Back Button Focusing

[jenkins]

<p>I'm going to ask some pretty basic questions here about this as at the moment I am struggling with it a little, it does feel rather alien to me and I have a fair share of blurry pictures.</p>

<p>I've got a feeling I am over thinking this as it is a new way of working for me. I don't usually recompose when I take pictures using auto focus so bear that in mind. </p>

<p>So there is a deer in a field, centre point on deers eye and focus, recompose, hit the shutter.</p>

<p>Isn't there a danger of this deer moving in this time, if only a smidgen? I got the picture I wanted but a few were off. Also while I am at it, does the recompose mean I can zoom in too or does that take another refocus?</p>

<p> </p><div></div>

[leslie_cheung]

The fl/aperture/distance are critical here. I usually have no problem but i use a wide zoom. When i use the 85mm at at close to wide open, i shot a bunch to be cautious...

[mike_halliwell]

<p>OK, EXIF says it's a D7000 with a 16-85mm @ 65mm @ 1/125@f8 ISO 100....date thinks it's 14th Aug <strong>2011?</strong><br /> <strong><br /></strong>So, with regard to the title, I assume you used the AF-ON back button, locked on whilst set on AF-S, reframed and used the shutter-button to shoot?</p>

<p>AFAIK, if you zoom with most lenses you will still need to refocus.</p>

<p>RE.. Deer movement, that's a risk whenever using AF-S. You could use a focus point a few to the right, ie over the deers eyes, and use AF-C.</p>

[Andrew Garrard]

<p>Focus and recompose always suffers both from the rotation of the focal plane (which Hasselblad try to compensate for with motion sensors) and subject movement. It's why I always select the correct focal point when possible (easier with a 51-point sensor). With cameras with fewer points, focus-and-recompose is more common, and you have to live with the issues. That's irrespective of whether you use AF-On or single-shot focus with shutter button half press. Given a decent depth of field and a static subject, and it probably doesn't matter much; shoot at f/2.8 with a 36MP sensor and it probably <i>does</i> matter.</p>

[leslie_cheung]

Side question...when was the

back af button first implemented

at nikon btw, F5?

[jenkins]

<p>Actually Mike I have it set to AF-C at the moment and not AF-S, and everything else set as you said, my thinking was say the deer started walking towards me then holding down the focus button would help me out, it is locked on a single focus area though.</p>

<p>I am cautious too Leslie, I am not very comfortable with this at the moment. </p>

<p> </p>

[joseph_smith3]

<p>With back button focusing, if the subject is moving, you keep the button pressed and the focus point centered on the portion of the subject you want in sharp focus, like the deer's eye or face. You have set AF-C, not AF-S. You want to be in Dynamic Area--AF, probably with D 9 set. You do not want to be in Auto Area AF. There is an excellent AF tutorial AF for the D 7000 that you can find on the Internet. It is entitled "Nikon D7000 Autofocus System explained." If D( does not result in good images, try D 21 or maybe even Single point--all under AF-C. D-39, if selected, may be causing the problem. Joe Smith</p>

[joseph_smith3]

<p>Here it is:</p>

<p><a href="http://www.pixelfinesse.com/_docs/D7000_AF_Explained.pdf">http://www.pixelfinesse.com/_docs/D7000_AF_Explained.pdf</a></p>

<p>Joe Smith</p>

[Dieter Schaefer]

<p>(a) once you get used to back button focusing (i.e. using AF-ON), you won't be going back! I've been using it for about a year now and can't believe I waited that long!</p>

<p>(b) I know of no reason why the camera should be on AF-S; AF-C is the way to go. It gives you continuous focusing with the button pressed and locks focus when the button is released - the choice is right in your thumb!</p>

<p>© AF-ON doesn't activate VR - which is still on the shutter release - this can be a bit problematic at times.</p>

<p>(d) I try to avoid the focus and recompose for the reasons already mentioned above by Andrew. Whenever possible, I select the AF area and position it where I want it to be. The choice of whether to use 9 or 21 is only relevant for tracking something that moves - using 9 is slightly faster but has the risk that none is actually "on target". If I want to make sure and am confident I am up to it, I only use a single area.</p>

<p>(e) I almost always shoot at least two or even three images - just to increase my chances that the AF didn't screw things up. My cameras are all on CH - I just need to be fast with my finger if I don't want to fill up the cards fast ;-)</p>

<p>(f) the lack of a dedicated/properly placed AF-ON button is one of the main reasons I don't like the D7000/D7100 and D600. It's not that I need the AE-L/AF-L button for something else - it's that its not properly located.</p>

