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Subject: "Auto Focus Confusion" Previous topic | Next topic
TomNJ Silver Member Nikonian since 23rd Nov 2006Mon 01-Apr-13 09:57 PM
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"Auto Focus Confusion"


Parlin, US
          

I am a little confused by all the auto focus options offered on my D7100. I am trying to set the camera for capturing birds and military aircraft in flight, usually against a sky background, using my Sigma 50-500 OS lens at 500mm. I would like to swing the subject into the viewfinder, half-press the shutter release, and have the camera find the subject, focus on it, and hold focus even as the moving subject shifts around in the viewfinder while panning. To do this, I am using AF-C focus mode with 51 focus points. Is this the best way to accomplish my objective, or should I be using 3D Tracking or Auto-Area AF?

Thanks!

TomNJ

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Replies to this topic
Subject Author Message Date ID
Reply message RE: Auto Focus Confusion
dm1dave Administrator
02nd Apr 2013
1
Reply message RE: Auto Focus Confusion
TomNJ Silver Member
04th Apr 2013
2
Reply message RE: Auto Focus Confusion
BrianNK
04th Apr 2013
3
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SaskPhotog
08th Apr 2013
13
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JosephK Silver Member
07th Apr 2013
7
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TomNJ Silver Member
07th Apr 2013
8
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gfinlayson Silver Member
07th Apr 2013
9
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VR8 Silver Member
06th Apr 2013
4
     Reply message RE: Auto Focus Confusion
gfinlayson Silver Member
06th Apr 2013
5
          Reply message RE: Auto Focus Confusion
VR8 Silver Member
06th Apr 2013
6
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SaskPhotog
08th Apr 2013
10
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VR8 Silver Member
08th Apr 2013
11
                         Reply message RE: Auto Focus Confusion
SaskPhotog
08th Apr 2013
12
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VR8 Silver Member
08th Apr 2013
14
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Clint S Silver Member
14th Apr 2013
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TomNJ Silver Member
14th Apr 2013
16
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gfinlayson Silver Member
14th Apr 2013
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TomNJ Silver Member
14th Apr 2013
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gfinlayson Silver Member
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dm1dave Administrator Awarded for high level knowledge and skills in various areas, most notably in Wildlife and Landscape Nikonian since 12th Sep 2006Tue 02-Apr-13 12:36 AM
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#1. "RE: Auto Focus Confusion"
In response to Reply # 0


Lowden, US
          

Yes - you are on the right track.

For shooting birds I usually use 9 or 21 focus points rather than all 51. Try to keep the subject as close to the center of the frame as possible.

If you find that focus jumps off of the subject often then try setting Custom Setting A3: Focus Tracking with Lock-On to a higher number. You may have to experiment with this setting to find what works best for you.

I do not recommend Auto Area AF or 3D tracking for birds and aircraft. Auto Area takes away all of your control of the AF system and the 3D tracking option works best with people and closer subjects.

Dave Summers
Lowden, Iowa
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TomNJ Silver Member Nikonian since 23rd Nov 2006Thu 04-Apr-13 04:43 PM
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#2. "RE: Auto Focus Confusion"
In response to Reply # 1


Parlin, US
          

Thanks Dave! The problem I am having is acquiring initial focus on a military jet flying overhead with the lens at 500mm. The jet swings around through the viewfinder, and I need to half depress the shutter release while the jet is on the center focus point in AF-C. If I catch the jet in the focus point, the camera will focus and track it well. But if I miss, only sky will be in the focus point and the lens will hunt, causing me to lose sight of the jet and miss the shot.

Would Auto Area AF work better in this circumstance, given that the jet is the only subject in a field of blank sky?

TomNJ

Please visit my Nikonian Gallery

Victorian Watercolors

  

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BrianNK Registered since 25th Feb 2013Thu 04-Apr-13 07:20 PM
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#3. "RE: Auto Focus Confusion"
In response to Reply # 2


US
          

Don't tell anybody on this site... but my favorite hobby is building/flying/crashing remote control airplanes. I would assume shooting a real plane is about the same as shooting R/C (at a slower speed )

I would recommend AF-C with Dynamic 21 point focus. 21 point gives you a little more room for error over 9 point. 51 seems to confuse the camera too much.

