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New to DSLRs? A Beginner's Guide to Exposure and an Explanation of Lens Diffraction

05.5.12 @ 9:58PM Tags : , , ,

Exposure is one of the most important aspects of shooting with DSLRs. If you’re new to shooting with digital cameras, it can be a bit overwhelming to fully understand all of the terminology and the options for controlling the exposure of the image. Film is pretty straightforward, where the film speed (or ISO, ASA, etc.) does not change. Shooting pictures is a bit more complicated, as the film speed can change, so you’ve got aperture, shutter speed, and ISO as three different settings to affect exposure. Shooting video is a bit different, as the shutter speed of DSLRs will typically not go below 1/30 of a second. We’ve got two videos explaining exposure and control, with the first being a beginner’s guide to overall exposure, and the second explaining what happens as you stop down your lens.

The Three Basics of Exposure and Photography from Matthew Gore:

Taking into considerations all of the factors that affect exposure is important. We must constantly be thinking about what we’d like our image to look like and how the camera settings will get us there. The guide is geared towards still photography, but the same factors apply to video, except of course, for shutter speed, which should stay between 1/30 and 1/60 of a second for proper looking motion. If you’re shooting 24fps, 1/50 is the “correct” shutter speed and if you’re shooting 30fps, 1/60 should be your setting. These will render normal looking motion for the given frame rates. Setting the shutter below these will give you more motion blur and ghosting, and setting above will give a more staccato and stroby feel.


There are certain times when you’ll be outside and your ISO is already at the lowest setting (usually 100 or 200), and the shutter is set at 1/50 or 1/60 for normal motion, but the image is overexposed. You’ve got two options, raise the f-stop, or raise the shutter. In some cases you’ll have to do both if you don’t have any neutral density filters to cut down light, but raising the f-stop too high (usually f/8 and above), may yield less than ideal sharpness in your videos. The embedded video below explains the repercussions for setting the f-stop too high, which exacerbates an effect know as lens diffraction:

The link to the D800 samples can be found here. If you want to get the most out of your lenses, you’ll need to know their diffraction point with your specific camera to get the sharpest images possible. Many professional cinematographers like staying between f/2.8 and f/5.6, as these are usually the sweet spot for lens performance and controlling depth of field (too shallow and they make it difficult for the assistant camera person to keep focus). Though there are certainly times when professionals will be shooting lenses wide open (f/1.3 – f/1.8), they are using much more expensive lenses that perform better than many DSLR lenses. So if you want the best performance from your DSLR lenses, stopping down 2-3 f-stops will usually get you to the “sweet spot” of the lens, and give you the most sharpness, while avoiding lens diffraction.

Once you’re ready to start editing your material, here’s a good resource to get you started.

[via Film School Channel on Vimeo]

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  • For a still-quick-but-a-bit-more-in-depth introduction to photography and video, I have this tutorial over here: http://www.similaar.com/foto/tuten/index.html

  • Interesting–I knew high F-stops were problematic, but never knew why.

    One question about shutter speed for video: while 1/50 is the “correct” shutter speed if you’re shooting 24p, doesn’t that also mean you run the risk of flicker in indoor lighting (in the U.S.)?

    I’ve heard many people recommend always leaving the shutter at 1/60 when you’re shooting indoors in the U.S. or any 60Hz country, no matter whether you shoot 24p or 29.97. I’ve followed that advice and found the difference between 1/50 and 1/60 to be pretty minimal in practice, and I’ve avoided flicker. But maybe that’s not the best approach? Maybe it’s still worth shooting 1/50 for the slight difference in look? What do you think?

    • Flicker really depends on the source, most incandescent light bulbs do not flicker in my experience – usually it’s fluorescent and other cheaper sources that pose more of a problem. The difference is minimal, but I’d say keep it to 1/50 until you actually see the flicker, which shouldn’t be too often actually. But obviously if you’re comfortable the way you’ve been doing it and you haven’t had any problems with the look, don’t let me stop you.

    • Daniel Mimura on 05.12.12 @ 7:49PM

      The bible (8th edition, p328) says, “regular 60-Hz ballasts (i.e.: not kinoflo or hydroponic grow lights with high speed ballasts) can be used with commercial tubes… As with any 60-Hz fluorescent lamps, 24-fps filming must be crystal-controlled to avoid pulsating brightness changes, and any high-speed work must be at crystal-controlled multiples of 30fps. These tubes are somewhat forgiving of off-speed filming because of the ‘lag’ of the phosphors.”

      Any digital movie is as regular as crystal-sync filming, so an adjustment is not necessary.

      Shooting at 1/60 is more distracting too b/c it doesn’t smooth out the motion as much and it’s not quite close enough to “normal” film shutter speeds.

      FYI, film speed is 1/48th of a second not 1/50th…not that anyone can tell that difference by eye, (which is why the 7D’s 1/45th of a second looks okay even though it’s not a normal cine-speed.) 1/30th or 1/60th of a second is different enough to be noticeably different looking.

  • He knows his fstops but he doesn’t know how to sync video and sound.. Drives me crazy when you see a great video and the sound isn’t synced properly

  • john jeffreys on 05.7.12 @ 12:42PM

    The best (and most fun) way to learn the elements of digital image composition (iso, shutter, f stop, white balance, and focus) is to take your camera and go outside. You won’t learn much by just staring at youtube videos all day, you need hands on experience :)

    • although you maybe correct, the amount of information and the quality is improving dramatically. Sites like this and others really shed some light on the subject.
      For you and others maybe past this knowledge, but for others: its a gold mine….
      Thank You NoFilmsSchool.

  • What was he talking about when he said the light will fit in a single pixel?

  • this explanation gives clarity to the “Tilt Shift” exposure where the captured image is out of focus in desired areas of the image. This all is done in camera when the light source makes contact with the sensor and the angle of that light contacting the surface of the sensor.

    Great way to make a difficult subject matter easy to understand. thanks Joe

  • Andrew Davidson on 08.24.12 @ 2:39PM

    Diffraction wouldn’t affect shooting on film, then, correct?

  • I’m kinda new to photography. I quit online gaming in exchange for this. Thanks a lot for this small tutorial, will be watching those video of yours of youtube. Thanks Joe XD

  • Wonderful video! I’ve been looking around the web via google and it simply beggars belief how many people give tutorials on exposure with seemingly no real understanding of the real physics involved. Hats off to you for making it this simple! At the time I saw this I understood exposure but was still reeling in shock as to how much guff I’d had to read – more than 90% was either wrong, over complicated or misleading I would say.

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