Technical question about aperture, focal length and shutter speed...

Discussion in 'Digital Photography' started by Tony Spadaro, Jul 10, 2004.

  1. Tony Spadaro

    Tony Spadaro Guest

    Tony Spadaro, Jul 10, 2004
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  2. Tony Spadaro

    scott Guest

    I've just got my Canon 300D (my first SLR) with standard lens kit and am
    well impressed, however I think I would like to get a longer lens for the
    sort of sporting events I go to (Formula 1!)...

    Say I have an 75mm lens and shoot a photo at F5.6 for 1/1000 sec. Now say I
    want to zoom in on the subject with a 300mm lens at F5.6. Would I need to
    set the shutter to 1/250 to get the same exposure? In other words, does the
    exposure level depend on the focal length as well as the aperture and
    shutter speed?

    Is shooting fast moving objects with a 300mm at 1/250 going to be useless
    handheld, should I go for an IS version? The Canon IS lens are almost 3x
    the cost... Does the IS lens work if you are tracking a moving object?

    I tried to shoot some photos of the cars going past and getting the
    background motion blurred nicely, I used 1/80 sec @ 55mm (88mm in 35mm
    terms) and about 2 out of every 3 came out with the car blurred too (the car
    is going 150mph don't forget...). The 1 in 3 do look great though,
    certainly some of the best photos I've ever taken.

    I'm still learning and loving it!

    scott, Jul 10, 2004
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  3. Tony Spadaro

    Kenny Guest

    Tony has answered the focal length question.


    If you intend to pan shots, then unless you are prepared to pay for
    lenses with dual mode IS (the 100-400L for example), you should not use
    IS anyway. Best bang for the buck in longer lenses is the 70-200 F4 and
    you can even add a 1.4 TC for some extra length and still retain AF.
    There are better solutions, but they are more expensive.

    You could have gone to 1/160 and still have had nice background blur.
    Don't forget, you can crank up the ISO to 400 if necessary without
    adding any appreciable noise.

    I am a motorsport photographer and spend most weekends behind Armco in
    the UK, sometimes too close behind. You have made a good start if you
    are getting 30% success on your first run out. It is all down to
    practice and I would suggest you get along to one of the F3 meetings to
    hone those skills. F1 is once a year, F3, FPA, etc. are nearly every

    Kenny, Jul 10, 2004
  4. I have always worked on the rule that you can hand hold exposures down to
    the reciprocal of the focal length, eg with a 75mm focal length you can get
    steady photos down to 1/75 of a second whilst a 500mm can only be held still
    for 1/500th of a second.
    Stuart Walker, Jul 10, 2004
  5. []
    At the risk of stating the obvious, as you say you are still learning,
    have you heard about panning, moving the camera to keep the car framed and
    let the background move? I've used this at a couple of events and had
    some reasonable results. My exposures were much shorter, though, perhaps
    1/250 or 1/500, and I prefocussed to where I expect the car to be and used
    a wide lens aperture. You still need to take a lot of shots and reject
    the many bad ones, though. At least it's cheaper with digital!

    David J Taylor, Jul 11, 2004
  6. Tony Spadaro

    scott Guest

    So the "cheap" normal Canon IS doesn't work for following things ... ok
    thanks, I thought it unlikely that it would.
    That's true, this was at ISO100. I really didn't get enough chance to
    experiment as much as I would have liked. I also only had a 128 mb flash
    card so every 40 shots or so had to get out the old laptop!
    Yes I definitely intend to start going to the smaller meetings again. I
    used to live pretty close to Thruxton and went there a lot, but I've kind of
    got out of the habit recently. I should be able to get closer to the action
    in the smaller meetings anyway, F1 keeps you pretty far away (for the
    general public).

    Thanks for the advice.
    scott, Jul 11, 2004
  7. []
    What I found was that panning and tracking technique has differed for me
    depending which camera I use. With the Nikon 990 (LCD finder fixed to
    body) I tended to hold the camera near but not look through the camera. I
    would swing my body to keep the camera pointing in the direction of the
    car. This was when I was mainly standing at an F1 test at Silverstone.
    When seated at Suzuka, overlooking the first corner, I would tend to have
    the camera close to my head, and look through the optical finder. More a
    head and upper body rotation. I haven't visited an F1 GP since I had my
    Nikon 5700, but I have used it to photograph moving things, and there I
    use the EVF (electronic viewfinder) rather than the LCD. Again, having
    the camera at my head rather than at arm's length (to see the LCD) proves
    more successful.

    Obviously, you should do what works best for you! Practice makes (nearer
    to) perfect.

    David J Taylor, Jul 11, 2004
  8. Tony Spadaro

    scott Guest

    Hehe yes, no problem. I found with F1 cars you have to pan even at 1/1000
    or they blur! In 1/1000 second an F1 car has moved 5-10cm, which would
    cause some blurring. I guess I just need to practise tracking them
    accurately at progressively lower shutter speeds.
    scott, Jul 11, 2004
  9. Tony Spadaro

    Don Stauffer Guest

    No. Exposure depends only on amount of light (fixed by scene), shutter
    speed, and lens f/number. That is why the concept of relative aperture
    (f/#) was created, so you DIDN'T have to worry about focal length (even
    though this was WAY before zoom lenses were invented).

    For handheld, here is my rule of thumb. I shoot normal focal length
    (50mm in 35mm equivilent) no slower than 1/60. I ratio that by focal
    length for shutter speed. So if I were shooting at 100mm, I would use a
    tripod for anything slower than 1/120, etc.
    Don Stauffer, Jul 11, 2004
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