[jenkins]

<p>Thanks for the link Joseph, this is basically what I have set on my camera. I am thinking about unlocking the single focus as I am not really confident on recomposing. But that means I am almost back where I started using auto focus? Isn't the point of this technique to focus outside the array?</p>

<p><a href="

[richard_driscoll]

<p>If you are in AF-S then I don't understand the difference between, a) using the AF-ON button and, b) holding down the release before recomposing which at the default setup will lock focus. Can someone enlighten me please?</p>

 

[eric_arnold]

<p>not sure why you'd need VR on in that situation but what others are saying is basically right: use AF-C for any moving subject, keep your finger on AF-On button, snap multiple frames, move focus point to where you want it. an object moving directly at you is the hardest for the AF system to track btw; if you can line it up on a diagonal axis its easier.</p>

[lex_jenkins]

<p>Keep in mind that for critical focus with fast lenses wide open, focus and recompose isn't the best technique. Focus can shift just enough off the desired target to cause problems. Matt created an illustration that shows the problem - maybe can post the link or repost the illustration.</p>

<p>With slower lenses, or stopping down faster lenses, especially with DX or smaller sensors, it's not as critical. Focus and recompose probably works well enough most of the time.</p>

<p>I use the thumb button focus only for stationary subjects, and I'll usually jog the single focus sensor over to cover the desired target while composing as desired for the final photo.</p>

<p>Otherwise, since I mostly shoot candids - and, frankly, I'm not particularly picky about focus, blur, or... well, hell, I"m not even picky about basic technique - I normally use continuous AF assigned to the shutter release button.</p>

<p>Ideally subject tracking focus would handle this but so far I haven't seen one foolproof enough to ensure critical focus on a subject's eye with shallow DOF. Subject tracking combined with face recognition is good enough for slowpoke variable aperture zooms, especially with DX or smaller sensors, since the DOF provides a nice cushion.</p>

[bob_flood1]

<p>A little historical trivia: the original and technically correct definition of a zoom lens is one that varies focal length AND maintains focus when zoomed. Use of the term zoom to mean a lens that doesn't maintain focus during zooming is incorrect, but has been universal practice at least since WWII. I am not aware of any variable focal length lens for a still camera made in my lifetime that meets the true and correct definition. A friend of mine who was a TV cameraman told me there are some zooms that maintain focus that are used for filming motion pictures and similar demanding projects, but I've never seen one.</p>

<p>Trivia Part 2: just to show you that your telephoto isn't a telephoto, the original definition was a long focal length lens that is physically shorter than its focal length. The term telephoto has also been used incorrectly since WWII.</p>

<p>We now return you to your regularly scheduled programming. :^)</p>

 

[sjoerd_leeuwenberg]

<p>great trivia Bob,<br>

Your telephoto remark tells me that my novoflex 600mm is not a telephoto, since it has only one lens and is 600mm long, haha.<br>

My solution to the problem would be that you write Nikon to implement more (cross) focus points and more widely spread over the image, then Nikon would implement this in the D400 that they can finally create then, we would buy it and be happy. I am wondering if they do not spread the points out more because that would require a bigger sub-mirror and that doesn't fit.</p>

[Andrew Garrard]

<p>Sjoerd: Yes, I believe the geometry of the secondary mirror makes AF point distribution hard. That's why the AF points are central on an FX camera - the same mirror box depth as DX is more restrictive on FX. Canon seem to have managed a little more flexibility even with a shorter flange distance on the 5D3, but there's still a lot of clustering; nobody makes an SLR with full frame phase-detect AF. The simplest solution is probably a combination of contrast-detect focus and on-sensor phase-detect, as in the 70D. Look on the bright side - split prism screens and rangefinders were (okay, <i>are</i>, Leica) far more restrictive.</p>

[robert_k1]

<p>OP, these may be of interest:<br>

http://www.photo.net/beginner-photography-questions-forum/00bsbr<br>

http://improvephotography.com/4552/back-button-focusing/<br>

http://digital-photography-school.com/back-button-focus<br>

http://www.zachandjody.com/blog/tuesday-photography-tips-tricks-back-button-focusing/15588/</p>

<p>BTW, like your site design and photos. But if you are in NC, why would you provide an international phone number for contact?</p>

 

[jim_momary]

<p>The diagram's link of which Lex speaks is ...<br>

<a href="/digital-camera-forum/00X8CU">http://www.photo.net/digital-camera-forum/00X8CU</a></p>

