A Rule Of Thumb To Help Stop Photo Blur – 31+ Days To Better Photography

Yesterday’s Topic: Quick Exposure Adjustments

Short and to the point, to help stop blur in a photo because you are moving the camera too much, use this formula:

Don't Shoot At A Slower Shutter Speed Than 1 Over Focal Length

This simple formula comes into use when you are hand-holding a camera. Those using a tripod can throw this out the window.

In practice it looks like this:

  • 18mm lens = No slower than 1/18th of a second
  • 50mm lens = No slower than 1/50th of a second
  • 300mm lens = No slower than 1/300th of a second

And so on.

This applies to full frame or ‘cropped’ sensor cameras. 4/3rds too.

As you might guess, most cameras don’t come with a 1/18th second of a shutter speed. For the most part, round down to the next fastest shutter speed (=higher denominator = larger number in your view finder). So that 1/18th can be rounded to 1/20th, just to be safe. The faster you go, the less blur you will cause just by the fact that you are a human and have blood coursing through your veins and a silly, constant need to breathe. Breathing and holding a camera properly are important and will tip the odds in your favor.

Questions? Fire away!

Next Up: Shooting Waterfalls

31 Days To Better Photography is a series written by professional photographer Peter West Carey on The Carey Adventures.Com. The series is designed to unravel the mysteries of photography so you can take better pictures. Subscribe here to receive all the updates and bonus material. Your comments are always welcome.

10 Replies to “A Rule Of Thumb To Help Stop Photo Blur – 31+ Days To Better Photography”

  1. Rick

    Yeah, with my caffeine intake I generally only handhold at fairly fast shutter speeds. I paid good money for that Manfrotto, I’m going to make the best use out of it that I can. 🙂

    Reply
  2. Wayne

    Is this affected by the ‘focal length multiplier’??. I have read that is it, but I’m not convinced. If I’m using 100mm focal length on a full-frame, the minimum shutter would be 1/100sec. If I’m using the same focal length on a crop sensor it would be 1/(100*1.6) or 1/160 sec.

    I think it would be 1/100 in both cases. I’d like to hear if others agree.

    Reply
    • Peter West Carey Post author

      Wayne,
      My thinking is it is not affected by a crop sensor and here’s why. If I have a lens that is 100mm in length (prime lens) and I have it on Camera A and I move the lens 1mm left and right…the amount of shake from the lens will represent the same across the entire piece of glass, front and back. Meaning, if I only looked at the right half of the lens, the shake would be the same as the left half. If I only looked at 5% of the center, it will be the same as looking at 100% of the image.
      If I moved up to a 200mm prime and moved it 1mm, that effect would be increased because of the longer physical length of the lens. If I use a 2000mm and moved it 1mm, it’s even greater.

      My thinking is it is the physical length that matters most, not the size of the sensor. If it were true that a cropped senor would see more shake than a full frame sensor at the exact same focal length, then an image, taken on a full frame sensor, would have more blur JUST in the middle part (the part covered by a cropped sensor) than over the whole range. And that, according to physics, does not happen.

      That’s just my reasoning.
      pwc

      Reply
  3. Ionut

    In the example you gave if you move the lens 1 mm left and right you get a certain amount of movement in the final picture (I don’t know how to calculate it but let’s say that it’s 100mm left and right of the image while the image represents let’s say two cars parallel parked of about 10m together). If you used the same focal length on a cropped sensor (let’s say a 4/3 with a 2x factor) you would get the same amount o movement but comparing it to the resulting image shouldn’t it appear as more (you would probably get only one of the two cars in the picture)?
    If you use a 2x teleconverter, it’s size compared to the physical length of the lens is very small so it should influence only a little the final result. I actually tried to use a 200mm lens + a 2x teleconverter on a 4/3 sensor and I couldn’t get a steady image unless i used 1/1000 or less although according to the rule 1/500 should be enough.
    It might be that I don’t have very steady hands but I think that the angle of view provided by the lens influences how much camera shake appears in the image and this changes with the size of the sensor.

    Reply
    • Peter West Carey Post author

      lonut,
      After talking with a client of mine last night, I am inclined to think you are right, that it will make a difference. How much is debatable, though, going from 300mm to 480mm, with a 1.6x crop factor, for instance.

      Reply
  4. Petrus Chan

    Peter,
    Thanks a lot for your tips! I have a question.

    Are we talking about the focal length being used, or the maximum focal length of the lens? For example, for a 55-300mm lens, if I am zoom all the way out, i.e. using the 55mm, would a 1/50s be sufficient? I tend to think so if the rationale of the rule is about the magnification factor of the lens, which will also magnify the movement when zooming all the way in.

    However, I have also heard that we should always use the max focal length of the lens. So, just want to hear what you think.

    Thanks a lot!

    PC

    Reply
    • Peter West Carey Post author

      Petrus,
      I can assure you the only relevant focal length is what is actually being used. I have used an 18-270 lens before and shots at 1/20th were fine at 18mm. That’s about 4 stops slower than this rule you heard of and there would be no way for me to get a sharp shot if that were true.

      Reply
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