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F3.5 vs F2.8 question?

Discussion in 'Lens Lust' started by Sphinx, Sep 26, 2008.

  1. Sphinx

    Sphinx

    61
    Feb 8, 2008
    UK
    Hi,

    Just a quick question.

    I have a Nikon 18-200VR F3.5-5.6 lense

    Although this lense is great as all rounder, I want to have a deciated lense for indoor photography e.g. children birthday party, and to get faster shutter speeds to avoid motion blur.

    Most shots i have taken so far between 20mm and 50mm seem to average around F4.5

    I was thinking about getting a Tamron 17-50mm F2.8.

    1) Would a F2.8 lense give a faster shutter speed?

    2) or have I got my camera setup wrong?

    Setup of the camera is Shutter Priority, Auto ISO.

    Thanks.
     
  2. Connahhh

    Connahhh

    Oct 27, 2007
    NH
    You would benefit from the F/2.8 in the long term. However, you can use your camera in aperture priority for the short term. That would help keep the aperture wide open and not worry so much about shutterspeed. Check what ISO these are being shot at, too, sometimes ISO Auto doesn't push it over 400.

    My opinion? Take it off ISO Auto and shutter priority, bump ISO to 800 and aperture priority and snap away.
     
  3. Sphinx

    Sphinx

    61
    Feb 8, 2008
    UK
    Hi Connahhh,
    Thanks for the tip.

    I did try what you suggested but I seem to always end up with a little motion blur.

    Usually is a hand or arm which has caused it.

    What sort of shutter speed would you get from F3.5 @ ISO 800.

    btw - i have a d80.
     
  4. The shutter speed is completely dependent on the available lighting. If you used fill flash you would be able to freeze the action a bit better even though the shutter speed is a bit slower.
     
  5. Connahhh

    Connahhh

    Oct 27, 2007
    NH
    It completely depends on the lighting situation. At 18mm, you can, at a minimum, hand hold at 1/30th of a second. At 50, 1/80th of a second. at 200, 1/250th of a second. It works by multiplying 1.5 times the focal length. So if you set iso to 800 and F/3.5 and don't have atleast 1/30th of a second, either up the ISO more or make a plan to purchase an F/2.8. It is almost a stop faster, so 1/20th or so will turn into a usable 1/50thish.

    I used approximate shutter speeds for this post, so keep that in mind.
     
  6. Julien

    Julien

    Jul 28, 2006
    Paris, France
    This is your general rule Connor but it's not set in stone, though it's probably a good starting point for beginners. Some can handhold at much lower speeds than that though ( for example I know that I can get sharp shots at 1/8 or 1/15 at 50mm on my rangefinder and on a DSLR I can easily be under the 1/"focal length" ).

    It all depends on the situation and how far up you can bump your ISO, or how far you're willing to bump it.
     
  7. mattsteg

    mattsteg

    455
    Aug 10, 2007
    MN
    Not to mention VR coming into play changes things a bit too. All of this is of course assuming that the subject isn't moving. Since Sphinx is getting blurred hands/arms due to subject motion, ultimate handholding shutter speeds aren't the issue.
     
  8. paulskimcb

    paulskimcb

    577
    Feb 12, 2007
    Midwest
    Well, he's talking about motion blur on the subject's end, which no amount of good hand-holding technique will fix.

    For that you need faster shutter speeds; these can be achieved by buying faster lenses (an f/2.8 would help) and/or bumping up your ISO and/or adding a good flash. An sb-600 is cheaper than many "fast" lenses and, since you can bounce the flash off of the ceiling, can help you avoid that washed-out flash look.
     
  9. Sphinx

    Sphinx

    61
    Feb 8, 2008
    UK
    Hi Paul.

    You are spot on. It is the subject end which is blurring.

    I do have a SB-800 however, to be honest I am a newbie to SLR and dont really have a foggiest how to operate it to full potentinal.

    I did try point the flash gun upwards to bounce the light, but for some reason I ended up with a half lit picture.

    How do I vary the intensity level of the flash? Is it set on the camera or the SB-800?