I would also recommend using 'Back button focusing' (AF-ON). This moves your focus button from the shutter button to the 'AE-L/AF-L' button on the back of the camera (hence the name.. back button focusing). You'll either love it or hate it. AF-ON (for me) separates the task of focusing AND targeting the plane. On the D7100 its super easy to switch back and forth (AF-ON vs. normal shutter button) with the 'i' button.

Then you need to get a tall monopod <--- This is a MUST!!

Good luck!

  

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SaskPhotog Registered since 07th Mar 2013Mon 08-Apr-13 06:18 PM
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#13. "RE: Auto Focus Confusion"
In response to Reply # 3


CA
          

Yup, use to the same with model aircrafts and dioramas. So you are not alone Brian. Try rocketing. You'll love it.. But you got to be fast!

  

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JosephK Silver Member Nikonian since 17th Apr 2006Sun 07-Apr-13 02:04 AM
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#7. "RE: Auto Focus Confusion"
In response to Reply # 2


Seattle, WA, US
          

If you have a clear sky, give the auto-area setting a try. If it works for you, great. If not, now you know.

My recommendation would be AF-C in 21-point mode. Start the lock-on and tracking _long_ before you are ready to take the picture.

---------+---------+---------+---------+---------+
Joseph K
Seattle, WA, USA

D700, D200, D70S, 24-70mm f/2.8, VR 70-200mm f/2.8 II,
50mm f/1.4 D, 70-300mm f/4.5-5.6 VR, 18-70mm f/3.5-4.5 DX

  

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TomNJ Silver Member Nikonian since 23rd Nov 2006Sun 07-Apr-13 01:35 PM
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#8. "RE: Auto Focus Confusion"
In response to Reply # 7


Parlin, US
          

Now that we have some beautiful weather here in swVA we should get some F15 flyovers today and I'll give the Auto setting a try. If not I'll practice on some hawks.

My problem is the initial target acquisition. I can get the flying jet in the viewfinder, but locking on with just the one center sensor is challenging. My understanding is that 21-point and 51-point options both require initial lock-on with just the one center sensor before the other sensors kick in to hold focus. Do I have that right?

Since the jet is the only object in a clear blue sky background I am hoping the Auto setting will find it and lock-on faster than I can.

TomNJ

Please visit my Nikonian Gallery

Victorian Watercolors

  

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gfinlayson Silver Member Nikonian since 24th Jan 2011Sun 07-Apr-13 04:28 PM
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#9. "RE: Auto Focus Confusion"
In response to Reply # 8


Maidenhead, GB
          

The 9, 21and 51 point dynamic modes require you to lock in the focus with your selected focus point first. It doesn't have to be the centre one. You then have to keep your subject under that focus point as much as possible. The AF system will then use the surrounding points to try to maintain focus if you drift off the chosen focus point.

  

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VR8 Silver Member Nikonian since 04th May 2008Sat 06-Apr-13 02:38 PM
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#4. "RE: Auto Focus Confusion"
In response to Reply # 1


Ottawa, CA
          

There is unfortunately very little on Dynamic Focus in any of the manuals. Any pointers on the best advice? Thanks


Victor

My website: www.rakmilphotography.com

  

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gfinlayson Silver Member Nikonian since 24th Jan 2011Sat 06-Apr-13 07:30 PM
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#5. "RE: Auto Focus Confusion"
In response to Reply # 4
Sat 06-Apr-13 07:35 PM by gfinlayson

Maidenhead, GB
          

The most comprehensive explanation of Nikon autofocus modes I've ever read is here: http://www.pixelfinesse.com/_docs/D7000_AF_Explained.pdf

It's written for the D7000, but it's equally applicable to the D7100, the only difference being 51 rather than 39 focus points to choose from.

The D9 and D21 are the best modes for following aircraft or birds in flight. The fewer AF points in use, the less hard the AF system has to work. You can improve your keeper rate massively by practising following birds in flight. The more you practise, the better you get at keeping your subject within the relevant group of focus points. I'd recommend starting with D21, and then tightening down to D9 as your skill improves.

I'm currently perusing the D7100 manual whilst waiting on the postman ringing the doorbell to announce the arrival of mine.

In the meantime, I'm wringing the neck of my D7000's AF system chasing birds in flight.

Graeme

  

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VR8 Silver Member Nikonian since 04th May 2008Sat 06-Apr-13 09:27 PM
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#6. "RE: Auto Focus Confusion"
In response to Reply # 5


Ottawa, CA
          

Much appreciated! Will read with interest. I had the chance the test today and I can see both the improvement and the need for practice! Now I have to work in fill flash..


