Thursday, January 23, 2014

Fast Prime Lenses - You Need One!

At least one, if not a couple.  Really.  While the zoom and super-zoom lenses may garner the lion's share of attention these days, a fixed focal length fast prime lens of f2.8 or larger can do absolutely wonderful things!  You zoom with your feet, obviously, but the low-light capability and paper-thin depth of field give you an extra advantage composing those awesome shots we all want.

AF Nikkor 50mm f1.8 fast prime lens on Nikon D300 DSLR.
Note the big window into the camera by way of that lens.  An aperture of f1.8 lets in a LOT of light, and that's what makes this special.  The large aperture, when run wide open, narrows the depth of field to something that's exceptionally shallow, allowing you the photographer to blur out everything but the subject of interest you intend to keep in focus.  Note the mold cavities compared to the book they're sitting on here:

Razor-sharp where you want it to be, soft where you don't.
The out-of-focus areas, called bokeh, have a soft, creamy composition without distracting edges.  Fast prime lenses are good for this, and as such are often called into use as dedicated portrait lenses.  You can selectively dial in or dial out the depth of field by varying the aperture of these lenses, to any degree you see fit.  Here's a view from inside my local camera shop as I tested out a 50mm f1.8 fast prime before buying it somewhere else.  (I might discuss that character flaw of mine later, we'll see...)

Focused at the computer monitors. 
Some shots lend themselves to a shallow depth of field.  That's always going to be a judgement call, based on what you're trying to convey for a theme in the finished product.  Experiment with that in mind, and don't be afraid to stop the lens down a bit for a few frames, then compare which of the images you like better.  Note how shallow the depth of field is in this one, but it seems to work ok:

Just the hammer and breechblock.
What's also not obvious about the above photo of the Sharps 1874 rifle is that the image was taken in fairly low light.  Fast prime lenses as shot wide open funnel a lot of light to the camera's sensor, and can make a big difference when there isn't a lot of available light illuminating your subject to begin with.  You can certainly enable the camera's flash, or bump up the ISO to get that proper exposure, but they'll change the dynamic of the image in different ways themselves.  A fast prime will give you the creative latitude to capture those images when you'd otherwise thought it was a lost cause. Case in point - this photo of a cluttered nightstand was taken with just the night light.

Low light, no problem.
 Since we're talking about fast prime lenses and portrait photography, a good use of said lenses is for capturing outdoor scenery.  Again, you have to be selective when it comes to your aperture settings, because that shallow depth of field can either make or break the composition.  Sunsets can be especially nice, playing the colors off the contrasts.  Here's a bitterly cold Wisconsin sunset, viewed from my front yard. I think it was -5 degrees ambient - a good test of the unheated camera's shutter!

It would have to warm up to snow!
As I alluded to earlier, a paper-thin depth of field can sometimes wreck a composition.  Likewise, optimal sharpness of images isn't always found at the widest aperture of a given lens.  You'll read many lens reviews out there that say a given lens is sharp wide open, but even better when closed down a stop or two.  I suppose it has to do with the intricacies of designing and manufacturing quality optics, but I've seen some flaws in imagery that did indeed improve when I went from f1.8 to say, f2.8 or smaller.  This bowl of my famous Chinese Stir-Fried Green Beans wasn't so great when captured wide open.  Stopped down a smidgen, and it's downright yummy!

Of course, I'm a Nikon kind of guy, but the other camera folks are also well-served by a nice assortment of fast prime lenses.  Prices of said lenses can range from dirt-cheap to ohmygawd, depending on focal length, autofocus, brand, and maximum aperture.  The AF Nikkor 50mm f1.8 used in this blog essay?  It retails for $130.00 new at my local camera shop.  While I spend a goodly amount of time and money there, I found the same lens at Goodwill for less than $50.00.  That's my character flaw, and you'll see it's also a recurring theme when it comes to my camera optics.  ;-)

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