Focus Mode / AF-Area Mode

Hi all,

I know that this subject is a photography basic but setting the Focus Mode and AF-Area Mode for two lenses (18-55 kit lens & Nikkor DX 35mm f.18) has been a continual frustration for me. Can anyone help? :miserable:

I continually read and re-read the instruction manual on these two subjects but seem to get more and more confused as I do. So, my questions really are:

• For general photography with both lenses, typically mainly static images but with a few motion ones of my children, etc, would it be sensible and appropriate to keep to the AF-A setting so that I don't have to keep changing for every shot? Would I ever need to change from this?
• I am baffled by AF-Area mode. When I take a photo of a group of people, which should I select so that the camera will focus on each person's face, using all of the black points in the viewfinder?
• Is there an optimum setting for each of the lenses?
• For the 35mm f 1.8 prime, would you recommend using the 3d-tracking area mode so as not to blur more of the image than wanted?

If anyone can help with any of the above I would be massively grateful! I am taking the camera and new prim lens on holiday in a week and I'm hoping to get some really good shots, but I'd just like some hints to make sure that I do. I'm the only one with a SLR, so there is a bit of pressure!!

Thank you in advance to anyone who responds.

Alex

I too find that one of the most confusing things and would be interested in some guidance. In fact, I am surprised at how complicated the focusing part of using my camera is. I had always struggled more with exposure, but am getting that down (most of the time). Focus is still a bit of a mystery. The term "autofocus" makes it sound so easy!

The one benefit that I have learned about moving out of AF-A mode is when you want to be sure that a particular item in the scene gets focus. AF-A doesn't know what is the item that you wish to highlight.

I highly recommend getting a more descriptive book on your camera. The manual is great for reference but books like Mastering the Nikon (insert model here) really digs into the ins and outs. Plus it explains how and why you would use those particular functions. AF is actually complex on our cameras (I'm not familiar with the D3100 but assume it's basically similar to what I'm used to). Even the author of the books mentioned above admits he has to occasionally refresh his memory on the different modes and their functions.

I really don't use AF-A mode that often but that doesn't mean it wouldn't suit your needs. When shooting static people I usually use AF-S with a single point and I move the point to a person's eye. When shooting a moving object (slow object) you can still use AF-S but you have to make sure you reacquire focus if you or the subject moves by redoing the half-press.

If a subject is really moving I'll usually use AF-C to allow the camera to continously focus without having to repress the half-press. I use a smaller focus area like dynamic 9 point for something I can easily track and 21 or 39 point for something that is a little more erratic and therefore harder to track. 3D tracking focusing adds the element of color. So it can also attempt to focus on the color (assuming the subject color is different than the background).

Your last question about the 35mm prime sounds more like you're referring to DoF rather than focus area. Keep asking, I'm sure you'll get better responses than mine.

- AF-A is a great "all purpose" setting and generally works well. The times you might consider using AF-C or AF-S is when you want to insure the subject is being properly focused. AF-A, as nice as it is, sometimes gets it wrong

- When photographing a number of people in AF-A, your camera software is calculating all the various subjects (faces) and will then determine the optimum hyperfocal point that will allow all the faces (or whatever it is you've told the camera is the subject) in focus.

- Optimum setting in what regard? Focus or aperture? For focus it depends upon your subject and how you want the image to look. If you mean aperture, the sharpest images a lens can produce is when you stop it down 1 to 1.5 stops smaller than wide open.

- Again, it all depends on the effect you're looking to capture in your image. The beauty of a DSLR is the control you have over the way your image will look. That said, a "one-size-fits-all" setting that would essentially turn your DSLR into a point-n-shoot and I don't think that's what you want to do with your fine camera. Read a few more camera technique books and get yourself a more thorough understanding of photography and I guarantee you'll be glad there's not a 'one-size-fits-all" setting on your camera.

Two things to remember lest you be forever confused:

• Focus modes determines how the camera focuses.
• AF-area modes determines where the Auto-focus decides to focus.

Here's a deeper explanation that should help you understand all these different modes: Understanding Nikon Auto Focus.

Thanks very much Dave D and Horoscope Fish - all really helpful tips and hints for me.
Can I ask one question, Dave?


When photographing a number of people in AF-A, your camera software is calculating all the various subjects (faces) and will then determine the optimum hyperfocal point that will allow all the faces (or whatever it is you've told the camera is the subject) in focus.