Victor

My website: www.rakmilphotography.com

  

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SaskPhotog Registered since 07th Mar 2013Mon 08-Apr-13 01:27 PM
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#10. "RE: Auto Focus Confusion"
In response to Reply # 6
Mon 08-Apr-13 01:35 PM by SaskPhotog

CA
          

Good morning Victor.

Just read your words. The fill in flash thing is v cool. In
the old days it was called the synchro sun technique.

I use it quite often on daylight conditions. Love it. If you
shooting with humans, as opposed to shooting humans, this
technique makes them really pop out in the image.

There are something to be careful about though.

If this interests you, I will be happy to expand.

Happy shooting! (not humans though)

Guy

BTW Victor, Ottawa CA is my home town. How did Winterlude go
this year?

  

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VR8 Silver Member Nikonian since 04th May 2008Mon 08-Apr-13 02:45 PM
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#11. "RE: Auto Focus Confusion"
In response to Reply # 10


Ottawa, CA
          


I use fill flash quite a bit on insects and birds (see my galleries in the link below). My comment was a bit of joke. There are too many variables to get right when seconds count with birds and insects. So any help with auto-focus is appreciated. Fill and auto iso don't work.

As for Winterliude, not much a of winter guy though I walked to whole canal to see what was what. My fear is this winter will never end, they are predicting snow for Friday!

All the best and hoping to get out to Saskatchewan one of these days.

Regards.

Victor

My website: www.rakmilphotography.com

  

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SaskPhotog Registered since 07th Mar 2013Mon 08-Apr-13 06:16 PM
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#12. "RE: Auto Focus Confusion"
In response to Reply # 11


CA
          

Hi Victor,

I'm not much of an entomologist, but I did play with a tarantula one early spring morning in the Santa Catalina mountains near Tuscon, AZ. It was cool (all pun intended) to be able to have this thing walk up on a stick, every so slowly. Dina get pics though, was too worried about the snow beginning to fall and all my stuff being spread out etc. Long story, but a great one.

OK, here's what I've learned to do with fill (synchro sun). Never mind dedicated flash, TTL or anything like That. That has never worked for me. except in the beginning when i really did not know what I was doing.

You may note in a previous post that I my background is in broadcasting. although an engineer by trade, I did learn to use a light meter through osmosis.

Could not do without one today. (Specially for video)

Sorry for the unfounded verbiage. I'll get to the point now.

It's about 18% grey. Always has been. ask Ansel Adams about that. Oops, you'd have to be on the other side to do that. LOL.The meter I use has both incident and reflected features. additionally, I can look through a part of the meter to spot check my exposure.

So basically, junk the auto stuff, go full manual and use the force Luke :)

Grey cards, specially Kodak ones are still the photog's best friend! I've got an 8x10 and a 3.5 x 5 in my kit at all times.

To meter something like an insect is a tough proposition. The reflectance range of it's body can range from white to black, from red to green and God knows how many levels of grey there are on some.

So basically, only to repeat myself, dump the auto everything. Go full manual. Shoot in NEF, then adjust to your heart's content before going HDR. (Yup, I've faked a few HDR results simply by using camera raw on NEF stuff to increase/reduce exposure, then HDR processing.

Man, I could NEVER do that with Kodachrome! (and I've pushed that stuff 4 stops. Kodak processed it anyhow, sent me back a number of free rolls and they were amazed). But once again, I digress.

Insofar as auto focus is concerned, I made the switch from Canon to Nikon when I bought my F90x. I still prefer split screen focusing mattes, but hey, rolling stone and all that. Oh, I'd love a leica range focus too. Not even sure if they make them anymore.

Used to be a time when predictive focus meant stopping down to increase depth of field. You;d be hard pressed to find a 50mm 1.2 auto lens today. Or even afford a 2.8 300mm.

Hope this helps!

Guy

Have faith, It will guide your fate.

BTW, if that is you in the pic, V cool gear mon ami!


  

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VR8 Silver Member Nikonian since 04th May 2008Mon 08-Apr-13 09:47 PM
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#14. "RE: Auto Focus Confusion"
In response to Reply # 12


Ottawa, CA
          

We are way off topic here but so what. When I started it was manual everything, including focus and like you I miss fresnel or split screen focusing, By force of habit I have a lightmeter that does spot and incident. I have a gray card but prefer datacolor's spydercheckr.
Manual operation of the Nikon cameras still has immense advantages, however, given all the attributes of my Nikon I am trying to figure out what of the built in technology works for me.

