TALKING IMAGES 17 – FOCUSING USING THE AF-ON BUTTON – AND A WORD OF WARNING RE OODLES OF MEGAPIXELS

 

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As a default at least, many digital cameras use the shutter button to lock focus –  a half-press of the shutter button locks focus (and maybe exposure too), after which complete depression of the shutter button takes the photo.  This seems a far from ideal way of doing things, at least for the kind of photography I do.  My Canon G11 PowerShot works in this way and that’s ok for what I use it to do.  But my Nikon DSLRs (D700 and D800) work differently, and I’m going to detail how I have them set up for use, in case anyone finds this useful – which I hope will be the case.

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Keep in mind that the various names of the buttons and processes involved may be different on your camera – the same processes may well be there, they may just be known by other names.

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FOCUSING USING THE AF-ON BUTTON

I use the shutter button solely to release the shutter.  Half-presses of this button have no functions with regard to auto focus or exposure.  Instead, auto focus is solely activated by either pressing or holding down the AF-ON button, which is sited at upper right on the camera’s rear, as shown in the photo of the D800 above, and the close up below.

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This and the AE-L AF-L button (which I’ll mention later) are ideally sited for very quick adjustments.  When holding the camera up to my eye, the lower three fingers on my right hand are holding the camera’s grip, my forefinger is on the shutter release – and my thumb falls naturally over these two buttons.  It is simply impossible to say what a perfect piece of design this is.  When my eye is at the viewfinder and my finger poised on the trigger, adjustments to focusing and exposure can be made within fractions of a second.

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The AF-ON button can be used in two ways.  First, if you’re the kind of photographer who likes to get focus before composing the shot, then you simply place the focusing point over the part of the photo for which you want precise focus, press the AF-ON button, and sharp focus is achieved in a moment.  I always use just the central focusing point for focusing.  After you’ve focused in this way, you then reframe to achieve the composition you’re after.

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Alternatively, if your subject is moving, you can place the focusing point over it and simply hold the AF-ON button down to obtain continuous focus – and then press the shutter button whenever the moment is right.  And if you’re into this kind of photography, then the choice between AF-S and AF-C priority selection is important.

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AF-S AND AF-C PRIORITY SELECTION

AF-S priority selection means that the shutter will only fire when the camera is focused on whatever is below the chosen focusing point.  I avoid AF-S priority like the plague because I often have intentionally out of focus detail in my photos – and if I’m hell-for-leather firing at something that is moving, I want the camera to fire WHENEVER the shutter release is pressed, whether focus has been achieved or not.  In a nutshell, I refuse to be in the situation where the camera is the one that decides whether or not the shot will be taken!!!

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So, AF-C priority is far, far more to my liking, because it allows me to fire the shutter at any time whatsoever – irrespective of whether focus has been achieved or not.  And, with my thumb holding down AF-ON, adjustment of focusing is continuous, so that whatever is moving fast out there in front of me, the camera is doing its damnedest to get it in focus (while also in fact trying to predict where the subject will move next – but that is another story).

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THE AE-L AF-L BUTTON

I have this set up to lock exposure when it is pressed, and to retain that exposure until either it is pressed again or the camera is switched off.

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This locking only works with centre-weighted and spot metering, it does not work with the multi-segment measurements that Nikon calls Matrix Metering.  But, once again, the ability to instantly lock exposure is exceedingly useful – and this button is again there, right under my thumb.

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I don’t enjoy being rushed when taking photos, but the methods outlined above help take some of the sting out of it – I hope they are useful.  Now for something else.

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AFTERTHOUGHT: CAMERAS WITH HIGH NUMBERS OF MEGAPIXELS – A WORD OF WARNING

Camera manufacturers need to sale their wares and will fasten onto any aspect of their cameras that they think will give them a sales advantage over their rivals.  A good example of this has been the megapixel (MP) race, with the basic, crude assumption having been that the more pixels there are the better – the more easily you will be able to take your photography up to that much vaunted “next level”.  It has materialised that simply cramming sensors with more and more pixels is not always the best way forward, and major manufacturers have in fact reduced pixel numbers in some cases, to achieve better quality and/or performance.

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But in full frame (i.e. 35mm format) digital cameras, which is the sphere I know a little about, there are some very successful high megapixel cameras – Nikon’s D800 and D810 for example, and Canon’s newly arrived EOS 5DS and EOS 5DS R – the latter two topping 50MP.

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Now, I am NOT saying that such high megapixel cameras do not have a place.  Some photographers have a need for them – and professional photographers looking for an alternative to medium format come immediately to mind.  And many amateurs will use them too – due to the incredible picture quality that can be achieved, and/or the fact that good quality images can be derived from quite small crops of the frame.