<p>Jim M.</p>

[rodeo_joe1]

<p>I'm with Richard on this, i.e. why use the AF-ON button at all? In this case I can't see any difference between using the back-button and half-pressing the shutter release after re-positioning the AF point over the subject. If you're relying on matrix metering then I know (to my cost) that the metering will be weighted to and centred on the AF point anyway, wherever it is in the frame.<br /> So unless you're using spot or average metering, or particularly need to hold a previous meter reading, then I see no need or advantage to using the back AF button over the shutter release.</p>

<p>Bob, I'm glad that someone else is still pedantic enough to care about the difference between a varifocal and a zoom, and between a long-focus lens and a telephoto. However, I believe that the original Voigtlander "Zoomar" was in fact a varifocal. It's also unwise, IME, to expect a zoom lens to hold absolute focus over its entire zoom range.<br /> Now if we could just stop people calling flashguns "strobes", writing dots-per-inch or dpi when they mean pixels-per-inch and calling close-up lenses "diopters", then the world would be a less confusing place.</p>

<p>PS. Simon, since this thread is indirectly about composition. Could I suggest a vertical format might have framed the subject better, as well as moving the camera position slightly to the left to avoid the ugly flats in the background?</p>

[jenkins]

<p><strong>PS. Simon, since this thread is indirectly about composition. Could I suggest a vertical format might have framed the subject better, as well as moving the camera position slightly to the left to avoid the ugly flats in the background.</strong><br>

<strong> </strong><br>

I have only encountered remarks about the flats from one other Englishmen which I am myself, but having spent 5 years in North Carolina and just returned, I realise that deer and flats are pretty unique, google deer and and flats and post a link? Man encroaching on nature was my thinking, do you get it?<strong><br /></strong></p>

<p> </p>

[lex_jenkins]

<p>Yeah, I grokked that the purpose of the photo was to show the odd context of deer near high rise residences. The closest thing I've seen to that was seeing foxes in small patches of wooded areas in the suburbs just north of Chicago. Possums, racoons and hawks are pretty common in my suburban neighborhood, and wild turkeys are common not far from here. But I'd be surprised to see a deer with a rack like that in my neighborhood.<br /><br /></p>

[keith reeder]

<blockquote>

<p>google deer and and flats and post a link?</p>

</blockquote>

<p>Simon:<br>

http://www.stevebloom.com/images/b/007391-SR1.jpg<br>

http://www.terrywhittaker.com/data/photos/398_1red_deer_urban_02.jpg<br>

http://news.bbc.co.uk/media/images/46727000/jpg/_46727623_reddeer(9).jpg<br>

<a href="https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcR4SruXsNx0VBO9hLlNRG2jGlacJlzAZ_ftZusZLTlh-3unctF5">https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcR4SruXsNx0VBO9hLlNRG2jGlacJlzAZ_ftZusZLTlh-3unctF5</a><br>

http://farm9.static.flickr.com/8213/8292744515_6107cf7f04.jpg<br>

<a href="http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2011/12/16/1324048622040/A-Red-Deer-stag-006.jpg">http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2011/12/16/1324048622040/A-Red-Deer-stag-006.jpg</a><br>

http://farm8.staticflickr.com/7228/6867519452_a4b1d99ad2_h.jpg</p>

<p>It's been done, mate.</p>

 

[jenkins]

<p><strong>It's been done, mate.</strong><br>

<strong> </strong><br>

Thanks Keith for reinforcing my view that Richmond Park with the flats in the background is a pretty unique scene to have a deer set in. If your thinking was as it appears I was the first photographer since the parks opening in 1634 to consider including the flats or point a camera in that general direction, well that's extremely funny. Thanks for the laugh.<strong><br /></strong></p>

<p> </p>

[lex_jenkins]

<p>Well, hell, time to trash my camera. <a href="

been done</a>.</p>

[jefflipsman]

<p><a href="/photodb/user?user_id=323291">Dieter Schaefer</a>: © AF-ON doesn't activate VR - which is still on the shutter release - this can be a bit problematic at times.<br>

<br />I didn't know that. I just switched to using the AF-ON button to activate focus earlier this summer during a two week photo class with Marsel Van Oosten. That might explain why the rhino photos weren't as sharp as I expected. But what's the upshot? VR is still engaged when you press the shutter release. Does it affect the precision of focus acquisition itself? You say, "...problematic at times." Can you elaborate? Thanks!</p>