For the past year, and this is on topic I have used the Ae-l button as AF-on, I find AF-c to be a miracle most of the time. My Sb-900, with a little tweaking does fill flash very well. All this got me good shot of a fly today. There would have been no time to use either a lightmeter or gray card. I would definitely use that for stills and in nature something like litchen.

Dynamic focus may work best for birds and I intend to try that with a 300 f2.8 as soon as I can.

In the end the D7100 is a jump up from the D7000 and I want to see what works and does not for me.

But the weather here seems to get worse not better which is messing with my planning!

All the best!

Victor

My website: www.rakmilphotography.com

  

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Clint S Silver Member Nikonian since 02nd Jan 2011Sun 14-Apr-13 05:22 AM
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#15. "RE: Auto Focus Confusion"
In response to Reply # 0


Chula Vista, US
          

Tom,
You really want the subject within the viewfinder, not flying through the viewfinder area, before you try and lock focus. You may want to zoom out to 300mm to get it in the viewfinder and then zoom back in.

Start with AF-C 21 point. As you get more skilled you will be able to move to 9 point then single, and keep it near the windshield/pilot area.

You may also want to use a tall monopod to see if the helps you pan with the plane. This is good for when aircraft are running touch and goes or normal training over populated areas. Not so much help at shows where you will want to be hand holding because of the sudden changes in motion up and down and acceleration.

Visit my Nikonians gallery - my Spare Time gallery

  

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TomNJ Silver Member Nikonian since 23rd Nov 2006Sun 14-Apr-13 01:45 PM
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#16. "RE: Auto Focus Confusion"
In response to Reply # 15


Parlin, US
          

Thanks Clint! I live under a practice route for F15s in the Blue Ridge Mountains and they often fly over rather low and fast. When I hear one coming, I grab the camera, run outside, and try to catch it as it passes over. No time for a monopod or zooming, and little time for acquisition.

I keep the lens set at 500mm and prefocused on the horizon, and the camera in A mode with Auto Iso set to raise the ISO to 1600 if the shutter speed drops below 1/1000. Most shots come out at 1/1000 sec and ISO 250 - 500. I can usually get the jet into the viewfinder, but since I am handholding and panning with a long and heavy lens, it bounces around a bit. If I hit the focus button when the jet is outside the center focus point, i.e. on the sky, the lens will hunt and the jet instantly disappears.

Here are the best shots I got so far. I'm thinking I need to go to 1/2000 second and plus 1 stop on the exposure.






I tried Auto Area AF on birds flying overhead against a sky background and it seems to recognize the subject and acquire focus faster than I can, but I need to do more practice with this on jets.

Lots of fun!

Tom

Please visit my Nikonian Gallery

Victorian Watercolors

Attachment #1, (jpg file)
Attachment #2, (jpg file)

  

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gfinlayson Silver Member Nikonian since 24th Jan 2011Sun 14-Apr-13 01:54 PM
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#17. "RE: Auto Focus Confusion"
In response to Reply # 16


Maidenhead, GB
          

If you're using matrix metering, try switching to centre-weighted metering with -0.3EV exposure dialled in. That should sort out your exposure.

  

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TomNJ Silver Member Nikonian since 23rd Nov 2006Sun 14-Apr-13 11:24 PM
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#18. "RE: Auto Focus Confusion"
In response to Reply # 17


Parlin, US
          

Yes I have been using matrix metering. I considered using center weighted, but was afraid it would capture mostly sky and under expose the jet. I'll have to give it a try.

Tom

Please visit my Nikonian Gallery

Victorian Watercolors

  

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gfinlayson Silver Member Nikonian since 24th Jan 2011Mon 15-Apr-13 08:26 AM
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#19. "RE: Auto Focus Confusion"
In response to Reply # 18


Maidenhead, GB
          

Matrix metering looks at the whole frame and will try to prevent blown-out highlights, often at the expense of underexposing the main subject.

With center-weighted, it still looks at the whole frame, but biases metering towards the central area. The size of this area can be adjusted using Custom Setting b4.

If you're framing your subject off-centre, then spot metering will meter at the active focus point. Again, I'd recommend about -0.3 EV compensation with spot metering.

  

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