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However, before taking the leap into high megapixels, I do urge you to consider whether you actually need such high numbers of pixels – because all these pixels bring disadvantages as well as advantages – as I know, being a user of both the 36MP D800 and the 12MP D700 Nikon DSLRs.

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On the upside of course, high megapixel cameras CAN provide astounding image quality BUT your photographic technique has to be of the highest order to achieve this – these high MP cameras are certainly unforgiving.  Using an old rule of thumb, the minimum shutter speed needed to be sure of avoiding camera shake with any lens is often quoted as (1/the focal length), so that for a 300mm telephoto, the minimum “safe” speed is 1/300th of a second.  But for the 36MP D800, it is openly advised in the photographic press that this “safe” speed should be 1/600th, if not 1/1000th for a 300mm lens – and I have plenty of experience to bear this out.  The alternative of course is to use such cameras on a tripod or other form of support but, especially outdoors, I find that overly restrictive.

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Then again, I really prefer the 12MP D700’s performance in low light – and the simple fact is that if I’m off photographing anywhere I think the shooting conditions might be challenging, I’ll take the D700 every time – it’ll be better if there’s low light, and if I have to take pictures fast or on the fly, it’ll forgive my sloppy technique and still give me useable images.  If I could find a little used D700 now, I’d snap it up at a moment’s notice.  Equally, I would love to see a, say, 15MP version of the D700.  (The D750 doesn’t do it for me, I have to say, not least because it lacks the wonderful siting of the AF-ON and AE-L AF-L  buttons mentioned earlier).

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And, quite apart from these performance characteristics of high MP cameras, there is the point that they produce large files – yesterday I was working on a file from the D800 that ended up at around 200 megabytes.  And, obviously, these larger files will eat up your disk’s storage space more quickly – files from the D700 average around 14 megabytes.  And, finally, your computer will need the processing power to handle such large photo files.

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So, I am not saying that such high megapixel cameras should be avoided, but rather that thought should be given beforehand as to (a) whether the vast detail that they provide is actually necessary for your photography, and especially so in view of  (b) the photographic technique constraints, large file sizes and computer processing power necessary for this type of photography.

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About Adrian Lewis
Photographer working in monochrome, colour and combinations of the two - with a great liking for all sorts of images, including Minimalism, landscapes, abstracts, soft colour, people, movement, nature - I like to be adventurous in my photography, trying new ideas and working in many genres. And I'm fond of Full English Breakfasts and Duvel golden ale, though not necessarily together.

12 Responses to TALKING IMAGES 17 – FOCUSING USING THE AF-ON BUTTON – AND A WORD OF WARNING RE OODLES OF MEGAPIXELS

  1. Nelson says:

    also you have to consider the quality of your lens, a higher MP camera will not give better photos with lens of mid-range quality

    Liked by 1 person

  2. underswansea says:

    Good article. I learned a great deal. Thanks. Take care. Bob

    Like

  3. Another thing to remember about the High MegaPixel cameras is the sensor is still the same size and crammed with more photosites. For night/long exposure photographers this means the sensor heats up faster. Which is another reason to stay with the lower MP cameras.

    Liked by 2 people

    • Adrian Lewis says:

      Steve, thank you very much – a very useful point. I’m wondering what full frame DSLR Nikon is going to bring out next – and hoping its not going to be some 50+MP monster. Something like the D700, with just a few more MP, would be ideal. Thanks again! Adrian

      Like

  4. paula graham says:

    Oh heavens…I just press the shutter on my 12 mp camera and hope for the best! You are right about everything you say, though and I do know that being familiar with ALL the settings and possibilities on your camera might be the difference twixt a super shot and a missed one…I know..I missed a few in my day.

    Like

    • Adrian Lewis says:

      I had a feeling that this would shake your tree, my friend, as my D700 is the cheapo version of your D3. But I’m not at all advocating being on top of ALL the settings etc on my camera by any means, these are just a very few that are extremely useful to the way in which I take photos – and the D700 is one thing, but get into the D800 and there are oodles (what a great word!) more – and I CERTAINLY don’t know what they all do!

      But if I can be so bold as to probe a little – don’t worry, it’ll only hurt when you laugh – do you use AF-S (not to be confused with AF-S lenses) or AF-C? Or manual? And aperture priority mode? Have you tried using AF-ON alone?

      I’ve no right to ask these (intimate!!!) questions because we each and every one of us have our own ways of using our cameras – apologies! Adrian

      Like

  5. mukul chand says:

    Interesting , thank you. Do keep reading to be swept off to lands unknown http://www.enchantedforests.wordpress.com and http://www.travelwithmukul.wordpress.com

    Liked by 1 person

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