Would I be wrong therefore to ever use AF-S when taking a photo of a group of, say, 3 or 4 people? Something such as a family shot or dinner party? Would AF-A work best? Also, with the focus area setting, if taking the same group shot, would I need to use Auto Area AF (or 3D tracking) in order to enable the camera to focus on a wider area rather than one of the single 11 black dot focus points?

Sorry if this seems a really daft question but thank you very much for your help.

Alex

It would really depend upon the depth of field and how far each face is in distance to your camera. Typically you can overcome this difference by expanding the depth of field to include all your subjects. As your aperture gets smaller your 3-dimensional in-focus "slice" of space will expand. So that anything within that "slice" of space will be in focus. So to answer your question, no, it's not bad provided all your subjects are within the focus slice (depth of field)...if that makes any sense.

As for 3-D tracking, I've not had a lot of success with that mode and tend not to use it. Each time I've tried to use the 3-D it seemed my subject was slightly out of focus.

PapaST said:

I use a smaller focus area like dynamic 9 point for something I can easily track and 21 or 39 point for something that is a little more erratic and therefore harder to track. 3D tracking focusing adds the element of color. So it can also attempt to focus on the color (assuming the subject color is different than the background).

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I am guessing this is not something one can set on the D3100. Or at least I don't think I have seen anything about setting the number of points. Or did I misunderstand what you were talking about?

Thanks to the OP for asking these questions, interesting stuff.

As for books to read, does anyone have any suggestions? I am looking for eBooks and have searched iBooks on my iPad and also looked at many of the apps that are available out there. What I would really like to get would be an inexpensive app as many of the ones I have read the descriptions for not only have the information in print but also have descriptive videos. I am also wondering about the videos that are available for purchase like at Best Buy, etc. that say they are instructional. Are they generally worth the money or would I be better off with an app or a book? I just like to idea of an app because I will always have my phone on me and if I have the information at my fingertips I am much more likely to use it. I will also search the forums to find threads about this but any suggestions would be GREATLY appreciated!

ladytonya said:

Thanks to the OP for asking these questions, interesting stuff.

As for books to read, does anyone have any suggestions? I am looking for eBooks and have searched iBooks on my iPad and also looked at many of the apps that are available out there. What I would really like to get would be an inexpensive app as many of the ones I have read the descriptions for not only have the information in print but also have descriptive videos. I am also wondering about the videos that are available for purchase like at Best Buy, etc. that say they are instructional. Are they generally worth the money or would I be better off with an app or a book? I just like to idea of an app because I will always have my phone on me and if I have the information at my fingertips I am much more likely to use it. I will also search the forums to find threads about this but any suggestions would be GREATLY appreciated!

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Good book for the '3100 is The D3100 Digital Field Guide. It's what the manual that came with your camera should have been. Tons of information that will demystify all those buttons and menu options without getting deeply technical.

A quick and dirty guide can be found on Ken Rockwell's site: D3100 Users Guide. While I'm no fan of KR, I gotta admit the information on the buttons and settings is pretty solid and since it's a webpage you can "take it with you".



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I really like Michael Freeman's books on composition. As for a basic photography book, I would suggest any edition of Langford's photography books. Langford's books are single most used textbook for both beginning and intermediate photography classes. Very in-depth and very readable.

MinnBen said:

I am guessing this is not something one can set on the D3100. Or at least I don't think I have seen anything about setting the number of points. Or did I misunderstand what you were talking about?

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You might be right MinnBen. I'm not too familiar with the D3100 so there might be features that are not included with that model. Sorry if I confused things.

Cool! The Digital Field Guide is available in digital format, at least in iBooks. The User's Guide doesn't appear to be. Actually, doesn't appear to have any digital books. Michael Freeman's books are available digitally but none of them seem to be specific to any particular camera, I need to learn to use my D3100 before I start reading about composition, etc. LOL! As for Langford, I do a search on that name and there are way too many results. How about a first name or the name of a book? Great advice, everything. Thanks!

PapaST said:

You might be right MinnBen. I'm not too familiar with the D3100 so there might be features that are not included with that model. Sorry if I confused things.

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No problem, PapaSt, I was just making sure.

​For what it's worth, I nearly always now focus manually because I just can't get the hang of auto settings. If it's a moving shot (birds, sport) I just take loads and hope one turns out okay (which is usually the case). I suspect this is probably heresy on here, but life's too short!