    Cheers.
     
  10. mattsteg

    mattsteg

    455
    Aug 10, 2007
    MN
    Yeah, the flash is probably the best route. You're certainly not going to get kids at a birthday party to stand still to stop motion blur, and even fast glass is still going to be marginal at best much of the time.
     
  11. Sphinx

    Sphinx

    61
    Feb 8, 2008
    UK
    Thanks matt.

    What do you think about the Tamron 17-50mm F2.8 lense?

    Any good?
     
  12. mattsteg

    mattsteg

    455
    Aug 10, 2007
    MN
    Check to make sure that the flash is making good contact with your body and is set to TTL mode and point it pretty much straight at the ceiling. If part of the light gets a straight shot at part of the subject it'll only light that part of the subject and the rest will be dim.

    The lens has a good reputation optically and seems well-built enough. I've only handled it in the store and taken a few test shots with it, though. While it would be a step up optically and in speed from the 18-200, you'll probably get more gains (and at no cost) from figuring out how to use your flash effectively than from a lens change.
     
  13. Sphinx

    Sphinx

    61
    Feb 8, 2008
    UK
    Cool.

    Do you use FV Lock very often when using the flash?
     
  14. SP77

    SP77

    Jun 4, 2007
    Rockville, MD
    Just use a flash. Even an f/2.8 is going to be too slow indoors to stop motion unless you have really really good light. You could go with a large aperture prime like an f/2 or faster, but then your problem is that there's so little depth of field that almost nothing will be in focus in your shots, and you'll be asking way too much of your AF system. iso400 + 1/125s + lens wide open (f/3.5 to f/5.6 range) and bounce flash and you're good to go.
     
  15. I've found this recipe very useful indoors:

    1/15 @ f/5.6, ISO 100, flash pointed at ceiling in TTL mode, -1, within 7' of subject.

    I generally use this as a starting point and adjust from there. The 1/15 sec shutter speed will allow for ambient light in the background. f/5.6 will give you enough DOF to get your subject in focus (even if they move and alter the focal plane). ISO 100 for image quality. Pointing the flash at the ceiling will give a soft, natural light to the scene. TTL will adjust the power of the flash and stop motion, and setting it to -1 will make sure that the subject is not overexposed compared to the background. If you move further away from your subject than 7', you'll have to increase the flash power.

    As an alternative to bouncing off the ceiling, I sometimes use a Lumiquest Pocket Bouncer. I find the light from the Pocket Bouncer to be much more natural in color than any other diffuser I've tried (including Sto-Fen, Gary Fong and ABBC).

    And as far as the Tamron 17-50 f/2.8, I think it's a great lens. I find the colors are not as rich and the contrast not as strong as my Nikon lenses, but I can easily make up for that in post. It certainly is a very sharp lens, and the speed can help when trying to isolate the subject.
     
  16. mattsteg

    mattsteg

    455
    Aug 10, 2007
    MN
    Not at all, as I don't have a button to spare to dedicate to that. I either trust the automagic with some compensation as needed or go to manual mode. It can be useful and I've used it in the past, but it's not something I can do with my current body without changing my overall approach dramatically.
     
  17. I think the f2.8 lens would help - you could set it at f4 for DoF at least -BUT - the flash is your full solution

    I would highly recommend a diffuser for your SB-800 - I think you will use it much more often then
     
  18. Sphinx

    Sphinx

    61
    Feb 8, 2008
    UK
    THanks guys.

    Just noticed sigma do 18-50mm f2.8

    Not sure which one to go for now? Tamron or Sigma?
     
  19. mattsteg

    mattsteg

    455
    Aug 10, 2007
    MN
    The Tamron's normally the best-regarded one, from what I've seen. Tokina has a 16-50, too.
     
  20. Connahhh

    Connahhh

    Oct 27, 2007
    NH
    I hear so much about the Tamron but for no reasons why it's better than the sigma. I researched them quite thoroughly and found that they are pretty much the same optically but the Tamron has that flash overexposing problem. I bought neither, but think if I did buy one, it would be the sigma.
     
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