Minimum shutter speed and focal length multipliers?

Discussion in 'Digital Photography' started by Andrew McDonald, Dec 4, 2003.

  1. I have always used the "1/focal length" as the minimum "safe" shutter
    speed for handheld shots. Since the purchase of my D100 I was
    multiplying focal length by 1.5 in this formula so to handhold a 300mm
    lens (450mm equivalent) I would need at least 1/500th of a second.

    However, upon rethinking it occurs to me that this is not actually true.
    The D100 is not magnifying the image by 1.5x, it's cropping the center
    2/3rds of the image so the 1.5x does not need to be applied in this
    formula, right?

    So a 300mm lens only needs 1/350th for safe handholding, a 200mm lens
    only needs 1/200th and so on.

    Is this right? It makes sense but I could be over (or under) thinking it.
     
    Andrew McDonald, Dec 4, 2003
    #1
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  2. Andrew McDonald

    Robertwgross Guest

    Andrew, the prevailing attitude is to use the effective focal length as the
    guideline for the reciprocal of shutter speed.

    So, if you have a lens of 200mm with a x1.5 factor, then use 1/300 sec or
    faster.

    ---Bob Gross---
     
    Robertwgross, Dec 4, 2003
    #2
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  3. Andrew McDonald

    Don Coon Guest

    There is no consensus re your question but I tend to agree with you. After
    all, if I take a shot and decide to crop it further, say using only half of
    it, do I need to multiply my shutter speed by 2X again? I don't think so.

    I've come to the conclusion that most respondents recommend applying the
    crop factor to be safe (after all faster is better) or to be politically
    correct. <ducking fast> : )
     
    Don Coon, Dec 4, 2003
    #3
  4. Handholdability has everything to do with image magnification and
    shutterspeed. Your crop factor (magnification) is 1.5, so your
    shutterspeed should increase by 1.5 too. Of course, if you choose to
    crop your digital image, you would need to increase the shutterspeed
    even more (assuming "average" camera steadiness).

    -Dave
     
    Dave Herzstein, Dec 4, 2003
    #4
  5. Andrew McDonald

    Alan Browne Guest

    The rule of thumb is really connected to the frame of the captured
    image. So the rule of thumb should be applied with the crop factor. A
    300 lens with a 1.5 crop factor sensor should be handheld at 1/450 or
    faster (1/500).

    It is just a rule-of-thumb. And you will read claims of people getting
    good, decent or great shots at speeds slower than the FL suggests.

    A tripod is always, always better.
     
    Alan Browne, Dec 4, 2003
    #5
  6. Andrew McDonald

    Todd Walker Guest

    Wrong. You do need to take the multiplier into account.

    --
    __________________________________
    Todd Walker
    Canon 10D
    http://www.toddwalker.net
    http://www.twphotography.net
    __________________________________
     
    Todd Walker, Dec 4, 2003
    #6
  7. Andrew McDonald

    Don Coon Guest

    PS: as I said we're in the unsafe minority : )
     
    Don Coon, Dec 4, 2003
    #7
  8. The rule of thumb must be adjusted based on effective focal length. The
    "lens" when using the extender includes the extender, it does not just crop
    the image, it becomes a new lens. A lens is one or more elements forming an
    image. The only image being formed is the one that is passing through all
    the glass. It just turns out that generally the final "lens" with the
    extender is not nearly as good as one designed from the beginning for the
    longer focal length.

    Now the real question what shutter speed do YOU need with YOUR camera
    and YOUR lens (with or without extender). The weight and size and balance
    of the lens along with your ability and skill at holding the camera steady
    will determine what the real answer is and it may not be close to the rule
    of thumb.
     
    Joseph Meehan, Dec 4, 2003
    #8
  9. Andrew McDonald

    Don Coon Guest

    Did I miss something? Extender? Where was that mentioned?
     
    Don Coon, Dec 4, 2003
    #9
  10. A side issue here is, how much faster does a possibly-existing person
    of "average ability and average skill" need to shoot with an ultracompact
    compared to a merely compact and something the size of a film SLR?
     
    Anthony Buckland, Dec 4, 2003
    #10
  11. So, my 10D manual has a chart near the back showing the shutter speed/
    aperture combinations chosen by the camera when in programmed auto mode.
    I don't have it in front of me, but I don't think it takes the lens focal
    length into account at all, even though the camera certainly knows it.
    And IIRC, it uses a baseline of 1/60 sec, which might have made sense
    for a 35mm film camera that couldn't tell what lens is in use, but is
    probably too slow when you include the x1.6 factor of the 10D.
     
    Bjorn Helgaas, Dec 4, 2003
    #11
  12. Just call me red faced tonight. You're right.
     
