Lens For Portraits

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  Tim Kamppinen Registered Users Posts: 816 Major grins

  June 23, 2009 edited June 23, 2009

  Purest Light Photography wrote:

  I was just wondering if anyone had any suggestions for Portrait lens. I currently own a Sony dSLR-A350x with a DT18-70mm F3.5-5.6 and a DT55-200mm F4-5.6 lenses. I am clueless when it comes to lenses. I own my Natural Light photography business and have been using the DT55-200mm lens. It has been giving me lots of trouble it seems that two thirds or my portraits come out blurry. But when I use my 18-70mm lens I dont really have that problem. Any suggestions would be great. Thanks in advance.

  
  Your blurry shots are probably caused by camera shake. As a general rule the minimum shutter speed that most people can handhold their camera's and still avoid camera shake is 1/x where x is the focal length of the lens in 35mm terms. So if your camera has a 1.5x crop sensor (not sure if it does as I'm not familiar with sony cameras) then the effective focal length of your 200mm lens is 200x1.5= 300mm. To get sharp images while handholding you'd want to shoot at 1/300 second minimum. Anything longer is a crap shoot. Now if you're good at handholding and have a solid grip on the camera, use good technique, squeeze the shutter instead of jerking it, etc. then you can often get good results with longer shutter speeds, but at some point everyone is going to start having camera shake problems.
  
  The solution to this is to either increase ISO or open up the aperture so that you can use a faster shutter, or use a tripod. For shooting moving subjects like people you need faster shutter speeds because even if your camera is locked down on a tripod you'll still have motion blur if the subject moves at all. The best thing you can do as far as lenses would be to get some fast constant aperture glass that will allow you to use larger apertures like f/2.8 for zoom lenses or f/1.8 or 1.4 for prime lenses. For instance, your 55-200mm lens at 200mm has a maximum aperture of f/5.6. A constant aperture zoom like my 80-200 2.8 (nikon lens but there's probably a sony equivalant) lets in four times as much light when used at f/2.8. So if you had to use a shutter speed of 1/100 sec. with the 5.6 lens, you'd be able to use a shutter speed of 1/400 sec with the 2.8 and your blurry photo problem would be solved. Constant aperture lenses as a rule are sharper and all around better optical quality than variable aperture lenses, as well.
  
  For someone who only does natural light photography having fast lenses is essential. Again, I don't know sony gear but canon and nikon both provide cheap 50mm 1.8 lenses that are sub $150. If sony has something similar it would be a great value and a good way to explore the huge advantages of fast glass.

  http://www.timkphotography.com
  http://blog.timkphotography.com

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  ziggy53 Super Moderators Posts: 23,905 moderator

  June 23, 2009 edited June 23, 2009

  What Tim says is true if you're not using the Sony "Super Steady Shot" stabilization built into the camera. If you use the camera stabilization when hand held then there could be other things going on. If the problem occurs when the camera is mounted on a tripod, then you might try turning the stabilization off.
  
  It would help us to help you diagnose the problem if you could post a couple of examples of the problem with links to full-sized images which have EXIF.

  ziggy53
  Moderator of the Cameras and Accessories forums

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