-peep to decide is is "sharp enough" or not.
    It's not just me, either. In my day job in PR I often function as photo editor, and I see the same focus issues in other photographers' work as I see in my own.
    I think the key is that you have to recognize the times when it's better to use MF just the same as when you recognize that you have to override what the meter is telling you. The trouble is that today's viewfinder focusing screens aren't really meant for manual focusing. Split-image rangefinders and microprism rings are gone, and the ground glass isn't ground enough to really be able to easily judge focus on.
    If I had to bet my life on perfectly focused pictures, give me a Nikon F2 with a K screen.
     
  10. To add to Craig's anecdotal evidence: There's a very nice shot that a professional photographer took of me and my wife at our wedding. Unfortunately, the camera decided to focus on the trees behind us. (Most of the other shots were in perfect focus, though.) I've also leant a camera - in centre spot focus mode, though it wouldn't have helped for that camera - to my sister, who wanted a photo of my wife and me, and she produced a lovely in-focus image of the wall behind us. I don't entirely trust my D800's (phase-detect) autofocus at larger apertures, but it's nothing that checking the images afterwards can't solve - but the electronic rangefinder would have been just as much trouble, and by extension the same would be true of a split screen (but without the fine tuning). It's also common to need to manual-focus at macro distances, since the AF can get confused.

    Essentially, I manual-focus if I want to be very sure of a single fixed focus point - but I usually use the electronic rangefinder or, sometimes, live view to do it. Usually, though, autofocus technology is good enough that you should use it with impunity.
     
  11. Andrew, That reminds me of something I learned while shooting basketball (where there are often nice contrasty objects like brick walls or bleachers behind the players). The focus sensor areas are not identical to the marks denoting their locations in the viewfinder. If you put your camera in single-point, center, continuous mode, and slowly sweep across something like a telephone pole against sky, you'll get an idea for how big the sensor area is. If the subject is smaller than that, and the background isn't uniform, then it starts to be uncertain where the camera will focus.
     
  12. most lenses still come with the option to manual focus​
    I really need manual focus, but I am sure they have it not because of me. The main reason is that it comes free with all lenses (does not cost more to have manual focus). On the other hand, how many P&S you have seen with manual focus lenses? The philosophy is if it works for you, use it, if not try to ignore it
     
  13. AF and MF are both tools, they can each be used to serve a purpose. AF is fine most of the time, and DSLR focusing screens aren't that great for manual focusing anyway. But sometimes it's necessary, for example, shooting a delicate spider web. The camera wants to focus on what it sees behind the spider web (if it can even detect the web at all), so the web will likely disappear. MF plays an important role in that case. It's also very helpful in macro photography, where the AF point may not pick the part of your subject that you want to have in focus, especially if you are taking a number of shots for focus stacking. Also, in low light, where your eyes can see, but the AF sensor may not be able to pick up enough contrast to focus, MF could mean the difference between taking a shot or missing it.
    On the flip side, AF is generally a heck of a lot faster at achieving focus than turning the focusing ring on your lens. If your shooting involves subjects at frequently changing distances, you may miss more shots by not being able to keep up.
    So it comes down to knowing which focusing method will best suit your needs under your given shooting conditions and desired effect, or at least recognizing that AF isn't delivering what you need and switching to MF to achieve what you want.
     
  14. As a discussion point I suggest you check out the small focus area than can be achieved with Panasonic's G3 M4/3 camera ....It is considerably smaller than any other camera I have seen and really enables one to select the point one wants to be the point of focus the way one manually focus with a good ground glass set-up.
     
  15. I use manual focus all the time. But the reason I use manual focus because it's EASIER for for me. Don't ever worry about whether you are in full manual or missing something if you don't use manual etc...
    Use whatever mode that works for you and is easiest. I do every thing in manual but just because that's easiest for me.
     
  16. Thanks all. I was just really curious. I have started recently using the back button to focus, and I find that it is easier for me to focus and recompose my shot if needed. I am still learning my 50mm 1.8, and it often misses focus, or is soft- which is more than likely user error, the back button is helping me to get more “good” shots though. Although when I first got this lens it was so super sharp. So I don’t know if I am getting more discerning about focus, or if it was just such a change from the kit lens because it is faster! (Or if it has to do with it being more sensitive to my shaky hands because it doesn’t have the IS.)
     

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