    Joseph Meehan, Dec 5, 2003
    #12
  13. Maybe faster, may be slower. You can't really say until you try
    specific examples. From experience I would say that most people do best
    with mid to a little larger size camera rather than smaller, but we are all
    different. The specifics of each camera means two of the same size, but
    slightly different shape or shutter location etc, can be far different
     
    Joseph Meehan, Dec 5, 2003
    #13
  14. Andrew McDonald

    Don Coon Guest

    OK, pale face : )
     
    Don Coon, Dec 5, 2003
    #14
  15. Andrew McDonald

    Chris Brown Guest

    Incorrect. Think of it this way - blur due to camera shake is a result of
    the image moving on the sensor/film while the shutter is open. Let's assume
    that you're using a 35mm Nikon camera and a D100, both with the same 50mm
    lens, and that you have enough camera shake for a given shot for the image
    to move 1mm on the sensor/film.

    Now, this movement is the same regardless of whether we're using a D100 or a
    35mm camera. Now let's assume we want to make prints of our images, and we
    wan tthe prints to be, say, 12cm by 8cm (keeping everything metric to
    simplify the arithmetic here). A 35mm frame is 36*24mm, a D100 frame is
    24*16mm.

    In order to make our 12*9 cm print, we have to magnify the 35mm frame by
    120/36 = 3.3 times, and the D100 frame by 120/24 = 5 times. That means that
    the 1mm blur on our sensor/film will translate to 3.3mm on the film print,
    and 5mm on the D100 print.

    The amount of blur for a given lens, and a given amount of shake, and a
    given print size, is therefore more on the cropped-frame DSLRs than it is on
    the 35mm frame.

    In order for the amount of blur to be the same, the amount by which the
    image moves on the 35mm frame needs to be more than the amount by which the
    image moves on the D100 frame, because we're magnifying the latter more when
    we make a print. Since we're magnifying the D100 frame by 5/3.5 = 1.5 times
    more when we make a print, we'd get the same amount of blur as if we
    magnified the amount of movement on the 35mm negative by 1.5 times. The way
    we do this is by using a lens on the 35mm camera which is 1.5 times the
    focal length of the lens used on the D100.

    As we can see, it's not right. Bear in mind that this isn't a rule at all,
    it's a guideline based on the amount an average person shakes their hands
    while holding a camera, and based on them making a print of a certain size.
    If you're going to magnify the image by more, then clearly you need to make
    a shorter exposure time, because when you magnify the image you also magnify
    the blur. The D100 image has to be magnified more to make a print of a given
    size, so you get more blur. That's the key.

    IOW, there ain't no such thing as a free lunch. If there was, we'd never get
    camera shake from P&S digicams, because they use lenses around the 5mm mark.
     
    Chris Brown, Dec 5, 2003
    #15
  16. Andrew McDonald

    Alan Terry Guest

     
    Alan Terry, Dec 5, 2003
    #16
  17. Andrew McDonald

    Chris Brown Guest

    Wrong kind of movement. Camera shake blur is caused by rotation, not
    translation.

    If, like me, you're sitting on one of those swivel chairs on wheels, try a
    little experiment. Make a "tube" with your hand, or a rolled up piece of
    paper, and look through it with one eye, closing the other one. Note the
    scene you're looking at, and then move the chair a centimetre-or-so to the
    side. Notice how the scehe hardly changes at all (unless you're *very* close
    to what you're looking at).

    Now try rotating the chair slightly - notice that the image changes
    dramatically in comparison.

    Camera shake is the same (unless you're doing macro photography). If you're
    taking a picture of a distant scene, a tiny movement to either side won't
    actually change the scene at all. In fact, if the scenery is far enough
    away, you could put the camera and tripod on rails and have it move along
    while the shutter is open. As long as the camera stays pointing in the same
    direction, with the lens parallel to the direction of travel, the scene will
    still not be blured.

    Now rotate the camera slightly about any axis, and it's a different story -
    the picture will blur.
     
    Chris Brown, Dec 5, 2003
    #17
  18. Andrew McDonald

    Alan Browne Guest

    My Maxxum 7xi has a camera shake indicator (Maxxum 9 doesn't, they
    figure if you operate that beast you should know what you're doing).
    The camera logic seems very aware of the lens FL (prime or zoom) and the
    little camera shake indicator comes on at speeds roughly similar to the
    1/FL rule of thumb.

    If Canon have an indicator, I would bet that the s/w is well aware of
    the crop factor.

    Cheers,
    Alan.
     
    Alan Browne, Dec 5, 2003
    #18
  19. Andrew McDonald

    Chris Brown Guest

    I wouldn't - their ETTL flashes don't compensate when adjusting their field
    of view.
     
    Chris Brown, Dec 5, 2003
    #19
  20. Andrew McDonald

    Junque Guest

    If you selectively enlarge by cropping and printing to the size you
    would use for full frame then you multiply the movement blur by the same
    factor, therefor if you expect to enlarge by more that the "standard"
    amount then you need to multiply the shutter speed by the same factor.
    However since it only a guide you might not experience a problem.
     
    Junque, Dec 5, 2003
    #20
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