The Second Most Important Button On Your DSLR

July 21, 2009

Todays tutorial is about using your digital SLR. People have been asking about my process for taking photos so I wanted to go over some of the basics of how to use digital SLRs first. I focus on how to use the Auto Exposure – Lock and Auto Focus – Lock button. It is a really powerful little button that helps you compose a better shot and fix problem scenes.


  • Nice tip, didn’t know that! Thanks!

    btw. is there a new macbook pro 17 glossy in front of you? 🙂

  • Do you typically shoot in auto, or some sort of priority mode?

  • Daniel Nascimento July 21, 2009 at 11:49 am

    What about the Manual Focus? Does you always use the Auto Focus?

  • dang is that what that button is for. thats is useful thanks.

  • i know my canon 40d has ae lock but not af lock…

    • What do you mean? By default keeping shutter half-pressed = AF lock on all Canon DSLRs I’ve used (granted, not _that_ many).

      There’s also a custom function or two where you can set variations when it comes to AE/AF behaviour between * and shutter (and AF-On if your camera has that one).

  • In my opinion, the important thing you can do with that button is to _separate_ focus and exposure.

    The last thing one should do is configure it to do both.

  • Hi Nick,

    My question isn’t related to your topic, but I have a Canon 400D and I’m thinking of buying a Canon 5D Mark II or the Nikon equivalent, but it will be really helpful if you could do a comparison, pro/con between Canon and Nikon in one of your posts.


    • I would think if you already have lens for your Canon I’d stick with the Canon.

      But you might better off comparing it on site like this

    • Hi Niku,

      One thing that you might want to consider is that with Canon digital cameras, you must use lenses designed expressly for Canon digital. Now, I’m not 100% sure about this but that’s what I’ve read. Perhaps newer models will allow mounting older lenses designed for film but I think they have different mounts.

      The D300 and other higher-end Nikons (but maybe not all…check the specs) work with older lenses because they have the same F-mount that Nikon has used since the 1950s. If you have older, non-digital lenses (Nikon calls them non-CPU lenses), you can save up to ten (on the D300) focal length/maximum aperture combinations onto the camera’s memory. When you mount a non-CPU lens, you just select its specs from the list you’ve created and this causes the camera’s metering system to compensate for the lens’ optics and the camera records the focal length and aperture settings in the image’s Exif metadata.

      There are lots of great new lenses out there but if your lens budget is limited, and you have a Nikon, you can pick up some nice old glass used at your local camera shop or on-line. On the other hand, if you have loads of cash, you could get yourself some phenomenal exotic optics that has been discontinued (like the legendary Nikkor 13mm f/5.6 for about $20,000!).

      I have a Nikon 500mm mirror lens that was made sometime around 1982 and it works great on my Nikon D300. I also have a 50mm f/1.2 that is non-CPU (manufactured in 2009) that also works like a charm except that most digital cameras’ focussing screens are not optimized for the critical manual focus that is required when shooting anywhere near f/1.2.

      Canon digitals, I am lead to believe, offer much better choice in the focussing screen department.

      If you need high resolution in a full-frame digital, Canon sells their 21 MP 5D Mark II for $2900 (here in Canada) where Nikon’s similarly-priced D700 gives you “only” 12 MP for $2600. If you want to go above 20 MP in Nikon’s line, you’ll have to spend $8000 on a 24.5 MP D3X…the same price you’d pay here for a 21 MP Canon EOS 1Ds Mark III.

      I own a APS-C sensor 12.5 MP Nikon D300, and I think it’s great. I’d love to get my hands on a full-frame 24.5 MP D3X, but don’t foresee having that kind of cash anytime soon, so I’ll just have to make do!

      Hope this helps and doesn’t confuse!

  • Hey, Nick!

    first of all, Thanks for your blog! {awesome}
    second, what I need to do if I begin traslate your tutorials for my russian friends in my country and post it in my web page…?
    third, thnx anyway)

  • This was your best one yet. Love the demonstration with the camera…it makes better sense seeing somebody else explain.


  • Hey nick! very nice and helpfull tutorial ;D
    i hope you can check out this video i made following your “cars” tutorial…and make some critics and all the people too 😀

  • Nice tips! I’d like to see you talking more about Cameras (brands, models, features…), as I’m planning on buying my first DSLR.

  • nice blog and specifically the idea of tutorials. love to hear more.

  • silly season….

  • Thanks for the tip. I was actually trying out a new 105mm 2.8 prime lens today and having a problem. Maybe someone here has an idea of what I might be doing wrong.

    I’m using it on a D40, set to Manual mode, and have the aperture ring locked so that I can change the f stop manually.

    However, when focusing on closer objects, the f stop increases (all the way to 5). I tried holding the AE/AF lock, with the same results. Is there way to keep the 2.8 aperture when focusing close on this lens?

  • Great video, as always.

    I’m liking the photography videos quite a bit! Thanks for keeping everything so simple. Sometimes reading a book or blog post about certain features can drive a person mad. Seeing it in real time is wonderful.

    Can’t wait for the next one.

  • What metering mode do you normally use?

    • Matrix metering. I posted the same question on and this was my response:

      “The effective aperture will decrease the closer you focus, this is perfectly normal.”

      So I guess I have my answer.

  • Hi Nick!
    good point on the ae lock! but… you should consider using the adjustable focus points of the camera (also right at your thumb : ) for a particular reason:
    When you shoot with wide open aperture -lets say 1.2 or 1.8 or whatever – the slightest camera movement will cause you a “backfocus”. cause when theres just few millimeters in focus, even a camera tilt will bring it out of. thats why some people wonder why they have always out of focus pictures, and the first thing i ask them if they do the point-at-the-eye-move-to-the-body-and-shoot-thingy which can cause quite frustrating results..
    just my two cents : )
    keep on your great posts!

  • Great tutorial Nick! Thanks for explaining this and helping us improve our photography repertoire. I’ve always wondered but was too lazy to seek it out :). Now I know…

  • NICK, again…


    keep doing this tutorial anytime you can.

  • Since discovering your site, my brain hurts with all the information being fed to me.

  • Good tutorial! Kind of forget it’s there sometimes. You should show us the photos you just took too.

  • Hi Nick,
    I love your blog, I learn a lot thanks to you.
    Recently, I took some pictures, which I tried to add some “your style”, here is example:
    Hope, you get a second to look at it.

  • Wish I had known about this years ago; it would have saved a bunch of time in not manually changing exposure after I recompose the shot every time. General lesson learned: buttons are in certain positions for a reason. If it’s easily accessed, find out what it does and how to use it, because it’s probably important!

  • oh… so that’s what that button does. ^_^ thanks for the tip.

    i used to experiment with the “running man” (i believe the correct term is continuous shooting) because the camera didn’t click fast enough. thanks again for the tip.

  • Brilliant video, definitely going to check that one out on my camera.

  • Great Stuff … Amazing blog .. love the idea of photography and graphics which is what i love … you tuts help me a lot at work… Thanks a lot.. cant wait to try it with my D60..

  • Hey,is their a way to replicate this feature on a Canon 500D? Im considering buying this or a D5000 and love the way Nick uses this button and its becoming a deciding factor on purchasing the camera, however the 500D seems to be better on every other point, bar the functionality of this button.

    Anyone got any ideas?



  • I know this is stupid, but I will ask anyway. So if I shoot manual mode and do manual focus, there is no use for that button right? I always shoot manual/manual. Thank you.

  • Do you have to keep holding the AE Lock AF Lock button until you press the shutter button or just one press will do it? Also, when you use a cable release, can you still use the AE Lock AF Lock button even though it might add a shake to the camera?

  • hi, and thanks for all the tutorials.
    One thing. this button isn’t the same thing as just keeping the finger half way in the Shutter Button? If I do thins, the focus and settings stay exactly the same and I can recompose my scene.
    Maybe I understood the tutorial wrong.

  • wonderful tip, like to see some of more tuts like thee.

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